Add backtrace generation to MALLOC_DEBUG memory corruption reports

This patch allows astmm to access the backtrace generation code in Asterisk.
When memory is allocated, a backtrace is created and stored with the memory
region that tracks the allocation. If a memory corruption is detected, the
backtrace is printed to the astmm log. The backtrace will make use of the
BETTER_BACKTRACES build option if available.

As a result, this patch moves the backtrace generation code into its own file
and uses the non-wrapped versions of the C library memory allocation routines.
This allows the memory allocation code to safely use the backtrace generation
routines without infinitely recursing.

Review: https://reviewboard.asterisk.org/r/2567


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@391012 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 222 insertions, 0 deletions

diff --git a/main/backtrace.c b/main/backtrace.c
new file mode 100644
index 000000000..001699d00
--- /dev/null
+++ b/main/backtrace.c
@@ -0,0 +1,222 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 1999 - 2013, Digium, Inc.
+ *
+ * Matt Jordan <mjordan@digium.com>
+ *
+ * See http://www.asterisk.org for more information about
+ * the Asterisk project. Please do not directly contact
+ * any of the maintainers of this project for assistance;
+ * the project provides a web site, mailing lists and IRC
+ * channels for your use.
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License Version 2. See the LICENSE file
+ * at the top of the source tree.
+ */
+
+/*! \file
+ * \brief Asterisk backtrace generation
+ *
+ * This file provides backtrace generation utilities
+ */
+
+/*** MODULEINFO
+	<support_level>core</support_level>
+ ***/
+
+#include "asterisk.h"
+ASTERISK_FILE_VERSION(__FILE__, "$Revision$");
+
+#include "asterisk/backtrace.h"
+#include "asterisk/utils.h"
+#include "asterisk/strings.h"
+
+#ifdef HAVE_BKTR
+#include <execinfo.h>
+#if defined(HAVE_DLADDR) && defined(HAVE_BFD) && defined(BETTER_BACKTRACES)
+#include <dlfcn.h>
+#include <bfd.h>
+#endif
+
+/* Undefine the overrides for memory allocation. astmm.c uses these functions
+ * as well.
+ */
+#undef calloc
+#undef malloc
+#undef free
+#undef realloc
+
+struct ast_bt *__ast_bt_create(void)
+{
+	struct ast_bt *bt = calloc(1, sizeof(*bt));
+	if (!bt) {
+		return NULL;
+	}
+	bt->alloced = 1;
+
+	ast_bt_get_addresses(bt);
+
+	return bt;
+}
+
+int __ast_bt_get_addresses(struct ast_bt *bt)
+{
+	bt->num_frames = backtrace(bt->addresses, AST_MAX_BT_FRAMES);
+	return 0;
+}
+
+void *__ast_bt_destroy(struct ast_bt *bt)
+{
+	if (bt->alloced) {
+		free(bt);
+	}
+	return NULL;
+}
+
+char **__ast_bt_get_symbols(void **addresses, size_t num_frames)
+{
+	char **strings = NULL;
+#if defined(BETTER_BACKTRACES)
+	int stackfr;
+	bfd *bfdobj;           /* bfd.h */
+	Dl_info dli;           /* dlfcn.h */
+	long allocsize;
+	asymbol **syms = NULL; /* bfd.h */
+	bfd_vma offset;        /* bfd.h */
+	const char *lastslash;
+	asection *section;
+	const char *file, *func;
+	unsigned int line;
+	char address_str[128];
+	char msg[1024];
+	size_t strings_size;
+	size_t *eachlen;
+#endif
+
+#if defined(BETTER_BACKTRACES)
+	strings_size = num_frames * sizeof(*strings);
+	eachlen = calloc(num_frames, sizeof(*eachlen));
+
+	if (!(strings = calloc(num_frames, sizeof(*strings)))) {
+		return NULL;
+	}
+
+	for (stackfr = 0; stackfr < num_frames; stackfr++) {
+		int found = 0, symbolcount;
+
+		msg[0] = '\0';
+
+		if (!dladdr(addresses[stackfr], &dli)) {
+			continue;
+		}
+
+		if (strcmp(dli.dli_fname, "asterisk") == 0) {
+			char asteriskpath[256];
+			if (!(dli.dli_fname = ast_utils_which("asterisk", asteriskpath, sizeof(asteriskpath)))) {
+				/* This will fail to find symbols */
+				dli.dli_fname = "asterisk";
+			}
+		}
+
+		lastslash = strrchr(dli.dli_fname, '/');
+		if (	(bfdobj = bfd_openr(dli.dli_fname, NULL)) &&
+				bfd_check_format(bfdobj, bfd_object) &&
+				(allocsize = bfd_get_symtab_upper_bound(bfdobj)) > 0 &&
+				(syms = malloc(allocsize)) &&
+				(symbolcount = bfd_canonicalize_symtab(bfdobj, syms))) {
+
+			if (bfdobj->flags & DYNAMIC) {
+				offset = addresses[stackfr] - dli.dli_fbase;
+			} else {
+				offset = addresses[stackfr] - (void *)0;
+			}
+
+			for (section = bfdobj->sections; section; section = section->next) {
+				if (	!bfd_get_section_flags(bfdobj, section) & SEC_ALLOC ||
+						section->vma > offset ||
+						section->size + section->vma < offset) {
+					continue;
+				}
+
+				if (!bfd_find_nearest_line(bfdobj, section, syms, offset - section->vma, &file, &func, &line)) {
+					continue;
+				}
+
+				/* file can possibly be null even with a success result from bfd_find_nearest_line */
+				file = file ? file : "";
+
+				/* Stack trace output */
+				found++;
+				if ((lastslash = strrchr(file, '/'))) {
+					const char *prevslash;
+					for (prevslash = lastslash - 1; *prevslash != '/' && prevslash >= file; prevslash--);
+					if (prevslash >= file) {
+						lastslash = prevslash;
+					}
+				}
+				if (dli.dli_saddr == NULL) {
+					address_str[0] = '\0';
+				} else {
+					snprintf(address_str, sizeof(address_str), " (%p+%lX)",
+						dli.dli_saddr,
+						(unsigned long) (addresses[stackfr] - dli.dli_saddr));
+				}
+				snprintf(msg, sizeof(msg), "%s:%u %s()%s",
+					lastslash ? lastslash + 1 : file, line,
+					S_OR(func, "???"),
+					address_str);
+
+				break; /* out of section iteration */
+			}
+		}
+		if (bfdobj) {
+			bfd_close(bfdobj);
+			free(syms);
+		}
+
+		/* Default output, if we cannot find the information within BFD */
+		if (!found) {
+			if (dli.dli_saddr == NULL) {
+				address_str[0] = '\0';
+			} else {
+				snprintf(address_str, sizeof(address_str), " (%p+%lX)",
+					dli.dli_saddr,
+					(unsigned long) (addresses[stackfr] - dli.dli_saddr));
+			}
+			snprintf(msg, sizeof(msg), "%s %s()%s",
+				lastslash ? lastslash + 1 : dli.dli_fname,
+				S_OR(dli.dli_sname, "<unknown>"),
+				address_str);
+		}
+
+		if (!ast_strlen_zero(msg)) {
+			char **tmp;
+			eachlen[stackfr] = strlen(msg);
+			if (!(tmp = realloc(strings, strings_size + eachlen[stackfr] + 1))) {
+				free(strings);
+				strings = NULL;
+				break; /* out of stack frame iteration */
+			}
+			strings = tmp;
+			strings[stackfr] = (char *) strings + strings_size;
+			ast_copy_string(strings[stackfr], msg, eachlen[stackfr] + 1);
+			strings_size += eachlen[stackfr] + 1;
+		}
+	}
+
+	if (strings) {
+		/* Recalculate the offset pointers */
+		strings[0] = (char *) strings + num_frames * sizeof(*strings);
+		for (stackfr = 1; stackfr < num_frames; stackfr++) {
+			strings[stackfr] = strings[stackfr - 1] + eachlen[stackfr - 1] + 1;
+		}
+	}
+#else /* !defined(BETTER_BACKTRACES) */
+	strings = backtrace_symbols(addresses, num_frames);
+#endif /* defined(BETTER_BACKTRACES) */
+	return strings;
+}
+
+#endif /* HAVE_BKTR */