5f0d5a3ae7
A group of Linux kernel hackers reported chasing a bug that resulted from their assumption that SLAB_DESTROY_BY_RCU provided an existence guarantee, that is, that no block from such a slab would be reallocated during an RCU read-side critical section. Of course, that is not the case. Instead, SLAB_DESTROY_BY_RCU only prevents freeing of an entire slab of blocks. However, there is a phrase for this, namely "type safety". This commit therefore renames SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU in order to avoid future instances of this sort of confusion. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: <linux-mm@kvack.org> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> [ paulmck: Add comments mentioning the old name, as requested by Eric Dumazet, in order to help people familiar with the old name find the new one. ] Acked-by: David Rientjes <rientjes@google.com>
125 lines
2.9 KiB
C
125 lines
2.9 KiB
C
#include <linux/gfp.h>
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#include <linux/mm_types.h>
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include "slab.h"
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#include <linux/kmemcheck.h>
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void kmemcheck_alloc_shadow(struct page *page, int order, gfp_t flags, int node)
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{
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struct page *shadow;
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int pages;
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int i;
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pages = 1 << order;
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/*
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* With kmemcheck enabled, we need to allocate a memory area for the
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* shadow bits as well.
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*/
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shadow = alloc_pages_node(node, flags | __GFP_NOTRACK, order);
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if (!shadow) {
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if (printk_ratelimit())
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pr_err("kmemcheck: failed to allocate shadow bitmap\n");
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return;
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}
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for(i = 0; i < pages; ++i)
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page[i].shadow = page_address(&shadow[i]);
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/*
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* Mark it as non-present for the MMU so that our accesses to
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* this memory will trigger a page fault and let us analyze
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* the memory accesses.
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*/
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kmemcheck_hide_pages(page, pages);
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}
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void kmemcheck_free_shadow(struct page *page, int order)
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{
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struct page *shadow;
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int pages;
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int i;
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if (!kmemcheck_page_is_tracked(page))
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return;
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pages = 1 << order;
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kmemcheck_show_pages(page, pages);
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shadow = virt_to_page(page[0].shadow);
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for(i = 0; i < pages; ++i)
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page[i].shadow = NULL;
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__free_pages(shadow, order);
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}
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void kmemcheck_slab_alloc(struct kmem_cache *s, gfp_t gfpflags, void *object,
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size_t size)
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{
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if (unlikely(!object)) /* Skip object if allocation failed */
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return;
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/*
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* Has already been memset(), which initializes the shadow for us
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* as well.
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*/
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if (gfpflags & __GFP_ZERO)
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return;
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/* No need to initialize the shadow of a non-tracked slab. */
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if (s->flags & SLAB_NOTRACK)
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return;
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if (!kmemcheck_enabled || gfpflags & __GFP_NOTRACK) {
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/*
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* Allow notracked objects to be allocated from
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* tracked caches. Note however that these objects
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* will still get page faults on access, they just
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* won't ever be flagged as uninitialized. If page
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* faults are not acceptable, the slab cache itself
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* should be marked NOTRACK.
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*/
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kmemcheck_mark_initialized(object, size);
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} else if (!s->ctor) {
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/*
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* New objects should be marked uninitialized before
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* they're returned to the called.
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*/
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kmemcheck_mark_uninitialized(object, size);
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}
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}
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void kmemcheck_slab_free(struct kmem_cache *s, void *object, size_t size)
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{
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/* TODO: RCU freeing is unsupported for now; hide false positives. */
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if (!s->ctor && !(s->flags & SLAB_TYPESAFE_BY_RCU))
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kmemcheck_mark_freed(object, size);
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}
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void kmemcheck_pagealloc_alloc(struct page *page, unsigned int order,
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gfp_t gfpflags)
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{
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int pages;
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if (gfpflags & (__GFP_HIGHMEM | __GFP_NOTRACK))
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return;
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pages = 1 << order;
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/*
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* NOTE: We choose to track GFP_ZERO pages too; in fact, they
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* can become uninitialized by copying uninitialized memory
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* into them.
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*/
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/* XXX: Can use zone->node for node? */
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kmemcheck_alloc_shadow(page, order, gfpflags, -1);
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if (gfpflags & __GFP_ZERO)
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kmemcheck_mark_initialized_pages(page, pages);
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else
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kmemcheck_mark_uninitialized_pages(page, pages);
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}
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