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#include <stdlib.h>
#include <sys/mman.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <alloca.h>
#include <assert.h>
#include <Kernel/Syscall.h>
#include <AK/Assertions.h>
extern "C" {
#define MALLOC_SCRUB_BYTE 0x85
#define FREE_SCRUB_BYTE 0x82
struct MallocHeader {
uint16_t first_chunk_index;
uint16_t chunk_count;
size_t size;
uint32_t compute_xorcheck() const
{
return 0x19820413 ^ ((first_chunk_index << 16) | chunk_count) ^ size;
}
};
struct MallocFooter {
uint32_t xorcheck;
};
#define CHUNK_SIZE 8
#define POOL_SIZE 128 * 1024
static const size_t malloc_budget = POOL_SIZE;
static byte s_malloc_map[POOL_SIZE / CHUNK_SIZE / 8];
static byte* s_malloc_pool;
static uint32_t s_malloc_sum_alloc = 0;
static uint32_t s_malloc_sum_free = POOL_SIZE;
void* malloc(size_t size)
{
// We need space for the MallocHeader structure at the head of the block.
size_t real_size = size + sizeof(MallocHeader) + sizeof(MallocFooter);
if (s_malloc_sum_free < real_size) {
fprintf(stderr, "malloc(): Out of memory\ns_malloc_sum_free=%u, real_size=%x\n", s_malloc_sum_free, real_size);
assert(false);
}
size_t chunks_needed = real_size / CHUNK_SIZE;
if (real_size % CHUNK_SIZE)
chunks_needed++;
size_t chunks_here = 0;
size_t first_chunk = 0;
for (unsigned i = 0; i < (POOL_SIZE / CHUNK_SIZE / 8); ++i) {
if (s_malloc_map[i] == 0xff) {
// Skip over completely full bucket.
chunks_here = 0;
continue;
}
// FIXME: This scan can be optimized further with TZCNT.
for (unsigned j = 0; j < 8; ++j) {
if ((s_malloc_map[i] & (1<<j))) {
// This is in use, so restart chunks_here counter.
chunks_here = 0;
continue;
}
if (chunks_here == 0) {
// Mark where potential allocation starts.
first_chunk = i * 8 + j;
}
++chunks_here;
if (chunks_here == chunks_needed) {
auto* header = (MallocHeader*)(s_malloc_pool + (first_chunk * CHUNK_SIZE));
byte* ptr = ((byte*)header) + sizeof(MallocHeader);
header->chunk_count = chunks_needed;
header->first_chunk_index = first_chunk;
header->size = size;
auto* footer = (MallocFooter*)((byte*)header + (header->chunk_count * CHUNK_SIZE) - sizeof(MallocFooter));
footer->xorcheck = header->compute_xorcheck();
for (size_t k = first_chunk; k < (first_chunk + chunks_needed); ++k)
s_malloc_map[k / 8] |= 1 << (k % 8);
s_malloc_sum_alloc += header->chunk_count * CHUNK_SIZE;
s_malloc_sum_free -= header->chunk_count * CHUNK_SIZE;
memset(ptr, MALLOC_SCRUB_BYTE, (header->chunk_count * CHUNK_SIZE) - (sizeof(MallocHeader) + sizeof(MallocFooter)));
return ptr;
}
}
}
fprintf(stderr, "malloc(): Out of memory (no consecutive chunks found for size %u)\n", size);
volatile char* crashme = (char*)0xc007d00d;
*crashme = 0;
return nullptr;
}
static void validate_mallocation(void* ptr, const char* func)
{
auto* header = (MallocHeader*)((((byte*)ptr) - sizeof(MallocHeader)));
if (header->size == 0) {
fprintf(stderr, "%s called on bad pointer %p, size=0\n", func, ptr);
assert(false);
}
auto* footer = (MallocFooter*)((byte*)header + (header->chunk_count * CHUNK_SIZE) - sizeof(MallocFooter));
uint32_t expected_xorcheck = header->compute_xorcheck();
if (footer->xorcheck != expected_xorcheck) {
fprintf(stderr, "%s called on bad pointer %p, xorcheck=%w (expected %w)\n", func, ptr, footer->xorcheck, expected_xorcheck);
assert(false);
}
}
void free(void* ptr)
{
if (!ptr)
return;
validate_mallocation(ptr, "free()");
auto* header = (MallocHeader*)((((byte*)ptr) - sizeof(MallocHeader)));
for (unsigned i = header->first_chunk_index; i < (header->first_chunk_index + header->chunk_count); ++i)
s_malloc_map[i / 8] &= ~(1 << (i % 8));
s_malloc_sum_alloc -= header->chunk_count * CHUNK_SIZE;
s_malloc_sum_free += header->chunk_count * CHUNK_SIZE;
memset(header, FREE_SCRUB_BYTE, header->chunk_count * CHUNK_SIZE);
}
void __malloc_init()
{
s_malloc_pool = (byte*)mmap(nullptr, malloc_budget, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
int rc = set_mmap_name(s_malloc_pool, malloc_budget, "malloc pool");
if (rc < 0)
perror("set_mmap_name failed");
}
void* calloc(size_t nmemb, size_t)
{
(void) nmemb;
ASSERT_NOT_REACHED();
return nullptr;
}
void* realloc(void *ptr, size_t size)
{
validate_mallocation(ptr, "realloc()");
auto* header = (MallocHeader*)((((byte*)ptr) - sizeof(MallocHeader)));
size_t old_size = header->size;
auto* new_ptr = malloc(size);
memcpy(new_ptr, ptr, old_size);
return new_ptr;
}
void exit(int status)
{
_exit(status);
assert(false);
}
void abort()
{
// FIXME: Implement proper abort().
exit(253);
}
char* getenv(const char* name)
{
for (size_t i = 0; environ[i]; ++i) {
const char* decl = environ[i];
char* eq = strchr(decl, '=');
if (!eq)
continue;
size_t varLength = eq - decl;
char* var = (char*)alloca(varLength + 1);
memcpy(var, decl, varLength);
var[varLength] = '\0';
if (!strcmp(var, name)) {
char* value = eq + 1;
return value;
}
}
return nullptr;
}
int atoi(const char* str)
{
size_t len = strlen(str);
int value = 0;
bool isNegative = false;
for (size_t i = 0; i < len; ++i) {
if (i == 0 && str[0] == '-') {
isNegative = true;
continue;
}
if (str[i] < '0' || str[i] > '9')
return value;
value = value * 10;
value += str[i] - '0';
}
return isNegative ? -value : value;
}
long atol(const char* str)
{
static_assert(sizeof(int) == sizeof(long));
return atoi(str);
}
}
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