diff options
Diffstat (limited to 'arch/x86/xen/xen-asm_64.S')
| -rw-r--r-- | arch/x86/xen/xen-asm_64.S | 285 |
1 files changed, 285 insertions, 0 deletions
diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S new file mode 100644 index 0000000..05794c5 --- /dev/null +++ b/arch/x86/xen/xen-asm_64.S @@ -0,0 +1,285 @@ +/* + Asm versions of Xen pv-ops, suitable for either direct use or inlining. + The inline versions are the same as the direct-use versions, with the + pre- and post-amble chopped off. + + This code is encoded for size rather than absolute efficiency, + with a view to being able to inline as much as possible. + + We only bother with direct forms (ie, vcpu in pda) of the operations + here; the indirect forms are better handled in C, since they're + generally too large to inline anyway. + */ + +#include <linux/linkage.h> + +#include <asm/asm-offsets.h> +#include <asm/processor-flags.h> +#include <asm/errno.h> +#include <asm/segment.h> + +#include <xen/interface/xen.h> + +#define RELOC(x, v) .globl x##_reloc; x##_reloc=v +#define ENDPATCH(x) .globl x##_end; x##_end=. + +/* Pseudo-flag used for virtual NMI, which we don't implement yet */ +#define XEN_EFLAGS_NMI 0x80000000 + +#if 1 +/* + x86-64 does not yet support direct access to percpu variables + via a segment override, so we just need to make sure this code + never gets used + */ +#define BUG ud2a +#define PER_CPU_VAR(var, off) 0xdeadbeef +#endif + +/* + Enable events. This clears the event mask and tests the pending + event status with one and operation. If there are pending + events, then enter the hypervisor to get them handled. + */ +ENTRY(xen_irq_enable_direct) + BUG + + /* Unmask events */ + movb $0, PER_CPU_VAR(xen_vcpu_info, XEN_vcpu_info_mask) + + /* Preempt here doesn't matter because that will deal with + any pending interrupts. The pending check may end up being + run on the wrong CPU, but that doesn't hurt. */ + + /* Test for pending */ + testb $0xff, PER_CPU_VAR(xen_vcpu_info, XEN_vcpu_info_pending) + jz 1f + +2: call check_events +1: +ENDPATCH(xen_irq_enable_direct) + ret + ENDPROC(xen_irq_enable_direct) + RELOC(xen_irq_enable_direct, 2b+1) + +/* + Disabling events is simply a matter of making the event mask + non-zero. + */ +ENTRY(xen_irq_disable_direct) + BUG + + movb $1, PER_CPU_VAR(xen_vcpu_info, XEN_vcpu_info_mask) +ENDPATCH(xen_irq_disable_direct) + ret + ENDPROC(xen_irq_disable_direct) + RELOC(xen_irq_disable_direct, 0) + +/* + (xen_)save_fl is used to get the current interrupt enable status. + Callers expect the status to be in X86_EFLAGS_IF, and other bits + may be set in the return value. We take advantage of this by + making sure that X86_EFLAGS_IF has the right value (and other bits + in that byte are 0), but other bits in the return value are + undefined. We need to toggle the state of the bit, because + Xen and x86 use opposite senses (mask vs enable). + */ +ENTRY(xen_save_fl_direct) + BUG + + testb $0xff, PER_CPU_VAR(xen_vcpu_info, XEN_vcpu_info_mask) + setz %ah + addb %ah,%ah +ENDPATCH(xen_save_fl_direct) + ret + ENDPROC(xen_save_fl_direct) + RELOC(xen_save_fl_direct, 0) + +/* + In principle the caller should be passing us a value return + from xen_save_fl_direct, but for robustness sake we test only + the X86_EFLAGS_IF flag rather than the whole byte. After + setting the interrupt mask state, it checks for unmasked + pending events and enters the hypervisor to get them delivered + if so. + */ +ENTRY(xen_restore_fl_direct) + BUG + + testb $X86_EFLAGS_IF>>8, %ah + setz PER_CPU_VAR(xen_vcpu_info, XEN_vcpu_info_mask) + /* Preempt here doesn't matter because that will deal with + any pending interrupts. The pending check may end up being + run on the wrong CPU, but that doesn't hurt. */ + + /* check for unmasked and pending */ + cmpw $0x0001, PER_CPU_VAR(xen_vcpu_info, XEN_vcpu_info_pending) + jz 1f +2: call check_events +1: +ENDPATCH(xen_restore_fl_direct) + ret + ENDPROC(xen_restore_fl_direct) + RELOC(xen_restore_fl_direct, 2b+1) + + +/* + Force an event check by making a hypercall, + but preserve regs before making the call. + */ +check_events: + push %rax + push %rcx + push %rdx + push %rsi + push %rdi + push %r8 + push %r9 + push %r10 + push %r11 + call xen_force_evtchn_callback + pop %r11 + pop %r10 + pop %r9 + pop %r8 + pop %rdi + pop %rsi + pop %rdx + pop %rcx + pop %rax + ret + +ENTRY(xen_adjust_exception_frame) + mov 8+0(%rsp),%rcx + mov 8+8(%rsp),%r11 + ret $16 + +hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32 +/* + Xen64 iret frame: + + ss + rsp + rflags + cs + rip <-- standard iret frame + + flags + + rcx } + r11 }<-- pushed by hypercall page +rsp -> rax } + */ +ENTRY(xen_iret) + pushq $0 +1: jmp hypercall_iret +ENDPATCH(xen_iret) +RELOC(xen_iret, 1b+1) + +/* + sysexit is not used for 64-bit processes, so it's + only ever used to return to 32-bit compat userspace. + */ +ENTRY(xen_sysexit) + pushq $__USER32_DS + pushq %rcx + pushq $X86_EFLAGS_IF + pushq $__USER32_CS + pushq %rdx + + pushq $0 +1: jmp hypercall_iret +ENDPATCH(xen_sysexit) +RELOC(xen_sysexit, 1b+1) + +ENTRY(xen_sysret64) + /* We're already on the usermode stack at this point, but still + with the kernel gs, so we can easily switch back */ + movq %rsp, %gs:pda_oldrsp + movq %gs:pda_kernelstack,%rsp + + pushq $__USER_DS + pushq %gs:pda_oldrsp + pushq %r11 + pushq $__USER_CS + pushq %rcx + + pushq $VGCF_in_syscall +1: jmp hypercall_iret +ENDPATCH(xen_sysret64) +RELOC(xen_sysret64, 1b+1) + +ENTRY(xen_sysret32) + /* We're already on the usermode stack at this point, but still + with the kernel gs, so we can easily switch back */ + movq %rsp, %gs:pda_oldrsp + movq %gs:pda_kernelstack, %rsp + + pushq $__USER32_DS + pushq %gs:pda_oldrsp + pushq %r11 + pushq $__USER32_CS + pushq %rcx + + pushq $VGCF_in_syscall +1: jmp hypercall_iret +ENDPATCH(xen_sysret32) +RELOC(xen_sysret32, 1b+1) + +/* + Xen handles syscall callbacks much like ordinary exceptions, + which means we have: + - kernel gs + - kernel rsp + - an iret-like stack frame on the stack (including rcx and r11): + ss + rsp + rflags + cs + rip + r11 + rsp-> rcx + + In all the entrypoints, we undo all that to make it look + like a CPU-generated syscall/sysenter and jump to the normal + entrypoint. + */ + +.macro undo_xen_syscall + mov 0*8(%rsp),%rcx + mov 1*8(%rsp),%r11 + mov 5*8(%rsp),%rsp +.endm + +/* Normal 64-bit system call target */ +ENTRY(xen_syscall_target) + undo_xen_syscall + jmp system_call_after_swapgs +ENDPROC(xen_syscall_target) + +#ifdef CONFIG_IA32_EMULATION + +/* 32-bit compat syscall target */ +ENTRY(xen_syscall32_target) + undo_xen_syscall + jmp ia32_cstar_target +ENDPROC(xen_syscall32_target) + +/* 32-bit compat sysenter target */ +ENTRY(xen_sysenter_target) + undo_xen_syscall + jmp ia32_sysenter_target +ENDPROC(xen_sysenter_target) + +#else /* !CONFIG_IA32_EMULATION */ + +ENTRY(xen_syscall32_target) +ENTRY(xen_sysenter_target) + lea 16(%rsp), %rsp /* strip %rcx,%r11 */ + mov $-ENOSYS, %rax + pushq $VGCF_in_syscall + jmp hypercall_iret +ENDPROC(xen_syscall32_target) +ENDPROC(xen_sysenter_target) + +#endif /* CONFIG_IA32_EMULATION */ |