commit: 9bd79390dc9221ed824fde16d7d6765e4018ac95
Author: Mike Gilbert <floppym <AT> gentoo <DOT> org>
AuthorDate: Thu Feb 6 16:55:36 2025 +0000
Commit: Mike Gilbert <floppym <AT> gentoo <DOT> org>
CommitDate: Sat Feb 15 01:42:46 2025 +0000
URL: https://gitweb.gentoo.org/proj/sandbox.git/commit/?id=9bd79390
Use mremap in realloc
Signed-off-by: Mike Gilbert <floppym <AT> gentoo.org>
libsandbox/memory.c | 39 +++++++++++++++++++++------------------
1 file changed, 21 insertions(+), 18 deletions(-)
diff --git a/libsandbox/memory.c b/libsandbox/memory.c
index a23e87a..0d2c890 100644
--- a/libsandbox/memory.c
+++ b/libsandbox/memory.c
@@ -33,6 +33,7 @@ static void *sb_mmap(void *addr, size_t length, int prot, int
flags, int fd, off
return _sb_mmap(addr, length, prot, flags, fd, offset);
}
#define mmap sb_mmap
+
static int (*_sb_munmap)(void *addr, size_t length);
static int sb_munmap(void *addr, size_t length)
{
@@ -42,6 +43,15 @@ static int sb_munmap(void *addr, size_t length)
}
#define munmap sb_munmap
+static void *(*_sb_mremap)(void *old_address, size_t old_size, size_t
new_size, int flags);
+static void *sb_mremap(void *old_address, size_t old_size, size_t new_size,
int flags)
+{
+ if (!_sb_mremap)
+ _sb_mremap = get_dlsym("mremap", NULL);
+ return _sb_mremap(old_address, old_size, new_size, flags);
+}
+#define mremap sb_mremap
+
#define SB_MALLOC_TO_MMAP(ptr) ((void*)((uintptr_t)(ptr) - MIN_ALIGN))
#define SB_MMAP_TO_MALLOC(ptr) ((void*)((uintptr_t)(ptr) + MIN_ALIGN))
#define SB_MALLOC_TO_MMAP_SIZE(ptr) (*((size_t*)SB_MALLOC_TO_MMAP(ptr)))
@@ -84,30 +94,23 @@ void *calloc(size_t nmemb, size_t size)
void *realloc(void *ptr, size_t size)
{
- void *ret;
- size_t old_malloc_size;
-
if (ptr == NULL)
return malloc(size);
if (size == 0) {
free(ptr);
return NULL;
}
-
- old_malloc_size = SB_MALLOC_TO_SIZE(ptr);
- /* Since mmap() is heavy, don't bother shrinking */
- if (size <= old_malloc_size)
- return ptr;
- ret = malloc(size);
- if (!ret)
- return ret;
- /* We already verified old_malloc_size is smaller than size above, so
- * we don't really need the MIN() here. We leave it to be defensive,
- * and because gcc optimizes away the check for us.
- */
- memcpy(ret, ptr, MIN(size, old_malloc_size));
- free(ptr);
- return ret;
+ if (__builtin_add_overflow(size, MIN_ALIGN, &size)) {
+ errno = ENOMEM;
+ return NULL;
+ }
+ size_t *sp = SB_MALLOC_TO_MMAP(ptr);
+ size_t old_size = *sp;
+ sp = mremap(sp, old_size, size, MREMAP_MAYMOVE);
+ if (sp == MAP_FAILED)
+ return NULL;
+ *sp = size;
+ return SB_MMAP_TO_MALLOC(sp);
}
char *strdup(const char *s)
