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