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https://gitlab.com/samba-team/samba/-/commit/14feb93d481011765f62614ab49b304e17e4f6fd
https://gitlab.com/samba-team/samba/-/merge_requests/2401?commit_id=ac8064cb0d79db377df75a22a240632dbc37f99f
https://bugs.gentoo.org/791349
From 14feb93d481011765f62614ab49b304e17e4f6fd Mon Sep 17 00:00:00 2001
From: Andrew Bartlett <abartlet@samba.org>
Date: Tue, 7 Jun 2022 15:07:59 +1200
Subject: [PATCH] lib/util: Prefer backtrace_symbols() for internal backtraces
Backtraces when Samba is in PANIC state are better with
backtrace_symbols() than with libunwind on Ubuntu 20.04 x86_64
so move libunwind to a off-by-default option, prompted for
if backtrace_symbols() is not available.
Based on a request by Fco Javier Felix <ffelix@inode64.com>
Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Joseph Sutton <josephsutton@catalyst.net.nz>
--- a/lib/util/fault.c
+++ b/lib/util/fault.c
@@ -222,9 +222,13 @@ _PUBLIC_ void smb_panic(const char *why)
void log_stack_trace(void)
{
#ifdef HAVE_LIBUNWIND
- /* Try to use libunwind before any other technique since on ia64
- * libunwind correctly walks the stack in more circumstances than
- * backtrace.
+ /*
+ * --with-libunwind is required to use libunwind, the
+ * backtrace_symbols() code below is the default.
+ *
+ * This code is available because a previous version of this
+ * comment asserted that on ia64 libunwind correctly walks the
+ * stack in more circumstances than backtrace.
*/
unw_cursor_t cursor;
unw_context_t uc;
--- a/lib/util/wscript
+++ b/lib/util/wscript
@@ -2,6 +2,15 @@ def options(opt):
''' This is a bit strange, but disable is the flag, not enable. '''
opt.add_option('--disable-fault-handling', action='store_true', dest='disable_fault_handling', help=('disable the fault handlers'), default=False)
+ # We do not want libunwind by default (backtrace_symbols() in
+ # glibc is better) but allow (eg) IA-64 to build with it where it
+ # might be better (per old comment in fault.c)
+ opt.samba_add_onoff_option('libunwind',
+ default=None,
+ help='''Use libunwind instead of the default backtrace_symbols()
+ from libc, for example on IA-64 where it might give a better
+ backtrace.''')
+
opt.add_option('--with-systemd',
help=("Enable systemd integration"),
action='store_true', dest='enable_systemd')
--- a/lib/util/wscript_configure
+++ b/lib/util/wscript_configure
@@ -1,23 +1,35 @@
#!/usr/bin/env python
-from waflib import Logs, Options
+from waflib import Logs, Options, Errors
import os, sys
if Options.options.disable_fault_handling:
conf.DEFINE('HAVE_DISABLE_FAULT_HANDLING',1)
-# backtrace could be in libexecinfo or in libc
+# backtrace could be in libexecinfo or in libc.
+# This is our preferred backtrace handler (more useful output than libunwind as at Ubuntu 20.04 x86_64)
conf.CHECK_FUNCS_IN('backtrace backtrace_symbols', 'execinfo', checklibc=True, headers='execinfo.h')
conf.CHECK_HEADERS('execinfo.h')
conf.SET_TARGET_TYPE('LIBUNWIND', 'EMPTY')
-if conf.check_cfg(package='libunwind-generic',
- args='--cflags --libs',
- msg='Checking for libunwind',
- uselib_store='LIBUNWIND',
- mandatory=False):
- if conf.CHECK_HEADERS('libunwind.h'):
- conf.SET_TARGET_TYPE('LIBUNWIND', 'SYSLIB')
+if Options.options.with_libunwind:
+ if conf.check_cfg(package='libunwind-generic',
+ args='--cflags --libs',
+ msg='Checking for libunwind',
+ uselib_store='LIBUNWIND',
+ mandatory=False):
+ if conf.CHECK_HEADERS('libunwind.h'):
+ conf.SET_TARGET_TYPE('LIBUNWIND', 'SYSLIB')
+ else:
+ raise Errors.WafError('--with-libunwind specified but libunwind not found')
+elif Options.options.with_libunwind == None:
+ if not conf.CONFIG_SET('HAVE_BACKTRACE_SYMBOLS') \
+ and not Options.options.disable_fault_handling:
+ raise Errors.WafError(
+'''backtrace_symbols() not found but
+--with-libunwind not specified.
+Use --without-libunwind to build without internal backtrace support or
+--disable-fault-handling to totally defer fault handling to the OS.''')
conf.CHECK_STRUCTURE_MEMBER('struct statvfs', 'f_frsize', define='HAVE_FRSIZE', headers='sys/statvfs.h')
--- a/script/autobuild.py
+++ b/script/autobuild.py
@@ -480,10 +480,11 @@ tasks = {
# MIT Kerberos from the current system. Runtime behaviour is
# confirmed via the ktest (static ccache and keytab) environment
+ # This environment also used to confirm we can still build with --with-libunwind
"samba-ktest-mit": {
"sequence": [
("random-sleep", random_sleep(300, 900)),
- ("configure", "./configure.developer --without-ad-dc --with-system-mitkrb5 " + samba_configure_params),
+ ("configure", "./configure.developer --without-ad-dc --with-libunwind --with-system-mitkrb5 " + samba_configure_params),
("make", "make -j"),
("test", make_test(include_envs=[
"ktest", # ktest is also tested in fileserver, samba and
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