[tip:perf/uprobes] uprobes/core: Decrement uprobe count before the pages are unmapped
From: tip-bot for Srikar Dronamraju
Date: Sat Apr 14 2012 - 14:26:29 EST
Commit-ID: cbc91f71b51b8335f1fc7ccfca8011f31a717367
Gitweb: http://git.kernel.org/tip/cbc91f71b51b8335f1fc7ccfca8011f31a717367
Author: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
AuthorDate: Wed, 11 Apr 2012 16:05:27 +0530
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Sat, 14 Apr 2012 13:25:48 +0200
uprobes/core: Decrement uprobe count before the pages are unmapped
Uprobes has a callback (uprobe_munmap()) in the unmap path to
maintain the uprobes count.
In the exit path this callback gets called in unlink_file_vma().
However by the time unlink_file_vma() is called, the pages would
have been unmapped (in unmap_vmas()) and the task->rss_stat counts
accounted (in zap_pte_range()).
If the exiting process has probepoints, uprobe_munmap() checks if
the breakpoint instruction was around before decrementing the probe
count.
This results in a file backed page being reread by uprobe_munmap()
and hence it does not find the breakpoint.
This patch fixes this problem by moving the callback to
unmap_single_vma(). Since unmap_single_vma() may not unmap the
complete vma, add start and end parameters to uprobe_munmap().
This bug became apparent courtesy of commit c3f0327f8e9d
("mm: add rss counters consistency check").
Signed-off-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
Cc: Jim Keniston <jkenisto@xxxxxxxxxxxxxxxxxx>
Cc: Linux-mm <linux-mm@xxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Anton Arapov <anton@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20120411103527.23245.9835.sendpatchset@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
include/linux/uprobes.h | 5 +++--
kernel/events/uprobes.c | 4 ++--
mm/memory.c | 3 +++
mm/mmap.c | 8 ++++----
4 files changed, 12 insertions(+), 8 deletions(-)
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index d594d3b..efe4b33 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -107,7 +107,7 @@ extern bool __weak is_swbp_insn(uprobe_opcode_t *insn);
extern int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
extern void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
extern int uprobe_mmap(struct vm_area_struct *vma);
-extern void uprobe_munmap(struct vm_area_struct *vma);
+extern void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end);
extern void uprobe_free_utask(struct task_struct *t);
extern void uprobe_copy_process(struct task_struct *t);
extern unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs);
@@ -134,7 +134,8 @@ static inline int uprobe_mmap(struct vm_area_struct *vma)
{
return 0;
}
-static inline void uprobe_munmap(struct vm_area_struct *vma)
+static inline void
+uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
{
}
static inline void uprobe_notify_resume(struct pt_regs *regs)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index c5caeec..985be4d 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1112,7 +1112,7 @@ int uprobe_mmap(struct vm_area_struct *vma)
/*
* Called in context of a munmap of a vma.
*/
-void uprobe_munmap(struct vm_area_struct *vma)
+void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
{
struct list_head tmp_list;
struct uprobe *uprobe, *u;
@@ -1138,7 +1138,7 @@ void uprobe_munmap(struct vm_area_struct *vma)
list_del(&uprobe->pending_list);
vaddr = vma_address(vma, uprobe->offset);
- if (vaddr >= vma->vm_start && vaddr < vma->vm_end) {
+ if (vaddr >= start && vaddr < end) {
/*
* An unregister could have removed the probe before
* unmap. So check before we decrement the count.
diff --git a/mm/memory.c b/mm/memory.c
index 6105f47..bf8b403 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1307,6 +1307,9 @@ static void unmap_single_vma(struct mmu_gather *tlb,
if (end <= vma->vm_start)
return;
+ if (vma->vm_file)
+ uprobe_munmap(vma, start, end);
+
if (vma->vm_flags & VM_ACCOUNT)
*nr_accounted += (end - start) >> PAGE_SHIFT;
diff --git a/mm/mmap.c b/mm/mmap.c
index b17a39f..15c21a1 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -218,7 +218,6 @@ void unlink_file_vma(struct vm_area_struct *vma)
mutex_lock(&mapping->i_mmap_mutex);
__remove_shared_vm_struct(vma, file, mapping);
mutex_unlock(&mapping->i_mmap_mutex);
- uprobe_munmap(vma);
}
}
@@ -548,10 +547,11 @@ again: remove_next = 1 + (end > next->vm_end);
mapping = file->f_mapping;
if (!(vma->vm_flags & VM_NONLINEAR)) {
root = &mapping->i_mmap;
- uprobe_munmap(vma);
+ uprobe_munmap(vma, vma->vm_start, vma->vm_end);
if (adjust_next)
- uprobe_munmap(next);
+ uprobe_munmap(next, next->vm_start,
+ next->vm_end);
}
mutex_lock(&mapping->i_mmap_mutex);
@@ -632,7 +632,7 @@ again: remove_next = 1 + (end > next->vm_end);
if (remove_next) {
if (file) {
- uprobe_munmap(next);
+ uprobe_munmap(next, next->vm_start, next->vm_end);
fput(file);
if (next->vm_flags & VM_EXECUTABLE)
removed_exe_file_vma(mm);
--
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