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abstract metadata allocation to allow guard slabs

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This commit is contained in:
Daniel Micay 2018-09-06 18:41:00 -04:00
parent d8e18e0011
commit cc1e79fdba
1 changed files with 13 additions and 15 deletions
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28
malloc.c
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@ -130,11 +130,16 @@ static const size_t real_class_region_size = class_region_size * 2;
static const size_t slab_region_size = real_class_region_size * N_SIZE_CLASSES; static const size_t slab_region_size = real_class_region_size * N_SIZE_CLASSES;
static_assert(PAGE_SIZE == 4096, "bitmap handling will need adjustment for other page sizes"); static_assert(PAGE_SIZE == 4096, "bitmap handling will need adjustment for other page sizes");
static void *get_slab(struct size_class *c, size_t slab_size, struct slab_metadata *metadata) {
size_t index = metadata - c->slab_info;
return (char *)c->class_region_start + (index * slab_size);
}
static size_t get_metadata_max(size_t slab_size) { static size_t get_metadata_max(size_t slab_size) {
return class_region_size / slab_size; return class_region_size / slab_size;
} }
static struct slab_metadata *alloc_metadata(struct size_class *c, size_t slab_size) { static struct slab_metadata *alloc_metadata(struct size_class *c, size_t slab_size, bool non_zero_size) {
if (unlikely(c->metadata_count == c->metadata_allocated)) { if (unlikely(c->metadata_count == c->metadata_allocated)) {
size_t metadata_max = get_metadata_max(slab_size); size_t metadata_max = get_metadata_max(slab_size);
if (c->metadata_count == metadata_max) { if (c->metadata_count == metadata_max) {
@ -152,6 +157,10 @@ static struct slab_metadata *alloc_metadata(struct size_class *c, size_t slab_si
} }
struct slab_metadata *metadata = c->slab_info + c->metadata_count; struct slab_metadata *metadata = c->slab_info + c->metadata_count;
void *slab = get_slab(c, slab_size, metadata);
if (non_zero_size && memory_protect_rw(slab, slab_size)) {
return NULL;
}
c->metadata_count++; c->metadata_count++;
return metadata; return metadata;
} }
@ -215,11 +224,6 @@ static bool is_free_slab(struct slab_metadata *metadata) {
return !metadata->bitmap; return !metadata->bitmap;
} }
static void *get_slab(struct size_class *c, size_t slab_size, struct slab_metadata *metadata) {
size_t index = metadata - c->slab_info;
return (char *)c->class_region_start + (index * slab_size);
}
static struct slab_metadata *get_metadata(struct size_class *c, void *p) { static struct slab_metadata *get_metadata(struct size_class *c, void *p) {
size_t offset = (char *)p - (char *)c->class_region_start; size_t offset = (char *)p - (char *)c->class_region_start;
size_t index = libdivide_u64_do(offset, &c->slab_size_divisor); size_t index = libdivide_u64_do(offset, &c->slab_size_divisor);
@ -297,21 +301,15 @@ static inline void *slab_allocate(size_t requested_size) {
return p; return p;
} }
struct slab_metadata *metadata = alloc_metadata(c, slab_size); struct slab_metadata *metadata = alloc_metadata(c, slab_size, requested_size);
if (metadata == NULL) { if (unlikely(metadata == NULL)) {
pthread_mutex_unlock(&c->mutex); pthread_mutex_unlock(&c->mutex);
return NULL; return NULL;
} }
metadata->canary_value = get_random_u64(&c->rng); metadata->canary_value = get_random_u64(&c->rng);
void *slab = get_slab(c, slab_size, metadata);
if (requested_size != 0 && memory_protect_rw(slab, slab_size)) {
c->metadata_count--;
pthread_mutex_unlock(&c->mutex);
return NULL;
}
c->partial_slabs = metadata; c->partial_slabs = metadata;
void *slab = get_slab(c, slab_size, metadata);
size_t slot = get_free_slot(&c->rng, slots, metadata); size_t slot = get_free_slot(&c->rng, slots, metadata);
set_slot(metadata, slot); set_slot(metadata, slot);
void *p = slot_pointer(size, slab, slot); void *p = slot_pointer(size, slab, slot);