kmemcheck.c

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#include <linux/gfp.h>
#include <linux/mm_types.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/kmemcheck.h>

void kmemcheck_alloc_shadow(struct page *page, int order, gfp_t flags, int node)
{
    struct page *shadow;
    int pages;
    int i;

    pages = 1 << order;

    /*
     * With kmemcheck enabled, we need to allocate a memory area for the
     * shadow bits as well.
     */
    shadow = alloc_pages_node(node, flags | __GFP_NOTRACK, order);
    if (!shadow) {
        if (printk_ratelimit())
            printk(KERN_ERR "kmemcheck: failed to allocate "
                "shadow bitmap\n");
        return;
    }

    for(i = 0; i < pages; ++i)
        page[i].shadow = page_address(&shadow[i]);

    /*
     * Mark it as non-present for the MMU so that our accesses to
     * this memory will trigger a page fault and let us analyze
     * the memory accesses.
     */
    kmemcheck_hide_pages(page, pages);
}

void kmemcheck_free_shadow(struct page *page, int order)
{
    struct page *shadow;
    int pages;
    int i;

    if (!kmemcheck_page_is_tracked(page))
        return;

    pages = 1 << order;

    kmemcheck_show_pages(page, pages);

    shadow = virt_to_page(page[0].shadow);

    for(i = 0; i < pages; ++i)
        page[i].shadow = NULL;

    __free_pages(shadow, order);
}

void kmemcheck_slab_alloc(struct kmem_cache *s, gfp_t gfpflags, void *object,
              size_t size)
{
    /*
     * Has already been memset(), which initializes the shadow for us
     * as well.
     */
    if (gfpflags & __GFP_ZERO)
        return;

    /* No need to initialize the shadow of a non-tracked slab. */
    if (s->flags & SLAB_NOTRACK)
        return;

    if (!kmemcheck_enabled || gfpflags & __GFP_NOTRACK) {
        /*
         * Allow notracked objects to be allocated from
         * tracked caches. Note however that these objects
         * will still get page faults on access, they just
         * won't ever be flagged as uninitialized. If page
         * faults are not acceptable, the slab cache itself
         * should be marked NOTRACK.
         */
        kmemcheck_mark_initialized(object, size);
    } else if (!s->ctor) {
        /*
         * New objects should be marked uninitialized before
         * they're returned to the called.
         */
        kmemcheck_mark_uninitialized(object, size);
    }
}

void kmemcheck_slab_free(struct kmem_cache *s, void *object, size_t size)
{
    /* TODO: RCU freeing is unsupported for now; hide false positives. */
    if (!s->ctor && !(s->flags & SLAB_DESTROY_BY_RCU))
        kmemcheck_mark_freed(object, size);
}

void kmemcheck_pagealloc_alloc(struct page *page, unsigned int order,
                   gfp_t gfpflags)
{
    int pages;

    if (gfpflags & (__GFP_HIGHMEM | __GFP_NOTRACK))
        return;

    pages = 1 << order;

    /*
     * NOTE: We choose to track GFP_ZERO pages too; in fact, they
     * can become uninitialized by copying uninitialized memory
     * into them.
     */

    /* XXX: Can use zone->node for node? */
    kmemcheck_alloc_shadow(page, order, gfpflags, -1);

    if (gfpflags & __GFP_ZERO)
        kmemcheck_mark_initialized_pages(page, pages);
    else
        kmemcheck_mark_uninitialized_pages(page, pages);
}