1 files changed, 259 insertions, 0 deletions
diff --git a/lib/util/talloc_stack.c b/lib/util/talloc_stack.c
new file mode 100644
index 0000000..fdd0a30
--- /dev/null
+++ b/lib/util/talloc_stack.c
@@ -0,0 +1,259 @@
+/*
+   Unix SMB/CIFS implementation.
+   Implement a stack of talloc contexts
+   Copyright (C) Volker Lendecke 2007
+   Copyright (C) Jeremy Allison 2009 - made thread safe.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+/*
+ * Implement a stack of talloc frames.
+ *
+ * When a new talloc stackframe is allocated with talloc_stackframe(), then
+ * the TALLOC_CTX returned with talloc_tos() is reset to that new
+ * frame. Whenever that stack frame is TALLOC_FREE()'ed, then the reverse
+ * happens: The previous talloc_tos() is restored.
+ *
+ * This API is designed to be robust in the sense that if someone forgets to
+ * TALLOC_FREE() a stackframe, then the next outer one correctly cleans up and
+ * resets the talloc_tos().
+ *
+ * This robustness feature means that we can't rely on a linked list with
+ * talloc destructors because in a hierarchy of talloc destructors the parent
+ * destructor is called before its children destructors. The child destructor
+ * called after the parent would set the talloc_tos() to the wrong value.
+ */
+
+#include "replace.h"
+#include <talloc.h>
+#include "lib/util/talloc_stack.h"
+#include "lib/util/smb_threads.h"
+#include "lib/util/smb_threads_internal.h"
+#include "lib/util/fault.h"
+#include "lib/util/debug.h"
+
+struct talloc_stackframe {
+	int talloc_stacksize;
+	int talloc_stack_arraysize;
+	TALLOC_CTX **talloc_stack;
+};
+
+/*
+ * In the single threaded case this is a pointer
+ * to the global talloc_stackframe. In the MT-case
+ * this is the pointer to the thread-specific key
+ * used to look up the per-thread talloc_stackframe
+ * pointer.
+ */
+
+static void *global_ts;
+
+/* Variable to ensure TLS value is only initialized once. */
+static smb_thread_once_t ts_initialized = SMB_THREAD_ONCE_INIT;
+
+static void talloc_stackframe_init(void * unused)
+{
+	if (SMB_THREAD_CREATE_TLS("talloc_stackframe", global_ts)) {
+		smb_panic("talloc_stackframe_init create_tls failed");
+	}
+}
+
+static struct talloc_stackframe *talloc_stackframe_create(void)
+{
+#if defined(PARANOID_MALLOC_CHECKER)
+#ifdef calloc
+#undef calloc
+#endif
+#endif
+	struct talloc_stackframe *ts = (struct talloc_stackframe *)calloc(
+		1, sizeof(struct talloc_stackframe));
+#if defined(PARANOID_MALLOC_CHECKER)
+#define calloc(n, s) __ERROR_DONT_USE_MALLOC_DIRECTLY
+#endif
+
+	if (!ts) {
+		smb_panic("talloc_stackframe_init malloc failed");
+	}
+
+	SMB_THREAD_ONCE(&ts_initialized, talloc_stackframe_init, NULL);
+
+	if (SMB_THREAD_SET_TLS(global_ts, ts)) {
+		smb_panic("talloc_stackframe_init set_tls failed");
+	}
+	return ts;
+}
+
+static int talloc_pop(TALLOC_CTX *frame)
+{
+	struct talloc_stackframe *ts =
+		(struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
+	size_t blocks;
+	int i;
+
+	/* Catch lazy frame-freeing. */
+	if (ts->talloc_stack[ts->talloc_stacksize-1] != frame) {
+		DEBUG(0, ("Freed frame %s, expected %s.\n",
+			  talloc_get_name(frame),
+			  talloc_get_name(ts->talloc_stack
+					  [ts->talloc_stacksize-1])));
+#ifdef DEVELOPER
+		smb_panic("Frame not freed in order.");
+#endif
+	}
+
+	for (i=0; i<10; i++) {
+
+		/*
+		 * We have to free our children first, calling all
+		 * destructors. If a destructor hanging deeply off
+		 * "frame" uses talloc_tos() itself while freeing the
+		 * toplevel frame, we panic because that nested
+		 * talloc_tos() in the destructor does not find a
+		 * stackframe anymore.
+		 *
+		 * Do it in a loop up to 10 times as the destructors
+		 * might use more of talloc_tos().
+		 */
+
+		talloc_free_children(frame);
+
+		blocks = talloc_total_blocks(frame);
+		if (blocks == 1) {
+			break;
+		}
+	}
+
+	if (blocks != 1) {
+		DBG_WARNING("Left %zu blocks after %i "
+			    "talloc_free_children(frame) calls\n",
+			    blocks, i);
+	}
+
+	for (i=ts->talloc_stacksize-1; i>0; i--) {
+		if (frame == ts->talloc_stack[i]) {
+			break;
+		}
+		TALLOC_FREE(ts->talloc_stack[i]);
+	}
+
+	ts->talloc_stack[i] = NULL;
+	ts->talloc_stacksize = i;
+	return 0;
+}
+
+/*
+ * Create a new talloc stack frame.
+ *
+ * When free'd, it frees all stack frames that were created after this one and
+ * not explicitly freed.
+ */
+
+static TALLOC_CTX *talloc_stackframe_internal(const char *location,
+					      size_t poolsize)
+{
+	TALLOC_CTX **tmp, *top;
+	struct talloc_stackframe *ts =
+		(struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
+
+	if (ts == NULL) {
+		ts = talloc_stackframe_create();
+	}
+
+	if (ts->talloc_stack_arraysize < ts->talloc_stacksize + 1) {
+		tmp = talloc_realloc(NULL, ts->talloc_stack, TALLOC_CTX *,
+					   ts->talloc_stacksize + 1);
+		if (tmp == NULL) {
+			goto fail;
+		}
+		ts->talloc_stack = tmp;
+		ts->talloc_stack_arraysize = ts->talloc_stacksize + 1;
+        }
+
+	if (poolsize) {
+		top = talloc_pool(ts->talloc_stack, poolsize);
+	} else {
+		TALLOC_CTX *parent;
+		/* We chain parentage, so if one is a pool we draw from it. */
+		if (ts->talloc_stacksize == 0) {
+			parent = ts->talloc_stack;
+		} else {
+			parent = ts->talloc_stack[ts->talloc_stacksize-1];
+		}
+		top = talloc_new(parent);
+	}
+
+	if (top == NULL) {
+		goto fail;
+	}
+	talloc_set_name_const(top, location);
+	talloc_set_destructor(top, talloc_pop);
+
+	ts->talloc_stack[ts->talloc_stacksize++] = top;
+	return top;
+
+ fail:
+	smb_panic("talloc_stackframe failed");
+	return NULL;
+}
+
+TALLOC_CTX *_talloc_stackframe(const char *location)
+{
+	return talloc_stackframe_internal(location, 0);
+}
+
+TALLOC_CTX *_talloc_stackframe_pool(const char *location, size_t poolsize)
+{
+	return talloc_stackframe_internal(location, poolsize);
+}
+
+/*
+ * Get us the current top of the talloc stack.
+ */
+
+TALLOC_CTX *_talloc_tos(const char *location)
+{
+	struct talloc_stackframe *ts =
+		(struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
+
+	if (ts == NULL || ts->talloc_stacksize == 0) {
+		_talloc_stackframe(location);
+		ts = (struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
+		DEBUG(0, ("no talloc stackframe at %s, leaking memory\n",
+			  location));
+#ifdef DEVELOPER
+		smb_panic("No talloc stackframe");
+#endif
+	}
+
+	return ts->talloc_stack[ts->talloc_stacksize-1];
+}
+
+/*
+ * return true if a talloc stackframe exists
+ * this can be used to prevent memory leaks for code that can
+ * optionally use a talloc stackframe (eg. nt_errstr())
+ */
+
+bool talloc_stackframe_exists(void)
+{
+	struct talloc_stackframe *ts =
+		(struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
+
+	if (ts == NULL || ts->talloc_stacksize == 0) {
+		return false;
+	}
+	return true;
+}