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Diffstat (limited to 'src/malloc/malloc.c')
-rw-r--r--src/malloc/malloc.c86
1 files changed, 28 insertions, 58 deletions
diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c
index a42aeede..290fda1c 100644
--- a/src/malloc/malloc.c
+++ b/src/malloc/malloc.c
@@ -13,7 +13,6 @@
#define inline inline __attribute__((always_inline))
#endif
-uintptr_t __brk(uintptr_t);
void *__mmap(void *, size_t, int, int, int, off_t);
int __munmap(void *, size_t);
void *__mremap(void *, size_t, size_t, int, ...);
@@ -31,13 +30,9 @@ struct bin {
};
static struct {
- uintptr_t brk;
- size_t *heap;
volatile uint64_t binmap;
struct bin bins[64];
- volatile int brk_lock[2];
volatile int free_lock[2];
- unsigned mmap_step;
} mal;
@@ -152,77 +147,52 @@ void __dump_heap(int x)
}
#endif
-static int is_near_stack(uintptr_t b)
-{
- const uintptr_t c = 8<<20;
- uintptr_t a = (uintptr_t)libc.auxv;
- uintptr_t d = (uintptr_t)&b;
- return a-b<=c || d-b<=c;
-}
+void *__expand_heap(size_t *);
static struct chunk *expand_heap(size_t n)
{
- static int init;
+ static int heap_lock[2];
+ static void *end;
+ void *p;
struct chunk *w;
- uintptr_t new;
-
- lock(mal.brk_lock);
- if (!init) {
- mal.brk = __brk(0);
-#ifdef SHARED
- mal.brk = mal.brk + PAGE_SIZE-1 & -PAGE_SIZE;
-#endif
- mal.brk = mal.brk + 2*SIZE_ALIGN-1 & -SIZE_ALIGN;
- mal.heap = (void *)mal.brk;
- init = 1;
- }
+ /* 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;
- if (n > SIZE_MAX - mal.brk - 2*PAGE_SIZE) goto fail;
- new = mal.brk + n + SIZE_ALIGN + PAGE_SIZE - 1 & -PAGE_SIZE;
- n = new - mal.brk;
+ lock(heap_lock);
- if (is_near_stack(mal.brk) || __brk(new) != new) {
- size_t min = (size_t)PAGE_SIZE << mal.mmap_step/2;
- n += -n & PAGE_SIZE-1;
- if (n < min) n = min;
- void *area = __mmap(0, n, PROT_READ|PROT_WRITE,
- MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
- if (area == MAP_FAILED) goto fail;
+ p = __expand_heap(&n);
+ if (!p) {
+ unlock(heap_lock);
+ return 0;
+ }
- mal.mmap_step++;
- area = (char *)area + SIZE_ALIGN - OVERHEAD;
- w = area;
+ /* 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;
- w->csize = n | C_INUSE;
- w = NEXT_CHUNK(w);
- w->psize = n | C_INUSE;
- w->csize = 0 | C_INUSE;
-
- unlock(mal.brk_lock);
-
- return area;
}
- w = MEM_TO_CHUNK(mal.heap);
- w->psize = 0 | C_INUSE;
-
- w = MEM_TO_CHUNK(new);
+ /* 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;
- w = MEM_TO_CHUNK(mal.brk);
+ /* 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;
- mal.brk = new;
-
- unlock(mal.brk_lock);
+
+ unlock(heap_lock);
return w;
-fail:
- unlock(mal.brk_lock);
- errno = ENOMEM;
- return 0;
}
static int adjust_size(size_t *n)