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Commit 704bde3c authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
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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: default avatarOleg 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: default avatarIngo Molnar <mingo@kernel.org>
parent f58bea2f

kernel/events/uprobes.c

+20 −10
Original line number Diff line number Diff line
@@ -99,8 +99,9 @@ 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];



	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
@@ -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;