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eliminate OOB array hacks in malloc

This commit is contained in:
Rich Felker 2011-06-26 16:12:43 -04:00
parent e22c2d3ee6
commit 5d0965cb56
1 changed files with 45 additions and 46 deletions
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91
src/malloc/malloc.c
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@ -16,9 +16,8 @@ void *__mremap(void *, size_t, size_t, int, ...);
int __madvise(void *, size_t, int); int __madvise(void *, size_t, int);
struct chunk { struct chunk {
size_t data[1]; size_t psize, csize;
struct chunk *next; struct chunk *next, *prev;
struct chunk *prev;
}; };
struct bin { struct bin {
@ -44,19 +43,19 @@ static struct {
#define DONTCARE 16 #define DONTCARE 16
#define RECLAIM 163840 #define RECLAIM 163840
#define CHUNK_SIZE(c) ((c)->data[0] & SIZE_MASK) #define CHUNK_SIZE(c) ((c)->csize & SIZE_MASK)
#define CHUNK_PSIZE(c) ((c)->data[-1] & SIZE_MASK) #define CHUNK_PSIZE(c) ((c)->psize & SIZE_MASK)
#define PREV_CHUNK(c) ((struct chunk *)((char *)(c) - CHUNK_PSIZE(c))) #define PREV_CHUNK(c) ((struct chunk *)((char *)(c) - CHUNK_PSIZE(c)))
#define NEXT_CHUNK(c) ((struct chunk *)((char *)(c) + CHUNK_SIZE(c))) #define NEXT_CHUNK(c) ((struct chunk *)((char *)(c) + CHUNK_SIZE(c)))
#define MEM_TO_CHUNK(p) (struct chunk *)((size_t *)p - 1) #define MEM_TO_CHUNK(p) (struct chunk *)((char *)(p) - OVERHEAD)
#define CHUNK_TO_MEM(c) (void *)((c)->data+1) #define CHUNK_TO_MEM(c) (void *)((char *)(c) + OVERHEAD)
#define BIN_TO_CHUNK(i) (MEM_TO_CHUNK(&mal.bins[i].head)) #define BIN_TO_CHUNK(i) (MEM_TO_CHUNK(&mal.bins[i].head))
#define C_INUSE ((size_t)1) #define C_INUSE ((size_t)1)
#define C_FLAGS ((size_t)3) #define C_FLAGS ((size_t)3)
#define C_SIZE SIZE_MASK #define C_SIZE SIZE_MASK
#define IS_MMAPPED(c) !((c)->data[0] & (C_INUSE)) #define IS_MMAPPED(c) !((c)->csize & (C_INUSE))
/* Synchronization tools */ /* Synchronization tools */
@ -138,8 +137,8 @@ void __dump_heap(int x)
for (c = (void *)mal.heap; CHUNK_SIZE(c); c = NEXT_CHUNK(c)) for (c = (void *)mal.heap; CHUNK_SIZE(c); c = NEXT_CHUNK(c))
fprintf(stderr, "base %p size %zu (%d) flags %d/%d\n", fprintf(stderr, "base %p size %zu (%d) flags %d/%d\n",
c, CHUNK_SIZE(c), bin_index(CHUNK_SIZE(c)), c, CHUNK_SIZE(c), bin_index(CHUNK_SIZE(c)),
c->data[0] & 15, c->csize & 15,
NEXT_CHUNK(c)->data[-1] & 15); NEXT_CHUNK(c)->psize & 15);
for (i=0; i<64; i++) { for (i=0; i<64; i++) {
if (mal.bins[i].head != BIN_TO_CHUNK(i) && mal.bins[i].head) { if (mal.bins[i].head != BIN_TO_CHUNK(i) && mal.bins[i].head) {
fprintf(stderr, "bin %d: %p\n", i, mal.bins[i].head); fprintf(stderr, "bin %d: %p\n", i, mal.bins[i].head);
@ -165,11 +164,11 @@ static struct chunk *expand_heap(size_t n)
if (__brk(new) != new) goto fail; if (__brk(new) != new) goto fail;
w = MEM_TO_CHUNK(new); w = MEM_TO_CHUNK(new);
w->data[-1] = n | C_INUSE; w->psize = n | C_INUSE;
w->data[0] = 0 | C_INUSE; w->csize = 0 | C_INUSE;
w = MEM_TO_CHUNK(mal.brk); w = MEM_TO_CHUNK(mal.brk);
w->data[0] = n | C_INUSE; w->csize = n | C_INUSE;
mal.brk = new; mal.brk = new;
unlock(mal.brk_lock); unlock(mal.brk_lock);
@ -206,7 +205,7 @@ static int init_malloc(size_t n)
} }
mal.heap = (void *)c; mal.heap = (void *)c;
c->data[-1] = 0 | C_INUSE; c->psize = 0 | C_INUSE;
free(CHUNK_TO_MEM(c)); free(CHUNK_TO_MEM(c));
a_store(&init, 2); a_store(&init, 2);
@ -236,18 +235,18 @@ static void unbin(struct chunk *c, int i)
a_and_64(&mal.binmap, ~(1ULL<<i)); a_and_64(&mal.binmap, ~(1ULL<<i));
c->prev->next = c->next; c->prev->next = c->next;
c->next->prev = c->prev; c->next->prev = c->prev;
c->data[0] |= C_INUSE; c->csize |= C_INUSE;
NEXT_CHUNK(c)->data[-1] |= C_INUSE; NEXT_CHUNK(c)->psize |= C_INUSE;
} }
static int alloc_fwd(struct chunk *c) static int alloc_fwd(struct chunk *c)
{ {
int i; int i;
size_t k; size_t k;
while (!((k=c->data[0]) & C_INUSE)) { while (!((k=c->csize) & C_INUSE)) {
i = bin_index(k); i = bin_index(k);
lock_bin(i); lock_bin(i);
if (c->data[0] == k) { if (c->csize == k) {
unbin(c, i); unbin(c, i);
unlock_bin(i); unlock_bin(i);
return 1; return 1;
@ -261,10 +260,10 @@ static int alloc_rev(struct chunk *c)
{ {
int i; int i;
size_t k; size_t k;
while (!((k=c->data[-1]) & C_INUSE)) { while (!((k=c->psize) & C_INUSE)) {
i = bin_index(k); i = bin_index(k);
lock_bin(i); lock_bin(i);
if (c->data[-1] == k) { if (c->psize == k) {
unbin(PREV_CHUNK(c), i); unbin(PREV_CHUNK(c), i);
unlock_bin(i); unlock_bin(i);
return 1; return 1;
@ -301,10 +300,10 @@ static int pretrim(struct chunk *self, size_t n, int i, int j)
split->next = self->next; split->next = self->next;
split->prev->next = split; split->prev->next = split;
split->next->prev = split; split->next->prev = split;
split->data[-1] = n | C_INUSE; split->psize = n | C_INUSE;
split->data[0] = n1-n; split->csize = n1-n;
next->data[-1] = n1-n; next->psize = n1-n;
self->data[0] = n | C_INUSE; self->csize = n | C_INUSE;
return 1; return 1;
} }
@ -318,10 +317,10 @@ static void trim(struct chunk *self, size_t n)
next = NEXT_CHUNK(self); next = NEXT_CHUNK(self);
split = (void *)((char *)self + n); split = (void *)((char *)self + n);
split->data[-1] = n | C_INUSE; split->psize = n | C_INUSE;
split->data[0] = n1-n | C_INUSE; split->csize = n1-n | C_INUSE;
next->data[-1] = n1-n | C_INUSE; next->psize = n1-n | C_INUSE;
self->data[0] = n | C_INUSE; self->csize = n | C_INUSE;
free(CHUNK_TO_MEM(split)); free(CHUNK_TO_MEM(split));
} }
@ -338,9 +337,9 @@ void *malloc(size_t n)
char *base = __mmap(0, len, PROT_READ|PROT_WRITE, char *base = __mmap(0, len, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
if (base == (void *)-1) return 0; if (base == (void *)-1) return 0;
c = (void *)(base + SIZE_ALIGN - sizeof(size_t)); c = (void *)(base + SIZE_ALIGN - OVERHEAD);
c->data[0] = len - (SIZE_ALIGN - sizeof(size_t)); c->csize = len - (SIZE_ALIGN - OVERHEAD);
c->data[-1] = SIZE_ALIGN - sizeof(size_t); c->psize = SIZE_ALIGN - OVERHEAD;
return CHUNK_TO_MEM(c); return CHUNK_TO_MEM(c);
} }
@ -354,15 +353,15 @@ void *malloc(size_t n)
if (alloc_rev(c)) { if (alloc_rev(c)) {
struct chunk *x = c; struct chunk *x = c;
c = PREV_CHUNK(c); c = PREV_CHUNK(c);
NEXT_CHUNK(x)->data[-1] = c->data[0] = NEXT_CHUNK(x)->psize = c->csize =
x->data[0] + CHUNK_SIZE(c); x->csize + CHUNK_SIZE(c);
} }
break; break;
} }
j = first_set(mask); j = first_set(mask);
lock_bin(j); lock_bin(j);
c = mal.bins[j].head; c = mal.bins[j].head;
if (c != BIN_TO_CHUNK(j) && j == bin_index(c->data[0])) { if (c != BIN_TO_CHUNK(j) && j == bin_index(c->csize)) {
if (!pretrim(c, n, i, j)) unbin(c, j); if (!pretrim(c, n, i, j)) unbin(c, j);
unlock_bin(j); unlock_bin(j);
break; break;
@ -390,7 +389,7 @@ void *realloc(void *p, size_t n)
n1 = n0 = CHUNK_SIZE(self); n1 = n0 = CHUNK_SIZE(self);
if (IS_MMAPPED(self)) { if (IS_MMAPPED(self)) {
size_t extra = self->data[-1]; size_t extra = self->psize;
char *base = (char *)self - extra; char *base = (char *)self - extra;
size_t oldlen = n0 + extra; size_t oldlen = n0 + extra;
size_t newlen = n + extra; size_t newlen = n + extra;
@ -407,7 +406,7 @@ void *realloc(void *p, size_t n)
if (base == (void *)-1) if (base == (void *)-1)
return newlen < oldlen ? p : 0; return newlen < oldlen ? p : 0;
self = (void *)(base + extra); self = (void *)(base + extra);
self->data[0] = newlen - extra; self->csize = newlen - extra;
return CHUNK_TO_MEM(self); return CHUNK_TO_MEM(self);
} }
@ -425,8 +424,8 @@ void *realloc(void *p, size_t n)
self = PREV_CHUNK(self); self = PREV_CHUNK(self);
n1 += CHUNK_SIZE(self); n1 += CHUNK_SIZE(self);
} }
self->data[0] = n1 | C_INUSE; self->csize = n1 | C_INUSE;
next->data[-1] = n1 | C_INUSE; next->psize = n1 | C_INUSE;
/* If we got enough space, split off the excess and return */ /* If we got enough space, split off the excess and return */
if (n <= n1) { if (n <= n1) {
@ -454,7 +453,7 @@ void free(void *p)
if (!p) return; if (!p) return;
if (IS_MMAPPED(self)) { if (IS_MMAPPED(self)) {
size_t extra = self->data[-1]; size_t extra = self->psize;
char *base = (char *)self - extra; char *base = (char *)self - extra;
size_t len = CHUNK_SIZE(self) + extra; size_t len = CHUNK_SIZE(self) + extra;
/* Crash on double free */ /* Crash on double free */
@ -468,7 +467,7 @@ void free(void *p)
for (;;) { for (;;) {
/* Replace middle of large chunks with fresh zero pages */ /* Replace middle of large chunks with fresh zero pages */
if (reclaim && (self->data[-1] & next->data[0] & C_INUSE)) { if (reclaim && (self->psize & next->csize & C_INUSE)) {
uintptr_t a = (uintptr_t)self + SIZE_ALIGN+PAGE_SIZE-1 & -PAGE_SIZE; uintptr_t a = (uintptr_t)self + SIZE_ALIGN+PAGE_SIZE-1 & -PAGE_SIZE;
uintptr_t b = (uintptr_t)next - SIZE_ALIGN & -PAGE_SIZE; uintptr_t b = (uintptr_t)next - SIZE_ALIGN & -PAGE_SIZE;
#if 1 #if 1
@ -479,13 +478,13 @@ void free(void *p)
#endif #endif
} }
if (self->data[-1] & next->data[0] & C_INUSE) { if (self->psize & next->csize & C_INUSE) {
self->data[0] = final_size | C_INUSE; self->csize = final_size | C_INUSE;
next->data[-1] = final_size | C_INUSE; next->psize = final_size | C_INUSE;
i = bin_index(final_size); i = bin_index(final_size);
lock_bin(i); lock_bin(i);
lock(mal.free_lock); lock(mal.free_lock);
if (self->data[-1] & next->data[0] & C_INUSE) if (self->psize & next->csize & C_INUSE)
break; break;
unlock(mal.free_lock); unlock(mal.free_lock);
unlock_bin(i); unlock_bin(i);
@ -508,8 +507,8 @@ void free(void *p)
} }
} }
self->data[0] = final_size; self->csize = final_size;
next->data[-1] = final_size; next->psize = final_size;
unlock(mal.free_lock); unlock(mal.free_lock);
self->next = BIN_TO_CHUNK(i); self->next = BIN_TO_CHUNK(i);