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authorOleg Nesterov <oleg@redhat.com>2015-07-21 13:40:33 (GMT)
committerIngo Molnar <mingo@kernel.org>2015-07-31 08:38:06 (GMT)
commit704bde3cc26a4cb34386c164107b59e09745a022 (patch)
treeb39f19b69d473d16717179c86da7bf13f0943da2
parentf58bea2fec63db72f8050ade709358257e9102ab (diff)
downloadlinux-704bde3cc26a4cb34386c164107b59e09745a022.tar.xz
uprobes: Use vm_special_mapping to name the XOL vma
Change xol_add_vma() to use _install_special_mapping(), this way we can name the vma installed by uprobes. Currently it looks like private anonymous mapping, this is confusing and complicates the debugging. With this change /proc/$pid/maps reports "[uprobes]". As a side effect this will cause core dumps to include the XOL vma and I think this is good; this can help to debug the problem if the app crashed because it was probed. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Pratyush Anand <panand@redhat.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150721134033.GA4796@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--kernel/events/uprobes.c30
1 files changed, 20 insertions, 10 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 4b8ac5f..2d5b7bd 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -96,17 +96,18 @@ struct uprobe {
* allocated.
*/
struct xol_area {
- wait_queue_head_t wq; /* if all slots are busy */
- atomic_t slot_count; /* number of in-use slots */
- unsigned long *bitmap; /* 0 = free slot */
- struct page *pages[2];
+ wait_queue_head_t wq; /* if all slots are busy */
+ atomic_t slot_count; /* number of in-use slots */
+ unsigned long *bitmap; /* 0 = free slot */
+ struct vm_special_mapping xol_mapping;
+ struct page *pages[2];
/*
* We keep the vma's vm_start rather than a pointer to the vma
* itself. The probed process or a naughty kernel module could make
* the vma go away, and we must handle that reasonably gracefully.
*/
- unsigned long vaddr; /* Page(s) of instruction slots */
+ unsigned long vaddr; /* Page(s) of instruction slots */
};
/*
@@ -1125,11 +1126,14 @@ void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned lon
/* Slot allocation for XOL */
static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
{
- int ret = -EALREADY;
+ struct vm_area_struct *vma;
+ int ret;
down_write(&mm->mmap_sem);
- if (mm->uprobes_state.xol_area)
+ if (mm->uprobes_state.xol_area) {
+ ret = -EALREADY;
goto fail;
+ }
if (!area->vaddr) {
/* Try to map as high as possible, this is only a hint. */
@@ -1141,11 +1145,15 @@ static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
}
}
- ret = install_special_mapping(mm, area->vaddr, PAGE_SIZE,
- VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO, area->pages);
- if (ret)
+ vma = _install_special_mapping(mm, area->vaddr, PAGE_SIZE,
+ VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO,
+ &area->xol_mapping);
+ if (IS_ERR(vma)) {
+ ret = PTR_ERR(vma);
goto fail;
+ }
+ ret = 0;
smp_wmb(); /* pairs with get_xol_area() */
mm->uprobes_state.xol_area = area;
fail:
@@ -1168,6 +1176,8 @@ static struct xol_area *__create_xol_area(unsigned long vaddr)
if (!area->bitmap)
goto free_area;
+ area->xol_mapping.name = "[uprobes]";
+ area->xol_mapping.pages = area->pages;
area->pages[0] = alloc_page(GFP_HIGHUSER);
if (!area->pages[0])
goto free_bitmap;