Commit-ID: 704bde3cc26a4cb34386c164107b59e09745a022
Gitweb: http://git.kernel.org/tip/704bde3cc26a4cb34386c164107b59e09745a022
Author: Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate: Tue, 21 Jul 2015 15:40:33 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 31 Jul 2015 10:38:06 +0200
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@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Pratyush Anand <panand@xxxxxxxxxx>
Cc: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20150721134033.GA4796@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/events/uprobes.c | 30 ++++++++++++++++++++----------
1 file 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;
--
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