Add tracked arena allocator

Available under -DZEND_TRACK_ARENA_ALLOC. This will use the system
allocator combined with arena checkpointing & release semantics
and allows analyzing arena usage under asan/valgrind.

I've sacrificed the duplicate arena implementation in mysqlnd, as
the integration with mysqlnd alloc is not worth the code duplication
to me.

Author: nikic

Zend/zend_arena.h

@@ -21,6 +21,8 @@
 
 #include "zend.h"
 
+#ifndef ZEND_TRACK_ARENA_ALLOC
+
 typedef struct _zend_arena zend_arena;
 
 struct _zend_arena {
@@ -48,8 +50,6 @@ static zend_always_inline void zend_arena_destroy(zend_arena *arena)
 	} while (arena);
 }
 
-#define ZEND_ARENA_ALIGNMENT 8U
-
 static zend_always_inline void* zend_arena_alloc(zend_arena **arena_ptr, size_t size)
 {
 	zend_arena *arena = *arena_ptr;
@@ -121,4 +121,104 @@ static zend_always_inline zend_bool zend_arena_contains(zend_arena *arena, void
 	return 0;
 }
 
+#else
+
+/* Use normal allocations and keep track of them for mass-freeing.
+ * This is intended for use with asan/valgrind. */
+
+typedef struct _zend_arena zend_arena;
+
+struct _zend_arena {
+	void **ptr;
+	void **end;
+	struct _zend_arena *prev;
+	void *ptrs[0];
+};
+
+#define ZEND_TRACKED_ARENA_SIZE 1000
+
+static zend_always_inline zend_arena *zend_arena_create(size_t _size)
+{
+	zend_arena *arena = (zend_arena*) emalloc(
+		sizeof(zend_arena) + sizeof(void *) * ZEND_TRACKED_ARENA_SIZE);
+	arena->ptr = &arena->ptrs[0];
+	arena->end = &arena->ptrs[ZEND_TRACKED_ARENA_SIZE];
+	arena->prev = NULL;
+	return arena;
+}
+
+static zend_always_inline void zend_arena_destroy(zend_arena *arena)
+{
+	do {
+		zend_arena *prev = arena->prev;
+		void **ptr;
+		for (ptr = arena->ptrs; ptr < arena->ptr; ptr++) {
+			efree(*ptr);
+		}
+		efree(arena);
+		arena = prev;
+	} while (arena);
+}
+
+static zend_always_inline void *zend_arena_alloc(zend_arena **arena_ptr, size_t size)
+{
+	zend_arena *arena = *arena_ptr;
+	if (arena->ptr == arena->end) {
+		*arena_ptr = zend_arena_create(0);
+		(*arena_ptr)->prev = arena;
+		arena = *arena_ptr;
+	}
+
+	return *arena->ptr++ = emalloc(size);
+}
+
+static zend_always_inline void* zend_arena_calloc(zend_arena **arena_ptr, size_t count, size_t unit_size)
+{
+	int overflow;
+	size_t size;
+	void *ret;
+
+	size = zend_safe_address(unit_size, count, 0, &overflow);
+	if (UNEXPECTED(overflow)) {
+		zend_error(E_ERROR, "Possible integer overflow in zend_arena_calloc() (%zu * %zu)", unit_size, count);
+	}
+	ret = zend_arena_alloc(arena_ptr, size);
+	memset(ret, 0, size);
+	return ret;
+}
+
+static zend_always_inline void* zend_arena_checkpoint(zend_arena *arena)
+{
+	return arena->ptr;
+}
+
+static zend_always_inline void zend_arena_release(zend_arena **arena_ptr, void *checkpoint)
+{
+	while (1) {
+		zend_arena *arena = *arena_ptr;
+		zend_arena *prev = arena->prev;
+		while (1) {
+			if (arena->ptr == (void **) checkpoint) {
+				return;
+			}
+			if (arena->ptr == arena->ptrs) {
+				break;
+			}
+			arena->ptr--;
+			efree(*arena->ptr);
+		}
+		efree(arena);
+		*arena_ptr = prev;
+		ZEND_ASSERT(*arena_ptr);
+	}
+}
+
+static zend_always_inline zend_bool zend_arena_contains(zend_arena *arena, void *ptr)
+{
+	/* TODO: Dummy */
+	return 1;
+}
+
+#endif
+
 #endif /* _ZEND_ARENA_H_ */

ext/mysqlnd/mysqlnd_block_alloc.c

@@ -24,83 +24,13 @@
 #include "mysqlnd_debug.h"
 #include "mysqlnd_priv.h"
 
-
-/* {{{ mysqlnd_arena_create */
-static zend_always_inline zend_arena* mysqlnd_arena_create(size_t size)
-{
-	zend_arena *arena = (zend_arena*)mnd_emalloc(size);
-
-	arena->ptr = (char*) arena + ZEND_MM_ALIGNED_SIZE(sizeof(zend_arena));
-	arena->end = (char*) arena + size;
-	arena->prev = NULL;
-	return arena;
-}
-/* }}} */
-
-/* {{{ mysqlnd_arena_destroy */
-static zend_always_inline void mysqlnd_arena_destroy(zend_arena *arena)
-{
-	do {
-		zend_arena *prev = arena->prev;
-		mnd_efree(arena);
-		arena = prev;
-	} while (arena);
-}
-/* }}} */
-
-/* {{{ mysqlnd_arena_alloc */
-static zend_always_inline void* mysqlnd_arena_alloc(zend_arena **arena_ptr, size_t size)
-{
-	zend_arena *arena = *arena_ptr;
-	char *ptr = arena->ptr;
-
-	size = ZEND_MM_ALIGNED_SIZE(size);
-
-	if (EXPECTED(size <= (size_t)(arena->end - ptr))) {
-		arena->ptr = ptr + size;
-	} else {
-		size_t arena_size =
-			UNEXPECTED((size + ZEND_MM_ALIGNED_SIZE(sizeof(zend_arena))) > (size_t)(arena->end - (char*) arena)) ?
-				(size + ZEND_MM_ALIGNED_SIZE(sizeof(zend_arena))) :
-				(size_t)(arena->end - (char*) arena);
-		zend_arena *new_arena = (zend_arena*)mnd_emalloc(arena_size);
-
-		ptr = (char*) new_arena + ZEND_MM_ALIGNED_SIZE(sizeof(zend_arena));
-		new_arena->ptr = (char*) new_arena + ZEND_MM_ALIGNED_SIZE(sizeof(zend_arena)) + size;
-		new_arena->end = (char*) new_arena + arena_size;
-		new_arena->prev = arena;
-		*arena_ptr = new_arena;
-	}
-
-	return (void*) ptr;
-}
-/* }}} */
-
-static zend_always_inline void* mysqlnd_arena_checkpoint(zend_arena *arena)
-{
-	return arena->ptr;
-}
-
-static zend_always_inline void mysqlnd_arena_release(zend_arena **arena_ptr, void *checkpoint)
-{
-	zend_arena *arena = *arena_ptr;
-
-	while (UNEXPECTED((char*)checkpoint > arena->end) ||
-	       UNEXPECTED((char*)checkpoint <= (char*)arena)) {
-		zend_arena *prev = arena->prev;
-		mnd_efree(arena);
-		*arena_ptr = arena = prev;
-	}
-	ZEND_ASSERT((char*)checkpoint > (char*)arena && (char*)checkpoint <= arena->end);
-	arena->ptr = (char*)checkpoint;
-}
-
 /* {{{ mysqlnd_mempool_free_chunk */
 static void
 mysqlnd_mempool_free_chunk(MYSQLND_MEMORY_POOL * pool, void * ptr)
 {
 	DBG_ENTER("mysqlnd_mempool_free_chunk");
 	/* Try to back-off and guess if this is the last block allocated */
+#ifndef ZEND_TRACK_ARENA_ALLOC
 	if (ptr == pool->last) {
 		/*
 			This was the last allocation. Lucky us, we can free
@@ -109,6 +39,7 @@ mysqlnd_mempool_free_chunk(MYSQLND_MEMORY_POOL * pool, void * ptr)
 		pool->arena->ptr = (char*)ptr;
 		pool->last = NULL;
 	}
+#endif
 	DBG_VOID_RETURN;
 }
 /* }}} */
@@ -120,6 +51,7 @@ mysqlnd_mempool_resize_chunk(MYSQLND_MEMORY_POOL * pool, void * ptr, size_t old_
 {
 	DBG_ENTER("mysqlnd_mempool_resize_chunk");
 
+#ifndef ZEND_TRACK_ARENA_ALLOC
 	/* Try to back-off and guess if this is the last block allocated */
 	if (ptr == pool->last
 	  && (ZEND_MM_ALIGNED_SIZE(size) <= ((char*)pool->arena->end - (char*)ptr))) {
@@ -128,11 +60,13 @@ mysqlnd_mempool_resize_chunk(MYSQLND_MEMORY_POOL * pool, void * ptr, size_t old_
 			a bit of memory from the pool. Next time we will return from the same ptr.
 		*/
 		pool->arena->ptr = (char*)ptr + ZEND_MM_ALIGNED_SIZE(size);
-	} else {
-		void *new_ptr = mysqlnd_arena_alloc(&pool->arena, size);
-		memcpy(new_ptr, ptr, MIN(old_size, size));
-		pool->last = ptr = new_ptr;
+		DBG_RETURN(ptr);
 	}
+#endif
+
+	void *new_ptr = zend_arena_alloc(&pool->arena, size);
+	memcpy(new_ptr, ptr, MIN(old_size, size));
+	pool->last = ptr = new_ptr;
 	DBG_RETURN(ptr);
 }
 /* }}} */
@@ -145,7 +79,7 @@ mysqlnd_mempool_get_chunk(MYSQLND_MEMORY_POOL * pool, size_t size)
 	void *ptr = NULL;
 	DBG_ENTER("mysqlnd_mempool_get_chunk");
 
-	ptr = mysqlnd_arena_alloc(&pool->arena, size);
+	ptr = zend_arena_alloc(&pool->arena, size);
 	pool->last = ptr;
 
 	DBG_RETURN(ptr);
@@ -161,8 +95,8 @@ mysqlnd_mempool_create(size_t arena_size)
 	MYSQLND_MEMORY_POOL * ret;
 
 	DBG_ENTER("mysqlnd_mempool_create");
-	arena = mysqlnd_arena_create(MAX(arena_size, sizeof(zend_arena)));
-	ret = mysqlnd_arena_alloc(&arena, sizeof(MYSQLND_MEMORY_POOL));
+	arena = zend_arena_create(MAX(arena_size, sizeof(zend_arena)));
+	ret = zend_arena_alloc(&arena, sizeof(MYSQLND_MEMORY_POOL));
 	ret->arena = arena;
 	ret->last = NULL;
 	ret->checkpoint = NULL;
@@ -180,7 +114,7 @@ mysqlnd_mempool_destroy(MYSQLND_MEMORY_POOL * pool)
 {
 	DBG_ENTER("mysqlnd_mempool_destroy");
 	/* mnd_free will reference LOCK_access and might crash, depending on the caller...*/
-	mysqlnd_arena_destroy(pool->arena);
+	zend_arena_destroy(pool->arena);
 	DBG_VOID_RETURN;
 }
 /* }}} */
@@ -190,7 +124,7 @@ PHPAPI void
 mysqlnd_mempool_save_state(MYSQLND_MEMORY_POOL * pool)
 {
 	DBG_ENTER("mysqlnd_mempool_save_state");
-	pool->checkpoint = mysqlnd_arena_checkpoint(pool->arena);
+	pool->checkpoint = zend_arena_checkpoint(pool->arena);
 	DBG_VOID_RETURN;
 }
 /* }}} */
@@ -201,7 +135,7 @@ mysqlnd_mempool_restore_state(MYSQLND_MEMORY_POOL * pool)
 {
 	DBG_ENTER("mysqlnd_mempool_restore_state");
 	if (pool->checkpoint) {
-		mysqlnd_arena_release(&pool->arena, pool->checkpoint);
+		zend_arena_release(&pool->arena, pool->checkpoint);
 		pool->last = NULL;
 		pool->checkpoint = NULL;
 	}