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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: 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>
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1 changed files with 20 additions and 10 deletions
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@ -96,17 +96,18 @@ struct uprobe {
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* allocated.
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*/
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struct xol_area {
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wait_queue_head_t wq; /* if all slots are busy */
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atomic_t slot_count; /* number of in-use slots */
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unsigned long *bitmap; /* 0 = free slot */
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struct page *pages[2];
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wait_queue_head_t wq; /* if all slots are busy */
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atomic_t slot_count; /* number of in-use slots */
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unsigned long *bitmap; /* 0 = free slot */
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struct vm_special_mapping xol_mapping;
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struct page *pages[2];
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/*
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* We keep the vma's vm_start rather than a pointer to the vma
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* itself. The probed process or a naughty kernel module could make
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* the vma go away, and we must handle that reasonably gracefully.
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*/
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unsigned long vaddr; /* Page(s) of instruction slots */
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unsigned long vaddr; /* Page(s) of instruction slots */
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};
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/*
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@ -1125,11 +1126,14 @@ void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned lon
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/* Slot allocation for XOL */
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static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
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{
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int ret = -EALREADY;
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struct vm_area_struct *vma;
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int ret;
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down_write(&mm->mmap_sem);
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if (mm->uprobes_state.xol_area)
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if (mm->uprobes_state.xol_area) {
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ret = -EALREADY;
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goto fail;
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}
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if (!area->vaddr) {
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/* Try to map as high as possible, this is only a hint. */
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@ -1141,11 +1145,15 @@ static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
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}
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}
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ret = install_special_mapping(mm, area->vaddr, PAGE_SIZE,
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VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO, area->pages);
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if (ret)
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vma = _install_special_mapping(mm, area->vaddr, PAGE_SIZE,
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VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO,
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&area->xol_mapping);
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if (IS_ERR(vma)) {
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ret = PTR_ERR(vma);
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goto fail;
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}
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ret = 0;
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smp_wmb(); /* pairs with get_xol_area() */
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mm->uprobes_state.xol_area = area;
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fail:
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@ -1168,6 +1176,8 @@ static struct xol_area *__create_xol_area(unsigned long vaddr)
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if (!area->bitmap)
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goto free_area;
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area->xol_mapping.name = "[uprobes]";
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area->xol_mapping.pages = area->pages;
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area->pages[0] = alloc_page(GFP_HIGHUSER);
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if (!area->pages[0])
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goto free_bitmap;
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