linux-stable/include/linux/slab_def.h
Andrey Konovalov 5b7c414822 mm: move obj_to_index to include/linux/slab_def.h
While with SLUB we can actually preassign tags for caches with contructors
and store them in pointers in the freelist, SLAB doesn't allow that since
the freelist is stored as an array of indexes, so there are no pointers to
store the tags.

Instead we compute the tag twice, once when a slab is created before
calling the constructor and then again each time when an object is
allocated with kmalloc.  Tag is computed simply by taking the lowest byte
of the index that corresponds to the object.  However in kasan_kmalloc we
only have access to the objects pointer, so we need a way to find out
which index this object corresponds to.

This patch moves obj_to_index from slab.c to include/linux/slab_def.h to
be reused by KASAN.

Link: http://lkml.kernel.org/r/c02cd9e574cfd93858e43ac94b05e38f891fef64.1544099024.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-12-28 12:11:44 -08:00

120 lines
2.9 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_SLAB_DEF_H
#define _LINUX_SLAB_DEF_H
#include <linux/reciprocal_div.h>
/*
* Definitions unique to the original Linux SLAB allocator.
*/
struct kmem_cache {
struct array_cache __percpu *cpu_cache;
/* 1) Cache tunables. Protected by slab_mutex */
unsigned int batchcount;
unsigned int limit;
unsigned int shared;
unsigned int size;
struct reciprocal_value reciprocal_buffer_size;
/* 2) touched by every alloc & free from the backend */
slab_flags_t flags; /* constant flags */
unsigned int num; /* # of objs per slab */
/* 3) cache_grow/shrink */
/* order of pgs per slab (2^n) */
unsigned int gfporder;
/* force GFP flags, e.g. GFP_DMA */
gfp_t allocflags;
size_t colour; /* cache colouring range */
unsigned int colour_off; /* colour offset */
struct kmem_cache *freelist_cache;
unsigned int freelist_size;
/* constructor func */
void (*ctor)(void *obj);
/* 4) cache creation/removal */
const char *name;
struct list_head list;
int refcount;
int object_size;
int align;
/* 5) statistics */
#ifdef CONFIG_DEBUG_SLAB
unsigned long num_active;
unsigned long num_allocations;
unsigned long high_mark;
unsigned long grown;
unsigned long reaped;
unsigned long errors;
unsigned long max_freeable;
unsigned long node_allocs;
unsigned long node_frees;
unsigned long node_overflow;
atomic_t allochit;
atomic_t allocmiss;
atomic_t freehit;
atomic_t freemiss;
#ifdef CONFIG_DEBUG_SLAB_LEAK
atomic_t store_user_clean;
#endif
/*
* If debugging is enabled, then the allocator can add additional
* fields and/or padding to every object. 'size' contains the total
* object size including these internal fields, while 'obj_offset'
* and 'object_size' contain the offset to the user object and its
* size.
*/
int obj_offset;
#endif /* CONFIG_DEBUG_SLAB */
#ifdef CONFIG_MEMCG
struct memcg_cache_params memcg_params;
#endif
#ifdef CONFIG_KASAN
struct kasan_cache kasan_info;
#endif
#ifdef CONFIG_SLAB_FREELIST_RANDOM
unsigned int *random_seq;
#endif
unsigned int useroffset; /* Usercopy region offset */
unsigned int usersize; /* Usercopy region size */
struct kmem_cache_node *node[MAX_NUMNODES];
};
static inline void *nearest_obj(struct kmem_cache *cache, struct page *page,
void *x)
{
void *object = x - (x - page->s_mem) % cache->size;
void *last_object = page->s_mem + (cache->num - 1) * cache->size;
if (unlikely(object > last_object))
return last_object;
else
return object;
}
/*
* We want to avoid an expensive divide : (offset / cache->size)
* Using the fact that size is a constant for a particular cache,
* we can replace (offset / cache->size) by
* reciprocal_divide(offset, cache->reciprocal_buffer_size)
*/
static inline unsigned int obj_to_index(const struct kmem_cache *cache,
const struct page *page, void *obj)
{
u32 offset = (obj - page->s_mem);
return reciprocal_divide(offset, cache->reciprocal_buffer_size);
}
#endif /* _LINUX_SLAB_DEF_H */