#include <stdint.h>
#include <limits.h>
#include <errno.h>
+#include <sys/mman.h>
#include "libc.h"
-
-uintptr_t __brk(uintptr_t);
+#include "lock.h"
+#include "syscall.h"
+#include "fork_impl.h"
#define ALIGN 16
-void *__simple_malloc(size_t n)
+/* 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)
{
- static uintptr_t cur, brk;
- uintptr_t base, new;
- static int lock[2];
+ 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;
+}
+
+static volatile int lock[1];
+volatile int *const __bump_lockptr = lock;
+
+static void *__simple_malloc(size_t n)
+{
+ static uintptr_t brk, cur, end;
+ static unsigned mmap_step;
size_t align=1;
+ void *p;
- if (!n) n++;
- if (n > SIZE_MAX/2) goto toobig;
+ if (n > SIZE_MAX/2) {
+ errno = ENOMEM;
+ return 0;
+ }
+ if (!n) n++;
while (align<n && align<ALIGN)
align += align;
- n = n + align - 1 & -align;
LOCK(lock);
- if (!cur) cur = brk = __brk(0)+16;
- base = cur + align-1 & -align;
- if (n > SIZE_MAX - PAGE_SIZE - base) goto fail;
- if (base+n > brk) {
- new = base+n + PAGE_SIZE-1 & -PAGE_SIZE;
- if (__brk(new) != new) goto fail;
- brk = new;
+
+ cur += -cur & align-1;
+
+ if (n > end-cur) {
+ size_t req = n - (end-cur) + PAGE_SIZE-1 & -PAGE_SIZE;
+
+ if (!cur) {
+ brk = __syscall(SYS_brk, 0);
+ brk += -brk & PAGE_SIZE-1;
+ cur = end = brk;
+ }
+
+ if (brk == end && req < SIZE_MAX-brk
+ && !traverses_stack_p(brk, brk+req)
+ && __syscall(SYS_brk, brk+req)==brk+req) {
+ brk = end += req;
+ } else {
+ int new_area = 0;
+ req = n + PAGE_SIZE-1 & -PAGE_SIZE;
+ /* Only make a new area rather than individual mmap
+ * if wasted space would be over 1/8 of the map. */
+ if (req-n > req/8) {
+ /* Geometric area size growth up to 64 pages,
+ * bounding waste by 1/8 of the area. */
+ size_t min = PAGE_SIZE<<(mmap_step/2);
+ if (min-n > end-cur) {
+ if (req < min) {
+ req = min;
+ if (mmap_step < 12)
+ mmap_step++;
+ }
+ new_area = 1;
+ }
+ }
+ void *mem = __mmap(0, req, PROT_READ|PROT_WRITE,
+ MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+ if (mem == MAP_FAILED || !new_area) {
+ UNLOCK(lock);
+ return mem==MAP_FAILED ? 0 : mem;
+ }
+ cur = (uintptr_t)mem;
+ end = cur + req;
+ }
}
- cur = base+n;
+
+ p = (void *)cur;
+ cur += n;
UNLOCK(lock);
+ return p;
+}
- return (void *)base;
+weak_alias(__simple_malloc, __libc_malloc_impl);
-fail:
- UNLOCK(lock);
-toobig:
- errno = ENOMEM;
- return 0;
+void *__libc_malloc(size_t n)
+{
+ return __libc_malloc_impl(n);
+}
+
+static void *default_malloc(size_t n)
+{
+ return __libc_malloc_impl(n);
}
-weak_alias(__simple_malloc, malloc);
+weak_alias(default_malloc, malloc);