uprobes: Teach find_active_uprobe() to provide the "is_swbp" info (d790d346) · Commits · 戴 / test

A separate patch to simplify the review, and for the documentation. The patch adds another "int *is_swbp" argument to find_active_uprobe(), so far its only caller doesn't use this info. With this patch find_active_uprobe() additionally does: - if find_vma() + ->vm_start check fails, *is_swbp = -EFAULT - otherwise, if valid_vma() + find_uprobe() fails, it holds the result of is_swbp_at_addr(), can be negative too. The latter is only possible if we raced with another thread which did munmap/etc after we hit this bp. IOW. If find_active_uprobe(&is_swbp) returns NULL, the caller can look at is_swbp to figure out whether the current insn is bp or not, or detect the race with another thread if it is negative. Note: I think that performance-wise this change is fine. This adds is_swbp_at_addr(), but only if we raced with uprobe_unregister() or if we hit the "normal" int3 but this mm has uprobes as well. And even in this case the slow read_opcode() path is very unlikely, this insn recently triggered do_int3(), __copy_from_user_inatomic() shouldn't fail in the likely case. Signed-off-by:

Oleg Nesterov <oleg@redhat.com> Acked-by:

Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Anton Arapov <anton@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120529192914.GD8057@redhat.com Signed-off-by:

Ingo Molnar <mingo@kernel.org>

kernel/events/uprobes.c

+8 −3

Original line number	Original line	Diff line number	Diff line
	@@ -1489,7 +1489,7 @@ static bool can_skip_sstep(struct uprobe uprobe, struct pt_regs regs)
	return false;		return false;
	}		}

	static struct uprobe *find_active_uprobe(unsigned long bp_vaddr)		static struct uprobe find_active_uprobe(unsigned long bp_vaddr, int is_swbp)
	{		{
	struct mm_struct *mm = current->mm;		struct mm_struct *mm = current->mm;
	struct uprobe *uprobe = NULL;		struct uprobe *uprobe = NULL;
	@@ -1497,7 +1497,6 @@ static struct uprobe *find_active_uprobe(unsigned long bp_vaddr)

	down_read(&mm->mmap_sem);		down_read(&mm->mmap_sem);
	vma = find_vma(mm, bp_vaddr);		vma = find_vma(mm, bp_vaddr);

	if (vma && vma->vm_start <= bp_vaddr) {		if (vma && vma->vm_start <= bp_vaddr) {
	if (valid_vma(vma, false)) {		if (valid_vma(vma, false)) {
	struct inode *inode;		struct inode *inode;
	@@ -1508,6 +1507,11 @@ static struct uprobe *find_active_uprobe(unsigned long bp_vaddr)
	offset += (vma->vm_pgoff << PAGE_SHIFT);		offset += (vma->vm_pgoff << PAGE_SHIFT);
	uprobe = find_uprobe(inode, offset);		uprobe = find_uprobe(inode, offset);
	}		}

			if (!uprobe)
			*is_swbp = is_swbp_at_addr(mm, bp_vaddr);
			} else {
			*is_swbp = -EFAULT;
	}		}

	srcu_read_unlock_raw(&uprobes_srcu, current->uprobe_srcu_id);		srcu_read_unlock_raw(&uprobes_srcu, current->uprobe_srcu_id);
	@@ -1526,9 +1530,10 @@ static void handle_swbp(struct pt_regs *regs)
	struct uprobe_task *utask;		struct uprobe_task *utask;
	struct uprobe *uprobe;		struct uprobe *uprobe;
	unsigned long bp_vaddr;		unsigned long bp_vaddr;
			int is_swbp;

	bp_vaddr = uprobe_get_swbp_addr(regs);		bp_vaddr = uprobe_get_swbp_addr(regs);
	uprobe = find_active_uprobe(bp_vaddr);		uprobe = find_active_uprobe(bp_vaddr, &is_swbp);

	if (!uprobe) {		if (!uprobe) {
	/* No matching uprobe; signal SIGTRAP. */		/* No matching uprobe; signal SIGTRAP. */

Admin message