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#include "stddef.h" // for NULL
#include <atomic.h> // for LIBC_UNLOCK, LIBC_LOCK
#include <features.h> // for __weak
#include <libc.h> // for (anonymous struct)::(anonymous), (anonymous)
#include <malloc.h> // for page, page::(anonymous), class, global_size_c...
#include <stdatomic.h> // for atomic_flag_clear
#include <stdint.h> // for uint32_t, uint8_t, uintptr_t
#include <stdlib.h> // for malloc
#include <string.h> // for memset
#include <sys/mman.h> // for size_t, mmap, munmap, MAP_ANONYMOUS, MAP_FAILED
struct page *__malloc_pvec = NULL;
static __inline uint32_t get_size_class(size_t size)
{
uintptr_t minblock_count = (size + (16 - 1)) / 16;
if (size <= (16 * 64)) {
return (uint32_t)(minblock_count ? minblock_count : 1);
}
const uint32_t most_significant_bit =
(uint32_t)(63 - (int)__builtin_clzll(minblock_count));
const uint32_t subclass_bits =
(minblock_count >> (most_significant_bit - 2)) & 0x03;
return (uint32_t)((most_significant_bit << 2) + subclass_bits) + 41;
}
__weak void *malloc(size_t size);
void *malloc(size_t size)
{
if (size == 0)
return NULL;
LIBC_LOCK(libc.lock.malloc);
uint32_t class_index = get_size_class(size);
if (class_index >=
sizeof(global_size_class) / sizeof(global_size_class[0])) {
LIBC_UNLOCK(libc.lock.malloc);
return NULL;
}
const struct class *cls = &global_size_class[class_index];
struct page *p = __malloc_pvec;
while (p) {
if (p->flags == PAGE_SMALL && cls->size <= 16 * 64) {
LIBC_LOCK(p->lock);
if (p->block.used < p->block.count &&
p->block.size == cls->size) {
for (uint32_t i = 0; i < p->block.count; i++) {
int byte_index = i / 8;
int bit_index = i % 8;
if (!(p->bitmap[byte_index] &
(1 << bit_index))) {
p->bitmap[byte_index] |=
(1 << bit_index);
p->block.used++;
LIBC_UNLOCK(p->lock);
LIBC_UNLOCK(libc.lock.malloc);
if (p->heap == NULL)
return NULL;
return p->heap +
(i * p->block.size);
}
}
}
LIBC_UNLOCK(p->lock);
} else if (p->flags == PAGE_MEDIUM && cls->size > 16 * 64 &&
cls->size <= 16 * 8192) {
LIBC_LOCK(p->lock);
if (p->block.used < p->block.count &&
p->block.size == cls->size) {
for (uint32_t i = 0; i < p->block.count; i++) {
int byte_index = i / 8;
int bit_index = i % 8;
if (!(p->bitmap[byte_index] &
(1 << bit_index))) {
// Mark block as used
p->bitmap[byte_index] |=
(1 << bit_index);
p->block.used++;
LIBC_UNLOCK(p->lock);
LIBC_UNLOCK(libc.lock.malloc);
if (p->heap == NULL)
return NULL;
return p->heap +
(i * p->block.size);
}
}
}
LIBC_UNLOCK(p->lock);
} else if (p->flags == PAGE_LARGE && cls->size > 16 * 8192) {
LIBC_LOCK(p->lock);
if (p->block.used < p->block.count &&
p->block.size == cls->size) {
// Find free block
for (uint32_t i = 0; i < p->block.count; i++) {
int byte_index = i / 8;
int bit_index = i % 8;
if (!(p->bitmap[byte_index] &
(1 << bit_index))) {
p->bitmap[byte_index] |=
(1 << bit_index);
p->block.used++;
LIBC_UNLOCK(p->lock);
LIBC_UNLOCK(libc.lock.malloc);
if (p->heap == NULL)
return NULL;
return p->heap +
(i * p->block.size);
}
}
}
LIBC_UNLOCK(p->lock);
}
p = p->next;
}
size_t page_size;
enum { PAGE_TYPE_SMALL, PAGE_TYPE_MEDIUM, PAGE_TYPE_LARGE } page_type;
if (cls->size <= 16 * 64) {
page_size = SMALL_PAGE_SIZE;
page_type = PAGE_TYPE_SMALL;
} else if (cls->size <= 16 * 8192) {
page_size = MEDIUM_PAGE_SIZE;
page_type = PAGE_TYPE_MEDIUM;
} else {
page_size = LARGE_PAGE_SIZE;
page_type = PAGE_TYPE_LARGE;
}
size_t bitmap_size = (cls->count + 7) / 8;
void *mem = mmap(NULL, page_size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (mem == MAP_FAILED) {
LIBC_UNLOCK(libc.lock.malloc);
return NULL;
}
struct page *new_page = (struct page *)mem;
new_page->flags = (page_type == PAGE_TYPE_SMALL) ? PAGE_SMALL :
(page_type == PAGE_TYPE_MEDIUM) ? PAGE_MEDIUM :
PAGE_LARGE;
new_page->block.size = cls->size;
new_page->block.used = 0;
new_page->block.count = cls->count;
new_page->bitmap = (uint8_t *)mem + sizeof(struct page);
memset(new_page->bitmap, 0, bitmap_size);
new_page->heap = (uint8_t *)mem + sizeof(struct page) + bitmap_size;
if (new_page->heap == NULL || new_page->bitmap == NULL) {
munmap(mem, page_size);
LIBC_UNLOCK(libc.lock.malloc);
return NULL;
}
atomic_flag_clear(&new_page->lock);
new_page->next = __malloc_pvec;
new_page->prev = NULL;
if (__malloc_pvec) {
__malloc_pvec->prev = new_page;
}
__malloc_pvec = new_page;
// Mark the first block as used and return it
new_page->bitmap[0] |= 1;
new_page->block.used = 1;
LIBC_UNLOCK(libc.lock.malloc);
return new_page->heap;
}
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