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uprobes: Introduce find_active_uprobe() helper

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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: Oleg Nesterov <[email protected]>
Acked-by: Srikar Dronamraju <[email protected]>
Cc: Ananth N Mavinakayanahalli <[email protected]>
Cc: Anton Arapov <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Oleg Nesterov 2012-05-29 21:28:57 +02:00 • committed by Ingo Molnar
commit 3a9ea0520f
1 changed files with 28 additions and 19 deletions
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49
kernel/events/uprobes.c
View file

@ -1489,37 +1489,46 @@ static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs)
return false;
}
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;
down_read(&mm->mmap_sem);
vma = find_vma(mm, bp_vaddr);
if (vma && vma->vm_start <= bp_vaddr) {
if (valid_vma(vma, false)) {
struct inode *inode;
loff_t offset;
inode = vma->vm_file->f_mapping->host;
offset = bp_vaddr - vma->vm_start;
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 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)) {
struct inode *inode;
loff_t offset;
inode = vma->vm_file->f_mapping->host;
offset = bp_vaddr - vma->vm_start;
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);
uprobe = find_active_uprobe(bp_vaddr);
if (!uprobe) {
/* No matching uprobe; signal SIGTRAP. */