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authorOleg Nesterov <oleg@redhat.com>2012-08-08 17:11:42 +0200
committerAnton Arapov <anton@redhat.com>2012-10-29 11:42:35 +0100
commit07f61d55c42ce77708f5ba2772070985451fd28c (patch)
treef2c79b946897f0ea44fc66bda0e7681c5e92b851
parent3e3f38eba706cd760057085b69a1ea25db85533d (diff)
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uprobes: Introduce MMF_HAS_UPROBES
Add the new MMF_HAS_UPROBES flag. It is set by install_breakpoint() and it is copied by dup_mmap(), uprobe_pre_sstep_notifier() checks it to avoid the slow path if the task was never probed. Perhaps it makes sense to check it in valid_vma(is_register => false) as well. This needs the new dup_mmap()->uprobe_dup_mmap() hook. We can't use uprobe_reset_state() or put MMF_HAS_UPROBES into MMF_INIT_MASK, we need oldmm->mmap_sem to avoid the race with uprobe_register() or mmap() from another thread. Currently we never clear this bit, it can be false-positive after uprobe_unregister() or uprobe_munmap() or if dup_mmap() hits the probed VM_DONTCOPY vma. But this is fine correctness-wise and has no effect unless the task hits the non-uprobe breakpoint. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
-rw-r--r--include/linux/sched.h2
-rw-r--r--include/linux/uprobes.h5
-rw-r--r--kernel/events/uprobes.c22
-rw-r--r--kernel/fork.c1
4 files changed, 29 insertions, 1 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 23bddac..adae87f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -446,6 +446,8 @@ extern int get_dumpable(struct mm_struct *mm);
#define MMF_VM_HUGEPAGE 17 /* set when VM_HUGEPAGE is set on vma */
#define MMF_EXE_FILE_CHANGED 18 /* see prctl_set_mm_exe_file() */
+#define MMF_HAS_UPROBES 19 /* might have uprobes */
+
#define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK)
struct sighand_struct {
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 03ae547..4a37ab1 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -108,6 +108,7 @@ extern int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_con
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, unsigned long start, unsigned long end);
+extern void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm);
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);
@@ -138,6 +139,10 @@ static inline void
uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
{
}
+static inline void
+uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm)
+{
+}
static inline void uprobe_notify_resume(struct pt_regs *regs)
{
}
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 3e2996b..33870b1 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -647,6 +647,7 @@ static int
install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
struct vm_area_struct *vma, unsigned long vaddr)
{
+ bool first_uprobe;
int ret;
/*
@@ -678,7 +679,17 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
uprobe->flags |= UPROBE_COPY_INSN;
}
+ /*
+ * set MMF_HAS_UPROBES in advance for uprobe_pre_sstep_notifier(),
+ * the task can hit this breakpoint right after __replace_page().
+ */
+ first_uprobe = !test_bit(MMF_HAS_UPROBES, &mm->flags);
+ if (first_uprobe)
+ set_bit(MMF_HAS_UPROBES, &mm->flags);
+
ret = set_swbp(&uprobe->arch, mm, vaddr);
+ if (ret && first_uprobe)
+ clear_bit(MMF_HAS_UPROBES, &mm->flags);
return ret;
}
@@ -1032,6 +1043,9 @@ void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned lon
if (!atomic_read(&vma->vm_mm->mm_users)) /* called by mmput() ? */
return;
+ if (!test_bit(MMF_HAS_UPROBES, &vma->vm_mm->flags))
+ return;
+
/* TODO: unmapping uprobe(s) will need more work */
}
@@ -1142,6 +1156,12 @@ void uprobe_reset_state(struct mm_struct *mm)
mm->uprobes_state.xol_area = NULL;
}
+void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm)
+{
+ if (test_bit(MMF_HAS_UPROBES, &oldmm->flags))
+ set_bit(MMF_HAS_UPROBES, &newmm->flags);
+}
+
/*
* - search for a free slot.
*/
@@ -1507,7 +1527,7 @@ int uprobe_pre_sstep_notifier(struct pt_regs *regs)
{
struct uprobe_task *utask;
- if (!current->mm)
+ if (!current->mm || !test_bit(MMF_HAS_UPROBES, &current->mm->flags))
return 0;
utask = current->utask;
diff --git a/kernel/fork.c b/kernel/fork.c
index 912b6f6..cbb5f9f 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -353,6 +353,7 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
down_write(&oldmm->mmap_sem);
flush_cache_dup_mm(oldmm);
+ uprobe_dup_mmap(oldmm, mm);
/*
* Not linked in yet - no deadlock potential:
*/