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-rw-r--r--lib/util/talloc_stack.c259
1 files changed, 259 insertions, 0 deletions
diff --git a/lib/util/talloc_stack.c b/lib/util/talloc_stack.c
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+++ b/lib/util/talloc_stack.c
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+/*
+ 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;
+}