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hardened_malloc
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implement in-place shrinking for large allocations

pull/50/head
Daniel Micay 2018-09-05 05:17:40 -04:00
parent 645209dcbf
commit 3a532b17dc
1 changed files with 24 additions and 1 deletions
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25
malloc.c
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@ -785,6 +785,7 @@ EXPORT void *h_realloc(void *old, size_t size) {
fatal_error("invalid realloc");
}
old_size = region->size;
size_t old_guard_size = region->guard_size;
if (PAGE_CEILING(old_size) == PAGE_CEILING(size)) {
region->size = size;
pthread_mutex_unlock(&regions_lock);
@ -792,6 +793,29 @@ EXPORT void *h_realloc(void *old, size_t size) {
}
pthread_mutex_unlock(&regions_lock);
// in-place shrink
if (size < old_size && size > max_slab_size_class) {
size_t rounded_size = PAGE_CEILING(size);
size_t old_rounded_size = PAGE_CEILING(old_size);
void *new_end = (char *)old + rounded_size;
if (memory_map_fixed(new_end, old_guard_size)) {
return NULL;
}
void *new_guard_end = (char *)new_end + old_guard_size;
memory_unmap(new_guard_end, old_rounded_size - rounded_size);
pthread_mutex_lock(&regions_lock);
struct region_info *region = regions_find(old);
if (region == NULL) {
fatal_error("invalid realloc");
}
region->size = size;
pthread_mutex_unlock(&regions_lock);
return old;
}
size_t copy_size = size < old_size ? size : old_size;
if (copy_size >= mremap_threshold) {
void *new = allocate(size);
@ -804,7 +828,6 @@ EXPORT void *h_realloc(void *old, size_t size) {
if (region == NULL) {
fatal_error("invalid realloc");
}
size_t old_guard_size = region->guard_size;
regions_delete(region);
pthread_mutex_unlock(&regions_lock);