Commit 92850134 authored by Andrey Konovalov's avatar Andrey Konovalov Committed by Linus Torvalds
Browse files

kasan, mm: don't save alloc stacks twice 

Patch series "kasan: optimizations and fixes for HW_TAGS", v4.

This patchset makes the HW_TAGS mode more efficient, mostly by reworking
poisoning approaches and simplifying/inlining some internal helpers.

With this change, the overhead of HW_TAGS annotations excluding setting
and checking memory tags is ~3%.  The performance impact caused by tags
will be unknown until we have hardware that supports MTE.

As a side-effect, this patchset speeds up generic KASAN by ~15%.

This patch (of 13):

Currently KASAN saves allocation stacks in both kasan_slab_alloc() and
kasan_kmalloc() annotations.  This patch changes KASAN to save allocation
stacks for slab objects from kmalloc caches in kasan_kmalloc() only, and
stacks for other slab objects in kasan_slab_alloc() only.

This change requires ____kasan_kmalloc() knowing whether the object
belongs to a kmalloc cache.  This is implemented by adding a flag field to
the kasan_info structure.  That flag is only set for kmalloc caches via a
new kasan_cache_create_kmalloc() annotation.

Link: https://lkml.kernel.org/r/cover.1612546384.git.andreyknvl@google.com
Link: https://lkml.kernel.org/r/7c673ebca8d00f40a7ad6f04ab9a2bddeeae2097.1612546384.git.andreyknvl@google.com


Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: default avatarMarco Elver <elver@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d3a61f74

include/linux/kasan.h

+9 −0
Original line number Diff line number Diff line
@@ -83,6 +83,7 @@ static inline void kasan_disable_current(void) {} 
struct kasan_cache {

	int alloc_meta_offset;

	int free_meta_offset;

	bool is_kmalloc;

};



#ifdef CONFIG_KASAN_HW_TAGS
@@ -143,6 +144,13 @@ static __always_inline void kasan_cache_create(struct kmem_cache *cache, 
		__kasan_cache_create(cache, size, flags);

}



void __kasan_cache_create_kmalloc(struct kmem_cache *cache);

static __always_inline void kasan_cache_create_kmalloc(struct kmem_cache *cache)

{

	if (kasan_enabled())

		__kasan_cache_create_kmalloc(cache);

}



size_t __kasan_metadata_size(struct kmem_cache *cache);

static __always_inline size_t kasan_metadata_size(struct kmem_cache *cache)

{
@@ -278,6 +286,7 @@ static inline void kasan_free_pages(struct page *page, unsigned int order) {} 
static inline void kasan_cache_create(struct kmem_cache *cache,

				      unsigned int *size,

				      slab_flags_t *flags) {}

static inline void kasan_cache_create_kmalloc(struct kmem_cache *cache) {}

static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; }

static inline void kasan_poison_slab(struct page *page) {}

static inline void kasan_unpoison_object_data(struct kmem_cache *cache,

mm/kasan/common.c

+14 −4
Original line number Diff line number Diff line
@@ -210,6 +210,11 @@ void __kasan_cache_create(struct kmem_cache *cache, unsigned int *size, 
		*size = optimal_size;

}



void __kasan_cache_create_kmalloc(struct kmem_cache *cache)

{

	cache->kasan_info.is_kmalloc = true;

}



size_t __kasan_metadata_size(struct kmem_cache *cache)

{

	if (!kasan_stack_collection_enabled())
@@ -394,17 +399,22 @@ void __kasan_slab_free_mempool(void *ptr, unsigned long ip) 
	}

}



static void set_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)

static void set_alloc_info(struct kmem_cache *cache, void *object,

				gfp_t flags, bool is_kmalloc)

{

	struct kasan_alloc_meta *alloc_meta;



	/* Don't save alloc info for kmalloc caches in kasan_slab_alloc(). */

	if (cache->kasan_info.is_kmalloc && !is_kmalloc)

		return;



	alloc_meta = kasan_get_alloc_meta(cache, object);

	if (alloc_meta)

		kasan_set_track(&alloc_meta->alloc_track, flags);

}



static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object,

				size_t size, gfp_t flags, bool keep_tag)

				size_t size, gfp_t flags, bool is_kmalloc)

{

	unsigned long redzone_start;

	unsigned long redzone_end;
@@ -423,7 +433,7 @@ static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object, 
				KASAN_GRANULE_SIZE);

	redzone_end = round_up((unsigned long)object + cache->object_size,

				KASAN_GRANULE_SIZE);

	tag = assign_tag(cache, object, false, keep_tag);

	tag = assign_tag(cache, object, false, is_kmalloc);



	/* Tag is ignored in set_tag without CONFIG_KASAN_SW/HW_TAGS */

	kasan_unpoison(set_tag(object, tag), size);
@@ -431,7 +441,7 @@ static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object, 
			   KASAN_KMALLOC_REDZONE);



	if (kasan_stack_collection_enabled())

		set_alloc_info(cache, (void *)object, flags);

		set_alloc_info(cache, (void *)object, flags, is_kmalloc);



	return set_tag(object, tag);

}

mm/slab_common.c

+1 −0
Original line number Diff line number Diff line
@@ -643,6 +643,7 @@ struct kmem_cache *__init create_kmalloc_cache(const char *name, 
		panic("Out of memory when creating slab %s\n", name);



	create_boot_cache(s, name, size, flags, useroffset, usersize);

	kasan_cache_create_kmalloc(s);

	list_add(&s->list, &slab_caches);

	s->refcount = 1;

	return s;