1 files changed, 190 insertions, 0 deletions
diff --git a/src/lib/mempool-datastack.c b/src/lib/mempool-datastack.c
new file mode 100644
index 0000000..b3c1094
--- /dev/null
+++ b/src/lib/mempool-datastack.c
@@ -0,0 +1,190 @@
+/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "mempool.h"
+
+/*
+ * The datastack pool is a thin wrapper around the datastack API.  It exists
+ * to allow datastack allocations via the pool API.
+ *
+ * Note: Do not confuse it with the *unsafe* datastack pool.
+ *
+ * Implementation
+ * ==============
+ *
+ * A datastack pool maintains information about the datastack frame that was
+ * in use when the pool was created so it can sanity check all p_new(),
+ * p_malloc(), and p_realloc() calls.
+ *
+ * Creation
+ * --------
+ *
+ * When a datastack pool is created, a new pool structure is allocated from
+ * the datastack (via t_new()).  The current datastack frame number is saved
+ * into the pool's private data (struct datastack_pool).
+ *
+ * Allocation & Reallocation
+ * -------------------------
+ *
+ * After verifying that the saved datastack frame id matches the currently
+ * active one, the p_malloc() and p_realloc() calls get directed to
+ * t_malloc0() and t_try_realloc(), respectively.  There is no
+ * per-allocation information to track.
+ *
+ * Freeing
+ * -------
+ *
+ * Freeing is a no-op unless the currently active data stack frame id is
+ * different from the one saved during pool creation, in which case the
+ * process panics.
+ *
+ * Clearing
+ * --------
+ *
+ * A no-op.
+ *
+ * Destruction
+ * -----------
+ *
+ * Since the memory backing the pool structure itself is allocated from the
+ * datastack via t_new(), the pool and all allocations it made are freed
+ * when the datastack frame is popped.
+ *
+ * Even though the pool maintains a reference count, no memory is freed when
+ * it reaches zero.  Once the reference count reaches zero, the state of the
+ * pool is undefined and none of its memory maybe be used.
+ */
+
+static const char *pool_data_stack_get_name(pool_t pool);
+static void pool_data_stack_ref(pool_t pool);
+static void pool_data_stack_unref(pool_t *pool);
+static void *pool_data_stack_malloc(pool_t pool, size_t size);
+static void pool_data_stack_free(pool_t pool, void *mem);
+static void *pool_data_stack_realloc(pool_t pool, void *mem,
+				     size_t old_size, size_t new_size);
+static void pool_data_stack_clear(pool_t pool);
+static size_t pool_data_stack_get_max_easy_alloc_size(pool_t pool);
+
+static struct pool_vfuncs static_data_stack_pool_vfuncs = {
+	pool_data_stack_get_name,
+
+	pool_data_stack_ref,
+	pool_data_stack_unref,
+
+	pool_data_stack_malloc,
+	pool_data_stack_free,
+
+	pool_data_stack_realloc,
+
+	pool_data_stack_clear,
+	pool_data_stack_get_max_easy_alloc_size
+};
+
+static const struct pool static_data_stack_pool = {
+	.v = &static_data_stack_pool_vfuncs,
+
+	.alloconly_pool = TRUE,
+	.datastack_pool = TRUE
+};
+
+struct datastack_pool {
+	struct pool pool;
+	int refcount;
+
+	unsigned int data_stack_frame;
+};
+
+pool_t pool_datastack_create(void)
+{
+	struct datastack_pool *dpool;
+
+	dpool = t_new(struct datastack_pool, 1);
+	dpool->pool = static_data_stack_pool;
+	dpool->refcount = 1;
+	dpool->data_stack_frame = data_stack_frame_id;
+	return &dpool->pool;
+}
+
+static const char *pool_data_stack_get_name(pool_t pool ATTR_UNUSED)
+{
+	return "data stack";
+}
+
+static void pool_data_stack_ref(pool_t pool)
+{
+	struct datastack_pool *dpool =
+		container_of(pool, struct datastack_pool, pool);
+
+	if (unlikely(dpool->data_stack_frame != data_stack_frame_id))
+		i_panic("pool_data_stack_ref(): stack frame changed");
+
+	dpool->refcount++;
+}
+
+static void pool_data_stack_unref(pool_t *pool)
+{
+	struct datastack_pool *dpool =
+		container_of(*pool, struct datastack_pool, pool);
+
+	if (unlikely(dpool->data_stack_frame != data_stack_frame_id))
+		i_panic("pool_data_stack_unref(): stack frame changed");
+
+	dpool->refcount--;
+	i_assert(dpool->refcount >= 0);
+
+	*pool = NULL;
+}
+
+static void *pool_data_stack_malloc(pool_t pool ATTR_UNUSED, size_t size)
+{
+	struct datastack_pool *dpool =
+		container_of(pool, struct datastack_pool, pool);
+
+	if (unlikely(dpool->data_stack_frame != data_stack_frame_id))
+		i_panic("pool_data_stack_malloc(): stack frame changed");
+
+	return t_malloc0(size);
+}
+
+static void pool_data_stack_free(pool_t pool, void *mem ATTR_UNUSED)
+{
+	struct datastack_pool *dpool =
+		container_of(pool, struct datastack_pool, pool);
+
+	if (unlikely(dpool->data_stack_frame != data_stack_frame_id))
+		i_panic("pool_data_stack_free(): stack frame changed");
+}
+
+static void *pool_data_stack_realloc(pool_t pool, void *mem,
+				     size_t old_size, size_t new_size)
+{
+	struct datastack_pool *dpool =
+		container_of(pool, struct datastack_pool, pool);
+	void *new_mem;
+
+	/* @UNSAFE */
+	if (unlikely(dpool->data_stack_frame != data_stack_frame_id))
+		i_panic("pool_data_stack_realloc(): stack frame changed");
+
+	if (old_size >= new_size)
+		return mem;
+
+	if (!t_try_realloc(mem, new_size)) {
+		new_mem = t_malloc_no0(new_size);
+		memcpy(new_mem, mem, old_size);
+		mem = new_mem;
+	}
+
+	memset((char *) mem + old_size, 0, new_size - old_size);
+	return mem;
+}
+
+static void pool_data_stack_clear(pool_t pool ATTR_UNUSED)
+{
+}
+
+static size_t
+pool_data_stack_get_max_easy_alloc_size(pool_t pool ATTR_UNUSED)
+{
+	return t_get_bytes_available();
+}