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Commit 3a9ea052 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
Browse files

uprobes: Introduce find_active_uprobe() helper 



No functional changes. Move the "find uprobe" code from
handle_swbp() to the new helper, find_active_uprobe().

Note: with or without this change, the find-active-uprobe logic
is not exactly right. We can race with another thread which
unmaps the memory with the valid uprobe before we take
mm->mmap_sem. We can't find this uprobe simply because
find_vma() fails. In this case we wrongly assume that this trap
was not caused by uprobe and send the erroneous SIGTRAP. See the
next changes.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarSrikar 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/20120529192857.GC8057@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent a3d7bb47

kernel/events/uprobes.c

+28 −19
Original line number Diff line number Diff line
@@ -1489,25 +1489,17 @@ static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs) 
	return false;

}



/*

 * Run handler and ask thread to singlestep.

 * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.

 */

static void handle_swbp(struct pt_regs *regs)

static struct uprobe *find_active_uprobe(unsigned long bp_vaddr)

{

	struct mm_struct *mm = current->mm;

	struct uprobe *uprobe = NULL;

	struct vm_area_struct *vma;

	struct uprobe_task *utask;

	struct uprobe *uprobe;

	struct mm_struct *mm;

	unsigned long bp_vaddr;



	uprobe = NULL;

	bp_vaddr = uprobe_get_swbp_addr(regs);

	mm = current->mm;

	down_read(&mm->mmap_sem);

	vma = find_vma(mm, bp_vaddr);



	if (vma && vma->vm_start <= bp_vaddr && valid_vma(vma, false)) {

	if (vma && vma->vm_start <= bp_vaddr) {

		if (valid_vma(vma, false)) {

			struct inode *inode;

			loff_t offset;
@@ -1516,11 +1508,28 @@ static void handle_swbp(struct pt_regs *regs) 
			offset += (vma->vm_pgoff << PAGE_SHIFT);

			uprobe = find_uprobe(inode, offset);

		}

	}



	srcu_read_unlock_raw(&uprobes_srcu, current->uprobe_srcu_id);

	current->uprobe_srcu_id = -1;

	up_read(&mm->mmap_sem);



	return uprobe;

}



/*

 * Run handler and ask thread to singlestep.

 * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.

 */

static void handle_swbp(struct pt_regs *regs)

{

	struct uprobe_task *utask;

	struct uprobe *uprobe;

	unsigned long bp_vaddr;



	bp_vaddr = uprobe_get_swbp_addr(regs);

	uprobe = find_active_uprobe(bp_vaddr);



	if (!uprobe) {

		/* No matching uprobe; signal SIGTRAP. */

		send_sig(SIGTRAP, current, 0);