eliminate OOB array hacks in malloc

diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c
index 207b6ef..db4287e 100644 (file)
--- a/src/malloc/malloc.c
+++ b/src/malloc/malloc.c
@@ -16,9 +16,8 @@ void *__mremap(void *, size_t, size_t, int, ...);
 int __madvise(void *, size_t, int);
 
 struct chunk {
-       size_t data[1];
-       struct chunk *next;
-       struct chunk *prev;
+       size_t psize, csize;
+       struct chunk *next, *prev;
 };
 
 struct bin {
@@ -44,19 +43,19 @@ static struct {
 #define DONTCARE 16
 #define RECLAIM 163840
 
-#define CHUNK_SIZE(c) ((c)->data[0] & SIZE_MASK)
-#define CHUNK_PSIZE(c) ((c)->data[-1] & SIZE_MASK)
+#define CHUNK_SIZE(c) ((c)->csize & SIZE_MASK)
+#define CHUNK_PSIZE(c) ((c)->psize & SIZE_MASK)
 #define PREV_CHUNK(c) ((struct chunk *)((char *)(c) - CHUNK_PSIZE(c)))
 #define NEXT_CHUNK(c) ((struct chunk *)((char *)(c) + CHUNK_SIZE(c)))
-#define MEM_TO_CHUNK(p) (struct chunk *)((size_t *)p - 1)
-#define CHUNK_TO_MEM(c) (void *)((c)->data+1)
+#define MEM_TO_CHUNK(p) (struct chunk *)((char *)(p) - OVERHEAD)
+#define CHUNK_TO_MEM(c) (void *)((char *)(c) + OVERHEAD)
 #define BIN_TO_CHUNK(i) (MEM_TO_CHUNK(&mal.bins[i].head))
 
 #define C_INUSE  ((size_t)1)
 #define C_FLAGS  ((size_t)3)
 #define C_SIZE   SIZE_MASK
 
-#define IS_MMAPPED(c) !((c)->data[0] & (C_INUSE))
+#define IS_MMAPPED(c) !((c)->csize & (C_INUSE))
 
 
 /* Synchronization tools */
@@ -138,8 +137,8 @@ void __dump_heap(int x)
        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->data[0] & 15,
-                       NEXT_CHUNK(c)->data[-1] & 15);
+                       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);
@@ -165,11 +164,11 @@ static struct chunk *expand_heap(size_t n)
        if (__brk(new) != new) goto fail;
 
        w = MEM_TO_CHUNK(new);
-       w->data[-1] = n | C_INUSE;
-       w->data[0] = 0 | C_INUSE;
+       w->psize = n | C_INUSE;
+       w->csize = 0 | C_INUSE;
 
        w = MEM_TO_CHUNK(mal.brk);
-       w->data[0] = n | C_INUSE;
+       w->csize = n | C_INUSE;
        mal.brk = new;
        
        unlock(mal.brk_lock);
@@ -206,7 +205,7 @@ static int init_malloc(size_t n)
        }
 
        mal.heap = (void *)c;
-       c->data[-1] = 0 | C_INUSE;
+       c->psize = 0 | C_INUSE;
        free(CHUNK_TO_MEM(c));
 
        a_store(&init, 2);
@@ -236,18 +235,18 @@ static void unbin(struct chunk *c, int i)
                a_and_64(&mal.binmap, ~(1ULL<<i));
        c->prev->next = c->next;
        c->next->prev = c->prev;
-       c->data[0] |= C_INUSE;
-       NEXT_CHUNK(c)->data[-1] |= C_INUSE;
+       c->csize |= C_INUSE;
+       NEXT_CHUNK(c)->psize |= C_INUSE;
 }
 
 static int alloc_fwd(struct chunk *c)
 {
        int i;
        size_t k;
-       while (!((k=c->data[0]) & C_INUSE)) {
+       while (!((k=c->csize) & C_INUSE)) {
                i = bin_index(k);
                lock_bin(i);
-               if (c->data[0] == k) {
+               if (c->csize == k) {
                        unbin(c, i);
                        unlock_bin(i);
                        return 1;
@@ -261,10 +260,10 @@ static int alloc_rev(struct chunk *c)
 {
        int i;
        size_t k;
-       while (!((k=c->data[-1]) & C_INUSE)) {
+       while (!((k=c->psize) & C_INUSE)) {
                i = bin_index(k);
                lock_bin(i);
-               if (c->data[-1] == k) {
+               if (c->psize == k) {
                        unbin(PREV_CHUNK(c), i);
                        unlock_bin(i);
                        return 1;
@@ -301,10 +300,10 @@ static int pretrim(struct chunk *self, size_t n, int i, int j)
        split->next = self->next;
        split->prev->next = split;
        split->next->prev = split;
-       split->data[-1] = n | C_INUSE;
-       split->data[0] = n1-n;
-       next->data[-1] = n1-n;
-       self->data[0] = n | C_INUSE;
+       split->psize = n | C_INUSE;
+       split->csize = n1-n;
+       next->psize = n1-n;
+       self->csize = n | C_INUSE;
        return 1;
 }
 
@@ -318,10 +317,10 @@ static void trim(struct chunk *self, size_t n)
        next = NEXT_CHUNK(self);
        split = (void *)((char *)self + n);
 
-       split->data[-1] = n | C_INUSE;
-       split->data[0] = n1-n | C_INUSE;
-       next->data[-1] = n1-n | C_INUSE;
-       self->data[0] = n | C_INUSE;
+       split->psize = n | C_INUSE;
+       split->csize = n1-n | C_INUSE;
+       next->psize = n1-n | C_INUSE;
+       self->csize = n | C_INUSE;
 
        free(CHUNK_TO_MEM(split));
 }
@@ -338,9 +337,9 @@ void *malloc(size_t n)
                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 - sizeof(size_t));
-               c->data[0] = len - (SIZE_ALIGN - sizeof(size_t));
-               c->data[-1] = SIZE_ALIGN - sizeof(size_t);
+               c = (void *)(base + SIZE_ALIGN - OVERHEAD);
+               c->csize = len - (SIZE_ALIGN - OVERHEAD);
+               c->psize = SIZE_ALIGN - OVERHEAD;
                return CHUNK_TO_MEM(c);
        }
 
@@ -354,15 +353,15 @@ void *malloc(size_t n)
                        if (alloc_rev(c)) {
                                struct chunk *x = c;
                                c = PREV_CHUNK(c);
-                               NEXT_CHUNK(x)->data[-1] = c->data[0] =
-                                       x->data[0] + CHUNK_SIZE(c);
+                               NEXT_CHUNK(x)->psize = c->csize =
+                                       x->csize + CHUNK_SIZE(c);
                        }
                        break;
                }
                j = first_set(mask);
                lock_bin(j);
                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);
                        unlock_bin(j);
                        break;
@@ -390,7 +389,7 @@ void *realloc(void *p, size_t n)
        n1 = n0 = CHUNK_SIZE(self);
 
        if (IS_MMAPPED(self)) {
-               size_t extra = self->data[-1];
+               size_t extra = self->psize;
                char *base = (char *)self - extra;
                size_t oldlen = n0 + extra;
                size_t newlen = n + extra;
@@ -407,7 +406,7 @@ void *realloc(void *p, size_t n)
                if (base == (void *)-1)
                        return newlen < oldlen ? p : 0;
                self = (void *)(base + extra);
-               self->data[0] = newlen - extra;
+               self->csize = newlen - extra;
                return CHUNK_TO_MEM(self);
        }
 
@@ -425,8 +424,8 @@ void *realloc(void *p, size_t n)
                self = PREV_CHUNK(self);
                n1 += CHUNK_SIZE(self);
        }
-       self->data[0] = n1 | C_INUSE;
-       next->data[-1] = n1 | C_INUSE;
+       self->csize = n1 | C_INUSE;
+       next->psize = n1 | C_INUSE;
 
        /* If we got enough space, split off the excess and return */
        if (n <= n1) {
@@ -454,7 +453,7 @@ void free(void *p)
        if (!p) return;
 
        if (IS_MMAPPED(self)) {
-               size_t extra = self->data[-1];
+               size_t extra = self->psize;
                char *base = (char *)self - extra;
                size_t len = CHUNK_SIZE(self) + extra;
                /* Crash on double free */
@@ -468,7 +467,7 @@ void free(void *p)
 
        for (;;) {
                /* 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 b = (uintptr_t)next - SIZE_ALIGN & -PAGE_SIZE;
 #if 1
@@ -479,13 +478,13 @@ void free(void *p)
 #endif
                }
 
-               if (self->data[-1] & next->data[0] & C_INUSE) {
-                       self->data[0] = final_size | C_INUSE;
-                       next->data[-1] = final_size | C_INUSE;
+               if (self->psize & next->csize & C_INUSE) {
+                       self->csize = final_size | C_INUSE;
+                       next->psize = final_size | C_INUSE;
                        i = bin_index(final_size);
                        lock_bin(i);
                        lock(mal.free_lock);
-                       if (self->data[-1] & next->data[0] & C_INUSE)
+                       if (self->psize & next->csize & C_INUSE)
                                break;
                        unlock(mal.free_lock);
                        unlock_bin(i);
@@ -508,8 +507,8 @@ void free(void *p)
                }
        }
 
-       self->data[0] = final_size;
-       next->data[-1] = final_size;
+       self->csize = final_size;
+       next->psize = final_size;
        unlock(mal.free_lock);
 
        self->next = BIN_TO_CHUNK(i);