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hardened_malloc/malloc.c

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#include <assert.h>
#include <errno.h>
#include <stdatomic.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <sys/mman.h>
#include <unistd.h>
#include "third_party/libdivide.h"
#include "config.h"
#include "malloc.h"
#include "mutex.h"
#include "memory.h"
#include "pages.h"
#include "random.h"
#include "util.h"
// use __register_atfork directly to avoid linking with libpthread for glibc < 2.28
#ifdef __GLIBC__
extern void *__dso_handle;
extern int __register_atfork(void (*)(void), void (*)(void), void (*)(void), void *);
#define atfork(prepare, parent, child) __register_atfork(prepare, parent, child, __dso_handle)
#else
#define atfork pthread_atfork
#endif
static_assert(sizeof(void *) == 8, "64-bit only");
static_assert(!WRITE_AFTER_FREE_CHECK || ZERO_ON_FREE, "WRITE_AFTER_FREE_CHECK depends on ZERO_ON_FREE");
// either sizeof(u64) or 0
static const size_t canary_size = SLAB_CANARY ? sizeof(u64) : 0;
#define CACHELINE_SIZE 64
static union {
struct {
void *slab_region_start;
void *slab_region_end;
struct size_class *size_class_metadata;
struct region_allocator *region_allocator;
struct region_metadata *regions[2];
#ifdef USE_PKEY
int metadata_pkey;
#endif
atomic_bool initialized;
};
char padding[PAGE_SIZE];
} ro __attribute__((aligned(PAGE_SIZE)));
struct slab_metadata {
u64 bitmap[4];
struct slab_metadata *next;
struct slab_metadata *prev;
u64 canary_value;
};
static const size_t min_align = 16;
static const size_t max_slab_size_class = 16384;
static const u16 size_classes[] = {
/* 0 */ 0,
/* 16 */ 16, 32, 48, 64, 80, 96, 112, 128,
/* 32 */ 160, 192, 224, 256,
/* 64 */ 320, 384, 448, 512,
/* 128 */ 640, 768, 896, 1024,
/* 256 */ 1280, 1536, 1792, 2048,
/* 512 */ 2560, 3072, 3584, 4096,
/* 1024 */ 5120, 6144, 7168, 8192,
/* 2048 */ 10240, 12288, 14336, 16384
};
static const u16 size_class_slots[] = {
/* 0 */ 256,
/* 16 */ 256, 128, 85, 64, 51, 42, 36, 64,
/* 32 */ 51, 64, 54, 64,
/* 64 */ 64, 64, 64, 64,
/* 128 */ 64, 64, 64, 64,
/* 256 */ 16, 16, 16, 16,
/* 512 */ 8, 8, 8, 8,
/* 1024 */ 8, 8, 8, 8,
/* 2048 */ 6, 5, 4, 4
};
int get_metadata_key(void) {
#ifdef USE_PKEY
return ro.metadata_pkey;
#else
return -1;
#endif
}
#ifdef USE_PKEY
static inline void thread_set_metadata_access(unsigned access) {
if (ro.metadata_pkey == -1) {
return;
}
pkey_set(ro.metadata_pkey, access);
}
#endif
static inline void thread_unseal_metadata(void) {
#ifdef USE_PKEY
thread_set_metadata_access(0);
#endif
}
static inline void thread_seal_metadata(void) {
#ifdef USE_PKEY
thread_set_metadata_access(PKEY_DISABLE_ACCESS);
#endif
}
#define N_SIZE_CLASSES (sizeof(size_classes) / sizeof(size_classes[0]))
struct size_info {
size_t size;
size_t class;
};
static inline struct size_info get_size_info(size_t size) {
if (size == 0) {
return (struct size_info){0, 0};
}
if (size <= 128) {
return (struct size_info){(size + 15) & ~15, ((size - 1) >> 4) + 1};
}
for (unsigned class = 9; class < N_SIZE_CLASSES; class++) {
size_t real_size = size_classes[class];
if (size <= real_size) {
return (struct size_info){real_size, class};
}
}
fatal_error("invalid size for slabs");
}
// alignment must be a power of 2 <= PAGE_SIZE since slabs are only page aligned
static inline struct size_info get_size_info_align(size_t size, size_t alignment) {
for (unsigned class = 1; class < N_SIZE_CLASSES; class++) {
size_t real_size = size_classes[class];
if (size <= real_size && !(real_size & (alignment - 1))) {
return (struct size_info){real_size, class};
}
}
fatal_error("invalid size for slabs");
}
static size_t get_slab_size(size_t slots, size_t size) {
return PAGE_CEILING(slots * size);
}
// limit on the number of cached empty slabs before attempting purging instead
static const size_t max_empty_slabs_total = 64 * 1024;
struct __attribute__((aligned(CACHELINE_SIZE))) size_class {
struct mutex lock;
void *class_region_start;
struct slab_metadata *slab_info;
struct libdivide_u32_t size_divisor;
struct libdivide_u64_t slab_size_divisor;
// slabs with at least one allocated slot and at least one free slot
//
// LIFO doubly-linked list
struct slab_metadata *partial_slabs;
// slabs without allocated slots that are cached for near-term usage
//
// LIFO singly-linked list
struct slab_metadata *empty_slabs;
size_t empty_slabs_total; // length * slab_size
// slabs without allocated slots that are purged and memory protected
//
// FIFO singly-linked list
struct slab_metadata *free_slabs_head;
struct slab_metadata *free_slabs_tail;
struct slab_metadata *free_slabs_quarantine[FREE_SLABS_QUARANTINE_RANDOM_SIZE];
struct random_state rng;
size_t metadata_allocated;
size_t metadata_count;
size_t metadata_count_unguarded;
};
#define CLASS_REGION_SIZE (128ULL * 1024 * 1024 * 1024)
#define REAL_CLASS_REGION_SIZE (CLASS_REGION_SIZE * 2)
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 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);
}
#define MAX_METADATA_MAX (CLASS_REGION_SIZE / PAGE_SIZE)
static size_t get_metadata_max(size_t slab_size) {
return CLASS_REGION_SIZE / 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)) {
size_t metadata_max = get_metadata_max(slab_size);
if (c->metadata_count >= metadata_max) {
errno = ENOMEM;
return NULL;
}
size_t allocate = max(c->metadata_allocated * 2, PAGE_SIZE / sizeof(struct slab_metadata));
if (allocate > metadata_max) {
allocate = metadata_max;
}
if (memory_protect_rw_metadata(c->slab_info, allocate * sizeof(struct slab_metadata))) {
return NULL;
}
c->metadata_allocated = allocate;
}
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_unguarded++;
if (c->metadata_count_unguarded >= GUARD_SLABS_INTERVAL) {
c->metadata_count++;
c->metadata_count_unguarded = 0;
}
return metadata;
}
static void set_slot(struct slab_metadata *metadata, size_t index) {
size_t bucket = index / 64;
metadata->bitmap[bucket] |= 1UL << (index - bucket * 64);
}
static void clear_slot(struct slab_metadata *metadata, size_t index) {
size_t bucket = index / 64;
metadata->bitmap[bucket] &= ~(1UL << (index - bucket * 64));
}
static bool get_slot(struct slab_metadata *metadata, size_t index) {
size_t bucket = index / 64;
return (metadata->bitmap[bucket] >> (index - bucket * 64)) & 1UL;
}
static u64 get_mask(size_t slots) {
return slots < 64 ? ~0UL << slots : 0;
}
static size_t get_free_slot(struct random_state *rng, size_t slots, struct slab_metadata *metadata) {
if (SLOT_RANDOMIZE) {
// randomize start location for linear search (uniform random choice is too slow)
unsigned random_index = get_random_u16_uniform(rng, slots);
unsigned first_bitmap = random_index / 64;
u64 random_split = ~(~0UL << (random_index - first_bitmap * 64));
for (unsigned i = first_bitmap; i <= (slots - 1) / 64; i++) {
u64 masked = metadata->bitmap[i];
if (i == slots / 64) {
masked |= get_mask(slots - i * 64);
}
if (i == first_bitmap) {
masked |= random_split;
}
if (masked == ~0UL) {
continue;
}
return ffzl(masked) - 1 + i * 64;
}
}
for (unsigned i = 0; i <= (slots - 1) / 64; i++) {
u64 masked = metadata->bitmap[i];
if (i == (slots - 1) / 64) {
masked |= get_mask(slots - i * 64);
}
if (masked == ~0UL) {
continue;
}
return ffzl(masked) - 1 + i * 64;
}
fatal_error("no zero bits");
}
static bool has_free_slots(size_t slots, struct slab_metadata *metadata) {
if (slots <= 64) {
u64 masked = metadata->bitmap[0] | get_mask(slots);
return masked != ~0UL;
} else if (slots <= 128) {
u64 masked = metadata->bitmap[1] | get_mask(slots - 64);
return metadata->bitmap[0] != ~0UL || masked != ~0UL;
} else if (slots <= 192) {
u64 masked = metadata->bitmap[2] | get_mask(slots - 128);
return metadata->bitmap[0] != ~0UL || metadata->bitmap[1] != ~0UL || masked != ~0UL;
}
u64 masked = metadata->bitmap[3] | get_mask(slots - 192);
return metadata->bitmap[0] != ~0UL || metadata->bitmap[1] != ~0UL || metadata->bitmap[2] != ~0UL || masked != ~0UL;
}
static bool is_free_slab(struct slab_metadata *metadata) {
return !metadata->bitmap[0] && !metadata->bitmap[1] && !metadata->bitmap[2] &&
!metadata->bitmap[3];
}
static struct slab_metadata *get_metadata(struct size_class *c, void *p) {
size_t offset = (char *)p - (char *)c->class_region_start;
size_t index = libdivide_u64_do(offset, &c->slab_size_divisor);
// still caught without this check either as a read access violation or "double free"
if (index >= c->metadata_allocated) {
fatal_error("invalid free within a slab yet to be used");
}
return c->slab_info + index;
}
static void *slot_pointer(size_t size, void *slab, size_t slot) {
return (char *)slab + slot * size;
}
static void write_after_free_check(const void *p, size_t size) {
if (!WRITE_AFTER_FREE_CHECK) {
return;
}
for (size_t i = 0; i < size; i += sizeof(u64)) {
if (*(const u64 *)(p + i)) {
fatal_error("detected write after free");
}
}
}
static const u64 canary_mask = __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ ?
0xffffffffffffff00UL :
0x00ffffffffffffffUL;
static void set_canary(struct slab_metadata *metadata, void *p, size_t size) {
memcpy((char *)p + size - canary_size, &metadata->canary_value, canary_size);
}
static inline void *allocate_small(size_t requested_size) {
struct size_info info = get_size_info(requested_size);
size_t size = info.size ? info.size : 16;
struct size_class *c = &ro.size_class_metadata[info.class];
size_t slots = size_class_slots[info.class];
size_t slab_size = get_slab_size(slots, size);
mutex_lock(&c->lock);
if (c->partial_slabs == NULL) {
if (c->empty_slabs != NULL) {
struct slab_metadata *metadata = c->empty_slabs;
c->empty_slabs = c->empty_slabs->next;
c->empty_slabs_total -= slab_size;
metadata->next = NULL;
metadata->prev = NULL;
c->partial_slabs = metadata;
void *slab = get_slab(c, slab_size, metadata);
size_t slot = get_free_slot(&c->rng, slots, metadata);
set_slot(metadata, slot);
void *p = slot_pointer(size, slab, slot);
if (requested_size) {
write_after_free_check(p, size - canary_size);
set_canary(metadata, p, size);
}
mutex_unlock(&c->lock);
return p;
} else if (c->free_slabs_head != NULL) {
struct slab_metadata *metadata = c->free_slabs_head;
metadata->canary_value = get_random_u64(&c->rng);
void *slab = get_slab(c, slab_size, metadata);
if (requested_size && memory_protect_rw(slab, slab_size)) {
mutex_unlock(&c->lock);
return NULL;
}
c->free_slabs_head = c->free_slabs_head->next;
if (c->free_slabs_head == NULL) {
c->free_slabs_tail = NULL;
}
metadata->next = NULL;
metadata->prev = NULL;
c->partial_slabs = metadata;
size_t slot = get_free_slot(&c->rng, slots, metadata);
set_slot(metadata, slot);
void *p = slot_pointer(size, slab, slot);
if (requested_size) {
set_canary(metadata, p, size);
}
mutex_unlock(&c->lock);
return p;
}
struct slab_metadata *metadata = alloc_metadata(c, slab_size, requested_size);
if (unlikely(metadata == NULL)) {
mutex_unlock(&c->lock);
return NULL;
}
metadata->canary_value = get_random_u64(&c->rng) & canary_mask;
c->partial_slabs = metadata;
void *slab = get_slab(c, slab_size, metadata);
size_t slot = get_free_slot(&c->rng, slots, metadata);
set_slot(metadata, slot);
void *p = slot_pointer(size, slab, slot);
if (requested_size) {
set_canary(metadata, p, size);
}
mutex_unlock(&c->lock);
return p;
}
struct slab_metadata *metadata = c->partial_slabs;
size_t slot = get_free_slot(&c->rng, slots, metadata);
set_slot(metadata, slot);
if (!has_free_slots(slots, metadata)) {
c->partial_slabs = c->partial_slabs->next;
if (c->partial_slabs) {
c->partial_slabs->prev = NULL;
}
}
void *slab = get_slab(c, slab_size, metadata);
void *p = slot_pointer(size, slab, slot);
if (requested_size) {
write_after_free_check(p, size - canary_size);
set_canary(metadata, p, size);
}
mutex_unlock(&c->lock);
return p;
}
static size_t slab_size_class(void *p) {
size_t offset = (char *)p - (char *)ro.slab_region_start;
return offset / REAL_CLASS_REGION_SIZE;
}
static size_t slab_usable_size(void *p) {
return size_classes[slab_size_class(p)];
}
static void enqueue_free_slab(struct size_class *c, struct slab_metadata *metadata) {
metadata->next = NULL;
static_assert(FREE_SLABS_QUARANTINE_RANDOM_SIZE < (u16)-1, "free slabs quarantine too large");
size_t index = get_random_u16_uniform(&c->rng, FREE_SLABS_QUARANTINE_RANDOM_SIZE);
struct slab_metadata *substitute = c->free_slabs_quarantine[index];
c->free_slabs_quarantine[index] = metadata;
if (substitute == NULL) {
return;
}
if (c->free_slabs_tail != NULL) {
c->free_slabs_tail->next = substitute;
} else {
c->free_slabs_head = substitute;
}
c->free_slabs_tail = substitute;
}
static inline void deallocate_small(void *p, const size_t *expected_size) {
size_t class = slab_size_class(p);
struct size_class *c = &ro.size_class_metadata[class];
size_t size = size_classes[class];
if (expected_size && size != *expected_size) {
fatal_error("sized deallocation mismatch (small)");
}
bool is_zero_size = size == 0;
if (is_zero_size) {
size = 16;
}
size_t slots = size_class_slots[class];
size_t slab_size = get_slab_size(slots, size);
mutex_lock(&c->lock);
struct slab_metadata *metadata = get_metadata(c, p);
void *slab = get_slab(c, slab_size, metadata);
size_t slot = libdivide_u32_do((char *)p - (char *)slab, &c->size_divisor);
if (slot_pointer(size, slab, slot) != p) {
fatal_error("invalid unaligned free");
}
if (!get_slot(metadata, slot)) {
fatal_error("double free");
}
if (!is_zero_size) {
if (ZERO_ON_FREE) {
memset(p, 0, size - canary_size);
}
if (canary_size) {
u64 canary_value;
memcpy(&canary_value, (char *)p + size - canary_size, canary_size);
if (unlikely(canary_value != metadata->canary_value)) {
fatal_error("canary corrupted");
}
}
}
if (!has_free_slots(slots, metadata)) {
metadata->next = c->partial_slabs;
metadata->prev = NULL;
if (c->partial_slabs) {
c->partial_slabs->prev = metadata;
}
c->partial_slabs = metadata;
}
clear_slot(metadata, slot);
if (is_free_slab(metadata)) {
if (metadata->prev) {
metadata->prev->next = metadata->next;
} else {
c->partial_slabs = metadata->next;
}
if (metadata->next) {
metadata->next->prev = metadata->prev;
}
metadata->prev = NULL;
if (c->empty_slabs_total + slab_size > max_empty_slabs_total) {
if (!memory_map_fixed(slab, slab_size)) {
enqueue_free_slab(c, metadata);
mutex_unlock(&c->lock);
return;
}
// handle out-of-memory by just putting it into the empty slabs list
}
metadata->next = c->empty_slabs;
c->empty_slabs = metadata;
c->empty_slabs_total += slab_size;
}
mutex_unlock(&c->lock);
}
struct region_metadata {
void *p;
size_t size;
size_t guard_size;
};
struct quarantine_info {
void *p;
size_t size;
};
#define INITIAL_REGION_TABLE_SIZE 256
#define MAX_REGION_TABLE_SIZE (CLASS_REGION_SIZE / PAGE_SIZE / sizeof(struct region_metadata))
struct region_allocator {
struct mutex lock;
struct region_metadata *regions;
size_t total;
size_t free;
struct quarantine_info quarantine_random[REGION_QUARANTINE_RANDOM_SIZE];
struct quarantine_info quarantine_queue[REGION_QUARANTINE_QUEUE_SIZE];
size_t quarantine_queue_index;
struct random_state rng;
};
struct __attribute__((aligned(PAGE_SIZE))) slab_info_mapping {
struct slab_metadata slab_info[MAX_METADATA_MAX];
};
struct __attribute__((aligned(PAGE_SIZE))) allocator_state {
struct size_class size_class_metadata[N_SIZE_CLASSES];
struct region_allocator region_allocator;
// padding until next page boundary for mprotect
struct region_metadata regions_a[MAX_REGION_TABLE_SIZE] __attribute__((aligned(PAGE_SIZE)));
// padding until next page boundary for mprotect
struct region_metadata regions_b[MAX_REGION_TABLE_SIZE] __attribute__((aligned(PAGE_SIZE)));
// padding until next page boundary for mprotect
struct slab_info_mapping slab_info_mapping[N_SIZE_CLASSES];
// padding until next page boundary for mprotect
};
static void regions_quarantine_deallocate_pages(void *p, size_t size, size_t guard_size) {
if (size >= REGION_QUARANTINE_SKIP_THRESHOLD) {
deallocate_pages(p, size, guard_size);
return;
}
if (unlikely(memory_map_fixed(p, size))) {
deallocate_pages(p, size, guard_size);
return;
}
struct quarantine_info a =
(struct quarantine_info){(char *)p - guard_size, size + guard_size * 2};
struct region_allocator *ra = ro.region_allocator;
mutex_lock(&ra->lock);
size_t index = get_random_u64_uniform(&ra->rng, REGION_QUARANTINE_RANDOM_SIZE);
struct quarantine_info b = ra->quarantine_random[index];
ra->quarantine_random[index] = a;
if (b.p == NULL) {
mutex_unlock(&ra->lock);
return;
}
a = ra->quarantine_queue[ra->quarantine_queue_index];
ra->quarantine_queue[ra->quarantine_queue_index] = b;
ra->quarantine_queue_index = (ra->quarantine_queue_index + 1) % REGION_QUARANTINE_QUEUE_SIZE;
mutex_unlock(&ra->lock);
if (a.p != NULL) {
memory_unmap(a.p, a.size);
}
}
static size_t hash_page(void *p) {
uintptr_t u = (uintptr_t)p >> PAGE_SHIFT;
size_t sum = u;
sum = (sum << 7) - sum + (u >> 16);
sum = (sum << 7) - sum + (u >> 32);
sum = (sum << 7) - sum + (u >> 48);
return sum;
}
static int regions_grow(void) {
struct region_allocator *ra = ro.region_allocator;
if (ra->total > SIZE_MAX / sizeof(struct region_metadata) / 2) {
return 1;
}
size_t newtotal = ra->total * 2;
size_t newsize = newtotal * sizeof(struct region_metadata);
size_t mask = newtotal - 1;
if (newtotal > MAX_REGION_TABLE_SIZE) {
return 1;
}
struct region_metadata *p = ra->regions == ro.regions[0] ?
ro.regions[1] : ro.regions[0];
if (memory_protect_rw_metadata(p, newsize)) {
return 1;
}
for (size_t i = 0; i < ra->total; i++) {
void *q = ra->regions[i].p;
if (q != NULL) {
size_t index = hash_page(q) & mask;
while (p[index].p != NULL) {
index = (index - 1) & mask;
}
p[index] = ra->regions[i];
}
}
memory_map_fixed(ra->regions, ra->total * sizeof(struct region_metadata));
ra->free = ra->free + ra->total;
ra->total = newtotal;
ra->regions = p;
return 0;
}
static int regions_insert(void *p, size_t size, size_t guard_size) {
struct region_allocator *ra = ro.region_allocator;
if (ra->free * 4 < ra->total) {
if (regions_grow()) {
return 1;
}
}
size_t mask = ra->total - 1;
size_t index = hash_page(p) & mask;
void *q = ra->regions[index].p;
while (q != NULL) {
index = (index - 1) & mask;
q = ra->regions[index].p;
}
ra->regions[index].p = p;
ra->regions[index].size = size;
ra->regions[index].guard_size = guard_size;
ra->free--;
return 0;
}
static struct region_metadata *regions_find(void *p) {
struct region_allocator *ra = ro.region_allocator;
size_t mask = ra->total - 1;
size_t index = hash_page(p) & mask;
void *r = ra->regions[index].p;
while (r != p && r != NULL) {
index = (index - 1) & mask;
r = ra->regions[index].p;
}
return (r == p && r != NULL) ? &ra->regions[index] : NULL;
}
static void regions_delete(struct region_metadata *region) {
struct region_allocator *ra = ro.region_allocator;
size_t mask = ra->total - 1;
ra->free++;
size_t i = region - ra->regions;
for (;;) {
ra->regions[i].p = NULL;
ra->regions[i].size = 0;
size_t j = i;
for (;;) {
i = (i - 1) & mask;
if (ra->regions[i].p == NULL) {
return;
}
size_t r = hash_page(ra->regions[i].p) & mask;
if ((i <= r && r < j) || (r < j && j < i) || (j < i && i <= r)) {
continue;
}
ra->regions[j] = ra->regions[i];
break;
}
}
}
static void full_lock(void) {
thread_unseal_metadata();
mutex_lock(&ro.region_allocator->lock);
for (unsigned class = 0; class < N_SIZE_CLASSES; class++) {
mutex_lock(&ro.size_class_metadata[class].lock);
}
thread_seal_metadata();
}
static void full_unlock(void) {
thread_unseal_metadata();
mutex_unlock(&ro.region_allocator->lock);
for (unsigned class = 0; class < N_SIZE_CLASSES; class++) {
mutex_unlock(&ro.size_class_metadata[class].lock);
}
thread_seal_metadata();
}
static void post_fork_child(void) {
thread_unseal_metadata();
#ifdef USE_PKEY
// disable sealing to work around kernel bug causing fork to lose the pkey setup
memory_protect_rw(&ro, sizeof(ro));
ro.metadata_pkey = -1;
memory_protect_ro(&ro, sizeof(ro));
#endif
mutex_init(&ro.region_allocator->lock);
random_state_init(&ro.region_allocator->rng);
for (unsigned class = 0; class < N_SIZE_CLASSES; class++) {
struct size_class *c = &ro.size_class_metadata[class];
mutex_init(&c->lock);
random_state_init(&c->rng);
}
thread_seal_metadata();
}
static inline bool is_init(void) {
return atomic_load_explicit(&ro.initialized, memory_order_acquire);
}
static inline void enforce_init(void) {
if (!is_init()) {
fatal_error("invalid uninitialized allocator usage");
}
}
COLD static void init_slow_path(void) {
static struct mutex lock = MUTEX_INITIALIZER;
mutex_lock(&lock);
if (is_init()) {
mutex_unlock(&lock);
return;
}
#ifdef USE_PKEY
ro.metadata_pkey = pkey_alloc(0, 0);
#endif
if (sysconf(_SC_PAGESIZE) != PAGE_SIZE) {
fatal_error("page size mismatch");
}
struct random_state *rng = allocate_pages(sizeof(struct random_state), PAGE_SIZE, true);
if (rng == NULL) {
fatal_error("failed to allocate init rng");
}
random_state_init(rng);
size_t metadata_guard_size =
(get_random_u64_uniform(rng, REAL_CLASS_REGION_SIZE / PAGE_SIZE) + 1) * PAGE_SIZE;
struct allocator_state *allocator_state =
allocate_pages(sizeof(struct allocator_state), metadata_guard_size, false);
if (allocator_state == NULL) {
fatal_error("failed to reserve allocator state");
}
if (memory_protect_rw_metadata(allocator_state, offsetof(struct allocator_state, regions_a))) {
fatal_error("failed to unprotect allocator state");
}
ro.region_allocator = &allocator_state->region_allocator;
struct region_allocator *ra = ro.region_allocator;
mutex_init(&ra->lock);
random_state_init(&ra->rng);
ro.regions[0] = allocator_state->regions_a;
ro.regions[1] = allocator_state->regions_b;
ra->regions = ro.regions[0];
ra->total = INITIAL_REGION_TABLE_SIZE;
ra->free = INITIAL_REGION_TABLE_SIZE;
if (memory_protect_rw_metadata(ra->regions, ra->total * sizeof(struct region_metadata))) {
fatal_error("failed to unprotect memory for regions table");
}
ro.slab_region_start = memory_map(slab_region_size);
if (ro.slab_region_start == NULL) {
fatal_error("failed to allocate slab region");
}
ro.slab_region_end = (char *)ro.slab_region_start + slab_region_size;
ro.size_class_metadata = allocator_state->size_class_metadata;
for (unsigned class = 0; class < N_SIZE_CLASSES; class++) {
struct size_class *c = &ro.size_class_metadata[class];
mutex_init(&c->lock);
random_state_init(&c->rng);
size_t bound = (REAL_CLASS_REGION_SIZE - CLASS_REGION_SIZE) / PAGE_SIZE - 1;
size_t gap = (get_random_u64_uniform(rng, bound) + 1) * PAGE_SIZE;
c->class_region_start = (char *)ro.slab_region_start + REAL_CLASS_REGION_SIZE * class + gap;
size_t size = size_classes[class];
if (size == 0) {
size = 16;
}
c->size_divisor = libdivide_u32_gen(size);
size_t slab_size = get_slab_size(size_class_slots[class], size);
c->slab_size_divisor = libdivide_u64_gen(slab_size);
c->slab_info = allocator_state->slab_info_mapping[class].slab_info;
}
deallocate_pages(rng, sizeof(struct random_state), PAGE_SIZE);
atomic_store_explicit(&ro.initialized, true, memory_order_release);
if (memory_protect_ro(&ro, sizeof(ro))) {
fatal_error("failed to protect allocator data");
}
mutex_unlock(&lock);
// may allocate, so wait until the allocator is initialized to avoid deadlocking
if (atfork(full_lock, full_unlock, post_fork_child)) {
fatal_error("pthread_atfork failed");
}
}
static inline void init(void) {
if (unlikely(!is_init())) {
init_slow_path();
}
}
// trigger early initialization to set up pthread_atfork and protect state as soon as possible
COLD __attribute__((constructor(101))) static void trigger_early_init(void) {
// avoid calling init directly to skip it if this isn't the malloc implementation
h_free(h_malloc(16));
}
static size_t get_guard_size(struct random_state *state, size_t size) {
return (get_random_u64_uniform(state, size / PAGE_SIZE / GUARD_SIZE_DIVISOR) + 1) * PAGE_SIZE;
}
static void *allocate(size_t size) {
if (size <= max_slab_size_class) {
return allocate_small(size);
}
struct region_allocator *ra = ro.region_allocator;
mutex_lock(&ra->lock);
size_t guard_size = get_guard_size(&ra->rng, size);
mutex_unlock(&ra->lock);
void *p = allocate_pages(size, guard_size, true);
if (p == NULL) {
return NULL;
}
mutex_lock(&ra->lock);
if (regions_insert(p, size, guard_size)) {
mutex_unlock(&ra->lock);
deallocate_pages(p, size, guard_size);
return NULL;
}
mutex_unlock(&ra->lock);
return p;
}
static void deallocate_large(void *p, const size_t *expected_size) {
enforce_init();
thread_unseal_metadata();
struct region_allocator *ra = ro.region_allocator;
mutex_lock(&ra->lock);
struct region_metadata *region = regions_find(p);
if (region == NULL) {
fatal_error("invalid free");
}
size_t size = region->size;
if (expected_size && size != *expected_size) {
fatal_error("sized deallocation mismatch (large)");
}
size_t guard_size = region->guard_size;
regions_delete(region);
mutex_unlock(&ra->lock);
regions_quarantine_deallocate_pages(p, size, guard_size);
}
static size_t adjust_size_for_canaries(size_t size) {
if (size > 0 && size <= max_slab_size_class) {
return size + canary_size;
}
return size;
}
EXPORT void *h_malloc(size_t size) {
init();
thread_unseal_metadata();
size = adjust_size_for_canaries(size);
void *p = allocate(size);
thread_seal_metadata();
return p;
}
EXPORT void *h_calloc(size_t nmemb, size_t size) {
size_t total_size;
if (unlikely(__builtin_mul_overflow(nmemb, size, &total_size))) {
errno = ENOMEM;
return NULL;
}
init();
thread_unseal_metadata();
total_size = adjust_size_for_canaries(total_size);
if (ZERO_ON_FREE) {
void *p = allocate(total_size);
thread_seal_metadata();
return p;
}
void *p = allocate(total_size);
thread_seal_metadata();
if (unlikely(p == NULL)) {
return NULL;
}
if (size && size <= max_slab_size_class) {
memset(p, 0, total_size - canary_size);
}
return p;
}
#define MREMAP_MOVE_THRESHOLD (32 * 1024 * 1024)
static_assert(MREMAP_MOVE_THRESHOLD >= REGION_QUARANTINE_SKIP_THRESHOLD,
"mremap move threshold must be above region quarantine limit");
EXPORT void *h_realloc(void *old, size_t size) {
if (old == NULL) {
init();
thread_unseal_metadata();
size = adjust_size_for_canaries(size);
void *p = allocate(size);
thread_seal_metadata();
return p;
}
size = adjust_size_for_canaries(size);
size_t old_size;
if (old >= ro.slab_region_start && old < ro.slab_region_end) {
old_size = slab_usable_size(old);
if (size <= max_slab_size_class && get_size_info(size).size == old_size) {
return old;
}
enforce_init();
thread_unseal_metadata();
} else {
enforce_init();
thread_unseal_metadata();
struct region_allocator *ra = ro.region_allocator;
mutex_lock(&ra->lock);
struct region_metadata *region = regions_find(old);
if (region == NULL) {
fatal_error("invalid realloc");
}
old_size = region->size;
size_t old_guard_size = region->guard_size;
if (PAGE_CEILING(old_size) == PAGE_CEILING(size)) {
region->size = size;
mutex_unlock(&ra->lock);
thread_seal_metadata();
return old;
}
mutex_unlock(&ra->lock);
size_t old_rounded_size = PAGE_CEILING(old_size);
size_t rounded_size = PAGE_CEILING(size);
if (size > max_slab_size_class) {
// in-place shrink
if (size < old_size) {
void *new_end = (char *)old + rounded_size;
if (memory_map_fixed(new_end, old_guard_size)) {
thread_seal_metadata();
return NULL;
}
void *new_guard_end = (char *)new_end + old_guard_size;
regions_quarantine_deallocate_pages(new_guard_end, old_rounded_size - rounded_size, 0);
mutex_lock(&ra->lock);
struct region_metadata *region = regions_find(old);
if (region == NULL) {
fatal_error("invalid realloc");
}
region->size = size;
mutex_unlock(&ra->lock);
thread_seal_metadata();
return old;
}
// in-place growth
void *guard_end = (char *)old + old_rounded_size + old_guard_size;
size_t extra = rounded_size - old_rounded_size;
if (!memory_remap((char *)old + old_rounded_size, old_guard_size, old_guard_size + extra)) {
if (memory_protect_rw((char *)old + old_rounded_size, extra)) {
memory_unmap(guard_end, extra);
} else {
mutex_lock(&ra->lock);
struct region_metadata *region = regions_find(old);
if (region == NULL) {
fatal_error("invalid realloc");
}
region->size = size;
mutex_unlock(&ra->lock);
thread_seal_metadata();
return old;
}
}
size_t copy_size = min(size, old_size);
if (copy_size >= MREMAP_MOVE_THRESHOLD) {
void *new = allocate(size);
if (new == NULL) {
thread_seal_metadata();
return NULL;
}
mutex_lock(&ra->lock);
struct region_metadata *region = regions_find(old);
if (region == NULL) {
fatal_error("invalid realloc");
}
regions_delete(region);
mutex_unlock(&ra->lock);
if (memory_remap_fixed(old, old_size, new, size)) {
memcpy(new, old, copy_size);
deallocate_pages(old, old_size, old_guard_size);
} else {
memory_unmap((char *)old - old_guard_size, old_guard_size);
memory_unmap((char *)old + PAGE_CEILING(old_size), old_guard_size);
}
thread_seal_metadata();
return new;
}
}
}
void *new = allocate(size);
if (new == NULL) {
thread_seal_metadata();
return NULL;
}
size_t copy_size = min(size, old_size);
if (size > 0 && size <= max_slab_size_class) {
copy_size -= canary_size;
}
memcpy(new, old, copy_size);
if (old_size <= max_slab_size_class) {
deallocate_small(old, NULL);
} else {
deallocate_large(old, NULL);
}
thread_seal_metadata();
return new;
}
static int alloc_aligned(void **memptr, size_t alignment, size_t size, size_t min_alignment) {
if ((alignment - 1) & alignment || alignment < min_alignment) {
return EINVAL;
}
if (alignment <= PAGE_SIZE) {
if (size <= max_slab_size_class && alignment > min_align) {
size = get_size_info_align(size, alignment).size;
}
void *p = allocate(size);
if (p == NULL) {
return ENOMEM;
}
*memptr = p;
return 0;
}
struct region_allocator *ra = ro.region_allocator;
mutex_lock(&ra->lock);
size_t guard_size = get_guard_size(&ra->rng, size);
mutex_unlock(&ra->lock);
void *p = allocate_pages_aligned(size, alignment, guard_size);
if (p == NULL) {
return ENOMEM;
}
mutex_lock(&ra->lock);
if (regions_insert(p, size, guard_size)) {
mutex_unlock(&ra->lock);
deallocate_pages(p, size, guard_size);
return ENOMEM;
}
mutex_unlock(&ra->lock);
*memptr = p;
return 0;
}
static void *alloc_aligned_simple(size_t alignment, size_t size) {
void *ptr;
int ret = alloc_aligned(&ptr, alignment, size, 1);
if (ret) {
errno = ret;
return NULL;
}
return ptr;
}
EXPORT int h_posix_memalign(void **memptr, size_t alignment, size_t size) {
init();
thread_unseal_metadata();
size = adjust_size_for_canaries(size);
int ret = alloc_aligned(memptr, alignment, size, sizeof(void *));
thread_seal_metadata();
return ret;
}
EXPORT void *h_aligned_alloc(size_t alignment, size_t size) {
init();
thread_unseal_metadata();
size = adjust_size_for_canaries(size);
void *p = alloc_aligned_simple(alignment, size);
thread_seal_metadata();
return p;
}
EXPORT void *h_memalign(size_t alignment, size_t size) ALIAS(h_aligned_alloc);
EXPORT void *h_valloc(size_t size) {
init();
thread_unseal_metadata();
size = adjust_size_for_canaries(size);
void *p = alloc_aligned_simple(PAGE_SIZE, size);
thread_seal_metadata();
return p;
}
EXPORT void *h_pvalloc(size_t size) {
size = PAGE_CEILING(size);
if (!size) {
errno = ENOMEM;
return NULL;
}
init();
thread_unseal_metadata();
size = adjust_size_for_canaries(size);
void *p = alloc_aligned_simple(PAGE_SIZE, size);
thread_seal_metadata();
return p;
}
EXPORT void h_free(void *p) {
if (p == NULL) {
return;
}
if (p >= ro.slab_region_start && p < ro.slab_region_end) {
thread_unseal_metadata();
deallocate_small(p, NULL);
return;
}
deallocate_large(p, NULL);
thread_seal_metadata();
}
EXPORT void h_cfree(void *ptr) ALIAS(h_free);
EXPORT void h_free_sized(void *p, size_t expected_size) {
if (p == NULL) {
return;
}
if (p >= ro.slab_region_start && p < ro.slab_region_end) {
thread_unseal_metadata();
expected_size = get_size_info(adjust_size_for_canaries(expected_size)).size;
deallocate_small(p, &expected_size);
return;
}
deallocate_large(p, &expected_size);
thread_seal_metadata();
}
EXPORT size_t h_malloc_usable_size(void *p) {
if (p == NULL) {
return 0;
}
if (p >= ro.slab_region_start && p < ro.slab_region_end) {
size_t size = slab_usable_size(p);
return size ? size - canary_size : 0;
}
enforce_init();
thread_unseal_metadata();
struct region_allocator *ra = ro.region_allocator;
mutex_lock(&ra->lock);
struct region_metadata *region = regions_find(p);
if (p == NULL) {
fatal_error("invalid malloc_usable_size");
}
size_t size = region->size;
mutex_unlock(&ra->lock);
thread_seal_metadata();
return size;
}
EXPORT size_t h_malloc_object_size(void *p) {
if (p == NULL) {
return 0;
}
if (p >= ro.slab_region_start && p < ro.slab_region_end) {
size_t size = slab_usable_size(p);
return size ? size - canary_size : 0;
}
if (unlikely(!is_init())) {
return 0;
}
thread_unseal_metadata();
struct region_allocator *ra = ro.region_allocator;
mutex_lock(&ra->lock);
struct region_metadata *region = regions_find(p);
size_t size = p == NULL ? SIZE_MAX : region->size;
mutex_unlock(&ra->lock);
thread_seal_metadata();
return size;
}
EXPORT size_t h_malloc_object_size_fast(void *p) {
if (p == NULL) {
return 0;
}
if (p >= ro.slab_region_start && p < ro.slab_region_end) {
size_t size = slab_usable_size(p);
return size ? size - canary_size : 0;
}
if (unlikely(!is_init())) {
return 0;
}
return SIZE_MAX;
}
EXPORT int h_mallopt(UNUSED int param, UNUSED int value) {
return 0;
}
EXPORT int h_malloc_trim(UNUSED size_t pad) {
if (unlikely(!is_init())) {
return 0;
}
thread_unseal_metadata();
bool is_trimmed = false;
// skip zero byte size class since there's nothing to change
for (unsigned class = 1; class < N_SIZE_CLASSES; class++) {
struct size_class *c = &ro.size_class_metadata[class];
size_t slab_size = get_slab_size(size_class_slots[class], size_classes[class]);
mutex_lock(&c->lock);
struct slab_metadata *iterator = c->empty_slabs;
while (iterator) {
void *slab = get_slab(c, slab_size, iterator);
if (memory_map_fixed(slab, slab_size)) {
break;
}
struct slab_metadata *trimmed = iterator;
iterator = iterator->next;
c->empty_slabs_total -= slab_size;
enqueue_free_slab(c, trimmed);
is_trimmed = true;
}
c->empty_slabs = iterator;
mutex_unlock(&c->lock);
}
thread_seal_metadata();
return is_trimmed;
}
EXPORT void h_malloc_stats(void) {}
#if defined(__GLIBC__) || defined(__ANDROID__)
EXPORT struct mallinfo h_mallinfo(void) {
return (struct mallinfo){0};
}
#endif
EXPORT int h_malloc_info(UNUSED int options, UNUSED FILE *fp) {
errno = ENOSYS;
return -1;
}
COLD EXPORT void *h_malloc_get_state(void) {
return NULL;
}
COLD EXPORT int h_malloc_set_state(UNUSED void *state) {
return -2;
}
#ifdef __ANDROID__
EXPORT size_t __mallinfo_narenas(void) {
return 0;
}
EXPORT size_t __mallinfo_nbins(void) {
return 0;
}
EXPORT struct mallinfo __mallinfo_arena_info(UNUSED size_t arena) {
return (struct mallinfo){0};
}
EXPORT struct mallinfo __mallinfo_bin_info(UNUSED size_t arena, UNUSED size_t bin) {
return (struct mallinfo){0};
}
COLD EXPORT int h_iterate(UNUSED uintptr_t base, UNUSED size_t size,
UNUSED void (*callback)(uintptr_t ptr, size_t size, void *arg),
UNUSED void *arg) {
fatal_error("not implemented");
}
COLD EXPORT void h_malloc_disable(void) {
init();
thread_unseal_metadata();
full_lock();
thread_seal_metadata();
}
COLD EXPORT void h_malloc_enable(void) {
init();
thread_unseal_metadata();
full_unlock();
thread_seal_metadata();
}
#endif
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