[PATCH] os: use libunwind to generate backtraces
Marcin Slusarz
marcin.slusarz at gmail.com
Mon Feb 18 13:40:13 PST 2013
On Mon, Feb 18, 2013 at 10:22:20PM +0100, Julien Cristau wrote:
> On Sat, Feb 16, 2013 at 16:45:54 +0100, Marcin Slusarz wrote:
>
> > Libunwind generates backtraces much more reliably than glibc's "backtrace".
> >
> mind adding an example in the commit message (before/after)?
Sure.
---
From: Marcin Slusarz <marcin.slusarz at gmail.com>
Subject: [PATCH] os: use libunwind to generate backtraces
Libunwind generates backtraces much more reliably than glibc "backtrace".
Before:
0: /opt/xserver/bin/X (0x400000+0x18ce36) [0x58ce36]
1: /opt/xserver/bin/X (xorg_backtrace+0x9) [0x58d119]
2: /opt/xserver/bin/X (0x400000+0x190d69) [0x590d69]
3: /lib64/libpthread.so.0 (0x7fb904268000+0x10a90) [0x7fb904278a90]
4: /lib64/libc.so.6 (ioctl+0x7) [0x7fb902fbf987]
5: /usr/lib64/libdrm.so.2 (drmIoctl+0x28) [0x7fb90405ffa8]
6: /usr/lib64/libdrm.so.2 (drmCommandWrite+0x1b) [0x7fb90406235b]
7: /usr/lib64/libdrm_nouveau.so.2 (nouveau_bo_wait+0x89) [0x7fb902009719]
8: /opt/xserver/lib/xorg/modules/drivers/nouveau_drv.so (0x7fb90220e000+0x76f3) [0x7fb9022156f3]
9: /opt/xserver/lib/xorg/modules/libexa.so (0x7fb9019c7000+0xbae0) [0x7fb9019d2ae0]
10: /opt/xserver/bin/X (0x400000+0x17d2b3) [0x57d2b3]
11: /opt/xserver/bin/X (0x400000+0xc9930) [0x4c9930]
12: /opt/xserver/bin/X (0x400000+0x3a81a) [0x43a81a]
13: /opt/xserver/bin/X (0x400000+0x3d6a1) [0x43d6a1]
14: /opt/xserver/bin/X (0x400000+0x2c2ca) [0x42c2ca]
15: /lib64/libc.so.6 (__libc_start_main+0xf5) [0x7fb902f019b5]
16: /opt/xserver/bin/X (0x400000+0x2c60d) [0x42c60d]
17: ?? [0x0]
After:
0: /opt/xserver/bin/X (OsSigHandler+0x39) [0x590d69]
1: /lib64/libpthread.so.0 (__restore_rt+0x0) [0x7fb904278a8f]
2: /lib64/libc.so.6 (ioctl+0x7) [0x7fb902fbf987]
3: /usr/lib64/libdrm.so.2 (drmIoctl+0x28) [0x7fb90405ffa8]
4: /usr/lib64/libdrm.so.2 (drmCommandWrite+0x1b) [0x7fb90406235b]
5: /usr/lib64/libdrm_nouveau.so.2 (nouveau_bo_wait+0x89) [0x7fb902009719]
6: /opt/xserver/lib/xorg/modules/drivers/nouveau_drv.so (nouveau_exa_download_from_screen+0x1a3) [0x7fb9022156f3]
7: /opt/xserver/lib/xorg/modules/libexa.so (exaGetImage+0x1f0) [0x7fb9019d2ae0]
8: /opt/xserver/bin/X (miSpriteGetImage+0x173) [0x57d2b3]
9: /opt/xserver/bin/X (compGetImage+0xb0) [0x4c9930]
10: /opt/xserver/bin/X (ProcGetImage+0x55a) [0x43a81a]
11: /opt/xserver/bin/X (Dispatch+0x341) [0x43d6a1]
12: /opt/xserver/bin/X (main+0x3ba) [0x42c2ca]
13: /lib64/libc.so.6 (__libc_start_main+0xf5) [0x7fb902f019b5]
14: /opt/xserver/bin/X (_start+0x29) [0x42c60d]
15: ? (?+0x29) [0x29]
Signed-off-by: Marcin Slusarz <marcin.slusarz at gmail.com>
---
configure.ac | 7 +++++
include/dix-config.h.in | 3 +++
os/Makefile.am | 5 ++++
os/backtrace.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 85 insertions(+)
diff --git a/configure.ac b/configure.ac
index 9415a54..4a292da 100644
--- a/configure.ac
+++ b/configure.ac
@@ -309,6 +309,13 @@ AC_CHECK_HEADER([execinfo.h],[
])]
)
+PKG_CHECK_MODULES(LIBUNWIND, libunwind, [HAVE_LIBUNWIND=yes], [HAVE_LIBUNWIND=no])
+if test "x$HAVE_LIBUNWIND" = xyes; then
+ AC_DEFINE(HAVE_LIBUNWIND, 1, [Have libunwind support])
+fi
+AM_CONDITIONAL(HAVE_LIBUNWIND, [test "x$HAVE_LIBUNWIND" = xyes])
+
+
dnl ---------------------------------------------------------------------------
dnl Bus options and CPU capabilities. Replaces logic in
dnl hw/xfree86/os-support/bus/Makefile.am, among others.
diff --git a/include/dix-config.h.in b/include/dix-config.h.in
index 578f249..5102263 100644
--- a/include/dix-config.h.in
+++ b/include/dix-config.h.in
@@ -60,6 +60,9 @@
/* Has backtrace support */
#undef HAVE_BACKTRACE
+/* Has libunwind support */
+#undef HAVE_LIBUNWIND
+
/* Define to 1 if you have the <byteswap.h> header file. */
#undef HAVE_BYTESWAP_H
diff --git a/os/Makefile.am b/os/Makefile.am
index 8891485..364b6da 100644
--- a/os/Makefile.am
+++ b/os/Makefile.am
@@ -34,6 +34,11 @@ if XDMCP
libos_la_SOURCES += $(XDMCP_SRCS)
endif
+if HAVE_LIBUNWIND
+AM_CFLAGS += $(LIBUNWIND_CFLAGS)
+libos_la_LIBADD += $(LIBUNWIND_LIBS)
+endif
+
EXTRA_DIST = $(SECURERPC_SRCS) $(XDMCP_SRCS)
if SPECIAL_DTRACE_OBJECTS
diff --git a/os/backtrace.c b/os/backtrace.c
index daac60c..02aeb03 100644
--- a/os/backtrace.c
+++ b/os/backtrace.c
@@ -30,6 +30,75 @@
#include <errno.h>
#include <string.h>
+#ifdef HAVE_LIBUNWIND
+
+#define UNW_LOCAL_ONLY
+#include <libunwind.h>
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#include <dlfcn.h>
+
+void
+xorg_backtrace(void)
+{
+ unw_cursor_t cursor;
+ unw_context_t context;
+ unw_word_t off;
+ unw_proc_info_t pip;
+ int ret, i = 0;
+ char procname[256];
+ const char *filename;
+ Dl_info dlinfo;
+
+ pip.unwind_info = NULL;
+ ret = unw_getcontext(&context);
+ if (ret) {
+ ErrorFSigSafe("unw_getcontext: %d\n", ret);
+ return;
+ }
+
+ ret = unw_init_local(&cursor, &context);
+ if (ret) {
+ ErrorFSigSafe("unw_init_local: %d\n", ret);
+ return;
+ }
+
+ ErrorFSigSafe("\n");
+ ErrorFSigSafe("Backtrace:\n");
+ ret = unw_step(&cursor);
+ while (ret > 0) {
+ ret = unw_get_proc_info(&cursor, &pip);
+ if (ret) {
+ ErrorFSigSafe("unw_get_proc_info: %d\n", ret);
+ break;
+ }
+
+ ret = unw_get_proc_name(&cursor, procname, 256, &off);
+ if (ret && ret != -UNW_ENOMEM) {
+ if (ret != -UNW_EUNSPEC)
+ ErrorFSigSafe("unw_get_proc_name: %d\n", ret);
+ procname[0] = '?';
+ procname[1] = 0;
+ }
+
+ if (dladdr((void *)(pip.start_ip + off), &dlinfo) && dlinfo.dli_fname &&
+ *dlinfo.dli_fname)
+ filename = dlinfo.dli_fname;
+ else
+ filename = "?";
+
+ ErrorFSigSafe("%u: %s (%s%s+0x%x) [%p]\n", i++, filename, procname,
+ ret == -UNW_ENOMEM ? "..." : "", (int)off, (void *)(pip.start_ip + off));
+
+ ret = unw_step(&cursor);
+ if (ret < 0)
+ ErrorFSigSafe("unw_step: %d\n", ret);
+ }
+ ErrorFSigSafe("\n");
+}
+#else
#ifdef HAVE_BACKTRACE
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
@@ -246,3 +315,4 @@ xorg_backtrace(void)
#endif
#endif
+#endif
--
1.8.1
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