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Refactored poisoning and unpoisoning freelist to simpler API
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@jemmaissroff @tenderlove
jemmaissroff authored and tenderlove committed Jul 26, 2022
1 parent 33f9e8f commit 36d0c71
Showing 1 changed file with 40 additions and 22 deletions.
62 changes: 40 additions & 22 deletions gc.c
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Expand Up @@ -958,6 +958,24 @@ struct heap_page {
bits_t pinned_bits[HEAP_PAGE_BITMAP_LIMIT];
};

/*
* When asan is enabled, this will prohibit writing to the freelist until it is unlocked
*/
static void
asan_lock_freelist(struct heap_page *page)
{
asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
}

/*
* When asan is enabled, this will enable the ability to write to the freelist
*/
static void
asan_unlock_freelist(struct heap_page *page)
{
asan_unpoison_memory_region(&page->freelist, sizeof(RVALUE*), false);
}

#define GET_PAGE_BODY(x) ((struct heap_page_body *)((bits_t)(x) & ~(HEAP_PAGE_ALIGN_MASK)))
#define GET_PAGE_HEADER(x) (&GET_PAGE_BODY(x)->header)
#define GET_HEAP_PAGE(x) (GET_PAGE_HEADER(x)->page)
Expand Down Expand Up @@ -1939,12 +1957,12 @@ heap_page_add_freeobj(rb_objspace_t *objspace, struct heap_page *page, VALUE obj

asan_unpoison_object(obj, false);

asan_unpoison_memory_region(&page->freelist, sizeof(RVALUE*), false);
asan_unlock_freelist(page);

p->as.free.flags = 0;
p->as.free.next = page->freelist;
page->freelist = p;
asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
asan_lock_freelist(page);

if (RGENGC_CHECK_MODE &&
/* obj should belong to page */
Expand All @@ -1961,7 +1979,7 @@ heap_page_add_freeobj(rb_objspace_t *objspace, struct heap_page *page, VALUE obj
static inline void
heap_add_freepage(rb_heap_t *heap, struct heap_page *page)
{
asan_unpoison_memory_region(&page->freelist, sizeof(RVALUE*), false);
asan_unlock_freelist(page);
GC_ASSERT(page->free_slots != 0);
GC_ASSERT(page->freelist != NULL);

Expand All @@ -1970,22 +1988,22 @@ heap_add_freepage(rb_heap_t *heap, struct heap_page *page)

RUBY_DEBUG_LOG("page:%p freelist:%p", (void *)page, (void *)page->freelist);

asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
asan_lock_freelist(page);
}

#if GC_ENABLE_INCREMENTAL_MARK
static inline void
heap_add_poolpage(rb_objspace_t *objspace, rb_heap_t *heap, struct heap_page *page)
{
asan_unpoison_memory_region(&page->freelist, sizeof(RVALUE*), false);
asan_unlock_freelist(page);
GC_ASSERT(page->free_slots != 0);
GC_ASSERT(page->freelist != NULL);

page->free_next = heap->pooled_pages;
heap->pooled_pages = page;
objspace->rincgc.pooled_slots += page->free_slots;

asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
asan_lock_freelist(page);
}
#endif

Expand Down Expand Up @@ -2209,7 +2227,7 @@ heap_page_allocate(rb_objspace_t *objspace, rb_size_pool_t *size_pool)
}
page->free_slots = limit;

asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
asan_lock_freelist(page);
return page;
}

Expand All @@ -2219,12 +2237,12 @@ heap_page_resurrect(rb_objspace_t *objspace, rb_size_pool_t *size_pool)
struct heap_page *page = 0, *next;

ccan_list_for_each_safe(&SIZE_POOL_TOMB_HEAP(size_pool)->pages, page, next, page_node) {
asan_unpoison_memory_region(&page->freelist, sizeof(RVALUE*), false);
if (page->freelist != NULL) {
heap_unlink_page(objspace, &size_pool->tomb_heap, page);
asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
return page;
}
asan_unlock_freelist(page);
if (page->freelist != NULL) {
heap_unlink_page(objspace, &size_pool->tomb_heap, page);
asan_lock_freelist(page);
return page;
}
}

return NULL;
Expand Down Expand Up @@ -2618,7 +2636,7 @@ heap_next_free_page(rb_objspace_t *objspace, rb_size_pool_t *size_pool, rb_heap_
GC_ASSERT(page->free_slots != 0);
RUBY_DEBUG_LOG("page:%p freelist:%p cnt:%d", (void *)page, (void *)page->freelist, page->free_slots);

asan_unpoison_memory_region(&page->freelist, sizeof(RVALUE*), false);
asan_unlock_freelist(page);

return page;
}
Expand Down Expand Up @@ -5659,13 +5677,13 @@ gc_sweep_page(rb_objspace_t *objspace, rb_heap_t *heap, struct gc_sweep_context

#if RGENGC_CHECK_MODE
short freelist_len = 0;
asan_unpoison_memory_region(&sweep_page->freelist, sizeof(RVALUE*), false);
asan_unlock_freelist(sweep_page);
RVALUE *ptr = sweep_page->freelist;
while (ptr) {
freelist_len++;
ptr = ptr->as.free.next;
}
asan_poison_memory_region(&sweep_page->freelist, sizeof(RVALUE*));
asan_lock_freelist(sweep_page);
if (freelist_len != sweep_page->free_slots) {
rb_bug("inconsistent freelist length: expected %d but was %d", sweep_page->free_slots, freelist_len);
}
Expand Down Expand Up @@ -5723,7 +5741,7 @@ static void
heap_page_freelist_append(struct heap_page *page, RVALUE *freelist)
{
if (freelist) {
asan_unpoison_memory_region(&page->freelist, sizeof(RVALUE*), false);
asan_unlock_freelist(page);
if (page->freelist) {
RVALUE *p = page->freelist;
asan_unpoison_object((VALUE)p, false);
Expand All @@ -5739,7 +5757,7 @@ heap_page_freelist_append(struct heap_page *page, RVALUE *freelist)
else {
page->freelist = freelist;
}
asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
asan_lock_freelist(page);
}
}

Expand Down Expand Up @@ -7934,7 +7952,7 @@ gc_verify_heap_pages_(rb_objspace_t *objspace, struct ccan_list_head *head)
struct heap_page *page = 0;

ccan_list_for_each(head, page, page_node) {
asan_unpoison_memory_region(&page->freelist, sizeof(RVALUE*), false);
asan_unlock_freelist(page);
RVALUE *p = page->freelist;
while (p) {
VALUE vp = (VALUE)p;
Expand All @@ -7946,7 +7964,7 @@ gc_verify_heap_pages_(rb_objspace_t *objspace, struct ccan_list_head *head)
p = p->as.free.next;
asan_poison_object(prev);
}
asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
asan_lock_freelist(page);

if (page->flags.has_remembered_objects == FALSE) {
remembered_old_objects += gc_verify_heap_page(objspace, page, Qfalse);
Expand Down Expand Up @@ -10582,8 +10600,8 @@ static int
gc_ref_update(void *vstart, void *vend, size_t stride, rb_objspace_t * objspace, struct heap_page *page)
{
VALUE v = (VALUE)vstart;
asan_unpoison_memory_region(&page->freelist, sizeof(RVALUE*), false);
asan_poison_memory_region(&page->freelist, sizeof(RVALUE*));
asan_unlock_freelist(page);
asan_lock_freelist(page);
page->flags.has_uncollectible_shady_objects = FALSE;
page->flags.has_remembered_objects = FALSE;

Expand Down

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