diff options
author | Ingo Molnar <mingo@kernel.org> | 2012-10-21 16:18:17 (GMT) |
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committer | Ingo Molnar <mingo@kernel.org> | 2012-10-21 16:18:17 (GMT) |
commit | f38787f4f921222d080d976ef59210ce3c6c6cb4 (patch) | |
tree | 55e643bc1e5b066f04323a4054fdc814726221be /kernel/events/uprobes.c | |
parent | 957b9095ed296311b36d26e4316d7f637351ac57 (diff) | |
parent | 71434f2fcba5c22d6e0d51878ba8e241a5dea5fb (diff) | |
download | linux-f38787f4f921222d080d976ef59210ce3c6c6cb4.tar.xz |
Merge branch 'uprobes/core' of git://git.kernel.org/pub/scm/linux/kernel/git/oleg/misc into perf/urgent
Pull various uprobes bugfixes from Oleg Nesterov - mostly race and
failure path fixes.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events/uprobes.c')
-rw-r--r-- | kernel/events/uprobes.c | 345 |
1 files changed, 162 insertions, 183 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 98256bc..5cc4e7e 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -78,15 +78,23 @@ static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ]; */ static atomic_t uprobe_events = ATOMIC_INIT(0); +/* Have a copy of original instruction */ +#define UPROBE_COPY_INSN 0 +/* Dont run handlers when first register/ last unregister in progress*/ +#define UPROBE_RUN_HANDLER 1 +/* Can skip singlestep */ +#define UPROBE_SKIP_SSTEP 2 + struct uprobe { struct rb_node rb_node; /* node in the rb tree */ atomic_t ref; struct rw_semaphore consumer_rwsem; + struct mutex copy_mutex; /* TODO: kill me and UPROBE_COPY_INSN */ struct list_head pending_list; struct uprobe_consumer *consumers; struct inode *inode; /* Also hold a ref to inode */ loff_t offset; - int flags; + unsigned long flags; struct arch_uprobe arch; }; @@ -100,17 +108,12 @@ struct uprobe { */ static bool valid_vma(struct vm_area_struct *vma, bool is_register) { - if (!vma->vm_file) - return false; - - if (!is_register) - return true; + vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_SHARED; - if ((vma->vm_flags & (VM_HUGETLB|VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)) - == (VM_READ|VM_EXEC)) - return true; + if (is_register) + flags |= VM_WRITE; - return false; + return vma->vm_file && (vma->vm_flags & flags) == VM_MAYEXEC; } static unsigned long offset_to_vaddr(struct vm_area_struct *vma, loff_t offset) @@ -193,19 +196,44 @@ bool __weak is_swbp_insn(uprobe_opcode_t *insn) return *insn == UPROBE_SWBP_INSN; } +static void copy_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *opcode) +{ + void *kaddr = kmap_atomic(page); + memcpy(opcode, kaddr + (vaddr & ~PAGE_MASK), UPROBE_SWBP_INSN_SIZE); + kunmap_atomic(kaddr); +} + +static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode) +{ + uprobe_opcode_t old_opcode; + bool is_swbp; + + copy_opcode(page, vaddr, &old_opcode); + is_swbp = is_swbp_insn(&old_opcode); + + if (is_swbp_insn(new_opcode)) { + if (is_swbp) /* register: already installed? */ + return 0; + } else { + if (!is_swbp) /* unregister: was it changed by us? */ + return 0; + } + + return 1; +} + /* * NOTE: * Expect the breakpoint instruction to be the smallest size instruction for * the architecture. If an arch has variable length instruction and the * breakpoint instruction is not of the smallest length instruction - * supported by that architecture then we need to modify read_opcode / + * supported by that architecture then we need to modify is_swbp_at_addr and * write_opcode accordingly. This would never be a problem for archs that * have fixed length instructions. */ /* * write_opcode - write the opcode at a given virtual address. - * @auprobe: arch breakpointing information. * @mm: the probed process address space. * @vaddr: the virtual address to store the opcode. * @opcode: opcode to be written at @vaddr. @@ -216,8 +244,8 @@ bool __weak is_swbp_insn(uprobe_opcode_t *insn) * For mm @mm, write the opcode at @vaddr. * Return 0 (success) or a negative errno. */ -static int write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, - unsigned long vaddr, uprobe_opcode_t opcode) +static int write_opcode(struct mm_struct *mm, unsigned long vaddr, + uprobe_opcode_t opcode) { struct page *old_page, *new_page; void *vaddr_old, *vaddr_new; @@ -226,10 +254,14 @@ static int write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, retry: /* Read the page with vaddr into memory */ - ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &old_page, &vma); + ret = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &old_page, &vma); if (ret <= 0) return ret; + ret = verify_opcode(old_page, vaddr, &opcode); + if (ret <= 0) + goto put_old; + ret = -ENOMEM; new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr); if (!new_page) @@ -264,63 +296,6 @@ put_old: } /** - * read_opcode - read the opcode at a given virtual address. - * @mm: the probed process address space. - * @vaddr: the virtual address to read the opcode. - * @opcode: location to store the read opcode. - * - * Called with mm->mmap_sem held (for read and with a reference to - * mm. - * - * For mm @mm, read the opcode at @vaddr and store it in @opcode. - * Return 0 (success) or a negative errno. - */ -static int read_opcode(struct mm_struct *mm, unsigned long vaddr, uprobe_opcode_t *opcode) -{ - struct page *page; - void *vaddr_new; - int ret; - - ret = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL); - if (ret <= 0) - return ret; - - vaddr_new = kmap_atomic(page); - vaddr &= ~PAGE_MASK; - memcpy(opcode, vaddr_new + vaddr, UPROBE_SWBP_INSN_SIZE); - kunmap_atomic(vaddr_new); - - put_page(page); - - return 0; -} - -static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr) -{ - uprobe_opcode_t opcode; - int result; - - if (current->mm == mm) { - pagefault_disable(); - result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr, - sizeof(opcode)); - pagefault_enable(); - - if (likely(result == 0)) - goto out; - } - - result = read_opcode(mm, vaddr, &opcode); - if (result) - return result; -out: - if (is_swbp_insn(&opcode)) - return 1; - - return 0; -} - -/** * set_swbp - store breakpoint at a given address. * @auprobe: arch specific probepoint information. * @mm: the probed process address space. @@ -331,18 +306,7 @@ out: */ int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr) { - int result; - /* - * See the comment near uprobes_hash(). - */ - result = is_swbp_at_addr(mm, vaddr); - if (result == 1) - return 0; - - if (result) - return result; - - return write_opcode(auprobe, mm, vaddr, UPROBE_SWBP_INSN); + return write_opcode(mm, vaddr, UPROBE_SWBP_INSN); } /** @@ -357,16 +321,7 @@ int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned int __weak set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr) { - int result; - - result = is_swbp_at_addr(mm, vaddr); - if (!result) - return -EINVAL; - - if (result != 1) - return result; - - return write_opcode(auprobe, mm, vaddr, *(uprobe_opcode_t *)auprobe->insn); + return write_opcode(mm, vaddr, *(uprobe_opcode_t *)auprobe->insn); } static int match_uprobe(struct uprobe *l, struct uprobe *r) @@ -473,7 +428,7 @@ static struct uprobe *insert_uprobe(struct uprobe *uprobe) spin_unlock(&uprobes_treelock); /* For now assume that the instruction need not be single-stepped */ - uprobe->flags |= UPROBE_SKIP_SSTEP; + __set_bit(UPROBE_SKIP_SSTEP, &uprobe->flags); return u; } @@ -495,6 +450,7 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset) uprobe->inode = igrab(inode); uprobe->offset = offset; init_rwsem(&uprobe->consumer_rwsem); + mutex_init(&uprobe->copy_mutex); /* add to uprobes_tree, sorted on inode:offset */ cur_uprobe = insert_uprobe(uprobe); @@ -515,7 +471,7 @@ static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs) { struct uprobe_consumer *uc; - if (!(uprobe->flags & UPROBE_RUN_HANDLER)) + if (!test_bit(UPROBE_RUN_HANDLER, &uprobe->flags)) return; down_read(&uprobe->consumer_rwsem); @@ -621,29 +577,43 @@ static int copy_insn(struct uprobe *uprobe, struct file *filp) return __copy_insn(mapping, filp, uprobe->arch.insn, bytes, uprobe->offset); } -/* - * How mm->uprobes_state.count gets updated - * uprobe_mmap() increments the count if - * - it successfully adds a breakpoint. - * - it cannot add a breakpoint, but sees that there is a underlying - * breakpoint (via a is_swbp_at_addr()). - * - * uprobe_munmap() decrements the count if - * - it sees a underlying breakpoint, (via is_swbp_at_addr) - * (Subsequent uprobe_unregister wouldnt find the breakpoint - * unless a uprobe_mmap kicks in, since the old vma would be - * dropped just after uprobe_munmap.) - * - * uprobe_register increments the count if: - * - it successfully adds a breakpoint. - * - * uprobe_unregister decrements the count if: - * - it sees a underlying breakpoint and removes successfully. - * (via is_swbp_at_addr) - * (Subsequent uprobe_munmap wouldnt find the breakpoint - * since there is no underlying breakpoint after the - * breakpoint removal.) - */ +static int prepare_uprobe(struct uprobe *uprobe, struct file *file, + struct mm_struct *mm, unsigned long vaddr) +{ + int ret = 0; + + if (test_bit(UPROBE_COPY_INSN, &uprobe->flags)) + return ret; + + mutex_lock(&uprobe->copy_mutex); + if (test_bit(UPROBE_COPY_INSN, &uprobe->flags)) + goto out; + + ret = copy_insn(uprobe, file); + if (ret) + goto out; + + ret = -ENOTSUPP; + if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn)) + goto out; + + ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr); + if (ret) + goto out; + + /* write_opcode() assumes we don't cross page boundary */ + BUG_ON((uprobe->offset & ~PAGE_MASK) + + UPROBE_SWBP_INSN_SIZE > PAGE_SIZE); + + smp_wmb(); /* pairs with rmb() in find_active_uprobe() */ + set_bit(UPROBE_COPY_INSN, &uprobe->flags); + + out: + mutex_unlock(&uprobe->copy_mutex); + + return ret; +} + static int install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, struct vm_area_struct *vma, unsigned long vaddr) @@ -661,24 +631,9 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, if (!uprobe->consumers) return 0; - if (!(uprobe->flags & UPROBE_COPY_INSN)) { - ret = copy_insn(uprobe, vma->vm_file); - if (ret) - return ret; - - if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn)) - return -ENOTSUPP; - - ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr); - if (ret) - return ret; - - /* write_opcode() assumes we don't cross page boundary */ - BUG_ON((uprobe->offset & ~PAGE_MASK) + - UPROBE_SWBP_INSN_SIZE > PAGE_SIZE); - - uprobe->flags |= UPROBE_COPY_INSN; - } + ret = prepare_uprobe(uprobe, vma->vm_file, mm, vaddr); + if (ret) + return ret; /* * set MMF_HAS_UPROBES in advance for uprobe_pre_sstep_notifier(), @@ -697,15 +652,15 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, return ret; } -static void +static int remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vaddr) { /* can happen if uprobe_register() fails */ if (!test_bit(MMF_HAS_UPROBES, &mm->flags)) - return; + return 0; set_bit(MMF_RECALC_UPROBES, &mm->flags); - set_orig_insn(&uprobe->arch, mm, vaddr); + return set_orig_insn(&uprobe->arch, mm, vaddr); } /* @@ -820,7 +775,7 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register) struct mm_struct *mm = info->mm; struct vm_area_struct *vma; - if (err) + if (err && is_register) goto free; down_write(&mm->mmap_sem); @@ -836,7 +791,7 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register) if (is_register) err = install_breakpoint(uprobe, mm, vma, info->vaddr); else - remove_breakpoint(uprobe, mm, info->vaddr); + err |= remove_breakpoint(uprobe, mm, info->vaddr); unlock: up_write(&mm->mmap_sem); @@ -893,13 +848,15 @@ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer * mutex_lock(uprobes_hash(inode)); uprobe = alloc_uprobe(inode, offset); - if (uprobe && !consumer_add(uprobe, uc)) { + if (!uprobe) { + ret = -ENOMEM; + } else if (!consumer_add(uprobe, uc)) { ret = __uprobe_register(uprobe); if (ret) { uprobe->consumers = NULL; __uprobe_unregister(uprobe); } else { - uprobe->flags |= UPROBE_RUN_HANDLER; + set_bit(UPROBE_RUN_HANDLER, &uprobe->flags); } } @@ -932,7 +889,7 @@ void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consume if (consumer_del(uprobe, uc)) { if (!uprobe->consumers) { __uprobe_unregister(uprobe); - uprobe->flags &= ~UPROBE_RUN_HANDLER; + clear_bit(UPROBE_RUN_HANDLER, &uprobe->flags); } } @@ -1393,10 +1350,11 @@ bool uprobe_deny_signal(void) */ static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs) { - if (arch_uprobe_skip_sstep(&uprobe->arch, regs)) - return true; - - uprobe->flags &= ~UPROBE_SKIP_SSTEP; + if (test_bit(UPROBE_SKIP_SSTEP, &uprobe->flags)) { + if (arch_uprobe_skip_sstep(&uprobe->arch, regs)) + return true; + clear_bit(UPROBE_SKIP_SSTEP, &uprobe->flags); + } return false; } @@ -1419,6 +1377,30 @@ static void mmf_recalc_uprobes(struct mm_struct *mm) clear_bit(MMF_HAS_UPROBES, &mm->flags); } +static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr) +{ + struct page *page; + uprobe_opcode_t opcode; + int result; + + pagefault_disable(); + result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr, + sizeof(opcode)); + pagefault_enable(); + + if (likely(result == 0)) + goto out; + + result = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL); + if (result < 0) + return result; + + copy_opcode(page, vaddr, &opcode); + put_page(page); + out: + return is_swbp_insn(&opcode); +} + static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp) { struct mm_struct *mm = current->mm; @@ -1489,38 +1471,41 @@ static void handle_swbp(struct pt_regs *regs) } return; } + /* + * TODO: move copy_insn/etc into _register and remove this hack. + * After we hit the bp, _unregister + _register can install the + * new and not-yet-analyzed uprobe at the same address, restart. + */ + smp_rmb(); /* pairs with wmb() in install_breakpoint() */ + if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags))) + goto restart; utask = current->utask; if (!utask) { utask = add_utask(); /* Cannot allocate; re-execute the instruction. */ if (!utask) - goto cleanup_ret; + goto restart; } - utask->active_uprobe = uprobe; + handler_chain(uprobe, regs); - if (uprobe->flags & UPROBE_SKIP_SSTEP && can_skip_sstep(uprobe, regs)) - goto cleanup_ret; + if (can_skip_sstep(uprobe, regs)) + goto out; - utask->state = UTASK_SSTEP; if (!pre_ssout(uprobe, regs, bp_vaddr)) { arch_uprobe_enable_step(&uprobe->arch); + utask->active_uprobe = uprobe; + utask->state = UTASK_SSTEP; return; } -cleanup_ret: - if (utask) { - utask->active_uprobe = NULL; - utask->state = UTASK_RUNNING; - } - if (!(uprobe->flags & UPROBE_SKIP_SSTEP)) - - /* - * cannot singlestep; cannot skip instruction; - * re-execute the instruction. - */ - instruction_pointer_set(regs, bp_vaddr); - +restart: + /* + * cannot singlestep; cannot skip instruction; + * re-execute the instruction. + */ + instruction_pointer_set(regs, bp_vaddr); +out: put_uprobe(uprobe); } @@ -1552,13 +1537,12 @@ static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs) } /* - * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag. (and on - * subsequent probe hits on the thread sets the state to UTASK_BP_HIT) and - * allows the thread to return from interrupt. + * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag and + * allows the thread to return from interrupt. After that handle_swbp() + * sets utask->active_uprobe. * - * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag and - * also sets the state to UTASK_SSTEP_ACK and allows the thread to return from - * interrupt. + * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag + * and allows the thread to return from interrupt. * * While returning to userspace, thread notices the TIF_UPROBE flag and calls * uprobe_notify_resume(). @@ -1567,11 +1551,13 @@ void uprobe_notify_resume(struct pt_regs *regs) { struct uprobe_task *utask; + clear_thread_flag(TIF_UPROBE); + utask = current->utask; - if (!utask || utask->state == UTASK_BP_HIT) - handle_swbp(regs); - else + if (utask && utask->active_uprobe) handle_singlestep(utask, regs); + else + handle_swbp(regs); } /* @@ -1580,17 +1566,10 @@ void uprobe_notify_resume(struct pt_regs *regs) */ int uprobe_pre_sstep_notifier(struct pt_regs *regs) { - struct uprobe_task *utask; - if (!current->mm || !test_bit(MMF_HAS_UPROBES, ¤t->mm->flags)) return 0; - utask = current->utask; - if (utask) - utask->state = UTASK_BP_HIT; - set_thread_flag(TIF_UPROBE); - return 1; } |