void *apmalloc(size_t size) {
if (size == 0) return NULL;
size_t request_size = ALIGN(size + sizeof(header_t));
// if it's more than our last bin's capacity, just mmap it
if (request_size >= (1 << MAX_BINS)) {
request_size = round_to_next_page(request_size);
void *ptr = MMAP(request_size);
if (ptr == MAP_FAILED) return NULL;
header_t *header = (header_t*)ptr;
header->size = request_size;
return (void*)(header + 1);
}
// look for free blocks in our lists
for (unsigned int request_bin = bin_index(request_size); request_bin < MAX_BINS; request_bin++) {
header_t *candidate = free_list[request_bin];
while (candidate != NULL) {
// we found a suitable block
if (candidate->size >= request_size) {
// take this block out of the free list
if (candidate->prev) candidate->prev->next = candidate->next;
if (candidate->next) candidate->next->prev = candidate->prev;
if (!(candidate->prev || candidate->next)) free_list[request_bin] = NULL;
// if there's a remainder, add it back to the appropriate list
if (candidate->size > request_size) {
header_t *remainder = (header_t*)((char*)candidate + request_size);
remainder->size = candidate->size - request_size;
apfree(remainder + 1);
candidate->size = request_size;
}
return (void*)(candidate + 1);
}
candidate = candidate->next;
}
}
// no block big enough found, request and split a big chunk
void *ptr = MMAP(PAGE_SIZE);
if (ptr == MAP_FAILED) return NULL;
header_t *remainder = (header_t*)((char*)ptr + request_size);
remainder->size = PAGE_SIZE - request_size;
apfree(remainder + 1);
header_t *header = (header_t*)ptr;
header->size = request_size;
return (void*)(header + 1);
}
void *allocate_executable_buffer(uint64_t *length) {
uint64_t sys_pagesize=sysconf(_SC_PAGESIZE);
uint64_t real_length=round_to_next_page(*length);//round size to nearest page size
uint8_t *buf=mmap(NULL,real_length,PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_ANONYMOUS|MAP_SHARED,-1,0);
if(buf == MAP_FAILED) {
perror("Error allocating memory\n");
return (void*)-1;//a function shouldn't exit the main program by itself
}
*length=real_length;
return buf;
}
