summaryrefslogtreecommitdiff
path: root/src/malloc/expand_heap.c
diff options
context:
space:
mode:
Diffstat (limited to 'src/malloc/expand_heap.c')
-rw-r--r--src/malloc/expand_heap.c71
1 files changed, 0 insertions, 71 deletions
diff --git a/src/malloc/expand_heap.c b/src/malloc/expand_heap.c
deleted file mode 100644
index e6a3d7a0..00000000
--- a/src/malloc/expand_heap.c
+++ /dev/null
@@ -1,71 +0,0 @@
-#include <limits.h>
-#include <stdint.h>
-#include <errno.h>
-#include <sys/mman.h>
-#include "libc.h"
-#include "syscall.h"
-#include "malloc_impl.h"
-
-/* 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. */
-
-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;
-}