diff options
Diffstat (limited to 'drivers/lguest')
| -rw-r--r-- | drivers/lguest/core.c | 119 | ||||
| -rw-r--r-- | drivers/lguest/hypercalls.c | 145 | ||||
| -rw-r--r-- | drivers/lguest/interrupts_and_traps.c | 288 | ||||
| -rw-r--r-- | drivers/lguest/lg.h | 32 | ||||
| -rw-r--r-- | drivers/lguest/lguest_device.c | 160 | ||||
| -rw-r--r-- | drivers/lguest/lguest_user.c | 232 | ||||
| -rw-r--r-- | drivers/lguest/page_tables.c | 489 | ||||
| -rw-r--r-- | drivers/lguest/segments.c | 106 | ||||
| -rw-r--r-- | drivers/lguest/x86/core.c | 374 | ||||
| -rw-r--r-- | drivers/lguest/x86/switcher_32.S | 22 |
10 files changed, 1330 insertions, 637 deletions
diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c index a6974e9..1e2cb84 100644 --- a/drivers/lguest/core.c +++ b/drivers/lguest/core.c @@ -1,6 +1,8 @@ -/*P:400 This contains run_guest() which actually calls into the Host<->Guest +/*P:400 + * This contains run_guest() which actually calls into the Host<->Guest * Switcher and analyzes the return, such as determining if the Guest wants the - * Host to do something. This file also contains useful helper routines. :*/ + * Host to do something. This file also contains useful helper routines. +:*/ #include <linux/module.h> #include <linux/stringify.h> #include <linux/stddef.h> @@ -24,7 +26,8 @@ static struct page **switcher_page; /* This One Big lock protects all inter-guest data structures. */ DEFINE_MUTEX(lguest_lock); -/*H:010 We need to set up the Switcher at a high virtual address. Remember the +/*H:010 + * We need to set up the Switcher at a high virtual address. Remember the * Switcher is a few hundred bytes of assembler code which actually changes the * CPU to run the Guest, and then changes back to the Host when a trap or * interrupt happens. @@ -33,7 +36,8 @@ DEFINE_MUTEX(lguest_lock); * Host since it will be running as the switchover occurs. * * Trying to map memory at a particular address is an unusual thing to do, so - * it's not a simple one-liner. */ + * it's not a simple one-liner. + */ static __init int map_switcher(void) { int i, err; @@ -47,8 +51,10 @@ static __init int map_switcher(void) * easy. */ - /* We allocate an array of struct page pointers. map_vm_area() wants - * this, rather than just an array of pages. */ + /* + * We allocate an array of struct page pointers. map_vm_area() wants + * this, rather than just an array of pages. + */ switcher_page = kmalloc(sizeof(switcher_page[0])*TOTAL_SWITCHER_PAGES, GFP_KERNEL); if (!switcher_page) { @@ -56,8 +62,10 @@ static __init int map_switcher(void) goto out; } - /* Now we actually allocate the pages. The Guest will see these pages, - * so we make sure they're zeroed. */ + /* + * Now we actually allocate the pages. The Guest will see these pages, + * so we make sure they're zeroed. + */ for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) { unsigned long addr = get_zeroed_page(GFP_KERNEL); if (!addr) { @@ -67,19 +75,23 @@ static __init int map_switcher(void) switcher_page[i] = virt_to_page(addr); } - /* First we check that the Switcher won't overlap the fixmap area at + /* + * First we check that the Switcher won't overlap the fixmap area at * the top of memory. It's currently nowhere near, but it could have - * very strange effects if it ever happened. */ + * very strange effects if it ever happened. + */ if (SWITCHER_ADDR + (TOTAL_SWITCHER_PAGES+1)*PAGE_SIZE > FIXADDR_START){ err = -ENOMEM; printk("lguest: mapping switcher would thwack fixmap\n"); goto free_pages; } - /* Now we reserve the "virtual memory area" we want: 0xFFC00000 + /* + * Now we reserve the "virtual memory area" we want: 0xFFC00000 * (SWITCHER_ADDR). We might not get it in theory, but in practice * it's worked so far. The end address needs +1 because __get_vm_area - * allocates an extra guard page, so we need space for that. */ + * allocates an extra guard page, so we need space for that. + */ switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE, VM_ALLOC, SWITCHER_ADDR, SWITCHER_ADDR + (TOTAL_SWITCHER_PAGES+1) * PAGE_SIZE); @@ -89,11 +101,13 @@ static __init int map_switcher(void) goto free_pages; } - /* This code actually sets up the pages we've allocated to appear at + /* + * This code actually sets up the pages we've allocated to appear at * SWITCHER_ADDR. map_vm_area() takes the vma we allocated above, the * kind of pages we're mapping (kernel pages), and a pointer to our * array of struct pages. It increments that pointer, but we don't - * care. */ + * care. + */ pagep = switcher_page; err = map_vm_area(switcher_vma, PAGE_KERNEL_EXEC, &pagep); if (err) { @@ -101,8 +115,10 @@ static __init int map_switcher(void) goto free_vma; } - /* Now the Switcher is mapped at the right address, we can't fail! - * Copy in the compiled-in Switcher code (from <arch>_switcher.S). */ + /* + * Now the Switcher is mapped at the right address, we can't fail! + * Copy in the compiled-in Switcher code (from <arch>_switcher.S). + */ memcpy(switcher_vma->addr, start_switcher_text, end_switcher_text - start_switcher_text); @@ -124,8 +140,7 @@ out: } /*:*/ -/* Cleaning up the mapping when the module is unloaded is almost... - * too easy. */ +/* Cleaning up the mapping when the module is unloaded is almost... too easy. */ static void unmap_switcher(void) { unsigned int i; @@ -151,16 +166,19 @@ static void unmap_switcher(void) * But we can't trust the Guest: it might be trying to access the Launcher * code. We have to check that the range is below the pfn_limit the Launcher * gave us. We have to make sure that addr + len doesn't give us a false - * positive by overflowing, too. */ + * positive by overflowing, too. + */ bool lguest_address_ok(const struct lguest *lg, unsigned long addr, unsigned long len) { return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr); } -/* This routine copies memory from the Guest. Here we can see how useful the +/* + * This routine copies memory from the Guest. Here we can see how useful the * kill_lguest() routine we met in the Launcher can be: we return a random - * value (all zeroes) instead of needing to return an error. */ + * value (all zeroes) instead of needing to return an error. + */ void __lgread(struct lg_cpu *cpu, void *b, unsigned long addr, unsigned bytes) { if (!lguest_address_ok(cpu->lg, addr, bytes) @@ -181,9 +199,11 @@ void __lgwrite(struct lg_cpu *cpu, unsigned long addr, const void *b, } /*:*/ -/*H:030 Let's jump straight to the the main loop which runs the Guest. +/*H:030 + * Let's jump straight to the the main loop which runs the Guest. * Remember, this is called by the Launcher reading /dev/lguest, and we keep - * going around and around until something interesting happens. */ + * going around and around until something interesting happens. + */ int run_guest(struct lg_cpu *cpu, unsigned long __user *user) { /* We stop running once the Guest is dead. */ @@ -195,10 +215,17 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user) if (cpu->hcall) do_hypercalls(cpu); - /* It's possible the Guest did a NOTIFY hypercall to the - * Launcher, in which case we return from the read() now. */ + /* + * It's possible the Guest did a NOTIFY hypercall to the + * Launcher. + */ if (cpu->pending_notify) { + /* + * Does it just needs to write to a registered + * eventfd (ie. the appropriate virtqueue thread)? + */ if (!send_notify_to_eventfd(cpu)) { + /* OK, we tell the main Laucher. */ if (put_user(cpu->pending_notify, user)) return -EFAULT; return sizeof(cpu->pending_notify); @@ -209,29 +236,39 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user) if (signal_pending(current)) return -ERESTARTSYS; - /* Check if there are any interrupts which can be delivered now: + /* + * Check if there are any interrupts which can be delivered now: * if so, this sets up the hander to be executed when we next - * run the Guest. */ + * run the Guest. + */ irq = interrupt_pending(cpu, &more); if (irq < LGUEST_IRQS) try_deliver_interrupt(cpu, irq, more); - /* All long-lived kernel loops need to check with this horrible + /* + * All long-lived kernel loops need to check with this horrible * thing called the freezer. If the Host is trying to suspend, - * it stops us. */ + * it stops us. + */ try_to_freeze(); - /* Just make absolutely sure the Guest is still alive. One of - * those hypercalls could have been fatal, for example. */ + /* + * Just make absolutely sure the Guest is still alive. One of + * those hypercalls could have been fatal, for example. + */ if (cpu->lg->dead) break; - /* If the Guest asked to be stopped, we sleep. The Guest's - * clock timer will wake us. */ + /* + * If the Guest asked to be stopped, we sleep. The Guest's + * clock timer will wake us. + */ if (cpu->halted) { set_current_state(TASK_INTERRUPTIBLE); - /* Just before we sleep, make sure no interrupt snuck in - * which we should be doing. */ + /* + * Just before we sleep, make sure no interrupt snuck in + * which we should be doing. + */ if (interrupt_pending(cpu, &more) < LGUEST_IRQS) set_current_state(TASK_RUNNING); else @@ -239,8 +276,10 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user) continue; } - /* OK, now we're ready to jump into the Guest. First we put up - * the "Do Not Disturb" sign: */ + /* + * OK, now we're ready to jump into the Guest. First we put up + * the "Do Not Disturb" sign: + */ local_irq_disable(); /* Actually run the Guest until something happens. */ @@ -327,8 +366,10 @@ static void __exit fini(void) } /*:*/ -/* The Host side of lguest can be a module. This is a nice way for people to - * play with it. */ +/* + * The Host side of lguest can be a module. This is a nice way for people to + * play with it. + */ module_init(init); module_exit(fini); MODULE_LICENSE("GPL"); diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c index c29ffa1..83511eb 100644 --- a/drivers/lguest/hypercalls.c +++ b/drivers/lguest/hypercalls.c @@ -1,8 +1,10 @@ -/*P:500 Just as userspace programs request kernel operations through a system +/*P:500 + * Just as userspace programs request kernel operations through a system * call, the Guest requests Host operations through a "hypercall". You might * notice this nomenclature doesn't really follow any logic, but the name has * been around for long enough that we're stuck with it. As you'd expect, this - * code is basically a one big switch statement. :*/ + * code is basically a one big switch statement. +:*/ /* Copyright (C) 2006 Rusty Russell IBM Corporation @@ -28,30 +30,41 @@ #include <asm/pgtable.h> #include "lg.h" -/*H:120 This is the core hypercall routine: where the Guest gets what it wants. - * Or gets killed. Or, in the case of LHCALL_SHUTDOWN, both. */ +/*H:120 + * This is the core hypercall routine: where the Guest gets what it wants. + * Or gets killed. Or, in the case of LHCALL_SHUTDOWN, both. + */ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args) { switch (args->arg0) { case LHCALL_FLUSH_ASYNC: - /* This call does nothing, except by breaking out of the Guest - * it makes us process all the asynchronous hypercalls. */ + /* + * This call does nothing, except by breaking out of the Guest + * it makes us process all the asynchronous hypercalls. + */ break; case LHCALL_SEND_INTERRUPTS: - /* This call does nothing too, but by breaking out of the Guest - * it makes us process any pending interrupts. */ + /* + * This call does nothing too, but by breaking out of the Guest + * it makes us process any pending interrupts. + */ break; case LHCALL_LGUEST_INIT: - /* You can't get here unless you're already initialized. Don't - * do that. */ + /* + * You can't get here unless you're already initialized. Don't + * do that. + */ kill_guest(cpu, "already have lguest_data"); break; case LHCALL_SHUTDOWN: { - /* Shutdown is such a trivial hypercall that we do it in four - * lines right here. */ char msg[128]; - /* If the lgread fails, it will call kill_guest() itself; the - * kill_guest() with the message will be ignored. */ + /* + * Shutdown is such a trivial hypercall that we do it in five + * lines right here. + * + * If the lgread fails, it will call kill_guest() itself; the + * kill_guest() with the message will be ignored. + */ __lgread(cpu, msg, args->arg1, sizeof(msg)); msg[sizeof(msg)-1] = '\0'; kill_guest(cpu, "CRASH: %s", msg); @@ -60,16 +73,17 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args) break; } case LHCALL_FLUSH_TLB: - /* FLUSH_TLB comes in two flavors, depending on the - * argument: */ + /* FLUSH_TLB comes in two flavors, depending on the argument: */ if (args->arg1) guest_pagetable_clear_all(cpu); else guest_pagetable_flush_user(cpu); break; - /* All these calls simply pass the arguments through to the right - * routines. */ + /* + * All these calls simply pass the arguments through to the right + * routines. + */ case LHCALL_NEW_PGTABLE: guest_new_pagetable(cpu, args->arg1); break; @@ -112,15 +126,16 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args) kill_guest(cpu, "Bad hypercall %li\n", args->arg0); } } -/*:*/ -/*H:124 Asynchronous hypercalls are easy: we just look in the array in the +/*H:124 + * Asynchronous hypercalls are easy: we just look in the array in the * Guest's "struct lguest_data" to see if any new ones are marked "ready". * * We are careful to do these in order: obviously we respect the order the * Guest put them in the ring, but we also promise the Guest that they will * happen before any normal hypercall (which is why we check this before - * checking for a normal hcall). */ + * checking for a normal hcall). + */ static void do_async_hcalls(struct lg_cpu *cpu) { unsigned int i; @@ -133,22 +148,28 @@ static void do_async_hcalls(struct lg_cpu *cpu) /* We process "struct lguest_data"s hcalls[] ring once. */ for (i = 0; i < ARRAY_SIZE(st); i++) { struct hcall_args args; - /* We remember where we were up to from last time. This makes + /* + * We remember where we were up to from last time. This makes * sure that the hypercalls are done in the order the Guest - * places them in the ring. */ + * places them in the ring. + */ unsigned int n = cpu->next_hcall; /* 0xFF means there's no call here (yet). */ if (st[n] == 0xFF) break; - /* OK, we have hypercall. Increment the "next_hcall" cursor, - * and wrap back to 0 if we reach the end. */ + /* + * OK, we have hypercall. Increment the "next_hcall" cursor, + * and wrap back to 0 if we reach the end. + */ if (++cpu->next_hcall == LHCALL_RING_SIZE) cpu->next_hcall = 0; - /* Copy the hypercall arguments into a local copy of - * the hcall_args struct. */ + /* + * Copy the hypercall arguments into a local copy of the + * hcall_args struct. + */ if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n], sizeof(struct hcall_args))) { kill_guest(cpu, "Fetching async hypercalls"); @@ -164,19 +185,25 @@ static void do_async_hcalls(struct lg_cpu *cpu) break; } - /* Stop doing hypercalls if they want to notify the Launcher: - * it needs to service this first. */ + /* + * Stop doing hypercalls if they want to notify the Launcher: + * it needs to service this first. + */ if (cpu->pending_notify) break; } } -/* Last of all, we look at what happens first of all. The very first time the - * Guest makes a hypercall, we end up here to set things up: */ +/* + * Last of all, we look at what happens first of all. The very first time the + * Guest makes a hypercall, we end up here to set things up: + */ static void initialize(struct lg_cpu *cpu) { - /* You can't do anything until you're initialized. The Guest knows the - * rules, so we're unforgiving here. */ + /* + * You can't do anything until you're initialized. The Guest knows the + * rules, so we're unforgiving here. + */ if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) { kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0); return; @@ -185,32 +212,44 @@ static void initialize(struct lg_cpu *cpu) if (lguest_arch_init_hypercalls(cpu)) kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); - /* The Guest tells us where we're not to deliver interrupts by putting - * the range of addresses into "struct lguest_data". */ + /* + * The Guest tells us where we're not to deliver interrupts by putting + * the range of addresses into "struct lguest_data". + */ if (get_user(cpu->lg->noirq_start, &cpu->lg->lguest_data->noirq_start) || get_user(cpu->lg->noirq_end, &cpu->lg->lguest_data->noirq_end)) kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); - /* We write the current time into the Guest's data page once so it can - * set its clock. */ + /* + * We write the current time into the Guest's data page once so it can + * set its clock. + */ write_timestamp(cpu); /* page_tables.c will also do some setup. */ page_table_guest_data_init(cpu); - /* This is the one case where the above accesses might have been the + /* + * This is the one case where the above accesses might have been the * first write to a Guest page. This may have caused a copy-on-write * fault, but the old page might be (read-only) in the Guest - * pagetable. */ + * pagetable. + */ guest_pagetable_clear_all(cpu); } /*:*/ -/*M:013 If a Guest reads from a page (so creates a mapping) that it has never +/*M:013 + * If a Guest reads from a page (so creates a mapping) that it has never * written to, and then the Launcher writes to it (ie. the output of a virtual * device), the Guest will still see the old page. In practice, this never * happens: why would the Guest read a page which it has never written to? But - * a similar scenario might one day bite us, so it's worth mentioning. :*/ + * a similar scenario might one day bite us, so it's worth mentioning. + * + * Note that if we used a shared anonymous mapping in the Launcher instead of + * mapping /dev/zero private, we wouldn't worry about cop-on-write. And we + * need that to switch the Launcher to processes (away from threads) anyway. +:*/ /*H:100 * Hypercalls @@ -229,17 +268,22 @@ void do_hypercalls(struct lg_cpu *cpu) return; } - /* The Guest has initialized. + /* + * The Guest has initialized. * - * Look in the hypercall ring for the async hypercalls: */ + * Look in the hypercall ring for the async hypercalls: + */ do_async_hcalls(cpu); - /* If we stopped reading the hypercall ring because the Guest did a + /* + * If we stopped reading the hypercall ring because the Guest did a * NOTIFY to the Launcher, we want to return now. Otherwise we do - * the hypercall. */ + * the hypercall. + */ if (!cpu->pending_notify) { do_hcall(cpu, cpu->hcall); - /* Tricky point: we reset the hcall pointer to mark the + /* + * Tricky point: we reset the hcall pointer to mark the * hypercall as "done". We use the hcall pointer rather than * the trap number to indicate a hypercall is pending. * Normally it doesn't matter: the Guest will run again and @@ -248,13 +292,16 @@ void do_hypercalls(struct lg_cpu *cpu) * However, if we are signalled or the Guest sends I/O to the * Launcher, the run_guest() loop will exit without running the * Guest. When it comes back it would try to re-run the - * hypercall. Finding that bug sucked. */ + * hypercall. Finding that bug sucked. + */ cpu->hcall = NULL; } } -/* This routine supplies the Guest with time: it's used for wallclock time at - * initial boot and as a rough time source if the TSC isn't available. */ +/* + * This routine supplies the Guest with time: it's used for wallclock time at + * initial boot and as a rough time source if the TSC isn't available. + */ void write_timestamp(struct lg_cpu *cpu) { struct timespec now; diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c index 0e9067b..1864818 100644 --- a/drivers/lguest/interrupts_and_traps.c +++ b/drivers/lguest/interrupts_and_traps.c @@ -1,4 +1,5 @@ -/*P:800 Interrupts (traps) are complicated enough to earn their own file. +/*P:800 + * Interrupts (traps) are complicated enough to earn their own file. * There are three classes of interrupts: * * 1) Real hardware interrupts which occur while we're running the Guest, @@ -10,7 +11,8 @@ * just like real hardware would deliver them. Traps from the Guest can be set * up to go directly back into the Guest, but sometimes the Host wants to see * them first, so we also have a way of "reflecting" them into the Guest as if - * they had been delivered to it directly. :*/ + * they had been delivered to it directly. +:*/ #include <linux/uaccess.h> #include <linux/interrupt.h> #include <linux/module.h> @@ -26,8 +28,10 @@ static unsigned long idt_address(u32 lo, u32 hi) return (lo & 0x0000FFFF) | (hi & 0xFFFF0000); } -/* The "type" of the interrupt handler is a 4 bit field: we only support a - * couple of types. */ +/* + * The "type" of the interrupt handler is a 4 bit field: we only support a + * couple of types. + */ static int idt_type(u32 lo, u32 hi) { return (hi >> 8) & 0xF; @@ -39,8 +43,10 @@ static bool idt_present(u32 lo, u32 hi) return (hi & 0x8000); } -/* We need a helper to "push" a value onto the Guest's stack, since that's a - * big part of what delivering an interrupt does. */ +/* + * We need a helper to "push" a value onto the Guest's stack, since that's a + * big part of what delivering an interrupt does. + */ static void push_guest_stack(struct lg_cpu *cpu, unsigned long *gstack, u32 val) { /* Stack grows upwards: move stack then write value. */ @@ -48,7 +54,8 @@ static void push_guest_stack(struct lg_cpu *cpu, unsigned long *gstack, u32 val) lgwrite(cpu, *gstack, u32, val); } -/*H:210 The set_guest_interrupt() routine actually delivers the interrupt or +/*H:210 + * The set_guest_interrupt() routine actually delivers the interrupt or * trap. The mechanics of delivering traps and interrupts to the Guest are the * same, except some traps have an "error code" which gets pushed onto the * stack as well: the caller tells us if this is one. @@ -59,7 +66,8 @@ static void push_guest_stack(struct lg_cpu *cpu, unsigned long *gstack, u32 val) * * We set up the stack just like the CPU does for a real interrupt, so it's * identical for the Guest (and the standard "iret" instruction will undo - * it). */ + * it). + */ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi, bool has_err) { @@ -67,20 +75,26 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi, u32 eflags, ss, irq_enable; unsigned long virtstack; - /* There are two cases for interrupts: one where the Guest is already + /* + * There are two cases for interrupts: one where the Guest is already * in the kernel, and a more complex one where the Guest is in - * userspace. We check the privilege level to find out. */ + * userspace. We check the privilege level to find out. + */ if ((cpu->regs->ss&0x3) != GUEST_PL) { - /* The Guest told us their kernel stack with the SET_STACK - * hypercall: both the virtual address and the segment */ + /* + * The Guest told us their kernel stack with the SET_STACK + * hypercall: both the virtual address and the segment. + */ virtstack = cpu->esp1; ss = cpu->ss1; origstack = gstack = guest_pa(cpu, virtstack); - /* We push the old stack segment and pointer onto the new + /* + * We push the old stack segment and pointer onto the new * stack: when the Guest does an "iret" back from the interrupt * handler the CPU will notice they're dropping privilege - * levels and expect these here. */ + * levels and expect these here. + */ push_guest_stack(cpu, &gstack, cpu->regs->ss); push_guest_stack(cpu, &gstack, cpu->regs->esp); } else { @@ -91,18 +105,22 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi, origstack = gstack = guest_pa(cpu, virtstack); } - /* Remember that we never let the Guest actually disable interrupts, so + /* + * Remember that we never let the Guest actually disable interrupts, so * the "Interrupt Flag" bit is always set. We copy that bit from the * Guest's "irq_enabled" field into the eflags word: we saw the Guest - * copy it back in "lguest_iret". */ + * copy it back in "lguest_iret". + */ eflags = cpu->regs->eflags; if (get_user(irq_enable, &cpu->lg->lguest_data->irq_enabled) == 0 && !(irq_enable & X86_EFLAGS_IF)) eflags &= ~X86_EFLAGS_IF; - /* An interrupt is expected to push three things on the stack: the old + /* + * An interrupt is expected to push three things on the stack: the old * "eflags" word, the old code segment, and the old instruction - * pointer. */ + * pointer. + */ push_guest_stack(cpu, &gstack, eflags); push_guest_stack(cpu, &gstack, cpu->regs->cs); push_guest_stack(cpu, &gstack, cpu->regs->eip); @@ -111,15 +129,19 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi, if (has_err) push_guest_stack(cpu, &gstack, cpu->regs->errcode); - /* Now we've pushed all the old state, we change the stack, the code - * segment and the address to execute. */ + /* + * Now we've pushed all the old state, we change the stack, the code + * segment and the address to execute. + */ cpu->regs->ss = ss; cpu->regs->esp = virtstack + (gstack - origstack); cpu->regs->cs = (__KERNEL_CS|GUEST_PL); cpu->regs->eip = idt_address(lo, hi); - /* There are two kinds of interrupt handlers: 0xE is an "interrupt - * gate" which expects interrupts to be disabled on entry. */ + /* + * There are two kinds of interrupt handlers: 0xE is an "interrupt + * gate" which expects interrupts to be disabled on entry. + */ if (idt_type(lo, hi) == 0xE) if (put_user(0, &cpu->lg->lguest_data->irq_enabled)) kill_guest(cpu, "Disabling interrupts"); @@ -130,7 +152,8 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi, * * interrupt_pending() returns the first pending interrupt which isn't blocked * by the Guest. It is called before every entry to the Guest, and just before - * we go to sleep when the Guest has halted itself. */ + * we go to sleep when the Guest has halted itself. + */ unsigned int interrupt_pending(struct lg_cpu *cpu, bool *more) { unsigned int irq; @@ -140,8 +163,10 @@ unsigned int interrupt_pending(struct lg_cpu *cpu, bool *more) if (!cpu->lg->lguest_data) return LGUEST_IRQS; - /* Take our "irqs_pending" array and remove any interrupts the Guest - * wants blocked: the result ends up in "blk". */ + /* + * Take our "irqs_pending" array and remove any interrupts the Guest + * wants blocked: the result ends up in "blk". + */ if (copy_from_user(&blk, cpu->lg->lguest_data->blocked_interrupts, sizeof(blk))) return LGUEST_IRQS; @@ -154,16 +179,20 @@ unsigned int interrupt_pending(struct lg_cpu *cpu, bool *more) return irq; } -/* This actually diverts the Guest to running an interrupt handler, once an - * interrupt has been identified by interrupt_pending(). */ +/* + * This actually diverts the Guest to running an interrupt handler, once an + * interrupt has been identified by interrupt_pending(). + */ void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more) { struct desc_struct *idt; BUG_ON(irq >= LGUEST_IRQS); - /* They may be in the middle of an iret, where they asked us never to - * deliver interrupts. */ + /* + * They may be in the middle of an iret, where they asked us never to + * deliver interrupts. + */ if (cpu->regs->eip >= cpu->lg->noirq_start && (cpu->regs->eip < cpu->lg->noirq_end)) return; @@ -187,29 +216,37 @@ void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more) } } - /* Look at the IDT entry the Guest gave us for this interrupt. The + /* + * Look at the IDT entry the Guest gave us for this interrupt. The * first 32 (FIRST_EXTERNAL_VECTOR) entries are for traps, so we skip - * over them. */ + * over them. + */ idt = &cpu->arch.idt[FIRST_EXTERNAL_VECTOR+irq]; /* If they don't have a handler (yet?), we just ignore it */ if (idt_present(idt->a, idt->b)) { /* OK, mark it no longer pending and deliver it. */ clear_bit(irq, cpu->irqs_pending); - /* set_guest_interrupt() takes the interrupt descriptor and a + /* + * set_guest_interrupt() takes the interrupt descriptor and a * flag to say whether this interrupt pushes an error code onto - * the stack as well: virtual interrupts never do. */ + * the stack as well: virtual interrupts never do. + */ set_guest_interrupt(cpu, idt->a, idt->b, false); } - /* Every time we deliver an interrupt, we update the timestamp in the + /* + * Every time we deliver an interrupt, we update the timestamp in the * Guest's lguest_data struct. It would be better for the Guest if we * did this more often, but it can actually be quite slow: doing it * here is a compromise which means at least it gets updated every - * timer interrupt. */ + * timer interrupt. + */ write_timestamp(cpu); - /* If there are no other interrupts we want to deliver, clear - * the pending flag. */ + /* + * If there are no other interrupts we want to deliver, clear + * the pending flag. + */ if (!more) put_user(0, &cpu->lg->lguest_data->irq_pending); } @@ -217,24 +254,29 @@ void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more) /* And this is the routine when we want to set an interrupt for the Guest. */ void set_interrupt(struct lg_cpu *cpu, unsigned int irq) { - /* Next time the Guest runs, the core code will see if it can deliver - * this interrupt. */ + /* + * Next time the Guest runs, the core code will see if it can deliver + * this interrupt. + */ set_bit(irq, cpu->irqs_pending); - /* Make sure it sees it; it might be asleep (eg. halted), or - * running the Guest right now, in which case kick_process() - * will knock it out. */ + /* + * Make sure it sees it; it might be asleep (eg. halted), or running + * the Guest right now, in which case kick_process() will knock it out. + */ if (!wake_up_process(cpu->tsk)) kick_process(cpu->tsk); } /*:*/ -/* Linux uses trap 128 for system calls. Plan9 uses 64, and Ron Minnich sent +/* + * Linux uses trap 128 for system calls. Plan9 uses 64, and Ron Minnich sent * me a patch, so we support that too. It'd be a big step for lguest if half * the Plan 9 user base were to start using it. * * Actually now I think of it, it's possible that Ron *is* half the Plan 9 - * userbase. Oh well. */ + * userbase. Oh well. + */ static bool could_be_syscall(unsigned int num) { /* Normal Linux SYSCALL_VECTOR or reserved vector? */ @@ -274,9 +316,11 @@ void free_interrupts(void) clear_bit(syscall_vector, used_vectors); } -/*H:220 Now we've got the routines to deliver interrupts, delivering traps like +/*H:220 + * Now we've got the routines to deliver interrupts, delivering traps like * page fault is easy. The only trick is that Intel decided that some traps - * should have error codes: */ + * should have error codes: + */ static bool has_err(unsigned int trap) { return (trap == 8 || (trap >= 10 && trap <= 14) || trap == 17); @@ -285,13 +329,17 @@ static bool has_err(unsigned int trap) /* deliver_trap() returns true if it could deliver the trap. */ bool deliver_trap(struct lg_cpu *cpu, unsigned int num) { - /* Trap numbers are always 8 bit, but we set an impossible trap number - * for traps inside the Switcher, so check that here. */ + /* + * Trap numbers are always 8 bit, but we set an impossible trap number + * for traps inside the Switcher, so check that here. + */ if (num >= ARRAY_SIZE(cpu->arch.idt)) return false; - /* Early on the Guest hasn't set the IDT entries (or maybe it put a - * bogus one in): if we fail here, the Guest will be killed. */ + /* + * Early on the Guest hasn't set the IDT entries (or maybe it put a + * bogus one in): if we fail here, the Guest will be killed. + */ if (!idt_present(cpu->arch.idt[num].a, cpu->arch.idt[num].b)) return false; set_guest_interrupt(cpu, cpu->arch.idt[num].a, @@ -299,7 +347,8 @@ bool deliver_trap(struct lg_cpu *cpu, unsigned int num) return true; } -/*H:250 Here's the hard part: returning to the Host every time a trap happens +/*H:250 + * Here's the hard part: returning to the Host every time a trap happens * and then calling deliver_trap() and re-entering the Guest is slow. * Particularly because Guest userspace system calls are traps (usually trap * 128). @@ -311,69 +360,87 @@ bool deliver_trap(struct lg_cpu *cpu, unsigned int num) * the other hypervisors would beat it up at lunchtime. * * This routine indicates if a particular trap number could be delivered - * directly. */ + * directly. + */ static bool direct_trap(unsigned int num) { - /* Hardware interrupts don't go to the Guest at all (except system - * call). */ + /* + * Hardware interrupts don't go to the Guest at all (except system + * call). + */ if (num >= FIRST_EXTERNAL_VECTOR && !could_be_syscall(num)) return false; - /* The Host needs to see page faults (for shadow paging and to save the + /* + * The Host needs to see page faults (for shadow paging and to save the * fault address), general protection faults (in/out emulation) and * device not available (TS handling), invalid opcode fault (kvm hcall), - * and of course, the hypercall trap. */ + * and of course, the hypercall trap. + */ return num != 14 && num != 13 && num != 7 && num != 6 && num != LGUEST_TRAP_ENTRY; } /*:*/ -/*M:005 The Guest has the ability to turn its interrupt gates into trap gates, +/*M:005 + * The Guest has the ability to turn its interrupt gates into trap gates, * if it is careful. The Host will let trap gates can go directly to the * Guest, but the Guest needs the interrupts atomically disabled for an * interrupt gate. It can do this by pointing the trap gate at instructions - * within noirq_start and noirq_end, where it can safely disable interrupts. */ + * within noirq_start and noirq_end, where it can safely disable interrupts. + */ -/*M:006 The Guests do not use the sysenter (fast system call) instruction, +/*M:006 + * The Guests do not use the sysenter (fast system call) instruction, * because it's hardcoded to enter privilege level 0 and so can't go direct. * It's about twice as fast as the older "int 0x80" system call, so it might * still be worthwhile to handle it in the Switcher and lcall down to the * Guest. The sysenter semantics are hairy tho: search for that keyword in - * entry.S :*/ + * entry.S +:*/ -/*H:260 When we make traps go directly into the Guest, we need to make sure +/*H:260 + * When we make traps go directly into the Guest, we need to make sure * the kernel stack is valid (ie. mapped in the page tables). Otherwise, the * CPU trying to deliver the trap will fault while trying to push the interrupt * words on the stack: this is called a double fault, and it forces us to kill * the Guest. * - * Which is deeply unfair, because (literally!) it wasn't the Guests' fault. */ + * Which is deeply unfair, because (literally!) it wasn't the Guests' fault. + */ void pin_stack_pages(struct lg_cpu *cpu) { unsigned int i; - /* Depending on the CONFIG_4KSTACKS option, the Guest can have one or - * two pages of stack space. */ + /* + * Depending on the CONFIG_4KSTACKS option, the Guest can have one or + * two pages of stack space. + */ for (i = 0; i < cpu->lg->stack_pages; i++) - /* The stack grows *upwards*, so the address we're given is the + /* + * The stack grows *upwards*, so the address we're given is the * start of the page after the kernel stack. Subtract one to * get back onto the first stack page, and keep subtracting to - * get to the rest of the stack pages. */ + * get to the rest of the stack pages. + */ pin_page(cpu, cpu->esp1 - 1 - i * PAGE_SIZE); } -/* Direct traps also mean that we need to know whenever the Guest wants to use +/* + * Direct traps also mean that we need to know whenever the Guest wants to use * a different kernel stack, so we can change the IDT entries to use that * stack. The IDT entries expect a virtual address, so unlike most addresses * the Guest gives us, the "esp" (stack pointer) value here is virtual, not * physical. * * In Linux each process has its own kernel stack, so this happens a lot: we - * change stacks on each context switch. */ + * change stacks on each context switch. + */ void guest_set_stack(struct lg_cpu *cpu, u32 seg, u32 esp, unsigned int pages) { - /* You are not allowed have a stack segment with privilege level 0: bad - * Guest! */ + /* + * You're not allowed a stack segment with privilege level 0: bad Guest! + */ if ((seg & 0x3) != GUEST_PL) kill_guest(cpu, "bad stack segment %i", seg); /* We only expect one or two stack pages. */ @@ -387,11 +454,15 @@ void guest_set_stack(struct lg_cpu *cpu, u32 seg, u32 esp, unsigned int pages) pin_stack_pages(cpu); } -/* All this reference to mapping stacks leads us neatly into the other complex - * part of the Host: page table handling. */ +/* + * All this reference to mapping stacks leads us neatly into the other complex + * part of the Host: page table handling. + */ -/*H:235 This is the routine which actually checks the Guest's IDT entry and - * transfers it into the entry in "struct lguest": */ +/*H:235 + * This is the routine which actually checks the Guest's IDT entry and + * transfers it into the entry in "struct lguest": + */ static void set_trap(struct lg_cpu *cpu, struct desc_struct *trap, unsigned int num, u32 lo, u32 hi) { @@ -407,30 +478,38 @@ static void set_trap(struct lg_cpu *cpu, struct desc_struct *trap, if (type != 0xE && type != 0xF) kill_guest(cpu, "bad IDT type %i", type); - /* We only copy the handler address, present bit, privilege level and + /* + * We only copy the handler address, present bit, privilege level and * type. The privilege level controls where the trap can be triggered * manually with an "int" instruction. This is usually GUEST_PL, - * except for system calls which userspace can use. */ + * except for system calls which userspace can use. + */ trap->a = ((__KERNEL_CS|GUEST_PL)<<16) | (lo&0x0000FFFF); trap->b = (hi&0xFFFFEF00); } -/*H:230 While we're here, dealing with delivering traps and interrupts to the +/*H:230 + * While we're here, dealing with delivering traps and interrupts to the * Guest, we might as well complete the picture: how the Guest tells us where * it wants them to go. This would be simple, except making traps fast * requires some tricks. * * We saw the Guest setting Interrupt Descriptor Table (IDT) entries with the - * LHCALL_LOAD_IDT_ENTRY hypercall before: that comes here. */ + * LHCALL_LOAD_IDT_ENTRY hypercall before: that comes here. + */ void load_guest_idt_entry(struct lg_cpu *cpu, unsigned int num, u32 lo, u32 hi) { - /* Guest never handles: NMI, doublefault, spurious interrupt or - * hypercall. We ignore when it tries to set them. */ + /* + * Guest never handles: NMI, doublefault, spurious interrupt or + * hypercall. We ignore when it tries to set them. + */ if (num == 2 || num == 8 || num == 15 || num == LGUEST_TRAP_ENTRY) return; - /* Mark the IDT as changed: next time the Guest runs we'll know we have - * to copy this again. */ + /* + * Mark the IDT as changed: next time the Guest runs we'll know we have + * to copy this again. + */ cpu->changed |= CHANGED_IDT; /* Check that the Guest doesn't try to step outside the bounds. */ @@ -440,9 +519,11 @@ void load_guest_idt_entry(struct lg_cpu *cpu, unsigned int num, u32 lo, u32 hi) set_trap(cpu, &cpu->arch.idt[num], num, lo, hi); } -/* The default entry for each interrupt points into the Switcher routines which +/* + * The default entry for each interrupt points into the Switcher routines which * simply return to the Host. The run_guest() loop will then call - * deliver_trap() to bounce it back into the Guest. */ + * deliver_trap() to bounce it back into the Guest. + */ static void default_idt_entry(struct desc_struct *idt, int trap, const unsigned long handler, @@ -451,13 +532,17 @@ static void default_idt_entry(struct desc_struct *idt, /* A present interrupt gate. */ u32 flags = 0x8e00; - /* Set the privilege level on the entry for the hypercall: this allows - * the Guest to use the "int" instruction to trigger it. */ + /* + * Set the privilege level on the entry for the hypercall: this allows + * the Guest to use the "int" instruction to trigger it. + */ if (trap == LGUEST_TRAP_ENTRY) flags |= (GUEST_PL << 13); else if (base) - /* Copy priv. level from what Guest asked for. This allows - * debug (int 3) traps from Guest userspace, for example. */ + /* + * Copy privilege level from what Guest asked for. This allows + * debug (int 3) traps from Guest userspace, for example. + */ flags |= (base->b & 0x6000); /* Now pack it into the IDT entry in its weird format. */ @@ -475,16 +560,20 @@ void setup_default_idt_entries(struct lguest_ro_state *state, default_idt_entry(&state->guest_idt[i], i, def[i], NULL); } -/*H:240 We don't use the IDT entries in the "struct lguest" directly, instead +/*H:240 + * We don't use the IDT entries in the "struct lguest" directly, instead * we copy them into the IDT which we've set up for Guests on this CPU, just - * before we run the Guest. This routine does that copy. */ + * before we run the Guest. This routine does that copy. + */ void copy_traps(const struct lg_cpu *cpu, struct desc_struct *idt, const unsigned long *def) { unsigned int i; - /* We can simply copy the direct traps, otherwise we use the default - * ones in the Switcher: they will return to the Host. */ + /* + * We can simply copy the direct traps, otherwise we use the default + * ones in the Switcher: they will return to the Host. + */ for (i = 0; i < ARRAY_SIZE(cpu->arch.idt); i++) { const struct desc_struct *gidt = &cpu->arch.idt[i]; @@ -492,14 +581,16 @@ void copy_traps(const struct lg_cpu *cpu, struct desc_struct *idt, if (!direct_trap(i)) continue; - /* Only trap gates (type 15) can go direct to the Guest. + /* + * Only trap gates (type 15) can go direct to the Guest. * Interrupt gates (type 14) disable interrupts as they are * entered, which we never let the Guest do. Not present * entries (type 0x0) also can't go direct, of course. * * If it can't go direct, we still need to copy the priv. level: * they might want to give userspace access to a software - * interrupt. */ + * interrupt. + */ if (idt_type(gidt->a, gidt->b) == 0xF) idt[i] = *gidt; else @@ -518,7 +609,8 @@ void copy_traps(const struct lg_cpu *cpu, struct desc_struct *idt, * the next timer interrupt (in nanoseconds). We use the high-resolution timer * infrastructure to set a callback at that time. * - * 0 means "turn off the clock". */ + * 0 means "turn off the clock". + */ void guest_set_clockevent(struct lg_cpu *cpu, unsigned long delta) { ktime_t expires; @@ -529,9 +621,11 @@ void guest_set_clockevent(struct lg_cpu *cpu, unsigned long delta) return; } - /* We use wallclock time here, so the Guest might not be running for + /* + * We use wallclock time here, so the Guest might not be running for * all the time between now and the timer interrupt it asked for. This - * is almost always the right thing to do. */ + * is almost always the right thing to do. + */ expires = ktime_add_ns(ktime_get_real(), delta); hrtimer_start(&cpu->hrt, expires, HRTIMER_MODE_ABS); } diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h index 01c5919..bc28745 100644 --- a/drivers/lguest/lg.h +++ b/drivers/lguest/lg.h @@ -16,15 +16,13 @@ void free_pagetables(void); int init_pagetables(struct page **switcher_page, unsigned int pages); -struct pgdir -{ +struct pgdir { unsigned long gpgdir; pgd_t *pgdir; }; /* We have two pages shared with guests, per cpu. */ -struct lguest_pages -{ +struct lguest_pages { /* This is the stack page mapped rw in guest */ char spare[PAGE_SIZE - sizeof(struct lguest_regs)]; struct lguest_regs regs; @@ -54,13 +52,13 @@ struct lg_cpu { unsigned long pending_notify; /* pfn from LHCALL_NOTIFY */ - /* At end of a page shared mapped over lguest_pages in guest. */ + /* At end of a page shared mapped over lguest_pages in guest. */ unsigned long regs_page; struct lguest_regs *regs; struct lguest_pages *last_pages; - int cpu_pgd; /* which pgd this cpu is currently using */ + int cpu_pgd; /* Which pgd this cpu is currently using */ /* If a hypercall was asked for, this points to the arguments. */ struct hcall_args *hcall; @@ -89,15 +87,17 @@ struct lg_eventfd_map { }; /* The private info the thread maintains about the guest. */ -struct lguest -{ +struct lguest { struct lguest_data __user *lguest_data; struct lg_cpu cpus[NR_CPUS]; unsigned int nr_cpus; u32 pfn_limit; - /* This provides the offset to the base of guest-physical - * memory in the Launcher. */ + + /* + * This provides the offset to the base of guest-physical memory in the + * Launcher. + */ void __user *mem_base; unsigned long kernel_address; @@ -122,11 +122,13 @@ bool lguest_address_ok(const struct lguest *lg, void __lgread(struct lg_cpu *, void *, unsigned long, unsigned); void __lgwrite(struct lg_cpu *, unsigned long, const void *, unsigned); -/*H:035 Using memory-copy operations like that is usually inconvient, so we +/*H:035 + * Using memory-copy operations like that is usually inconvient, so we * have the following helper macros which read and write a specific type (often * an unsigned long). * - * This reads into a variable of the given type then returns that. */ + * This reads into a variable of the given type then returns that. + */ #define lgread(cpu, addr, type) \ ({ type _v; __lgread((cpu), &_v, (addr), sizeof(_v)); _v; }) @@ -140,9 +142,11 @@ void __lgwrite(struct lg_cpu *, unsigned long, const void *, unsigned); int run_guest(struct lg_cpu *cpu, unsigned long __user *user); -/* Helper macros to obtain the first 12 or the last 20 bits, this is only the +/* + * Helper macros to obtain the first 12 or the last 20 bits, this is only the * first step in the migration to the kernel types. pte_pfn is already defined - * in the kernel. */ + * in the kernel. + */ #define pgd_flags(x) (pgd_val(x) & ~PAGE_MASK) #define pgd_pfn(x) (pgd_val(x) >> PAGE_SHIFT) #define pmd_flags(x) (pmd_val(x) & ~PAGE_MASK) diff --git a/drivers/lguest/lguest_device.c b/drivers/lguest/lguest_device.c index e082cda..b6200bc 100644 --- a/drivers/lguest/lguest_device.c +++ b/drivers/lguest/lguest_device.c @@ -1,10 +1,12 @@ -/*P:050 Lguest guests use a very simple method to describe devices. It's a +/*P:050 + * Lguest guests use a very simple method to describe devices. It's a * series of device descriptors contained just above the top of normal Guest * memory. * * We use the standard "virtio" device infrastructure, which provides us with a * console, a network and a block driver. Each one expects some configuration - * information and a "virtqueue" or two to send and receive data. :*/ + * information and a "virtqueue" or two to send and receive data. +:*/ #include <linux/init.h> #include <linux/bootmem.h> #include <linux/lguest_launcher.h> @@ -20,8 +22,10 @@ /* The pointer to our (page) of device descriptions. */ static void *lguest_devices; -/* For Guests, device memory can be used as normal memory, so we cast away the - * __iomem to quieten sparse. */ +/* + * For Guests, device memory can be used as normal memory, so we cast away the + * __iomem to quieten sparse. + */ static inline void *lguest_map(unsigned long phys_addr, unsigned long pages) { return (__force void *)ioremap_cache(phys_addr, PAGE_SIZE*pages); @@ -32,8 +36,10 @@ static inline void lguest_unmap(void *addr) iounmap((__force void __iomem *)addr); } -/*D:100 Each lguest device is just a virtio device plus a pointer to its entry - * in the lguest_devices page. */ +/*D:100 + * Each lguest device is just a virtio device plus a pointer to its entry + * in the lguest_devices page. + */ struct lguest_device { struct virtio_device vdev; @@ -41,9 +47,11 @@ struct lguest_device { struct lguest_device_desc *desc; }; -/* Since the virtio infrastructure hands us a pointer to the virtio_device all +/* + * Since the virtio infrastructure hands us a pointer to the virtio_device all * the time, it helps to have a curt macro to get a pointer to the struct - * lguest_device it's enclosed in. */ + * lguest_device it's enclosed in. + */ #define to_lgdev(vd) container_of(vd, struct lguest_device, vdev) /*D:130 @@ -55,7 +63,8 @@ struct lguest_device { * the driver will look at them during setup. * * A convenient routine to return the device's virtqueue config array: - * immediately after the descriptor. */ + * immediately after the descriptor. + */ static struct lguest_vqconfig *lg_vq(const struct lguest_device_desc *desc) { return (void *)(desc + 1); @@ -98,10 +107,12 @@ static u32 lg_get_features(struct virtio_device *vdev) return features; } -/* The virtio core takes the features the Host offers, and copies the - * ones supported by the driver into the vdev->features array. Once - * that's all sorted out, this routine is called so we can tell the - * Host which features we understand and accept. */ +/* + * The virtio core takes the features the Host offers, and copies the ones + * supported by the driver into the vdev->features array. Once that's all + * sorted out, this routine is called so we can tell the Host which features we + * understand and accept. + */ static void lg_finalize_features(struct virtio_device *vdev) { unsigned int i, bits; @@ -112,10 +123,11 @@ static void lg_finalize_features(struct virtio_device *vdev) /* Give virtio_ring a chance to accept features. */ vring_transport_features(vdev); - /* The vdev->feature array is a Linux bitmask: this isn't the - * same as a the simple array of bits used by lguest devices - * for features. So we do this slow, manual conversion which is - * completely general. */ + /* + * The vdev->feature array is a Linux bitmask: this isn't the same as a + * the simple array of bits used by lguest devices for features. So we + * do this slow, manual conversion which is completely general. + */ memset(out_features, 0, desc->feature_len); bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8; for (i = 0; i < bits; i++) { @@ -146,15 +158,19 @@ static void lg_set(struct virtio_device *vdev, unsigned int offset, memcpy(lg_config(desc) + offset, buf, len); } -/* The operations to get and set the status word just access the status field - * of the device descriptor. */ +/* + * The operations to get and set the status word just access the status field + * of the device descriptor. + */ static u8 lg_get_status(struct virtio_device *vdev) { return to_lgdev(vdev)->desc->status; } -/* To notify on status updates, we (ab)use the NOTIFY hypercall, with the - * descriptor address of the device. A zero status means "reset". */ +/* + * To notify on status updates, we (ab)use the NOTIFY hypercall, with the + * descriptor address of the device. A zero status means "reset". + */ static void set_status(struct virtio_device *vdev, u8 status) { unsigned long offset = (void *)to_lgdev(vdev)->desc - lguest_devices; @@ -191,8 +207,7 @@ static void lg_reset(struct virtio_device *vdev) */ /*D:140 This is the information we remember about each virtqueue. */ -struct lguest_vq_info -{ +struct lguest_vq_info { /* A copy of the information contained in the device config. */ struct lguest_vqconfig config; @@ -200,13 +215,17 @@ struct lguest_vq_info void *pages; }; -/* When the virtio_ring code wants to prod the Host, it calls us here and we +/* + * When the virtio_ring code wants to prod the Host, it calls us here and we * make a hypercall. We hand the physical address of the virtqueue so the Host - * knows which virtqueue we're talking about. */ + * knows which virtqueue we're talking about. + */ static void lg_notify(struct virtqueue *vq) { - /* We store our virtqueue information in the "priv" pointer of the - * virtqueue structure. */ + /* + * We store our virtqueue information in the "priv" pointer of the + * virtqueue structure. + */ struct lguest_vq_info *lvq = vq->priv; kvm_hypercall1(LHCALL_NOTIFY, lvq->config.pfn << PAGE_SHIFT); @@ -215,7 +234,8 @@ static void lg_notify(struct virtqueue *vq) /* An extern declaration inside a C file is bad form. Don't do it. */ extern void lguest_setup_irq(unsigned int irq); -/* This routine finds the first virtqueue described in the configuration of +/* + * This routine finds the Nth virtqueue described in the configuration of * this device and sets it up. * * This is kind of an ugly duckling. It'd be nicer to have a standard @@ -223,9 +243,7 @@ extern void lguest_setup_irq(unsigned int irq); * everyone wants to do it differently. The KVM coders want the Guest to * allocate its own pages and tell the Host where they are, but for lguest it's * simpler for the Host to simply tell us where the pages are. - * - * So we provide drivers with a "find the Nth virtqueue and set it up" - * function. */ + */ static struct virtqueue *lg_find_vq(struct virtio_device *vdev, unsigned index, void (*callback)(struct virtqueue *vq), @@ -244,9 +262,11 @@ static struct virtqueue *lg_find_vq(struct virtio_device *vdev, if (!lvq) return ERR_PTR(-ENOMEM); - /* Make a copy of the "struct lguest_vqconfig" entry, which sits after + /* + * Make a copy of the "struct lguest_vqconfig" entry, which sits after * the descriptor. We need a copy because the config space might not - * be aligned correctly. */ + * be aligned correctly. + */ memcpy(&lvq->config, lg_vq(ldev->desc)+index, sizeof(lvq->config)); printk("Mapping virtqueue %i addr %lx\n", index, @@ -261,8 +281,10 @@ static struct virtqueue *lg_find_vq(struct virtio_device *vdev, goto free_lvq; } - /* OK, tell virtio_ring.c to set up a virtqueue now we know its size - * and we've got a pointer to its pages. */ + /* + * OK, tell virtio_ring.c to set up a virtqueue now we know its size + * and we've got a pointer to its pages. + */ vq = vring_new_virtqueue(lvq->config.num, LGUEST_VRING_ALIGN, vdev, lvq->pages, lg_notify, callback, name); if (!vq) { @@ -273,18 +295,23 @@ static struct virtqueue *lg_find_vq(struct virtio_device *vdev, /* Make sure the interrupt is allocated. */ lguest_setup_irq(lvq->config.irq); - /* Tell the interrupt for this virtqueue to go to the virtio_ring - * interrupt handler. */ - /* FIXME: We used to have a flag for the Host to tell us we could use + /* + * Tell the interrupt for this virtqueue to go to the virtio_ring + * interrupt handler. + * + * FIXME: We used to have a flag for the Host to tell us we could use * the interrupt as a source of randomness: it'd be nice to have that - * back.. */ + * back. + */ err = request_irq(lvq->config.irq, vring_interrupt, IRQF_SHARED, dev_name(&vdev->dev), vq); if (err) goto destroy_vring; - /* Last of all we hook up our 'struct lguest_vq_info" to the - * virtqueue's priv pointer. */ + /* + * Last of all we hook up our 'struct lguest_vq_info" to the + * virtqueue's priv pointer. + */ vq->priv = lvq; return vq; @@ -358,11 +385,14 @@ static struct virtio_config_ops lguest_config_ops = { .del_vqs = lg_del_vqs, }; -/* The root device for the lguest virtio devices. This makes them appear as - * /sys/devices/lguest/0,1,2 not /sys/devices/0,1,2. */ +/* + * The root device for the lguest virtio devices. This makes them appear as + * /sys/devices/lguest/0,1,2 not /sys/devices/0,1,2. + */ static struct device *lguest_root; -/*D:120 This is the core of the lguest bus: actually adding a new device. +/*D:120 + * This is the core of the lguest bus: actually adding a new device. * It's a separate function because it's neater that way, and because an * earlier version of the code supported hotplug and unplug. They were removed * early on because they were never used. @@ -371,14 +401,14 @@ static struct device *lguest_root; * * It's worth reading this carefully: we start with a pointer to the new device * descriptor in the "lguest_devices" page, and the offset into the device - * descriptor page so we can uniquely identify it if things go badly wrong. */ + * descriptor page so we can uniquely identify it if things go badly wrong. + */ static void add_lguest_device(struct lguest_device_desc *d, unsigned int offset) { struct lguest_device *ldev; - /* Start with zeroed memory; Linux's device layer seems to count on - * it. */ + /* Start with zeroed memory; Linux's device layer counts on it. */ ldev = kzalloc(sizeof(*ldev), GFP_KERNEL); if (!ldev) { printk(KERN_EMERG "Cannot allocate lguest dev %u type %u\n", @@ -388,17 +418,25 @@ static void add_lguest_device(struct lguest_device_desc *d, /* This devices' parent is the lguest/ dir. */ ldev->vdev.dev.parent = lguest_root; - /* We have a unique device index thanks to the dev_index counter. */ + /* + * The device type comes straight from the descriptor. There's also a + * device vendor field in the virtio_device struct, which we leave as + * 0. + */ ldev->vdev.id.device = d->type; - /* We have a simple set of routines for querying the device's - * configuration information and setting its status. */ + /* + * We have a simple set of routines for querying the device's + * configuration information and setting its status. + */ ldev->vdev.config = &lguest_config_ops; /* And we remember the device's descriptor for lguest_config_ops. */ ldev->desc = d; - /* register_virtio_device() sets up the generic fields for the struct + /* + * register_virtio_device() sets up the generic fields for the struct * virtio_device and calls device_register(). This makes the bus - * infrastructure look for a matching driver. */ + * infrastructure look for a matching driver. + */ if (register_virtio_device(&ldev->vdev) != 0) { printk(KERN_ERR "Failed to register lguest dev %u type %u\n", offset, d->type); @@ -406,8 +444,10 @@ static void add_lguest_device(struct lguest_device_desc *d, } } -/*D:110 scan_devices() simply iterates through the device page. The type 0 is - * reserved to mean "end of devices". */ +/*D:110 + * scan_devices() simply iterates through the device page. The type 0 is + * reserved to mean "end of devices". + */ static void scan_devices(void) { unsigned int i; @@ -426,7 +466,8 @@ static void scan_devices(void) } } -/*D:105 Fairly early in boot, lguest_devices_init() is called to set up the +/*D:105 + * Fairly early in boot, lguest_devices_init() is called to set up the * lguest device infrastructure. We check that we are a Guest by checking * pv_info.name: there are other ways of checking, but this seems most * obvious to me. @@ -437,7 +478,8 @@ static void scan_devices(void) * correct sysfs incantation). * * Finally we call scan_devices() which adds all the devices found in the - * lguest_devices page. */ + * lguest_devices page. + */ static int __init lguest_devices_init(void) { if (strcmp(pv_info.name, "lguest") != 0) @@ -456,11 +498,13 @@ static int __init lguest_devices_init(void) /* We do this after core stuff, but before the drivers. */ postcore_initcall(lguest_devices_init); -/*D:150 At this point in the journey we used to now wade through the lguest +/*D:150 + * At this point in the journey we used to now wade through the lguest * devices themselves: net, block and console. Since they're all now virtio * devices rather than lguest-specific, I've decided to ignore them. Mostly, * they're kind of boring. But this does mean you'll never experience the * thrill of reading the forbidden love scene buried deep in the block driver. * * "make Launcher" beckons, where we answer questions like "Where do Guests - * come from?", and "What do you do when someone asks for optimization?". */ + * come from?", and "What do you do when someone asks for optimization?". + */ diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c index 9f9a295..b4d3f7c 100644 --- a/drivers/lguest/lguest_user.c +++ b/drivers/lguest/lguest_user.c @@ -1,8 +1,9 @@ /*P:200 This contains all the /dev/lguest code, whereby the userspace launcher * controls and communicates with the Guest. For example, the first write will - * tell us the Guest's memory layout, pagetable, entry point and kernel address - * offset. A read will run the Guest until something happens, such as a signal - * or the Guest doing a NOTIFY out to the Launcher. :*/ + * tell us the Guest's memory layout and entry point. A read will run the + * Guest until something happens, such as a signal or the Guest doing a NOTIFY + * out to the Launcher. +:*/ #include <linux/uaccess.h> #include <linux/miscdevice.h> #include <linux/fs.h> @@ -11,14 +12,41 @@ #include <linux/file.h> #include "lg.h" +/*L:056 + * Before we move on, let's jump ahead and look at what the kernel does when + * it needs to look up the eventfds. That will complete our picture of how we + * use RCU. + * + * The notification value is in cpu->pending_notify: we return true if it went + * to an eventfd. + */ bool send_notify_to_eventfd(struct lg_cpu *cpu) { unsigned int i; struct lg_eventfd_map *map; - /* lg->eventfds is RCU-protected */ + /* + * This "rcu_read_lock()" helps track when someone is still looking at + * the (RCU-using) eventfds array. It's not actually a lock at all; + * indeed it's a noop in many configurations. (You didn't expect me to + * explain all the RCU secrets here, did you?) + */ rcu_read_lock(); + /* + * rcu_dereference is the counter-side of rcu_assign_pointer(); it + * makes sure we don't access the memory pointed to by + * cpu->lg->eventfds before cpu->lg->eventfds is set. Sounds crazy, + * but Alpha allows this! Paul McKenney points out that a really + * aggressive compiler could have the same effect: + * http://lists.ozlabs.org/pipermail/lguest/2009-July/001560.html + * + * So play safe, use rcu_dereference to get the rcu-protected pointer: + */ map = rcu_dereference(cpu->lg->eventfds); + /* + * Simple array search: even if they add an eventfd while we do this, + * we'll continue to use the old array and just won't see the new one. + */ for (i = 0; i < map->num; i++) { if (map->map[i].addr == cpu->pending_notify) { eventfd_signal(map->map[i].event, 1); @@ -26,19 +54,50 @@ bool send_notify_to_eventfd(struct lg_cpu *cpu) break; } } + /* We're done with the rcu-protected variable cpu->lg->eventfds. */ rcu_read_unlock(); + + /* If we cleared the notification, it's because we found a match. */ return cpu->pending_notify == 0; } +/*L:055 + * One of the more tricksy tricks in the Linux Kernel is a technique called + * Read Copy Update. Since one point of lguest is to teach lguest journeyers + * about kernel coding, I use it here. (In case you're curious, other purposes + * include learning about virtualization and instilling a deep appreciation for + * simplicity and puppies). + * + * We keep a simple array which maps LHCALL_NOTIFY values to eventfds, but we + * add new eventfds without ever blocking readers from accessing the array. + * The current Launcher only does this during boot, so that never happens. But + * Read Copy Update is cool, and adding a lock risks damaging even more puppies + * than this code does. + * + * We allocate a brand new one-larger array, copy the old one and add our new + * element. Then we make the lg eventfd pointer point to the new array. + * That's the easy part: now we need to free the old one, but we need to make + * sure no slow CPU somewhere is still looking at it. That's what + * synchronize_rcu does for us: waits until every CPU has indicated that it has + * moved on to know it's no longer using the old one. + * + * If that's unclear, see http://en.wikipedia.org/wiki/Read-copy-update. + */ static int add_eventfd(struct lguest *lg, unsigned long addr, int fd) { struct lg_eventfd_map *new, *old = lg->eventfds; + /* + * We don't allow notifications on value 0 anyway (pending_notify of + * 0 means "nothing pending"). + */ if (!addr) return -EINVAL; - /* Replace the old array with the new one, carefully: others can - * be accessing it at the same time */ + /* + * Replace the old array with the new one, carefully: others can + * be accessing it at the same time. + */ new = kmalloc(sizeof(*new) + sizeof(new->map[0]) * (old->num + 1), GFP_KERNEL); if (!new) @@ -52,22 +111,41 @@ static int add_eventfd(struct lguest *lg, unsigned long addr, int fd) new->map[new->num].addr = addr; new->map[new->num].event = eventfd_ctx_fdget(fd); if (IS_ERR(new->map[new->num].event)) { + int err = PTR_ERR(new->map[new->num].event); kfree(new); - return PTR_ERR(new->map[new->num].event); + return err; } new->num++; - /* Now put new one in place. */ + /* + * Now put new one in place: rcu_assign_pointer() is a fancy way of + * doing "lg->eventfds = new", but it uses memory barriers to make + * absolutely sure that the contents of "new" written above is nailed + * down before we actually do the assignment. + * + * We have to think about these kinds of things when we're operating on + * live data without locks. + */ rcu_assign_pointer(lg->eventfds, new); - /* We're not in a big hurry. Wait until noone's looking at old - * version, then delete it. */ + /* + * We're not in a big hurry. Wait until noone's looking at old + * version, then free it. + */ synchronize_rcu(); kfree(old); return 0; } +/*L:052 + * Receiving notifications from the Guest is usually done by attaching a + * particular LHCALL_NOTIFY value to an event filedescriptor. The eventfd will + * become readable when the Guest does an LHCALL_NOTIFY with that value. + * + * This is really convenient for processing each virtqueue in a separate + * thread. + */ static int attach_eventfd(struct lguest *lg, const unsigned long __user *input) { unsigned long addr, fd; @@ -79,15 +157,22 @@ static int attach_eventfd(struct lguest *lg, const unsigned long __user *input) if (get_user(fd, input) != 0) return -EFAULT; + /* + * Just make sure two callers don't add eventfds at once. We really + * only need to lock against callers adding to the same Guest, so using + * the Big Lguest Lock is overkill. But this is setup, not a fast path. + */ mutex_lock(&lguest_lock); err = add_eventfd(lg, addr, fd); mutex_unlock(&lguest_lock); - return 0; + return err; } -/*L:050 Sending an interrupt is done by writing LHREQ_IRQ and an interrupt - * number to /dev/lguest. */ +/*L:050 + * Sending an interrupt is done by writing LHREQ_IRQ and an interrupt + * number to /dev/lguest. + */ static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input) { unsigned long irq; @@ -97,12 +182,18 @@ static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input) if (irq >= LGUEST_IRQS) return -EINVAL; + /* + * Next time the Guest runs, the core code will see if it can deliver + * this interrupt. + */ set_interrupt(cpu, irq); return 0; } -/*L:040 Once our Guest is initialized, the Launcher makes it run by reading - * from /dev/lguest. */ +/*L:040 + * Once our Guest is initialized, the Launcher makes it run by reading + * from /dev/lguest. + */ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) { struct lguest *lg = file->private_data; @@ -138,8 +229,10 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) return len; } - /* If we returned from read() last time because the Guest sent I/O, - * clear the flag. */ + /* + * If we returned from read() last time because the Guest sent I/O, + * clear the flag. + */ if (cpu->pending_notify) cpu->pending_notify = 0; @@ -147,8 +240,10 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) return run_guest(cpu, (unsigned long __user *)user); } -/*L:025 This actually initializes a CPU. For the moment, a Guest is only - * uniprocessor, so "id" is always 0. */ +/*L:025 + * This actually initializes a CPU. For the moment, a Guest is only + * uniprocessor, so "id" is always 0. + */ static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip) { /* We have a limited number the number of CPUs in the lguest struct. */ @@ -163,8 +258,10 @@ static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip) /* Each CPU has a timer it can set. */ init_clockdev(cpu); - /* We need a complete page for the Guest registers: they are accessible - * to the Guest and we can only grant it access to whole pages. */ + /* + * We need a complete page for the Guest registers: they are accessible + * to the Guest and we can only grant it access to whole pages. + */ cpu->regs_page = get_zeroed_page(GFP_KERNEL); if (!cpu->regs_page) return -ENOMEM; @@ -172,29 +269,38 @@ static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip) /* We actually put the registers at the bottom of the page. */ cpu->regs = (void *)cpu->regs_page + PAGE_SIZE - sizeof(*cpu->regs); - /* Now we initialize the Guest's registers, handing it the start - * address. */ + /* + * Now we initialize the Guest's registers, handing it the start + * address. + */ lguest_arch_setup_regs(cpu, start_ip); - /* We keep a pointer to the Launcher task (ie. current task) for when - * other Guests want to wake this one (eg. console input). */ + /* + * We keep a pointer to the Launcher task (ie. current task) for when + * other Guests want to wake this one (eg. console input). + */ cpu->tsk = current; - /* We need to keep a pointer to the Launcher's memory map, because if + /* + * We need to keep a pointer to the Launcher's memory map, because if * the Launcher dies we need to clean it up. If we don't keep a - * reference, it is destroyed before close() is called. */ + * reference, it is destroyed before close() is called. + */ cpu->mm = get_task_mm(cpu->tsk); - /* We remember which CPU's pages this Guest used last, for optimization - * when the same Guest runs on the same CPU twice. */ + /* + * We remember which CPU's pages this Guest used last, for optimization + * when the same Guest runs on the same CPU twice. + */ cpu->last_pages = NULL; /* No error == success. */ return 0; } -/*L:020 The initialization write supplies 3 pointer sized (32 or 64 bit) - * values (in addition to the LHREQ_INITIALIZE value). These are: +/*L:020 + * The initialization write supplies 3 pointer sized (32 or 64 bit) values (in + * addition to the LHREQ_INITIALIZE value). These are: * * base: The start of the Guest-physical memory inside the Launcher memory. * @@ -206,14 +312,15 @@ static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip) */ static int initialize(struct file *file, const unsigned long __user *input) { - /* "struct lguest" contains everything we (the Host) know about a - * Guest. */ + /* "struct lguest" contains all we (the Host) know about a Guest. */ struct lguest *lg; int err; unsigned long args[3]; - /* We grab the Big Lguest lock, which protects against multiple - * simultaneous initializations. */ + /* + * We grab the Big Lguest lock, which protects against multiple + * simultaneous initializations. + */ mutex_lock(&lguest_lock); /* You can't initialize twice! Close the device and start again... */ if (file->private_data) { @@ -248,8 +355,10 @@ static int initialize(struct file *file, const unsigned long __user *input) if (err) goto free_eventfds; - /* Initialize the Guest's shadow page tables, using the toplevel - * address the Launcher gave us. This allocates memory, so can fail. */ + /* + * Initialize the Guest's shadow page tables, using the toplevel + * address the Launcher gave us. This allocates memory, so can fail. + */ err = init_guest_pagetable(lg); if (err) goto free_regs; @@ -274,20 +383,24 @@ unlock: return err; } -/*L:010 The first operation the Launcher does must be a write. All writes +/*L:010 + * The first operation the Launcher does must be a write. All writes * start with an unsigned long number: for the first write this must be * LHREQ_INITIALIZE to set up the Guest. After that the Launcher can use - * writes of other values to send interrupts. + * writes of other values to send interrupts or set up receipt of notifications. * * Note that we overload the "offset" in the /dev/lguest file to indicate what - * CPU number we're dealing with. Currently this is always 0, since we only + * CPU number we're dealing with. Currently this is always 0 since we only * support uniprocessor Guests, but you can see the beginnings of SMP support - * here. */ + * here. + */ static ssize_t write(struct file *file, const char __user *in, size_t size, loff_t *off) { - /* Once the Guest is initialized, we hold the "struct lguest" in the - * file private data. */ + /* + * Once the Guest is initialized, we hold the "struct lguest" in the + * file private data. + */ struct lguest *lg = file->private_data; const unsigned long __user *input = (const unsigned long __user *)in; unsigned long req; @@ -322,13 +435,15 @@ static ssize_t write(struct file *file, const char __user *in, } } -/*L:060 The final piece of interface code is the close() routine. It reverses +/*L:060 + * The final piece of interface code is the close() routine. It reverses * everything done in initialize(). This is usually called because the * Launcher exited. * * Note that the close routine returns 0 or a negative error number: it can't * really fail, but it can whine. I blame Sun for this wart, and K&R C for - * letting them do it. :*/ + * letting them do it. +:*/ static int close(struct inode *inode, struct file *file) { struct lguest *lg = file->private_data; @@ -338,8 +453,10 @@ static int close(struct inode *inode, struct file *file) if (!lg) return 0; - /* We need the big lock, to protect from inter-guest I/O and other - * Launchers initializing guests. */ + /* + * We need the big lock, to protect from inter-guest I/O and other + * Launchers initializing guests. + */ mutex_lock(&lguest_lock); /* Free up the shadow page tables for the Guest. */ @@ -350,8 +467,10 @@ static int close(struct inode *inode, struct file *file) hrtimer_cancel(&lg->cpus[i].hrt); /* We can free up the register page we allocated. */ free_page(lg->cpus[i].regs_page); - /* Now all the memory cleanups are done, it's safe to release - * the Launcher's memory management structure. */ + /* + * Now all the memory cleanups are done, it's safe to release + * the Launcher's memory management structure. + */ mmput(lg->cpus[i].mm); } @@ -360,8 +479,10 @@ static int close(struct inode *inode, struct file *file) eventfd_ctx_put(lg->eventfds->map[i].event); kfree(lg->eventfds); - /* If lg->dead doesn't contain an error code it will be NULL or a - * kmalloc()ed string, either of which is ok to hand to kfree(). */ + /* + * If lg->dead doesn't contain an error code it will be NULL or a + * kmalloc()ed string, either of which is ok to hand to kfree(). + */ if (!IS_ERR(lg->dead)) kfree(lg->dead); /* Free the memory allocated to the lguest_struct */ @@ -385,7 +506,8 @@ static int close(struct inode *inode, struct file *file) * * We begin our understanding with the Host kernel interface which the Launcher * uses: reading and writing a character device called /dev/lguest. All the - * work happens in the read(), write() and close() routines: */ + * work happens in the read(), write() and close() routines: + */ static struct file_operations lguest_fops = { .owner = THIS_MODULE, .release = close, @@ -393,8 +515,10 @@ static struct file_operations lguest_fops = { .read = read, }; -/* This is a textbook example of a "misc" character device. Populate a "struct - * miscdevice" and register it with misc_register(). */ +/* + * This is a textbook example of a "misc" character device. Populate a "struct + * miscdevice" and register it with misc_register(). + */ static struct miscdevice lguest_dev = { .minor = MISC_DYNAMIC_MINOR, .name = "lguest", diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c index a6fe1ab..a8d0aee 100644 --- a/drivers/lguest/page_tables.c +++ b/drivers/lguest/page_tables.c @@ -1,9 +1,11 @@ -/*P:700 The pagetable code, on the other hand, still shows the scars of +/*P:700 + * The pagetable code, on the other hand, still shows the scars of * previous encounters. It's functional, and as neat as it can be in the * circumstances, but be wary, for these things are subtle and break easily. * The Guest provides a virtual to physical mapping, but we can neither trust * it nor use it: we verify and convert it here then point the CPU to the - * converted Guest pages when running the Guest. :*/ + * converted Guest pages when running the Guest. +:*/ /* Copyright (C) Rusty Russell IBM Corporation 2006. * GPL v2 and any later version */ @@ -17,18 +19,20 @@ #include <asm/bootparam.h> #include "lg.h" -/*M:008 We hold reference to pages, which prevents them from being swapped. +/*M:008 + * We hold reference to pages, which prevents them from being swapped. * It'd be nice to have a callback in the "struct mm_struct" when Linux wants * to swap out. If we had this, and a shrinker callback to trim PTE pages, we - * could probably consider launching Guests as non-root. :*/ + * could probably consider launching Guests as non-root. +:*/ /*H:300 * The Page Table Code * - * We use two-level page tables for the Guest. If you're not entirely - * comfortable with virtual addresses, physical addresses and page tables then - * I recommend you review arch/x86/lguest/boot.c's "Page Table Handling" (with - * diagrams!). + * We use two-level page tables for the Guest, or three-level with PAE. If + * you're not entirely comfortable with virtual addresses, physical addresses + * and page tables then I recommend you review arch/x86/lguest/boot.c's "Page + * Table Handling" (with diagrams!). * * The Guest keeps page tables, but we maintain the actual ones here: these are * called "shadow" page tables. Which is a very Guest-centric name: these are @@ -45,16 +49,18 @@ * (v) Flushing (throwing away) page tables, * (vi) Mapping the Switcher when the Guest is about to run, * (vii) Setting up the page tables initially. - :*/ +:*/ - -/* 1024 entries in a page table page maps 1024 pages: 4MB. The Switcher is - * conveniently placed at the top 4MB, so it uses a separate, complete PTE - * page. */ +/* + * The Switcher uses the complete top PTE page. That's 1024 PTE entries (4MB) + * or 512 PTE entries with PAE (2MB). + */ #define SWITCHER_PGD_INDEX (PTRS_PER_PGD - 1) -/* For PAE we need the PMD index as well. We use the last 2MB, so we - * will need the last pmd entry of the last pmd page. */ +/* + * For PAE we need the PMD index as well. We use the last 2MB, so we + * will need the last pmd entry of the last pmd page. + */ #ifdef CONFIG_X86_PAE #define SWITCHER_PMD_INDEX (PTRS_PER_PMD - 1) #define RESERVE_MEM 2U @@ -64,14 +70,18 @@ #define CHECK_GPGD_MASK _PAGE_TABLE #endif -/* We actually need a separate PTE page for each CPU. Remember that after the +/* + * We actually need a separate PTE page for each CPU. Remember that after the * Switcher code itself comes two pages for each CPU, and we don't want this - * CPU's guest to see the pages of any other CPU. */ + * CPU's guest to see the pages of any other CPU. + */ static DEFINE_PER_CPU(pte_t *, switcher_pte_pages); #define switcher_pte_page(cpu) per_cpu(switcher_pte_pages, cpu) -/*H:320 The page table code is curly enough to need helper functions to keep it - * clear and clean. +/*H:320 + * The page table code is curly enough to need helper functions to keep it + * clear and clean. The kernel itself provides many of them; one advantage + * of insisting that the Guest and Host use the same CONFIG_PAE setting. * * There are two functions which return pointers to the shadow (aka "real") * page tables. @@ -79,7 +89,8 @@ static DEFINE_PER_CPU(pte_t *, switcher_pte_pages); * spgd_addr() takes the virtual address and returns a pointer to the top-level * page directory entry (PGD) for that address. Since we keep track of several * page tables, the "i" argument tells us which one we're interested in (it's - * usually the current one). */ + * usually the current one). + */ static pgd_t *spgd_addr(struct lg_cpu *cpu, u32 i, unsigned long vaddr) { unsigned int index = pgd_index(vaddr); @@ -96,9 +107,11 @@ static pgd_t *spgd_addr(struct lg_cpu *cpu, u32 i, unsigned long vaddr) } #ifdef CONFIG_X86_PAE -/* This routine then takes the PGD entry given above, which contains the +/* + * This routine then takes the PGD entry given above, which contains the * address of the PMD page. It then returns a pointer to the PMD entry for the - * given address. */ + * given address. + */ static pmd_t *spmd_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr) { unsigned int index = pmd_index(vaddr); @@ -119,9 +132,11 @@ static pmd_t *spmd_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr) } #endif -/* This routine then takes the page directory entry returned above, which +/* + * This routine then takes the page directory entry returned above, which * contains the address of the page table entry (PTE) page. It then returns a - * pointer to the PTE entry for the given address. */ + * pointer to the PTE entry for the given address. + */ static pte_t *spte_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr) { #ifdef CONFIG_X86_PAE @@ -139,8 +154,10 @@ static pte_t *spte_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr) return &page[pte_index(vaddr)]; } -/* These two functions just like the above two, except they access the Guest - * page tables. Hence they return a Guest address. */ +/* + * These functions are just like the above two, except they access the Guest + * page tables. Hence they return a Guest address. + */ static unsigned long gpgd_addr(struct lg_cpu *cpu, unsigned long vaddr) { unsigned int index = vaddr >> (PGDIR_SHIFT); @@ -148,6 +165,7 @@ static unsigned long gpgd_addr(struct lg_cpu *cpu, unsigned long vaddr) } #ifdef CONFIG_X86_PAE +/* Follow the PGD to the PMD. */ static unsigned long gpmd_addr(pgd_t gpgd, unsigned long vaddr) { unsigned long gpage = pgd_pfn(gpgd) << PAGE_SHIFT; @@ -155,6 +173,7 @@ static unsigned long gpmd_addr(pgd_t gpgd, unsigned long vaddr) return gpage + pmd_index(vaddr) * sizeof(pmd_t); } +/* Follow the PMD to the PTE. */ static unsigned long gpte_addr(struct lg_cpu *cpu, pmd_t gpmd, unsigned long vaddr) { @@ -164,6 +183,7 @@ static unsigned long gpte_addr(struct lg_cpu *cpu, return gpage + pte_index(vaddr) * sizeof(pte_t); } #else +/* Follow the PGD to the PTE (no mid-level for !PAE). */ static unsigned long gpte_addr(struct lg_cpu *cpu, pgd_t gpgd, unsigned long vaddr) { @@ -175,17 +195,21 @@ static unsigned long gpte_addr(struct lg_cpu *cpu, #endif /*:*/ -/*M:014 get_pfn is slow: we could probably try to grab batches of pages here as - * an optimization (ie. pre-faulting). :*/ +/*M:014 + * get_pfn is slow: we could probably try to grab batches of pages here as + * an optimization (ie. pre-faulting). +:*/ -/*H:350 This routine takes a page number given by the Guest and converts it to +/*H:350 + * This routine takes a page number given by the Guest and converts it to * an actual, physical page number. It can fail for several reasons: the * virtual address might not be mapped by the Launcher, the write flag is set * and the page is read-only, or the write flag was set and the page was * shared so had to be copied, but we ran out of memory. * * This holds a reference to the page, so release_pte() is careful to put that - * back. */ + * back. + */ static unsigned long get_pfn(unsigned long virtpfn, int write) { struct page *page; @@ -198,33 +222,41 @@ static unsigned long get_pfn(unsigned long virtpfn, int write) return -1UL; } -/*H:340 Converting a Guest page table entry to a shadow (ie. real) page table +/*H:340 + * Converting a Guest page table entry to a shadow (ie. real) page table * entry can be a little tricky. The flags are (almost) the same, but the * Guest PTE contains a virtual page number: the CPU needs the real page - * number. */ + * number. + */ static pte_t gpte_to_spte(struct lg_cpu *cpu, pte_t gpte, int write) { unsigned long pfn, base, flags; - /* The Guest sets the global flag, because it thinks that it is using + /* + * The Guest sets the global flag, because it thinks that it is using * PGE. We only told it to use PGE so it would tell us whether it was * flushing a kernel mapping or a userspace mapping. We don't actually - * use the global bit, so throw it away. */ + * use the global bit, so throw it away. + */ flags = (pte_flags(gpte) & ~_PAGE_GLOBAL); /* The Guest's pages are offset inside the Launcher. */ base = (unsigned long)cpu->lg->mem_base / PAGE_SIZE; - /* We need a temporary "unsigned long" variable to hold the answer from + /* + * We need a temporary "unsigned long" variable to hold the answer from * get_pfn(), because it returns 0xFFFFFFFF on failure, which wouldn't * fit in spte.pfn. get_pfn() finds the real physical number of the - * page, given the virtual number. */ + * page, given the virtual number. + */ pfn = get_pfn(base + pte_pfn(gpte), write); if (pfn == -1UL) { kill_guest(cpu, "failed to get page %lu", pte_pfn(gpte)); - /* When we destroy the Guest, we'll go through the shadow page + /* + * When we destroy the Guest, we'll go through the shadow page * tables and release_pte() them. Make sure we don't think - * this one is valid! */ + * this one is valid! + */ flags = 0; } /* Now we assemble our shadow PTE from the page number and flags. */ @@ -234,8 +266,10 @@ static pte_t gpte_to_spte(struct lg_cpu *cpu, pte_t gpte, int write) /*H:460 And to complete the chain, release_pte() looks like this: */ static void release_pte(pte_t pte) { - /* Remember that get_user_pages_fast() took a reference to the page, in - * get_pfn()? We have to put it back now. */ + /* + * Remember that get_user_pages_fast() took a reference to the page, in + * get_pfn()? We have to put it back now. + */ if (pte_flags(pte) & _PAGE_PRESENT) put_page(pte_page(pte)); } @@ -273,7 +307,8 @@ static void check_gpmd(struct lg_cpu *cpu, pmd_t gpmd) * and return to the Guest without it knowing. * * If we fixed up the fault (ie. we mapped the address), this routine returns - * true. Otherwise, it was a real fault and we need to tell the Guest. */ + * true. Otherwise, it was a real fault and we need to tell the Guest. + */ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) { pgd_t gpgd; @@ -282,6 +317,7 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) pte_t gpte; pte_t *spte; + /* Mid level for PAE. */ #ifdef CONFIG_X86_PAE pmd_t *spmd; pmd_t gpmd; @@ -298,22 +334,26 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) { /* No shadow entry: allocate a new shadow PTE page. */ unsigned long ptepage = get_zeroed_page(GFP_KERNEL); - /* This is not really the Guest's fault, but killing it is - * simple for this corner case. */ + /* + * This is not really the Guest's fault, but killing it is + * simple for this corner case. + */ if (!ptepage) { kill_guest(cpu, "out of memory allocating pte page"); return false; } /* We check that the Guest pgd is OK. */ check_gpgd(cpu, gpgd); - /* And we copy the flags to the shadow PGD entry. The page - * number in the shadow PGD is the page we just allocated. */ + /* + * And we copy the flags to the shadow PGD entry. The page + * number in the shadow PGD is the page we just allocated. + */ set_pgd(spgd, __pgd(__pa(ptepage) | pgd_flags(gpgd))); } #ifdef CONFIG_X86_PAE gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t); - /* middle level not present? We can't map it in. */ + /* Middle level not present? We can't map it in. */ if (!(pmd_flags(gpmd) & _PAGE_PRESENT)) return false; @@ -324,8 +364,10 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) /* No shadow entry: allocate a new shadow PTE page. */ unsigned long ptepage = get_zeroed_page(GFP_KERNEL); - /* This is not really the Guest's fault, but killing it is - * simple for this corner case. */ + /* + * This is not really the Guest's fault, but killing it is + * simple for this corner case. + */ if (!ptepage) { kill_guest(cpu, "out of memory allocating pte page"); return false; @@ -334,27 +376,37 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) /* We check that the Guest pmd is OK. */ check_gpmd(cpu, gpmd); - /* And we copy the flags to the shadow PMD entry. The page - * number in the shadow PMD is the page we just allocated. */ + /* + * And we copy the flags to the shadow PMD entry. The page + * number in the shadow PMD is the page we just allocated. + */ native_set_pmd(spmd, __pmd(__pa(ptepage) | pmd_flags(gpmd))); } - /* OK, now we look at the lower level in the Guest page table: keep its - * address, because we might update it later. */ + /* + * OK, now we look at the lower level in the Guest page table: keep its + * address, because we might update it later. + */ gpte_ptr = gpte_addr(cpu, gpmd, vaddr); #else - /* OK, now we look at the lower level in the Guest page table: keep its - * address, because we might update it later. */ + /* + * OK, now we look at the lower level in the Guest page table: keep its + * address, because we might update it later. + */ gpte_ptr = gpte_addr(cpu, gpgd, vaddr); #endif + + /* Read the actual PTE value. */ gpte = lgread(cpu, gpte_ptr, pte_t); /* If this page isn't in the Guest page tables, we can't page it in. */ if (!(pte_flags(gpte) & _PAGE_PRESENT)) return false; - /* Check they're not trying to write to a page the Guest wants - * read-only (bit 2 of errcode == write). */ + /* + * Check they're not trying to write to a page the Guest wants + * read-only (bit 2 of errcode == write). + */ if ((errcode & 2) && !(pte_flags(gpte) & _PAGE_RW)) return false; @@ -362,8 +414,10 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) if ((errcode & 4) && !(pte_flags(gpte) & _PAGE_USER)) return false; - /* Check that the Guest PTE flags are OK, and the page number is below - * the pfn_limit (ie. not mapping the Launcher binary). */ + /* + * Check that the Guest PTE flags are OK, and the page number is below + * the pfn_limit (ie. not mapping the Launcher binary). + */ check_gpte(cpu, gpte); /* Add the _PAGE_ACCESSED and (for a write) _PAGE_DIRTY flag */ @@ -373,29 +427,40 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) /* Get the pointer to the shadow PTE entry we're going to set. */ spte = spte_addr(cpu, *spgd, vaddr); - /* If there was a valid shadow PTE entry here before, we release it. - * This can happen with a write to a previously read-only entry. */ + + /* + * If there was a valid shadow PTE entry here before, we release it. + * This can happen with a write to a previously read-only entry. + */ release_pte(*spte); - /* If this is a write, we insist that the Guest page is writable (the - * final arg to gpte_to_spte()). */ + /* + * If this is a write, we insist that the Guest page is writable (the + * final arg to gpte_to_spte()). + */ if (pte_dirty(gpte)) *spte = gpte_to_spte(cpu, gpte, 1); else - /* If this is a read, don't set the "writable" bit in the page + /* + * If this is a read, don't set the "writable" bit in the page * table entry, even if the Guest says it's writable. That way * we will come back here when a write does actually occur, so - * we can update the Guest's _PAGE_DIRTY flag. */ + * we can update the Guest's _PAGE_DIRTY flag. + */ native_set_pte(spte, gpte_to_spte(cpu, pte_wrprotect(gpte), 0)); - /* Finally, we write the Guest PTE entry back: we've set the - * _PAGE_ACCESSED and maybe the _PAGE_DIRTY flags. */ + /* + * Finally, we write the Guest PTE entry back: we've set the + * _PAGE_ACCESSED and maybe the _PAGE_DIRTY flags. + */ lgwrite(cpu, gpte_ptr, pte_t, gpte); - /* The fault is fixed, the page table is populated, the mapping + /* + * The fault is fixed, the page table is populated, the mapping * manipulated, the result returned and the code complete. A small * delay and a trace of alliteration are the only indications the Guest - * has that a page fault occurred at all. */ + * has that a page fault occurred at all. + */ return true; } @@ -408,7 +473,8 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) * mapped, so it's overkill. * * This is a quick version which answers the question: is this virtual address - * mapped by the shadow page tables, and is it writable? */ + * mapped by the shadow page tables, and is it writable? + */ static bool page_writable(struct lg_cpu *cpu, unsigned long vaddr) { pgd_t *spgd; @@ -428,21 +494,26 @@ static bool page_writable(struct lg_cpu *cpu, unsigned long vaddr) return false; #endif - /* Check the flags on the pte entry itself: it must be present and - * writable. */ + /* + * Check the flags on the pte entry itself: it must be present and + * writable. + */ flags = pte_flags(*(spte_addr(cpu, *spgd, vaddr))); return (flags & (_PAGE_PRESENT|_PAGE_RW)) == (_PAGE_PRESENT|_PAGE_RW); } -/* So, when pin_stack_pages() asks us to pin a page, we check if it's already +/* + * So, when pin_stack_pages() asks us to pin a page, we check if it's already * in the page tables, and if not, we call demand_page() with error code 2 - * (meaning "write"). */ + * (meaning "write"). + */ void pin_page(struct lg_cpu *cpu, unsigned long vaddr) { if (!page_writable(cpu, vaddr) && !demand_page(cpu, vaddr, 2)) kill_guest(cpu, "bad stack page %#lx", vaddr); } +/*:*/ #ifdef CONFIG_X86_PAE static void release_pmd(pmd_t *spmd) @@ -479,15 +550,21 @@ static void release_pgd(pgd_t *spgd) } #else /* !CONFIG_X86_PAE */ -/*H:450 If we chase down the release_pgd() code, it looks like this: */ +/*H:450 + * If we chase down the release_pgd() code, the non-PAE version looks like + * this. The PAE version is almost identical, but instead of calling + * release_pte it calls release_pmd(), which looks much like this. + */ static void release_pgd(pgd_t *spgd) { /* If the entry's not present, there's nothing to release. */ if (pgd_flags(*spgd) & _PAGE_PRESENT) { unsigned int i; - /* Converting the pfn to find the actual PTE page is easy: turn + /* + * Converting the pfn to find the actual PTE page is easy: turn * the page number into a physical address, then convert to a - * virtual address (easy for kernel pages like this one). */ + * virtual address (easy for kernel pages like this one). + */ pte_t *ptepage = __va(pgd_pfn(*spgd) << PAGE_SHIFT); /* For each entry in the page, we might need to release it. */ for (i = 0; i < PTRS_PER_PTE; i++) @@ -499,9 +576,12 @@ static void release_pgd(pgd_t *spgd) } } #endif -/*H:445 We saw flush_user_mappings() twice: once from the flush_user_mappings() + +/*H:445 + * We saw flush_user_mappings() twice: once from the flush_user_mappings() * hypercall and once in new_pgdir() when we re-used a top-level pgdir page. - * It simply releases every PTE page from 0 up to the Guest's kernel address. */ + * It simply releases every PTE page from 0 up to the Guest's kernel address. + */ static void flush_user_mappings(struct lguest *lg, int idx) { unsigned int i; @@ -510,10 +590,12 @@ static void flush_user_mappings(struct lguest *lg, int idx) release_pgd(lg->pgdirs[idx].pgdir + i); } -/*H:440 (v) Flushing (throwing away) page tables, +/*H:440 + * (v) Flushing (throwing away) page tables, * * The Guest has a hypercall to throw away the page tables: it's used when a - * large number of mappings have been changed. */ + * large number of mappings have been changed. + */ void guest_pagetable_flush_user(struct lg_cpu *cpu) { /* Drop the userspace part of the current page table. */ @@ -551,9 +633,11 @@ unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr) return pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK); } -/* We keep several page tables. This is a simple routine to find the page +/* + * We keep several page tables. This is a simple routine to find the page * table (if any) corresponding to this top-level address the Guest has given - * us. */ + * us. + */ static unsigned int find_pgdir(struct lguest *lg, unsigned long pgtable) { unsigned int i; @@ -563,9 +647,11 @@ static unsigned int find_pgdir(struct lguest *lg, unsigned long pgtable) return i; } -/*H:435 And this is us, creating the new page directory. If we really do +/*H:435 + * And this is us, creating the new page directory. If we really do * allocate a new one (and so the kernel parts are not there), we set - * blank_pgdir. */ + * blank_pgdir. + */ static unsigned int new_pgdir(struct lg_cpu *cpu, unsigned long gpgdir, int *blank_pgdir) @@ -575,8 +661,10 @@ static unsigned int new_pgdir(struct lg_cpu *cpu, pmd_t *pmd_table; #endif - /* We pick one entry at random to throw out. Choosing the Least - * Recently Used might be better, but this is easy. */ + /* + * We pick one entry at random to throw out. Choosing the Least + * Recently Used might be better, but this is easy. + */ next = random32() % ARRAY_SIZE(cpu->lg->pgdirs); /* If it's never been allocated at all before, try now. */ if (!cpu->lg->pgdirs[next].pgdir) { @@ -587,8 +675,10 @@ static unsigned int new_pgdir(struct lg_cpu *cpu, next = cpu->cpu_pgd; else { #ifdef CONFIG_X86_PAE - /* In PAE mode, allocate a pmd page and populate the - * last pgd entry. */ + /* + * In PAE mode, allocate a pmd page and populate the + * last pgd entry. + */ pmd_table = (pmd_t *)get_zeroed_page(GFP_KERNEL); if (!pmd_table) { free_page((long)cpu->lg->pgdirs[next].pgdir); @@ -598,8 +688,10 @@ static unsigned int new_pgdir(struct lg_cpu *cpu, set_pgd(cpu->lg->pgdirs[next].pgdir + SWITCHER_PGD_INDEX, __pgd(__pa(pmd_table) | _PAGE_PRESENT)); - /* This is a blank page, so there are no kernel - * mappings: caller must map the stack! */ + /* + * This is a blank page, so there are no kernel + * mappings: caller must map the stack! + */ *blank_pgdir = 1; } #else @@ -615,19 +707,23 @@ static unsigned int new_pgdir(struct lg_cpu *cpu, return next; } -/*H:430 (iv) Switching page tables +/*H:430 + * (iv) Switching page tables * * Now we've seen all the page table setting and manipulation, let's see * what happens when the Guest changes page tables (ie. changes the top-level - * pgdir). This occurs on almost every context switch. */ + * pgdir). This occurs on almost every context switch. + */ void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable) { int newpgdir, repin = 0; /* Look to see if we have this one already. */ newpgdir = find_pgdir(cpu->lg, pgtable); - /* If not, we allocate or mug an existing one: if it's a fresh one, - * repin gets set to 1. */ + /* + * If not, we allocate or mug an existing one: if it's a fresh one, + * repin gets set to 1. + */ if (newpgdir == ARRAY_SIZE(cpu->lg->pgdirs)) newpgdir = new_pgdir(cpu, pgtable, &repin); /* Change the current pgd index to the new one. */ @@ -637,9 +733,11 @@ void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable) pin_stack_pages(cpu); } -/*H:470 Finally, a routine which throws away everything: all PGD entries in all +/*H:470 + * Finally, a routine which throws away everything: all PGD entries in all * the shadow page tables, including the Guest's kernel mappings. This is used - * when we destroy the Guest. */ + * when we destroy the Guest. + */ static void release_all_pagetables(struct lguest *lg) { unsigned int i, j; @@ -656,8 +754,10 @@ static void release_all_pagetables(struct lguest *lg) spgd = lg->pgdirs[i].pgdir + SWITCHER_PGD_INDEX; pmdpage = __va(pgd_pfn(*spgd) << PAGE_SHIFT); - /* And release the pmd entries of that pmd page, - * except for the switcher pmd. */ + /* + * And release the pmd entries of that pmd page, + * except for the switcher pmd. + */ for (k = 0; k < SWITCHER_PMD_INDEX; k++) release_pmd(&pmdpage[k]); #endif @@ -667,10 +767,12 @@ static void release_all_pagetables(struct lguest *lg) } } -/* We also throw away everything when a Guest tells us it's changed a kernel +/* + * We also throw away everything when a Guest tells us it's changed a kernel * mapping. Since kernel mappings are in every page table, it's easiest to * throw them all away. This traps the Guest in amber for a while as - * everything faults back in, but it's rare. */ + * everything faults back in, but it's rare. + */ void guest_pagetable_clear_all(struct lg_cpu *cpu) { release_all_pagetables(cpu->lg); @@ -678,15 +780,19 @@ void guest_pagetable_clear_all(struct lg_cpu *cpu) pin_stack_pages(cpu); } /*:*/ -/*M:009 Since we throw away all mappings when a kernel mapping changes, our + +/*M:009 + * Since we throw away all mappings when a kernel mapping changes, our * performance sucks for guests using highmem. In fact, a guest with * PAGE_OFFSET 0xc0000000 (the default) and more than about 700MB of RAM is * usually slower than a Guest with less memory. * * This, of course, cannot be fixed. It would take some kind of... well, I - * don't know, but the term "puissant code-fu" comes to mind. :*/ + * don't know, but the term "puissant code-fu" comes to mind. +:*/ -/*H:420 This is the routine which actually sets the page table entry for then +/*H:420 + * This is the routine which actually sets the page table entry for then * "idx"'th shadow page table. * * Normally, we can just throw out the old entry and replace it with 0: if they @@ -715,31 +821,36 @@ static void do_set_pte(struct lg_cpu *cpu, int idx, spmd = spmd_addr(cpu, *spgd, vaddr); if (pmd_flags(*spmd) & _PAGE_PRESENT) { #endif - /* Otherwise, we start by releasing - * the existing entry. */ + /* Otherwise, start by releasing the existing entry. */ pte_t *spte = spte_addr(cpu, *spgd, vaddr); release_pte(*spte); - /* If they're setting this entry as dirty or accessed, - * we might as well put that entry they've given us - * in now. This shaves 10% off a - * copy-on-write micro-benchmark. */ + /* + * If they're setting this entry as dirty or accessed, + * we might as well put that entry they've given us in + * now. This shaves 10% off a copy-on-write + * micro-benchmark. + */ if (pte_flags(gpte) & (_PAGE_DIRTY | _PAGE_ACCESSED)) { check_gpte(cpu, gpte); native_set_pte(spte, gpte_to_spte(cpu, gpte, pte_flags(gpte) & _PAGE_DIRTY)); - } else - /* Otherwise kill it and we can demand_page() - * it in later. */ + } else { + /* + * Otherwise kill it and we can demand_page() + * it in later. + */ native_set_pte(spte, __pte(0)); + } #ifdef CONFIG_X86_PAE } #endif } } -/*H:410 Updating a PTE entry is a little trickier. +/*H:410 + * Updating a PTE entry is a little trickier. * * We keep track of several different page tables (the Guest uses one for each * process, so it makes sense to cache at least a few). Each of these have @@ -748,12 +859,15 @@ static void do_set_pte(struct lg_cpu *cpu, int idx, * all the page tables, not just the current one. This is rare. * * The benefit is that when we have to track a new page table, we can keep all - * the kernel mappings. This speeds up context switch immensely. */ + * the kernel mappings. This speeds up context switch immensely. + */ void guest_set_pte(struct lg_cpu *cpu, unsigned long gpgdir, unsigned long vaddr, pte_t gpte) { - /* Kernel mappings must be changed on all top levels. Slow, but doesn't - * happen often. */ + /* + * Kernel mappings must be changed on all top levels. Slow, but doesn't + * happen often. + */ if (vaddr >= cpu->lg->kernel_address) { unsigned int i; for (i = 0; i < ARRAY_SIZE(cpu->lg->pgdirs); i++) @@ -795,19 +909,25 @@ void guest_set_pgd(struct lguest *lg, unsigned long gpgdir, u32 idx) /* ... throw it away. */ release_pgd(lg->pgdirs[pgdir].pgdir + idx); } + #ifdef CONFIG_X86_PAE +/* For setting a mid-level, we just throw everything away. It's easy. */ void guest_set_pmd(struct lguest *lg, unsigned long pmdp, u32 idx) { guest_pagetable_clear_all(&lg->cpus[0]); } #endif -/* Once we know how much memory we have we can construct simple identity - * (which set virtual == physical) and linear mappings - * which will get the Guest far enough into the boot to create its own. +/*H:505 + * To get through boot, we construct simple identity page mappings (which + * set virtual == physical) and linear mappings which will get the Guest far + * enough into the boot to create its own. The linear mapping means we + * simplify the Guest boot, but it makes assumptions about their PAGE_OFFSET, + * as you'll see. * * We lay them out of the way, just below the initrd (which is why we need to - * know its size here). */ + * know its size here). + */ static unsigned long setup_pagetables(struct lguest *lg, unsigned long mem, unsigned long initrd_size) @@ -825,8 +945,10 @@ static unsigned long setup_pagetables(struct lguest *lg, unsigned int phys_linear; #endif - /* We have mapped_pages frames to map, so we need - * linear_pages page tables to map them. */ + /* + * We have mapped_pages frames to map, so we need linear_pages page + * tables to map them. + */ mapped_pages = mem / PAGE_SIZE; linear_pages = (mapped_pages + PTRS_PER_PTE - 1) / PTRS_PER_PTE; @@ -837,10 +959,16 @@ static unsigned long setup_pagetables(struct lguest *lg, linear = (void *)pgdir - linear_pages * PAGE_SIZE; #ifdef CONFIG_X86_PAE + /* + * And the single mid page goes below that. We only use one, but + * that's enough to map 1G, which definitely gets us through boot. + */ pmds = (void *)linear - PAGE_SIZE; #endif - /* Linear mapping is easy: put every page's address into the - * mapping in order. */ + /* + * Linear mapping is easy: put every page's address into the + * mapping in order. + */ for (i = 0; i < mapped_pages; i++) { pte_t pte; pte = pfn_pte(i, __pgprot(_PAGE_PRESENT|_PAGE_RW|_PAGE_USER)); @@ -848,11 +976,14 @@ static unsigned long setup_pagetables(struct lguest *lg, return -EFAULT; } - /* The top level points to the linear page table pages above. - * We setup the identity and linear mappings here. */ #ifdef CONFIG_X86_PAE + /* + * Make the Guest PMD entries point to the corresponding place in the + * linear mapping (up to one page worth of PMD). + */ for (i = j = 0; i < mapped_pages && j < PTRS_PER_PMD; i += PTRS_PER_PTE, j++) { + /* FIXME: native_set_pmd is overkill here. */ native_set_pmd(&pmd, __pmd(((unsigned long)(linear + i) - mem_base) | _PAGE_PRESENT | _PAGE_RW | _PAGE_USER)); @@ -860,18 +991,36 @@ static unsigned long setup_pagetables(struct lguest *lg, return -EFAULT; } + /* One PGD entry, pointing to that PMD page. */ set_pgd(&pgd, __pgd(((u32)pmds - mem_base) | _PAGE_PRESENT)); + /* Copy it in as the first PGD entry (ie. addresses 0-1G). */ if (copy_to_user(&pgdir[0], &pgd, sizeof(pgd)) != 0) return -EFAULT; + /* + * And the third PGD entry (ie. addresses 3G-4G). + * + * FIXME: This assumes that PAGE_OFFSET for the Guest is 0xC0000000. + */ if (copy_to_user(&pgdir[3], &pgd, sizeof(pgd)) != 0) return -EFAULT; #else + /* + * The top level points to the linear page table pages above. + * We setup the identity and linear mappings here. + */ phys_linear = (unsigned long)linear - mem_base; for (i = 0; i < mapped_pages; i += PTRS_PER_PTE) { pgd_t pgd; + /* + * Create a PGD entry which points to the right part of the + * linear PTE pages. + */ pgd = __pgd((phys_linear + i * sizeof(pte_t)) | (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER)); + /* + * Copy it into the PGD page at 0 and PAGE_OFFSET. + */ if (copy_to_user(&pgdir[i / PTRS_PER_PTE], &pgd, sizeof(pgd)) || copy_to_user(&pgdir[pgd_index(PAGE_OFFSET) + i / PTRS_PER_PTE], @@ -880,15 +1029,19 @@ static unsigned long setup_pagetables(struct lguest *lg, } #endif - /* We return the top level (guest-physical) address: remember where - * this is. */ + /* + * We return the top level (guest-physical) address: we remember where + * this is to write it into lguest_data when the Guest initializes. + */ return (unsigned long)pgdir - mem_base; } -/*H:500 (vii) Setting up the page tables initially. +/*H:500 + * (vii) Setting up the page tables initially. * * When a Guest is first created, the Launcher tells us where the toplevel of - * its first page table is. We set some things up here: */ + * its first page table is. We set some things up here: + */ int init_guest_pagetable(struct lguest *lg) { u64 mem; @@ -898,21 +1051,27 @@ int init_guest_pagetable(struct lguest *lg) pgd_t *pgd; pmd_t *pmd_table; #endif - /* Get the Guest memory size and the ramdisk size from the boot header - * located at lg->mem_base (Guest address 0). */ + /* + * Get the Guest memory size and the ramdisk size from the boot header + * located at lg->mem_base (Guest address 0). + */ if (copy_from_user(&mem, &boot->e820_map[0].size, sizeof(mem)) || get_user(initrd_size, &boot->hdr.ramdisk_size)) return -EFAULT; - /* We start on the first shadow page table, and give it a blank PGD - * page. */ + /* + * We start on the first shadow page table, and give it a blank PGD + * page. + */ lg->pgdirs[0].gpgdir = setup_pagetables(lg, mem, initrd_size); if (IS_ERR_VALUE(lg->pgdirs[0].gpgdir)) return lg->pgdirs[0].gpgdir; lg->pgdirs[0].pgdir = (pgd_t *)get_zeroed_page(GFP_KERNEL); if (!lg->pgdirs[0].pgdir) return -ENOMEM; + #ifdef CONFIG_X86_PAE + /* For PAE, we also create the initial mid-level. */ pgd = lg->pgdirs[0].pgdir; pmd_table = (pmd_t *) get_zeroed_page(GFP_KERNEL); if (!pmd_table) @@ -921,27 +1080,33 @@ int init_guest_pagetable(struct lguest *lg) set_pgd(pgd + SWITCHER_PGD_INDEX, __pgd(__pa(pmd_table) | _PAGE_PRESENT)); #endif + + /* This is the current page table. */ lg->cpus[0].cpu_pgd = 0; return 0; } -/* When the Guest calls LHCALL_LGUEST_INIT we do more setup. */ +/*H:508 When the Guest calls LHCALL_LGUEST_INIT we do more setup. */ void page_table_guest_data_init(struct lg_cpu *cpu) { /* We get the kernel address: above this is all kernel memory. */ if (get_user(cpu->lg->kernel_address, &cpu->lg->lguest_data->kernel_address) - /* We tell the Guest that it can't use the top 2 or 4 MB - * of virtual addresses used by the Switcher. */ + /* + * We tell the Guest that it can't use the top 2 or 4 MB + * of virtual addresses used by the Switcher. + */ || put_user(RESERVE_MEM * 1024 * 1024, &cpu->lg->lguest_data->reserve_mem) || put_user(cpu->lg->pgdirs[0].gpgdir, &cpu->lg->lguest_data->pgdir)) kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); - /* In flush_user_mappings() we loop from 0 to + /* + * In flush_user_mappings() we loop from 0 to * "pgd_index(lg->kernel_address)". This assumes it won't hit the - * Switcher mappings, so check that now. */ + * Switcher mappings, so check that now. + */ #ifdef CONFIG_X86_PAE if (pgd_index(cpu->lg->kernel_address) == SWITCHER_PGD_INDEX && pmd_index(cpu->lg->kernel_address) == SWITCHER_PMD_INDEX) @@ -964,12 +1129,14 @@ void free_guest_pagetable(struct lguest *lg) free_page((long)lg->pgdirs[i].pgdir); } -/*H:480 (vi) Mapping the Switcher when the Guest is about to run. +/*H:480 + * (vi) Mapping the Switcher when the Guest is about to run. * * The Switcher and the two pages for this CPU need to be visible in the * Guest (and not the pages for other CPUs). We have the appropriate PTE pages * for each CPU already set up, we just need to hook them in now we know which - * Guest is about to run on this CPU. */ + * Guest is about to run on this CPU. + */ void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages) { pte_t *switcher_pte_page = __get_cpu_var(switcher_pte_pages); @@ -980,30 +1147,38 @@ void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages) pmd_t switcher_pmd; pmd_t *pmd_table; + /* FIXME: native_set_pmd is overkill here. */ native_set_pmd(&switcher_pmd, pfn_pmd(__pa(switcher_pte_page) >> PAGE_SHIFT, PAGE_KERNEL_EXEC)); + /* Figure out where the pmd page is, by reading the PGD, and converting + * it to a virtual address. */ pmd_table = __va(pgd_pfn(cpu->lg-> pgdirs[cpu->cpu_pgd].pgdir[SWITCHER_PGD_INDEX]) << PAGE_SHIFT); + /* Now write it into the shadow page table. */ native_set_pmd(&pmd_table[SWITCHER_PMD_INDEX], switcher_pmd); #else pgd_t switcher_pgd; - /* Make the last PGD entry for this Guest point to the Switcher's PTE - * page for this CPU (with appropriate flags). */ + /* + * Make the last PGD entry for this Guest point to the Switcher's PTE + * page for this CPU (with appropriate flags). + */ switcher_pgd = __pgd(__pa(switcher_pte_page) | __PAGE_KERNEL_EXEC); cpu->lg->pgdirs[cpu->cpu_pgd].pgdir[SWITCHER_PGD_INDEX] = switcher_pgd; #endif - /* We also change the Switcher PTE page. When we're running the Guest, + /* + * We also change the Switcher PTE page. When we're running the Guest, * we want the Guest's "regs" page to appear where the first Switcher * page for this CPU is. This is an optimization: when the Switcher * saves the Guest registers, it saves them into the first page of this * CPU's "struct lguest_pages": if we make sure the Guest's register * page is already mapped there, we don't have to copy them out - * again. */ + * again. + */ pfn = __pa(cpu->regs_page) >> PAGE_SHIFT; native_set_pte(®s_pte, pfn_pte(pfn, PAGE_KERNEL)); native_set_pte(&switcher_pte_page[pte_index((unsigned long)pages)], @@ -1019,10 +1194,12 @@ static void free_switcher_pte_pages(void) free_page((long)switcher_pte_page(i)); } -/*H:520 Setting up the Switcher PTE page for given CPU is fairly easy, given +/*H:520 + * Setting up the Switcher PTE page for given CPU is fairly easy, given * the CPU number and the "struct page"s for the Switcher code itself. * - * Currently the Switcher is less than a page long, so "pages" is always 1. */ + * Currently the Switcher is less than a page long, so "pages" is always 1. + */ static __init void populate_switcher_pte_page(unsigned int cpu, struct page *switcher_page[], unsigned int pages) @@ -1043,13 +1220,16 @@ static __init void populate_switcher_pte_page(unsigned int cpu, native_set_pte(&pte[i], pfn_pte(page_to_pfn(switcher_page[i]), __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED|_PAGE_RW))); - /* The second page contains the "struct lguest_ro_state", and is - * read-only. */ + /* + * The second page contains the "struct lguest_ro_state", and is + * read-only. + */ native_set_pte(&pte[i+1], pfn_pte(page_to_pfn(switcher_page[i+1]), __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED))); } -/* We've made it through the page table code. Perhaps our tired brains are +/* + * We've made it through the page table code. Perhaps our tired brains are * still processing the details, or perhaps we're simply glad it's over. * * If nothing else, note that all this complexity in juggling shadow page tables @@ -1058,10 +1238,13 @@ static __init void populate_switcher_pte_page(unsigned int cpu, * uses exotic direct Guest pagetable manipulation, and why both Intel and AMD * have implemented shadow page table support directly into hardware. * - * There is just one file remaining in the Host. */ + * There is just one file remaining in the Host. + */ -/*H:510 At boot or module load time, init_pagetables() allocates and populates - * the Switcher PTE page for each CPU. */ +/*H:510 + * At boot or module load time, init_pagetables() allocates and populates + * the Switcher PTE page for each CPU. + */ __init int init_pagetables(struct page **switcher_page, unsigned int pages) { unsigned int i; diff --git a/drivers/lguest/segments.c b/drivers/lguest/segments.c index 482ed5a..951c57b 100644 --- a/drivers/lguest/segments.c +++ b/drivers/lguest/segments.c @@ -1,4 +1,5 @@ -/*P:600 The x86 architecture has segments, which involve a table of descriptors +/*P:600 + * The x86 architecture has segments, which involve a table of descriptors * which can be used to do funky things with virtual address interpretation. * We originally used to use segments so the Guest couldn't alter the * Guest<->Host Switcher, and then we had to trim Guest segments, and restore @@ -8,7 +9,8 @@ * * In these modern times, the segment handling code consists of simple sanity * checks, and the worst you'll experience reading this code is butterfly-rash - * from frolicking through its parklike serenity. :*/ + * from frolicking through its parklike serenity. +:*/ #include "lg.h" /*H:600 @@ -41,10 +43,12 @@ * begin. */ -/* There are several entries we don't let the Guest set. The TSS entry is the +/* + * There are several entries we don't let the Guest set. The TSS entry is the * "Task State Segment" which controls all kinds of delicate things. The * LGUEST_CS and LGUEST_DS entries are reserved for the Switcher, and the - * the Guest can't be trusted to deal with double faults. */ + * the Guest can't be trusted to deal with double faults. + */ static bool ignored_gdt(unsigned int num) { return (num == GDT_ENTRY_TSS @@ -53,42 +57,52 @@ static bool ignored_gdt(unsigned int num) || num == GDT_ENTRY_DOUBLEFAULT_TSS); } -/*H:630 Once the Guest gave us new GDT entries, we fix them up a little. We +/*H:630 + * Once the Guest gave us new GDT entries, we fix them up a little. We * don't care if they're invalid: the worst that can happen is a General * Protection Fault in the Switcher when it restores a Guest segment register * which tries to use that entry. Then we kill the Guest for causing such a - * mess: the message will be "unhandled trap 256". */ + * mess: the message will be "unhandled trap 256". + */ static void fixup_gdt_table(struct lg_cpu *cpu, unsigned start, unsigned end) { unsigned int i; for (i = start; i < end; i++) { - /* We never copy these ones to real GDT, so we don't care what - * they say */ + /* + * We never copy these ones to real GDT, so we don't care what + * they say + */ if (ignored_gdt(i)) continue; - /* Segment descriptors contain a privilege level: the Guest is + /* + * Segment descriptors contain a privilege level: the Guest is * sometimes careless and leaves this as 0, even though it's - * running at privilege level 1. If so, we fix it here. */ + * running at privilege level 1. If so, we fix it here. + */ if ((cpu->arch.gdt[i].b & 0x00006000) == 0) cpu->arch.gdt[i].b |= (GUEST_PL << 13); - /* Each descriptor has an "accessed" bit. If we don't set it + /* + * Each descriptor has an "accessed" bit. If we don't set it * now, the CPU will try to set it when the Guest first loads * that entry into a segment register. But the GDT isn't - * writable by the Guest, so bad things can happen. */ + * writable by the Guest, so bad things can happen. + */ cpu->arch.gdt[i].b |= 0x00000100; } } -/*H:610 Like the IDT, we never simply use the GDT the Guest gives us. We keep +/*H:610 + * Like the IDT, we never simply use the GDT the Guest gives us. We keep * a GDT for each CPU, and copy across the Guest's entries each time we want to * run the Guest on that CPU. * * This routine is called at boot or modprobe time for each CPU to set up the * constant GDT entries: the ones which are the same no matter what Guest we're - * running. */ + * running. + */ void setup_default_gdt_entries(struct lguest_ro_state *state) { struct desc_struct *gdt = state->guest_gdt; @@ -98,30 +112,37 @@ void setup_default_gdt_entries(struct lguest_ro_state *state) gdt[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT; gdt[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT; - /* The TSS segment refers to the TSS entry for this particular CPU. + /* + * The TSS segment refers to the TSS entry for this particular CPU. * Forgive the magic flags: the 0x8900 means the entry is Present, it's * privilege level 0 Available 386 TSS system segment, and the 0x67 - * means Saturn is eclipsed by Mercury in the twelfth house. */ + * means Saturn is eclipsed by Mercury in the twelfth house. + */ gdt[GDT_ENTRY_TSS].a = 0x00000067 | (tss << 16); gdt[GDT_ENTRY_TSS].b = 0x00008900 | (tss & 0xFF000000) | ((tss >> 16) & 0x000000FF); } -/* This routine sets up the initial Guest GDT for booting. All entries start - * as 0 (unusable). */ +/* + * This routine sets up the initial Guest GDT for booting. All entries start + * as 0 (unusable). + */ void setup_guest_gdt(struct lg_cpu *cpu) { - /* Start with full 0-4G segments... */ + /* + * Start with full 0-4G segments...except the Guest is allowed to use + * them, so set the privilege level appropriately in the flags. + */ cpu->arch.gdt[GDT_ENTRY_KERNEL_CS] = FULL_EXEC_SEGMENT; cpu->arch.gdt[GDT_ENTRY_KERNEL_DS] = FULL_SEGMENT; - /* ...except the Guest is allowed to use them, so set the privilege - * level appropriately in the flags. */ cpu->arch.gdt[GDT_ENTRY_KERNEL_CS].b |= (GUEST_PL << 13); cpu->arch.gdt[GDT_ENTRY_KERNEL_DS].b |= (GUEST_PL << 13); } -/*H:650 An optimization of copy_gdt(), for just the three "thead-local storage" - * entries. */ +/*H:650 + * An optimization of copy_gdt(), for just the three "thead-local storage" + * entries. + */ void copy_gdt_tls(const struct lg_cpu *cpu, struct desc_struct *gdt) { unsigned int i; @@ -130,26 +151,34 @@ void copy_gdt_tls(const struct lg_cpu *cpu, struct desc_struct *gdt) gdt[i] = cpu->arch.gdt[i]; } -/*H:640 When the Guest is run on a different CPU, or the GDT entries have - * changed, copy_gdt() is called to copy the Guest's GDT entries across to this - * CPU's GDT. */ +/*H:640 + * When the Guest is run on a different CPU, or the GDT entries have changed, + * copy_gdt() is called to copy the Guest's GDT entries across to this CPU's + * GDT. + */ void copy_gdt(const struct lg_cpu *cpu, struct desc_struct *gdt) { unsigned int i; - /* The default entries from setup_default_gdt_entries() are not - * replaced. See ignored_gdt() above. */ + /* + * The default entries from setup_default_gdt_entries() are not + * replaced. See ignored_gdt() above. + */ for (i = 0; i < GDT_ENTRIES; i++) if (!ignored_gdt(i)) gdt[i] = cpu->arch.gdt[i]; } -/*H:620 This is where the Guest asks us to load a new GDT entry - * (LHCALL_LOAD_GDT_ENTRY). We tweak the entry and copy it in. */ +/*H:620 + * This is where the Guest asks us to load a new GDT entry + * (LHCALL_LOAD_GDT_ENTRY). We tweak the entry and copy it in. + */ void load_guest_gdt_entry(struct lg_cpu *cpu, u32 num, u32 lo, u32 hi) { - /* We assume the Guest has the same number of GDT entries as the - * Host, otherwise we'd have to dynamically allocate the Guest GDT. */ + /* + * We assume the Guest has the same number of GDT entries as the + * Host, otherwise we'd have to dynamically allocate the Guest GDT. + */ if (num >= ARRAY_SIZE(cpu->arch.gdt)) kill_guest(cpu, "too many gdt entries %i", num); @@ -157,15 +186,19 @@ void load_guest_gdt_entry(struct lg_cpu *cpu, u32 num, u32 lo, u32 hi) cpu->arch.gdt[num].a = lo; cpu->arch.gdt[num].b = hi; fixup_gdt_table(cpu, num, num+1); - /* Mark that the GDT changed so the core knows it has to copy it again, - * even if the Guest is run on the same CPU. */ + /* + * Mark that the GDT changed so the core knows it has to copy it again, + * even if the Guest is run on the same CPU. + */ cpu->changed |= CHANGED_GDT; } -/* This is the fast-track version for just changing the three TLS entries. +/* + * This is the fast-track version for just changing the three TLS entries. * Remember that this happens on every context switch, so it's worth * optimizing. But wouldn't it be neater to have a single hypercall to cover - * both cases? */ + * both cases? + */ void guest_load_tls(struct lg_cpu *cpu, unsigned long gtls) { struct desc_struct *tls = &cpu->arch.gdt[GDT_ENTRY_TLS_MIN]; @@ -175,7 +208,6 @@ void guest_load_tls(struct lg_cpu *cpu, unsigned long gtls) /* Note that just the TLS entries have changed. */ cpu->changed |= CHANGED_GDT_TLS; } -/*:*/ /*H:660 * With this, we have finished the Host. diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c index eaf722f..6ae3888 100644 --- a/drivers/lguest/x86/core.c +++ b/drivers/lguest/x86/core.c @@ -17,13 +17,15 @@ * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ -/*P:450 This file contains the x86-specific lguest code. It used to be all +/*P:450 + * This file contains the x86-specific lguest code. It used to be all * mixed in with drivers/lguest/core.c but several foolhardy code slashers * wrestled most of the dependencies out to here in preparation for porting * lguest to other architectures (see what I mean by foolhardy?). * * This also contains a couple of non-obvious setup and teardown pieces which - * were implemented after days of debugging pain. :*/ + * were implemented after days of debugging pain. +:*/ #include <linux/kernel.h> #include <linux/start_kernel.h> #include <linux/string.h> @@ -82,25 +84,33 @@ static DEFINE_PER_CPU(struct lg_cpu *, last_cpu); */ static void copy_in_guest_info(struct lg_cpu *cpu, struct lguest_pages *pages) { - /* Copying all this data can be quite expensive. We usually run the + /* + * Copying all this data can be quite expensive. We usually run the * same Guest we ran last time (and that Guest hasn't run anywhere else * meanwhile). If that's not the case, we pretend everything in the - * Guest has changed. */ + * Guest has changed. + */ if (__get_cpu_var(last_cpu) != cpu || cpu->last_pages != pages) { __get_cpu_var(last_cpu) = cpu; cpu->last_pages = pages; cpu->changed = CHANGED_ALL; } - /* These copies are pretty cheap, so we do them unconditionally: */ - /* Save the current Host top-level page directory. */ + /* + * These copies are pretty cheap, so we do them unconditionally: */ + /* Save the current Host top-level page directory. + */ pages->state.host_cr3 = __pa(current->mm->pgd); - /* Set up the Guest's page tables to see this CPU's pages (and no - * other CPU's pages). */ + /* + * Set up the Guest's page tables to see this CPU's pages (and no + * other CPU's pages). + */ map_switcher_in_guest(cpu, pages); - /* Set up the two "TSS" members which tell the CPU what stack to use + /* + * Set up the two "TSS" members which tell the CPU what stack to use * for traps which do directly into the Guest (ie. traps at privilege - * level 1). */ + * level 1). + */ pages->state.guest_tss.sp1 = cpu->esp1; pages->state.guest_tss.ss1 = cpu->ss1; @@ -125,97 +135,126 @@ static void run_guest_once(struct lg_cpu *cpu, struct lguest_pages *pages) /* This is a dummy value we need for GCC's sake. */ unsigned int clobber; - /* Copy the guest-specific information into this CPU's "struct - * lguest_pages". */ + /* + * Copy the guest-specific information into this CPU's "struct + * lguest_pages". + */ copy_in_guest_info(cpu, pages); - /* Set the trap number to 256 (impossible value). If we fault while + /* + * Set the trap number to 256 (impossible value). If we fault while * switching to the Guest (bad segment registers or bug), this will - * cause us to abort the Guest. */ + * cause us to abort the Guest. + */ cpu->regs->trapnum = 256; - /* Now: we push the "eflags" register on the stack, then do an "lcall". + /* + * Now: we push the "eflags" register on the stack, then do an "lcall". * This is how we change from using the kernel code segment to using * the dedicated lguest code segment, as well as jumping into the * Switcher. * * The lcall also pushes the old code segment (KERNEL_CS) onto the * stack, then the address of this call. This stack layout happens to - * exactly match the stack layout created by an interrupt... */ + * exactly match the stack layout created by an interrupt... + */ asm volatile("pushf; lcall *lguest_entry" - /* This is how we tell GCC that %eax ("a") and %ebx ("b") - * are changed by this routine. The "=" means output. */ + /* + * This is how we tell GCC that %eax ("a") and %ebx ("b") + * are changed by this routine. The "=" means output. + */ : "=a"(clobber), "=b"(clobber) - /* %eax contains the pages pointer. ("0" refers to the + /* + * %eax contains the pages pointer. ("0" refers to the * 0-th argument above, ie "a"). %ebx contains the * physical address of the Guest's top-level page - * directory. */ + * directory. + */ : "0"(pages), "1"(__pa(cpu->lg->pgdirs[cpu->cpu_pgd].pgdir)) - /* We tell gcc that all these registers could change, + /* + * We tell gcc that all these registers could change, * which means we don't have to save and restore them in - * the Switcher. */ + * the Switcher. + */ : "memory", "%edx", "%ecx", "%edi", "%esi"); } /*:*/ -/*M:002 There are hooks in the scheduler which we can register to tell when we +/*M:002 + * There are hooks in the scheduler which we can register to tell when we * get kicked off the CPU (preempt_notifier_register()). This would allow us * to lazily disable SYSENTER which would regain some performance, and should * also simplify copy_in_guest_info(). Note that we'd still need to restore * things when we exit to Launcher userspace, but that's fairly easy. * - * We could also try using this hooks for PGE, but that might be too expensive. + * We could also try using these hooks for PGE, but that might be too expensive. * - * The hooks were designed for KVM, but we can also put them to good use. :*/ + * The hooks were designed for KVM, but we can also put them to good use. +:*/ -/*H:040 This is the i386-specific code to setup and run the Guest. Interrupts - * are disabled: we own the CPU. */ +/*H:040 + * This is the i386-specific code to setup and run the Guest. Interrupts + * are disabled: we own the CPU. + */ void lguest_arch_run_guest(struct lg_cpu *cpu) { - /* Remember the awfully-named TS bit? If the Guest has asked to set it + /* + * Remember the awfully-named TS bit? If the Guest has asked to set it * we set it now, so we can trap and pass that trap to the Guest if it - * uses the FPU. */ + * uses the FPU. + */ if (cpu->ts) unlazy_fpu(current); - /* SYSENTER is an optimized way of doing system calls. We can't allow + /* + * SYSENTER is an optimized way of doing system calls. We can't allow * it because it always jumps to privilege level 0. A normal Guest * won't try it because we don't advertise it in CPUID, but a malicious * Guest (or malicious Guest userspace program) could, so we tell the - * CPU to disable it before running the Guest. */ + * CPU to disable it before running the Guest. + */ if (boot_cpu_has(X86_FEATURE_SEP)) wrmsr(MSR_IA32_SYSENTER_CS, 0, 0); - /* Now we actually run the Guest. It will return when something + /* + * Now we actually run the Guest. It will return when something * interesting happens, and we can examine its registers to see what it - * was doing. */ + * was doing. + */ run_guest_once(cpu, lguest_pages(raw_smp_processor_id())); - /* Note that the "regs" structure contains two extra entries which are + /* + * Note that the "regs" structure contains two extra entries which are * not really registers: a trap number which says what interrupt or * trap made the switcher code come back, and an error code which some - * traps set. */ + * traps set. + */ /* Restore SYSENTER if it's supposed to be on. */ if (boot_cpu_has(X86_FEATURE_SEP)) wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0); - /* If the Guest page faulted, then the cr2 register will tell us the + /* + * If the Guest page faulted, then the cr2 register will tell us the * bad virtual address. We have to grab this now, because once we * re-enable interrupts an interrupt could fault and thus overwrite - * cr2, or we could even move off to a different CPU. */ + * cr2, or we could even move off to a different CPU. + */ if (cpu->regs->trapnum == 14) cpu->arch.last_pagefault = read_cr2(); - /* Similarly, if we took a trap because the Guest used the FPU, + /* + * Similarly, if we took a trap because the Guest used the FPU, * we have to restore the FPU it expects to see. * math_state_restore() may sleep and we may even move off to * a different CPU. So all the critical stuff should be done - * before this. */ + * before this. + */ else if (cpu->regs->trapnum == 7) math_state_restore(); } -/*H:130 Now we've examined the hypercall code; our Guest can make requests. +/*H:130 + * Now we've examined the hypercall code; our Guest can make requests. * Our Guest is usually so well behaved; it never tries to do things it isn't * allowed to, and uses hypercalls instead. Unfortunately, Linux's paravirtual * infrastructure isn't quite complete, because it doesn't contain replacements @@ -225,26 +264,33 @@ void lguest_arch_run_guest(struct lg_cpu *cpu) * * When the Guest uses one of these instructions, we get a trap (General * Protection Fault) and come here. We see if it's one of those troublesome - * instructions and skip over it. We return true if we did. */ + * instructions and skip over it. We return true if we did. + */ static int emulate_insn(struct lg_cpu *cpu) { u8 insn; unsigned int insnlen = 0, in = 0, shift = 0; - /* The eip contains the *virtual* address of the Guest's instruction: - * guest_pa just subtracts the Guest's page_offset. */ + /* + * The eip contains the *virtual* address of the Guest's instruction: + * guest_pa just subtracts the Guest's page_offset. + */ unsigned long physaddr = guest_pa(cpu, cpu->regs->eip); - /* This must be the Guest kernel trying to do something, not userspace! + /* + * This must be the Guest kernel trying to do something, not userspace! * The bottom two bits of the CS segment register are the privilege - * level. */ + * level. + */ if ((cpu->regs->cs & 3) != GUEST_PL) return 0; /* Decoding x86 instructions is icky. */ insn = lgread(cpu, physaddr, u8); - /* 0x66 is an "operand prefix". It means it's using the upper 16 bits - of the eax register. */ + /* + * 0x66 is an "operand prefix". It means it's using the upper 16 bits + * of the eax register. + */ if (insn == 0x66) { shift = 16; /* The instruction is 1 byte so far, read the next byte. */ @@ -252,8 +298,10 @@ static int emulate_insn(struct lg_cpu *cpu) insn = lgread(cpu, physaddr + insnlen, u8); } - /* We can ignore the lower bit for the moment and decode the 4 opcodes - * we need to emulate. */ + /* + * We can ignore the lower bit for the moment and decode the 4 opcodes + * we need to emulate. + */ switch (insn & 0xFE) { case 0xE4: /* in <next byte>,%al */ insnlen += 2; @@ -274,9 +322,11 @@ static int emulate_insn(struct lg_cpu *cpu) return 0; } - /* If it was an "IN" instruction, they expect the result to be read + /* + * If it was an "IN" instruction, they expect the result to be read * into %eax, so we change %eax. We always return all-ones, which - * traditionally means "there's nothing there". */ + * traditionally means "there's nothing there". + */ if (in) { /* Lower bit tells is whether it's a 16 or 32 bit access */ if (insn & 0x1) @@ -290,7 +340,8 @@ static int emulate_insn(struct lg_cpu *cpu) return 1; } -/* Our hypercalls mechanism used to be based on direct software interrupts. +/* + * Our hypercalls mechanism used to be based on direct software interrupts. * After Anthony's "Refactor hypercall infrastructure" kvm patch, we decided to * change over to using kvm hypercalls. * @@ -318,16 +369,20 @@ static int emulate_insn(struct lg_cpu *cpu) */ static void rewrite_hypercall(struct lg_cpu *cpu) { - /* This are the opcodes we use to patch the Guest. The opcode for "int + /* + * This are the opcodes we use to patch the Guest. The opcode for "int * $0x1f" is "0xcd 0x1f" but vmcall instruction is 3 bytes long, so we - * complete the sequence with a NOP (0x90). */ + * complete the sequence with a NOP (0x90). + */ u8 insn[3] = {0xcd, 0x1f, 0x90}; __lgwrite(cpu, guest_pa(cpu, cpu->regs->eip), insn, sizeof(insn)); - /* The above write might have caused a copy of that page to be made + /* + * The above write might have caused a copy of that page to be made * (if it was read-only). We need to make sure the Guest has * up-to-date pagetables. As this doesn't happen often, we can just - * drop them all. */ + * drop them all. + */ guest_pagetable_clear_all(cpu); } @@ -335,9 +390,11 @@ static bool is_hypercall(struct lg_cpu *cpu) { u8 insn[3]; - /* This must be the Guest kernel trying to do something. + /* + * This must be the Guest kernel trying to do something. * The bottom two bits of the CS segment register are the privilege - * level. */ + * level. + */ if ((cpu->regs->cs & 3) != GUEST_PL) return false; @@ -351,86 +408,105 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu) { switch (cpu->regs->trapnum) { case 13: /* We've intercepted a General Protection Fault. */ - /* Check if this was one of those annoying IN or OUT + /* + * Check if this was one of those annoying IN or OUT * instructions which we need to emulate. If so, we just go - * back into the Guest after we've done it. */ + * back into the Guest after we've done it. + */ if (cpu->regs->errcode == 0) { if (emulate_insn(cpu)) return; } - /* If KVM is active, the vmcall instruction triggers a - * General Protection Fault. Normally it triggers an - * invalid opcode fault (6): */ + /* + * If KVM is active, the vmcall instruction triggers a General + * Protection Fault. Normally it triggers an invalid opcode + * fault (6): + */ case 6: - /* We need to check if ring == GUEST_PL and - * faulting instruction == vmcall. */ + /* + * We need to check if ring == GUEST_PL and faulting + * instruction == vmcall. + */ if (is_hypercall(cpu)) { rewrite_hypercall(cpu); return; } break; case 14: /* We've intercepted a Page Fault. */ - /* The Guest accessed a virtual address that wasn't mapped. + /* + * The Guest accessed a virtual address that wasn't mapped. * This happens a lot: we don't actually set up most of the page * tables for the Guest at all when we start: as it runs it asks * for more and more, and we set them up as required. In this * case, we don't even tell the Guest that the fault happened. * * The errcode tells whether this was a read or a write, and - * whether kernel or userspace code. */ + * whether kernel or userspace code. + */ if (demand_page(cpu, cpu->arch.last_pagefault, cpu->regs->errcode)) return; - /* OK, it's really not there (or not OK): the Guest needs to + /* + * OK, it's really not there (or not OK): the Guest needs to * know. We write out the cr2 value so it knows where the * fault occurred. * * Note that if the Guest were really messed up, this could * happen before it's done the LHCALL_LGUEST_INIT hypercall, so - * lg->lguest_data could be NULL */ + * lg->lguest_data could be NULL + */ if (cpu->lg->lguest_data && put_user(cpu->arch.last_pagefault, &cpu->lg->lguest_data->cr2)) kill_guest(cpu, "Writing cr2"); break; case 7: /* We've intercepted a Device Not Available fault. */ - /* If the Guest doesn't want to know, we already restored the - * Floating Point Unit, so we just continue without telling - * it. */ + /* + * If the Guest doesn't want to know, we already restored the + * Floating Point Unit, so we just continue without telling it. + */ if (!cpu->ts) return; break; case 32 ... 255: - /* These values mean a real interrupt occurred, in which case + /* + * These values mean a real interrupt occurred, in which case * the Host handler has already been run. We just do a * friendly check if another process should now be run, then - * return to run the Guest again */ + * return to run the Guest again + */ cond_resched(); return; case LGUEST_TRAP_ENTRY: - /* Our 'struct hcall_args' maps directly over our regs: we set - * up the pointer now to indicate a hypercall is pending. */ + /* + * Our 'struct hcall_args' maps directly over our regs: we set + * up the pointer now to indicate a hypercall is pending. + */ cpu->hcall = (struct hcall_args *)cpu->regs; return; } /* We didn't handle the trap, so it needs to go to the Guest. */ if (!deliver_trap(cpu, cpu->regs->trapnum)) - /* If the Guest doesn't have a handler (either it hasn't + /* + * If the Guest doesn't have a handler (either it hasn't * registered any yet, or it's one of the faults we don't let - * it handle), it dies with this cryptic error message. */ + * it handle), it dies with this cryptic error message. + */ kill_guest(cpu, "unhandled trap %li at %#lx (%#lx)", cpu->regs->trapnum, cpu->regs->eip, cpu->regs->trapnum == 14 ? cpu->arch.last_pagefault : cpu->regs->errcode); } -/* Now we can look at each of the routines this calls, in increasing order of +/* + * Now we can look at each of the routines this calls, in increasing order of * complexity: do_hypercalls(), emulate_insn(), maybe_do_interrupt(), * deliver_trap() and demand_page(). After all those, we'll be ready to * examine the Switcher, and our philosophical understanding of the Host/Guest - * duality will be complete. :*/ + * duality will be complete. +:*/ static void adjust_pge(void *on) { if (on) @@ -439,13 +515,16 @@ static void adjust_pge(void *on) write_cr4(read_cr4() & ~X86_CR4_PGE); } -/*H:020 Now the Switcher is mapped and every thing else is ready, we need to do - * some more i386-specific initialization. */ +/*H:020 + * Now the Switcher is mapped and every thing else is ready, we need to do + * some more i386-specific initialization. + */ void __init lguest_arch_host_init(void) { int i; - /* Most of the i386/switcher.S doesn't care that it's been moved; on + /* + * Most of the i386/switcher.S doesn't care that it's been moved; on * Intel, jumps are relative, and it doesn't access any references to * external code or data. * @@ -453,7 +532,8 @@ void __init lguest_arch_host_init(void) * addresses are placed in a table (default_idt_entries), so we need to * update the table with the new addresses. switcher_offset() is a * convenience function which returns the distance between the - * compiled-in switcher code and the high-mapped copy we just made. */ + * compiled-in switcher code and the high-mapped copy we just made. + */ for (i = 0; i < IDT_ENTRIES; i++) default_idt_entries[i] += switcher_offset(); @@ -468,63 +548,81 @@ void __init lguest_arch_host_init(void) for_each_possible_cpu(i) { /* lguest_pages() returns this CPU's two pages. */ struct lguest_pages *pages = lguest_pages(i); - /* This is a convenience pointer to make the code fit one - * statement to a line. */ + /* This is a convenience pointer to make the code neater. */ struct lguest_ro_state *state = &pages->state; - /* The Global Descriptor Table: the Host has a different one + /* + * The Global Descriptor Table: the Host has a different one * for each CPU. We keep a descriptor for the GDT which says * where it is and how big it is (the size is actually the last - * byte, not the size, hence the "-1"). */ + * byte, not the size, hence the "-1"). + */ state->host_gdt_desc.size = GDT_SIZE-1; state->host_gdt_desc.address = (long)get_cpu_gdt_table(i); - /* All CPUs on the Host use the same Interrupt Descriptor + /* + * All CPUs on the Host use the same Interrupt Descriptor * Table, so we just use store_idt(), which gets this CPU's IDT - * descriptor. */ + * descriptor. + */ store_idt(&state->host_idt_desc); - /* The descriptors for the Guest's GDT and IDT can be filled + /* + * The descriptors for the Guest's GDT and IDT can be filled * out now, too. We copy the GDT & IDT into ->guest_gdt and - * ->guest_idt before actually running the Guest. */ + * ->guest_idt before actually running the Guest. + */ state->guest_idt_desc.size = sizeof(state->guest_idt)-1; state->guest_idt_desc.address = (long)&state->guest_idt; state->guest_gdt_desc.size = sizeof(state->guest_gdt)-1; state->guest_gdt_desc.address = (long)&state->guest_gdt; - /* We know where we want the stack to be when the Guest enters + /* + * We know where we want the stack to be when the Guest enters * the Switcher: in pages->regs. The stack grows upwards, so - * we start it at the end of that structure. */ + * we start it at the end of that structure. + */ state->guest_tss.sp0 = (long)(&pages->regs + 1); - /* And this is the GDT entry to use for the stack: we keep a - * couple of special LGUEST entries. */ + /* + * And this is the GDT entry to use for the stack: we keep a + * couple of special LGUEST entries. + */ state->guest_tss.ss0 = LGUEST_DS; - /* x86 can have a finegrained bitmap which indicates what I/O + /* + * x86 can have a finegrained bitmap which indicates what I/O * ports the process can use. We set it to the end of our - * structure, meaning "none". */ + * structure, meaning "none". + */ state->guest_tss.io_bitmap_base = sizeof(state->guest_tss); - /* Some GDT entries are the same across all Guests, so we can - * set them up now. */ + /* + * Some GDT entries are the same across all Guests, so we can + * set them up now. + */ setup_default_gdt_entries(state); /* Most IDT entries are the same for all Guests, too.*/ setup_default_idt_entries(state, default_idt_entries); - /* The Host needs to be able to use the LGUEST segments on this - * CPU, too, so put them in the Host GDT. */ + /* + * The Host needs to be able to use the LGUEST segments on this + * CPU, too, so put them in the Host GDT. + */ get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT; get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT; } - /* In the Switcher, we want the %cs segment register to use the + /* + * In the Switcher, we want the %cs segment register to use the * LGUEST_CS GDT entry: we've put that in the Host and Guest GDTs, so * it will be undisturbed when we switch. To change %cs and jump we - * need this structure to feed to Intel's "lcall" instruction. */ + * need this structure to feed to Intel's "lcall" instruction. + */ lguest_entry.offset = (long)switch_to_guest + switcher_offset(); lguest_entry.segment = LGUEST_CS; - /* Finally, we need to turn off "Page Global Enable". PGE is an + /* + * Finally, we need to turn off "Page Global Enable". PGE is an * optimization where page table entries are specially marked to show * they never change. The Host kernel marks all the kernel pages this * way because it's always present, even when userspace is running. @@ -534,16 +632,21 @@ void __init lguest_arch_host_init(void) * you'll get really weird bugs that you'll chase for two days. * * I used to turn PGE off every time we switched to the Guest and back - * on when we return, but that slowed the Switcher down noticibly. */ + * on when we return, but that slowed the Switcher down noticibly. + */ - /* We don't need the complexity of CPUs coming and going while we're - * doing this. */ + /* + * We don't need the complexity of CPUs coming and going while we're + * doing this. + */ get_online_cpus(); if (cpu_has_pge) { /* We have a broader idea of "global". */ /* Remember that this was originally set (for cleanup). */ cpu_had_pge = 1; - /* adjust_pge is a helper function which sets or unsets the PGE - * bit on its CPU, depending on the argument (0 == unset). */ + /* + * adjust_pge is a helper function which sets or unsets the PGE + * bit on its CPU, depending on the argument (0 == unset). + */ on_each_cpu(adjust_pge, (void *)0, 1); /* Turn off the feature in the global feature set. */ clear_cpu_cap(&boot_cpu_data, X86_FEATURE_PGE); @@ -590,26 +693,32 @@ int lguest_arch_init_hypercalls(struct lg_cpu *cpu) { u32 tsc_speed; - /* The pointer to the Guest's "struct lguest_data" is the only argument. - * We check that address now. */ + /* + * The pointer to the Guest's "struct lguest_data" is the only argument. + * We check that address now. + */ if (!lguest_address_ok(cpu->lg, cpu->hcall->arg1, sizeof(*cpu->lg->lguest_data))) return -EFAULT; - /* Having checked it, we simply set lg->lguest_data to point straight + /* + * Having checked it, we simply set lg->lguest_data to point straight * into the Launcher's memory at the right place and then use * copy_to_user/from_user from now on, instead of lgread/write. I put * this in to show that I'm not immune to writing stupid - * optimizations. */ + * optimizations. + */ cpu->lg->lguest_data = cpu->lg->mem_base + cpu->hcall->arg1; - /* We insist that the Time Stamp Counter exist and doesn't change with + /* + * We insist that the Time Stamp Counter exist and doesn't change with * cpu frequency. Some devious chip manufacturers decided that TSC * changes could be handled in software. I decided that time going * backwards might be good for benchmarks, but it's bad for users. * * We also insist that the TSC be stable: the kernel detects unreliable - * TSCs for its own purposes, and we use that here. */ + * TSCs for its own purposes, and we use that here. + */ if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && !check_tsc_unstable()) tsc_speed = tsc_khz; else @@ -625,38 +734,47 @@ int lguest_arch_init_hypercalls(struct lg_cpu *cpu) } /*:*/ -/*L:030 lguest_arch_setup_regs() +/*L:030 + * lguest_arch_setup_regs() * * Most of the Guest's registers are left alone: we used get_zeroed_page() to - * allocate the structure, so they will be 0. */ + * allocate the structure, so they will be 0. + */ void lguest_arch_setup_regs(struct lg_cpu *cpu, unsigned long start) { struct lguest_regs *regs = cpu->regs; - /* There are four "segment" registers which the Guest needs to boot: + /* + * There are four "segment" registers which the Guest needs to boot: * The "code segment" register (cs) refers to the kernel code segment * __KERNEL_CS, and the "data", "extra" and "stack" segment registers * refer to the kernel data segment __KERNEL_DS. * * The privilege level is packed into the lower bits. The Guest runs - * at privilege level 1 (GUEST_PL).*/ + * at privilege level 1 (GUEST_PL). + */ regs->ds = regs->es = regs->ss = __KERNEL_DS|GUEST_PL; regs->cs = __KERNEL_CS|GUEST_PL; - /* The "eflags" register contains miscellaneous flags. Bit 1 (0x002) + /* + * The "eflags" register contains miscellaneous flags. Bit 1 (0x002) * is supposed to always be "1". Bit 9 (0x200) controls whether * interrupts are enabled. We always leave interrupts enabled while - * running the Guest. */ + * running the Guest. + */ regs->eflags = X86_EFLAGS_IF | 0x2; - /* The "Extended Instruction Pointer" register says where the Guest is - * running. */ + /* + * The "Extended Instruction Pointer" register says where the Guest is + * running. + */ regs->eip = start; - /* %esi points to our boot information, at physical address 0, so don't - * touch it. */ + /* + * %esi points to our boot information, at physical address 0, so don't + * touch it. + */ - /* There are a couple of GDT entries the Guest expects when first - * booting. */ + /* There are a couple of GDT entries the Guest expects at boot. */ setup_guest_gdt(cpu); } diff --git a/drivers/lguest/x86/switcher_32.S b/drivers/lguest/x86/switcher_32.S index 3fc1531..40634b0 100644 --- a/drivers/lguest/x86/switcher_32.S +++ b/drivers/lguest/x86/switcher_32.S @@ -1,12 +1,15 @@ -/*P:900 This is the Switcher: code which sits at 0xFFC00000 astride both the - * Host and Guest to do the low-level Guest<->Host switch. It is as simple as - * it can be made, but it's naturally very specific to x86. +/*P:900 + * This is the Switcher: code which sits at 0xFFC00000 (or 0xFFE00000) astride + * both the Host and Guest to do the low-level Guest<->Host switch. It is as + * simple as it can be made, but it's naturally very specific to x86. * * You have now completed Preparation. If this has whet your appetite; if you * are feeling invigorated and refreshed then the next, more challenging stage - * can be found in "make Guest". :*/ + * can be found in "make Guest". + :*/ -/*M:012 Lguest is meant to be simple: my rule of thumb is that 1% more LOC must +/*M:012 + * Lguest is meant to be simple: my rule of thumb is that 1% more LOC must * gain at least 1% more performance. Since neither LOC nor performance can be * measured beforehand, it generally means implementing a feature then deciding * if it's worth it. And once it's implemented, who can say no? @@ -31,11 +34,14 @@ * Host (which is actually really easy). * * Two questions remain. Would the performance gain outweigh the complexity? - * And who would write the verse documenting it? :*/ + * And who would write the verse documenting it? +:*/ -/*M:011 Lguest64 handles NMI. This gave me NMI envy (until I looked at their +/*M:011 + * Lguest64 handles NMI. This gave me NMI envy (until I looked at their * code). It's worth doing though, since it would let us use oprofile in the - * Host when a Guest is running. :*/ + * Host when a Guest is running. +:*/ /*S:100 * Welcome to the Switcher itself! |