#define _GNU_SOURCE
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <stdint.h>
#include <errno.h>
#include <sys/mman.h>
#include "libc.h"
#include "atomic.h"
#include "pthread_impl.h"
#include "malloc_impl.h"
#include "fork_impl.h"
#define malloc __libc_malloc
#define realloc __libc_realloc
#define free __libc_free
#if defined(__GNUC__) && defined(__PIC__)
#define inline inline __attribute__((always_inline))
#endif
static struct {
volatile uint64_t binmap;
struct bin bins[64];
volatile int split_merge_lock[2];
} mal;
/* Synchronization tools */
static inline void lock(volatile int *lk)
{
int need_locks = libc.need_locks;
if (need_locks) {
while(a_swap(lk, 1)) __wait(lk, lk+1, 1, 1);
if (need_locks < 0) libc.need_locks = 0;
}
}
static inline void unlock(volatile int *lk)
{
if (lk[0]) {
a_store(lk, 0);
if (lk[1]) __wake(lk, 1, 1);
}
}
static inline void lock_bin(int i)
{
lock(mal.bins[i].lock);
if (!mal.bins[i].head)
mal.bins[i].head = mal.bins[i].tail = BIN_TO_CHUNK(i);
}
static inline void unlock_bin(int i)
{
unlock(mal.bins[i].lock);
}
static int first_set(uint64_t x)
{
#if 1
return a_ctz_64(x);
#else
static const char debruijn64[64] = {
0, 1, 2, 53, 3, 7, 54, 27, 4, 38, 41, 8, 34, 55, 48, 28,
62, 5, 39, 46, 44, 42, 22, 9, 24, 35, 59, 56, 49, 18, 29, 11,
63, 52, 6, 26, 37, 40, 33, 47, 61, 45, 43, 21, 23, 58, 17, 10,
51, 25, 36, 32, 60, 20, 57, 16, 50, 31, 19, 15, 30, 14, 13, 12
};
static const char debruijn32[32] = {
0, 1, 23, 2, 29, 24, 19, 3, 30, 27, 25, 11, 20, 8, 4, 13,
31, 22, 28, 18, 26, 10, 7, 12, 21, 17, 9, 6, 16, 5, 15, 14
};
if (sizeof(long) < 8) {
uint32_t y = x;
if (!y) {
y = x>>32;
return 32 + debruijn32[(y&-y)*0x076be629 >> 27];
}
return debruijn32[(y&-y)*0x076be629 >> 27];
}
return debruijn64[(x&-x)*0x022fdd63cc95386dull >> 58];
#endif
}
static const unsigned char bin_tab[60] = {
32,33,34,35,36,36,37,37,38,38,39,39,
40,40,40,40,41,41,41,41,42,42,42,42,43,43,43,43,
44,44,44,44,44,44,44,44,45,45,45,45,45,45,45,45,
46,46,46,46,46,46,46,46,47,47,47,47,47,47,47,47,
};
static int bin_index(size_t x)
{
x = x / SIZE_ALIGN - 1;
if (x <= 32) return x;
if (x < 512) return bin_tab[x/8-4];
if (x > 0x1c00) return 63;
return bin_tab[x/128-4] + 16;
}
static int bin_index_up(size_t x)
{
x = x / SIZE_ALIGN - 1;
if (x <= 32) return x;
x--;
if (x < 512) return bin_tab[x/8-4] + 1;
return bin_tab[x/128-4] + 17;
}
#if 0
void __dump_heap(int x)
{
struct chunk *c;
int i;
for (c = (void *)mal.heap; CHUNK_SIZE(c); c = NEXT_CHUNK(c))
fprintf(stderr, "base %p size %zu (%d) flags %d/%d\n",
c, CHUNK_SIZE(c), bin_index(CHUNK_SIZE(c)),
c->csize & 15,
NEXT_CHUNK(c)->psize & 15);
for (i=0; i<64; i++) {
if (mal.bins[i].head != BIN_TO_CHUNK(i) && mal.bins[i].head) {
fprintf(stderr, "bin %d: %p\n", i, mal.bins[i].head);
if (!(mal.binmap & 1ULL<<i))
fprintf(stderr, "missing from binmap!\n");
} else if (mal.binmap & 1ULL<<i)
fprintf(stderr, "binmap wrongly contains %d!\n", i);
}
}
#endif
/* This function returns true if the interval [old,new]
* intersects the 'len'-sized interval below &libc.auxv
* (interpreted as the main-thread stack) or below &b
* (the current stack). It is used to defend against
* buggy brk implementations that can cross the stack. */
static int traverses_stack_p(uintptr_t old, uintptr_t new)
{
const uintptr_t len = 8<<20;
uintptr_t a, b;
b = (uintptr_t)libc.auxv;
a = b > len ? b-len : 0;
if (new>a && old<b) return 1;
b = (uintptr_t)&b;
a = b > len ? b-len : 0;
if (new>a && old<b) return 1;
return 0;
}
/* Expand the heap in-place if brk can be used, or otherwise via mmap,
* using an exponential lower bound on growth by mmap to make
* fragmentation asymptotically irrelevant. The size argument is both
* an input and an output, since the caller needs to know the size
* allocated, which will be larger than requested due to page alignment
* and mmap minimum size rules. The caller is responsible for locking
* to prevent concurrent calls. */
static void *__expand_heap(size_t *pn)
{
static uintptr_t brk;
static unsigned mmap_step;
size_t n = *pn;
if (n > SIZE_MAX/2 - PAGE_SIZE) {
errno = ENOMEM;
return 0;
}
n += -n & PAGE_SIZE-1;
if (!brk) {
brk = __syscall(SYS_brk, 0);
brk += -brk & PAGE_SIZE-1;
}
if (n < SIZE_MAX-brk && !traverses_stack_p(brk, brk+n)
&& __syscall(SYS_brk, brk+n)==brk+n) {
*pn = n;
brk += n;
return (void *)(brk-n);
}
size_t min = (size_t)PAGE_SIZE << mmap_step/2;
if (n < min) n = min;
void *area = __mmap(0, n, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
if (area == MAP_FAILED) return 0;
*pn = n;
mmap_step++;
return area;
}
static struct chunk *expand_heap(size_t n)
{
static void *end;
void *p;
struct chunk *w;
/* The argument n already accounts for the caller's chunk
* overhead needs, but if the heap can't be extended in-place,
* we need room for an extra zero-sized sentinel chunk. */
n += SIZE_ALIGN;
p = __expand_heap(&n);
if (!p) return 0;
/* If not just expanding existing space, we need to make a
* new sentinel chunk below the allocated space. */
if (p != end) {
/* Valid/safe because of the prologue increment. */
n -= SIZE_ALIGN;
p = (char *)p + SIZE_ALIGN;
w = MEM_TO_CHUNK(p);
w->psize = 0 | C_INUSE;
}
/* Record new heap end and fill in footer. */
end = (char *)p + n;
w = MEM_TO_CHUNK(end);
w->psize = n | C_INUSE;
w->csize = 0 | C_INUSE;
/* Fill in header, which may be new or may be replacing a
* zero-size sentinel header at the old end-of-heap. */
w = MEM_TO_CHUNK(p);
w->csize = n | C_INUSE;
return w;
}
static int adjust_size(size_t *n)
{
/* Result of pointer difference must fit in ptrdiff_t. */
if (*n-1 > PTRDIFF_MAX - SIZE_ALIGN - PAGE_SIZE) {
if (*n) {
errno = ENOMEM;
return -1;
} else {
*n = SIZE_ALIGN;
return 0;
}
}
*n = (*n + OVERHEAD + SIZE_ALIGN - 1) & SIZE_MASK;
return 0;
}
static void unbin(struct chunk *c, int i)
{
if (c->prev == c->next)
a_and_64(&mal.binmap, ~(1ULL<<i));
c->prev->next = c->next;
c->next->prev = c->prev;
c->csize |= C_INUSE;
NEXT_CHUNK(c)->psize |= C_INUSE;
}
static void bin_chunk(struct chunk *self, int i)
{
self->next = BIN_TO_CHUNK(i);
self->prev = mal.bins[i].tail;
self->next->prev = self;
self->prev->next = self;
if (self->prev == BIN_TO_CHUNK(i))
a_or_64(&mal.binmap, 1ULL<<i);
}
static void trim(struct chunk *self, size_t n)
{
size_t n1 = CHUNK_SIZE(self);
struct chunk *next, *split;
if (n >= n1 - DONTCARE) return;
next = NEXT_CHUNK(self);
split = (void *)((char *)self + n);
split->psize = n | C_INUSE;
split->csize = n1-n;
next->psize = n1-n;
self->csize = n | C_INUSE;
int i = bin_index(n1-n);
lock_bin(i);
bin_chunk(split, i);
unlock_bin(i);
}
void *malloc(size_t n)
{
struct chunk *c;
int i, j;
uint64_t mask;
if (adjust_size(&n) < 0) return 0;
if (n > MMAP_THRESHOLD) {
size_t len = n + OVERHEAD + PAGE_SIZE - 1 & -PAGE_SIZE;
char *base = __mmap(0, len, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
if (base == (void *)-1) return 0;
c = (void *)(base + SIZE_ALIGN - OVERHEAD);
c->csize = len - (SIZE_ALIGN - OVERHEAD);
c->psize = SIZE_ALIGN - OVERHEAD;
return CHUNK_TO_MEM(c);
}
i = bin_index_up(n);
if (i<63 && (mal.binmap & (1ULL<<i))) {
lock_bin(i);
c = mal.bins[i].head;
if (c != BIN_TO_CHUNK(i) && CHUNK_SIZE(c)-n <= DONTCARE) {
unbin(c, i);
unlock_bin(i);
return CHUNK_TO_MEM(c);
}
unlock_bin(i);
}
lock(mal.split_merge_lock);
for (mask = mal.binmap & -(1ULL<<i); mask; mask -= (mask&-mask)) {
j = first_set(mask);
lock_bin(j);
c = mal.bins[j].head;
if (c != BIN_TO_CHUNK(j)) {
unbin(c, j);
unlock_bin(j);
break;
}
unlock_bin(j);
}
if (!mask) {
c = expand_heap(n);
if (!c) {
unlock(mal.split_merge_lock);
return 0;
}
}
trim(c, n);
unlock(mal.split_merge_lock);
return CHUNK_TO_MEM(c);
}
int __malloc_allzerop(void *p)
{
return IS_MMAPPED(MEM_TO_CHUNK(p));
}
void *realloc(void *p, size_t n)
{
struct chunk *self, *next;
size_t n0, n1;
void *new;
if (!p) return malloc(n);
if (adjust_size(&n) < 0) return 0;
self = MEM_TO_CHUNK(p);
n1 = n0 = CHUNK_SIZE(self);
if (n<=n0 && n0-n<=DONTCARE) return p;
if (IS_MMAPPED(self)) {
size_t extra = self->psize;
char *base = (char *)self - extra;
size_t oldlen = n0 + extra;
size_t newlen = n + extra;
/* Crash on realloc of freed chunk */
if (extra & 1) a_crash();
if (newlen < PAGE_SIZE && (new = malloc(n-OVERHEAD))) {
n0 = n;
goto copy_free_ret;
}
newlen = (newlen + PAGE_SIZE-1) & -PAGE_SIZE;
if (oldlen == newlen) return p;
base = __mremap(base, oldlen, newlen, MREMAP_MAYMOVE);
if (base == (void *)-1)
goto copy_realloc;
self = (void *)(base + extra);
self->csize = newlen - extra;
return CHUNK_TO_MEM(self);
}
next = NEXT_CHUNK(self);
/* Crash on corrupted footer (likely from buffer overflow) */
if (next->psize != self->csize) a_crash();
if (n < n0) {
int i = bin_index_up(n);
int j = bin_index(n0);
if (i<j && (mal.binmap & (1ULL << i)))
goto copy_realloc;
struct chunk *split = (void *)((char *)self + n);
self->csize = split->psize = n | C_INUSE;
split->csize = next->psize = n0-n | C_INUSE;
__bin_chunk(split);
return CHUNK_TO_MEM(self);
}
lock(mal.split_merge_lock);
size_t nsize = next->csize & C_INUSE ? 0 : CHUNK_SIZE(next);
if (n0+nsize >= n) {
int i = bin_index(nsize);
lock_bin(i);
if (!(next->csize & C_INUSE)) {
unbin(next, i);
unlock_bin(i);
next = NEXT_CHUNK(next);
self->csize = next->psize = n0+nsize | C_INUSE;
trim(self, n);
unlock(mal.split_merge_lock);
return CHUNK_TO_MEM(self);
}
unlock_bin(i);
}
unlock(mal.split_merge_lock);
copy_realloc:
/* As a last resort, allocate a new chunk and copy to it. */
new = malloc(n-OVERHEAD);
if (!new) return 0;
copy_free_ret:
memcpy(new, p, (n<n0 ? n : n0) - OVERHEAD);
free(CHUNK_TO_MEM(self));
return new;
}
void __bin_chunk(struct chunk *self)
{
struct chunk *next = NEXT_CHUNK(self);
/* Crash on corrupted footer (likely from buffer overflow) */
if (next->psize != self->csize) a_crash();
lock(mal.split_merge_lock);
size_t osize = CHUNK_SIZE(self), size = osize;
/* Since we hold split_merge_lock, only transition from free to
* in-use can race; in-use to free is impossible */
size_t psize = self->psize & C_INUSE ? 0 : CHUNK_PSIZE(self);
size_t nsize = next->csize & C_INUSE ? 0 : CHUNK_SIZE(next);
if (psize) {
int i = bin_index(psize);
lock_bin(i);
if (!(self->psize & C_INUSE)) {
struct chunk *prev = PREV_CHUNK(self);
unbin(prev, i);
self = prev;
size += psize;
}
unlock_bin(i);
}
if (nsize) {
int i = bin_index(nsize);
lock_bin(i);
if (!(next->csize & C_INUSE)) {
unbin(next, i);
next = NEXT_CHUNK(next);
size += nsize;
}
unlock_bin(i);
}
int i = bin_index(size);
lock_bin(i);
self->csize = size;
next->psize = size;
bin_chunk(self, i);
unlock(mal.split_merge_lock);
/* Replace middle of large chunks with fresh zero pages */
if (size > RECLAIM && (size^(size-osize)) > size-osize) {
uintptr_t a = (uintptr_t)self + SIZE_ALIGN+PAGE_SIZE-1 & -PAGE_SIZE;
uintptr_t b = (uintptr_t)next - SIZE_ALIGN & -PAGE_SIZE;
#if 1
__madvise((void *)a, b-a, MADV_DONTNEED);
#else
__mmap((void *)a, b-a, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED, -1, 0);
#endif
}
unlock_bin(i);
}
static void unmap_chunk(struct chunk *self)
{
size_t extra = self->psize;
char *base = (char *)self - extra;
size_t len = CHUNK_SIZE(self) + extra;
/* Crash on double free */
if (extra & 1) a_crash();
__munmap(base, len);
}
void free(void *p)
{
if (!p) return;
struct chunk *self = MEM_TO_CHUNK(p);
if (IS_MMAPPED(self))
unmap_chunk(self);
else
__bin_chunk(self);
}
void __malloc_donate(char *start, char *end)
{
size_t align_start_up = (SIZE_ALIGN-1) & (-(uintptr_t)start - OVERHEAD);
size_t align_end_down = (SIZE_ALIGN-1) & (uintptr_t)end;
/* Getting past this condition ensures that the padding for alignment
* and header overhead will not overflow and will leave a nonzero
* multiple of SIZE_ALIGN bytes between start and end. */
if (end - start <= OVERHEAD + align_start_up + align_end_down)
return;
start += align_start_up + OVERHEAD;
end -= align_end_down;
struct chunk *c = MEM_TO_CHUNK(start), *n = MEM_TO_CHUNK(end);
c->psize = n->csize = C_INUSE;
c->csize = n->psize = C_INUSE | (end-start);
__bin_chunk(c);
}
void __malloc_atfork(int who)
{
if (who<0) {
lock(mal.split_merge_lock);
for (int i=0; i<64; i++)
lock(mal.bins[i].lock);
} else if (!who) {
for (int i=0; i<64; i++)
unlock(mal.bins[i].lock);
unlock(mal.split_merge_lock);
} else {
for (int i=0; i<64; i++)
mal.bins[i].lock[0] = mal.bins[i].lock[1] = 0;
mal.split_merge_lock[1] = 0;
mal.split_merge_lock[0] = 0;
}
}
