mm/kmemcheck.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/gfp.h>
   3 #include <linux/mm_types.h>
   4 #include <linux/mm.h>
   5 #include <linux/slab.h>
   6 #include "slab.h"
   7 #include <linux/kmemcheck.h>
   8
   9 void kmemcheck_alloc_shadow(struct page *page, int order, gfp_t flags, int node)
  10 {
  11         struct page *shadow;
  12         int pages;
  13         int i;
  14
  15         pages = 1 << order;
  16
  17         /*
  18          * With kmemcheck enabled, we need to allocate a memory area for the
  19          * shadow bits as well.
  20          */
  21         shadow = alloc_pages_node(node, flags | __GFP_NOTRACK, order);
  22         if (!shadow) {
  23                 if (printk_ratelimit())
  24                         pr_err("kmemcheck: failed to allocate 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         if (unlikely(!object)) /* Skip object if allocation failed */
  64                 return;
  65
  66         /*
  67          * Has already been memset(), which initializes the shadow for us
  68          * as well.
  69          */
  70         if (gfpflags & __GFP_ZERO)
  71                 return;
  72
  73         /* No need to initialize the shadow of a non-tracked slab. */
  74         if (s->flags & SLAB_NOTRACK)
  75                 return;
  76
  77         if (!kmemcheck_enabled || gfpflags & __GFP_NOTRACK) {
  78                 /*
  79                  * Allow notracked objects to be allocated from
  80                  * tracked caches. Note however that these objects
  81                  * will still get page faults on access, they just
  82                  * won't ever be flagged as uninitialized. If page
  83                  * faults are not acceptable, the slab cache itself
  84                  * should be marked NOTRACK.
  85                  */
  86                 kmemcheck_mark_initialized(object, size);
  87         } else if (!s->ctor) {
  88                 /*
  89                  * New objects should be marked uninitialized before
  90                  * they're returned to the called.
  91                  */
  92                 kmemcheck_mark_uninitialized(object, size);
  93         }
  94 }
  95
  96 void kmemcheck_slab_free(struct kmem_cache *s, void *object, size_t size)
  97 {
  98         /* TODO: RCU freeing is unsupported for now; hide false positives. */
  99         if (!s->ctor && !(s->flags & SLAB_TYPESAFE_BY_RCU))
 100                 kmemcheck_mark_freed(object, size);
 101 }
 102
 103 void kmemcheck_pagealloc_alloc(struct page *page, unsigned int order,
 104                                gfp_t gfpflags)
 105 {
 106         int pages;
 107
 108         if (gfpflags & (__GFP_HIGHMEM | __GFP_NOTRACK))
 109                 return;
 110
 111         pages = 1 << order;
 112
 113         /*
 114          * NOTE: We choose to track GFP_ZERO pages too; in fact, they
 115          * can become uninitialized by copying uninitialized memory
 116          * into them.
 117          */
 118
 119         /* XXX: Can use zone->node for node? */
 120         kmemcheck_alloc_shadow(page, order, gfpflags, -1);
 121
 122         if (gfpflags & __GFP_ZERO)
 123                 kmemcheck_mark_initialized_pages(page, pages);
 124         else
 125                 kmemcheck_mark_uninitialized_pages(page, pages);
 126 }