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 <o...@redhat.com>
---
include/linux/sched.h | 2 ++
include/linux/uprobes.h | 5 +++++
kernel/events/uprobes.c | 22 +++++++++++++++++++++-
kernel/fork.c | 1 +
4 files changed, 29 insertions(+), 1 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index cbf3a71..c0fcfb7 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -441,6 +441,8 @@ 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 309309e..2a42319 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -649,6 +649,7 @@ static int
install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
struct vm_area_struct *vma, unsigned long vaddr)
{
+ bool first_uprobe;
int ret;
/*
@@ -680,7 +681,17 @@ 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;
}
@@ -1034,6 +1045,9 @@ 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 */
}
@@ -1144,6 +1158,12 @@ 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.
*/
@@ -1511,7 +1531,7 @@ int uprobe_pre_sstep_notifier(struct pt_regs *regs)
{
struct uprobe_task *utask;
- if (!current->mm)
+ if (!current->mm || !test_bit(MMF_HAS_UPROBES, ¤t->mm->flags))
return 0;
utask = current->utask;
diff --git a/kernel/fork.c b/kernel/fork.c
index 0e419ab..ab970c3 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -350,6 +350,7 @@ 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:
*/
--
1.5.5.1
--
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