mm/kmemcheck.c

   1 #include <linux/gfp.h>
   2 #include <linux/mm_types.h>
   3 #include <linux/mm.h>
   4 #include <linux/slab.h>
   5 #include "slab.h"
   6 #include <linux/kmemcheck.h>
   7
   8 void kmemcheck_alloc_shadow(struct page *page, int order, gfp_t flags, int node)
   9 {
  10         struct page *shadow;
  11         int pages;
  12         int i;
  13
  14         pages = 1 << order;
  15
  16         /*
  17          * With kmemcheck enabled, we need to allocate a memory area for the
  18          * shadow bits as well.
  19          */
  20         shadow = alloc_pages_node(node, flags | __GFP_NOTRACK, order);
  21         if (!shadow) {
  22                 if (printk_ratelimit())
  23                         pr_err("kmemcheck: failed to allocate shadow bitmap\n");
  24                 return;
  25         }
  26
  27         for(i = 0; i < pages; ++i)
  28                 page[i].shadow = page_address(&shadow[i]);
  29
  30         /*
  31          * Mark it as non-present for the MMU so that our accesses to
  32          * this memory will trigger a page fault and let us analyze
  33          * the memory accesses.
  34          */
  35         kmemcheck_hide_pages(page, pages);
  36 }
  37
  38 void kmemcheck_free_shadow(struct page *page, int order)
  39 {
  40         struct page *shadow;
  41         int pages;
  42         int i;
  43
  44         if (!kmemcheck_page_is_tracked(page))
  45                 return;
  46
  47         pages = 1 << order;
  48
  49         kmemcheck_show_pages(page, pages);
  50
  51         shadow = virt_to_page(page[0].shadow);
  52
  53         for(i = 0; i < pages; ++i)
  54                 page[i].shadow = NULL;
  55
  56         __free_pages(shadow, order);
  57 }
  58
  59 void kmemcheck_slab_alloc(struct kmem_cache *s, gfp_t gfpflags, void *object,
  60                           size_t size)
  61 {
  62         if (unlikely(!object)) /* Skip object if allocation failed */
  63                 return;
  64
  65         /*
  66          * Has already been memset(), which initializes the shadow for us
  67          * as well.
  68          */
  69         if (gfpflags & __GFP_ZERO)
  70                 return;
  71
  72         /* No need to initialize the shadow of a non-tracked slab. */
  73         if (s->flags & SLAB_NOTRACK)
  74                 return;
  75
  76         if (!kmemcheck_enabled || gfpflags & __GFP_NOTRACK) {
  77                 /*
  78                  * Allow notracked objects to be allocated from
  79                  * tracked caches. Note however that these objects
  80                  * will still get page faults on access, they just
  81                  * won't ever be flagged as uninitialized. If page
  82                  * faults are not acceptable, the slab cache itself
  83                  * should be marked NOTRACK.
  84                  */
  85                 kmemcheck_mark_initialized(object, size);
  86         } else if (!s->ctor) {
  87                 /*
  88                  * New objects should be marked uninitialized before
  89                  * they're returned to the called.
  90                  */
  91                 kmemcheck_mark_uninitialized(object, size);
  92         }
  93 }
  94
  95 void kmemcheck_slab_free(struct kmem_cache *s, void *object, size_t size)
  96 {
  97         /* TODO: RCU freeing is unsupported for now; hide false positives. */
  98         if (!s->ctor && !(s->flags & SLAB_DESTROY_BY_RCU))
  99                 kmemcheck_mark_freed(object, size);
 100 }
 101
 102 void kmemcheck_pagealloc_alloc(struct page *page, unsigned int order,
 103                                gfp_t gfpflags)
 104 {
 105         int pages;
 106
 107         if (gfpflags & (__GFP_HIGHMEM | __GFP_NOTRACK))
 108                 return;
 109
 110         pages = 1 << order;
 111
 112         /*
 113          * NOTE: We choose to track GFP_ZERO pages too; in fact, they
 114          * can become uninitialized by copying uninitialized memory
 115          * into them.
 116          */
 117
 118         /* XXX: Can use zone->node for node? */
 119         kmemcheck_alloc_shadow(page, order, gfpflags, -1);
 120
 121         if (gfpflags & __GFP_ZERO)
 122                 kmemcheck_mark_initialized_pages(page, pages);
 123         else
 124                 kmemcheck_mark_uninitialized_pages(page, pages);
 125 }