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Subject[tip:perf/core] uprobes: Teach find_active_uprobe() to provide the "is_swbp" info
Commit-ID:  d790d34653ab20c74034902f5f0889bba807949a
Author: Oleg Nesterov <>
AuthorDate: Tue, 29 May 2012 21:29:14 +0200
Committer: Ingo Molnar <>
CommitDate: Wed, 6 Jun 2012 17:15:24 +0200

uprobes: Teach find_active_uprobe() to provide the "is_swbp" info

A separate patch to simplify the review, and for the

The patch adds another "int *is_swbp" argument to
find_active_uprobe(), so far its only caller doesn't use this

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

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 <>
Acked-by: Srikar Dronamraju <>
Cc: Ananth N Mavinakayanahalli <>
Cc: Anton Arapov <>
Cc: Linus Torvalds <>
Cc: Masami Hiramatsu <>
Cc: Peter Zijlstra <>
Signed-off-by: Ingo Molnar <>
kernel/events/uprobes.c | 11 ++++++++---
1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index eaf4d55..ee3df70 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1489,7 +1489,7 @@ static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs)
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 uprobe *uprobe = NULL;
@@ -1497,7 +1497,6 @@ static struct uprobe *find_active_uprobe(unsigned long bp_vaddr)

vma = find_vma(mm, bp_vaddr);
if (vma && vma->vm_start <= bp_vaddr) {
if (valid_vma(vma, false)) {
struct inode *inode;
@@ -1508,6 +1507,11 @@ static struct uprobe *find_active_uprobe(unsigned long bp_vaddr)
offset += (vma->vm_pgoff << PAGE_SHIFT);
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);
@@ -1526,9 +1530,10 @@ static void handle_swbp(struct pt_regs *regs)
struct uprobe_task *utask;
struct uprobe *uprobe;
unsigned long bp_vaddr;
+ int is_swbp;

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

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

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