mirror of
https://github.com/openvswitch/ovs
synced 2025-08-22 18:07:40 +00:00
57cccb0763
Some systems may provide backtrace() in libc but for some reason
not provide any frames when attempting to use it.
On those systems the fatal_signal_init() function currently logs
this debug message: "Capturing of dummy backtrace has failed."
A consequence of this logging may be false negative test results.
Logging the fact that backtrace() does not work has limited value
on a production system and I propose we drop it.
Fixes: 759a29dc2d97 ("backtrace: Extend the backtrace functionality.")
Reported-at: https://launchpad.net/bugs/2032623
Acked-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Frode Nordahl <frode.nordahl@canonical.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
576 lines
15 KiB
C
576 lines
15 KiB
C
/*
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* Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <config.h>
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#include "backtrace.h"
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#include "fatal-signal.h"
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#include <errno.h>
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#include <signal.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "ovs-thread.h"
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#include "openvswitch/poll-loop.h"
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#include "openvswitch/shash.h"
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#include "sset.h"
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#include "signals.h"
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#include "socket-util.h"
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#include "util.h"
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#include "openvswitch/vlog.h"
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#include "openvswitch/type-props.h"
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#if defined(HAVE_UNWIND) || defined(HAVE_BACKTRACE)
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#include "daemon-private.h"
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#endif
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#ifdef HAVE_BACKTRACE
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#include <execinfo.h>
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#endif
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#ifndef SIG_ATOMIC_MAX
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#define SIG_ATOMIC_MAX TYPE_MAXIMUM(sig_atomic_t)
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#endif
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VLOG_DEFINE_THIS_MODULE(fatal_signal);
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/* Signals to catch. */
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#ifndef _WIN32
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static const int fatal_signals[] = { SIGTERM, SIGINT, SIGHUP, SIGALRM,
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SIGSEGV };
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#else
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static const int fatal_signals[] = { SIGTERM };
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#endif
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/* Hooks to call upon catching a signal */
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struct hook {
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void (*hook_cb)(void *aux);
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void (*cancel_cb)(void *aux);
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void *aux;
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bool run_at_exit;
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};
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#define MAX_HOOKS 32
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static struct hook hooks[MAX_HOOKS];
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static size_t n_hooks;
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static int signal_fds[2];
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static volatile sig_atomic_t stored_sig_nr = SIG_ATOMIC_MAX;
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#ifdef _WIN32
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static HANDLE wevent;
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#endif
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static struct ovs_mutex mutex;
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static void call_hooks(int sig_nr);
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#ifdef _WIN32
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static BOOL WINAPI ConsoleHandlerRoutine(DWORD dwCtrlType);
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#endif
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/* Sets up a pipe or event handle that will be used to wake up the current
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* process after signal is received, so it can be processed outside of the
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* signal handler context in fatal_signal_run(). */
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static void
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fatal_signal_create_wakeup_events(void)
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{
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#ifndef _WIN32
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xpipe_nonblocking(signal_fds);
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#else
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wevent = CreateEvent(NULL, TRUE, FALSE, NULL);
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if (!wevent) {
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char *msg_buf = ovs_lasterror_to_string();
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VLOG_FATAL("Failed to create a event (%s).", msg_buf);
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}
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#endif
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}
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static void
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fatal_signal_destroy_wakeup_events(void)
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{
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#ifndef _WIN32
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close(signal_fds[0]);
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signal_fds[0] = -1;
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close(signal_fds[1]);
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signal_fds[1] = -1;
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#else
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ResetEvent(wevent);
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CloseHandle(wevent);
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wevent = NULL;
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#endif
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}
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/* Initializes the fatal signal handling module. Calling this function is
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* optional, because calling any other function in the module will also
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* initialize it. However, in a multithreaded program, the module must be
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* initialized while the process is still single-threaded. */
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void
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fatal_signal_init(void)
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{
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static bool inited = false;
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if (!inited) {
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size_t i;
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assert_single_threaded();
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inited = true;
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ovs_mutex_init_recursive(&mutex);
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/* The dummy backtrace is needed.
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* See comment for send_backtrace_to_monitor(). */
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struct backtrace dummy_bt;
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backtrace_capture(&dummy_bt);
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fatal_signal_create_wakeup_events();
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#ifdef _WIN32
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/* Register a function to handle Ctrl+C. */
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SetConsoleCtrlHandler(ConsoleHandlerRoutine, true);
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#endif
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for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) {
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int sig_nr = fatal_signals[i];
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#ifndef _WIN32
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struct sigaction old_sa;
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xsigaction(sig_nr, NULL, &old_sa);
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if (old_sa.sa_handler == SIG_DFL
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&& signal(sig_nr, fatal_signal_handler) == SIG_ERR) {
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VLOG_FATAL("signal failed (%s)", ovs_strerror(errno));
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}
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#else
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if (signal(sig_nr, fatal_signal_handler) == SIG_ERR) {
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VLOG_FATAL("signal failed (%s)", ovs_strerror(errno));
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}
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#endif
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}
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atexit(fatal_signal_atexit_handler);
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}
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}
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/* Registers 'hook_cb' to be called from inside poll_block() following a fatal
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* signal. 'hook_cb' does not need to be async-signal-safe. In a
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* multithreaded program 'hook_cb' might be called from any thread, with
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* threads other than the one running 'hook_cb' in unknown states.
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*
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* If 'run_at_exit' is true, 'hook_cb' is also called during normal process
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* termination, e.g. when exit() is called or when main() returns.
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*
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* If the current process forks, fatal_signal_fork() may be called to clear the
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* parent process's fatal signal hooks, so that 'hook_cb' is only called when
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* the child terminates, not when the parent does. When fatal_signal_fork() is
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* called, it calls the 'cancel_cb' function if it is nonnull, passing 'aux',
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* to notify that the hook has been canceled. This allows the hook to free
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* memory, etc. */
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void
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fatal_signal_add_hook(void (*hook_cb)(void *aux), void (*cancel_cb)(void *aux),
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void *aux, bool run_at_exit)
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{
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fatal_signal_init();
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ovs_mutex_lock(&mutex);
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ovs_assert(n_hooks < MAX_HOOKS);
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hooks[n_hooks].hook_cb = hook_cb;
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hooks[n_hooks].cancel_cb = cancel_cb;
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hooks[n_hooks].aux = aux;
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hooks[n_hooks].run_at_exit = run_at_exit;
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n_hooks++;
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ovs_mutex_unlock(&mutex);
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}
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#ifdef HAVE_UNWIND
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/* Convert unsigned long long to string. This is needed because
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* using snprintf() is not async signal safe. */
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static inline int
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llong_to_hex_str(unsigned long long value, char *str)
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{
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int i = 0, res;
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if (value / 16 > 0) {
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i = llong_to_hex_str(value / 16, str);
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}
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res = value % 16;
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str[i] = "0123456789abcdef"[res];
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return i + 1;
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}
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/* Send the backtrace buffer to monitor thread.
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*
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* Note that this runs in the signal handling context, any system
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* library functions used here must be async-signal-safe.
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*/
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static inline void
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send_backtrace_to_monitor(void)
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{
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/* volatile added to prevent a "clobbered" error on ppc64le with gcc */
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volatile int dep;
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struct unw_backtrace unw_bt[UNW_MAX_DEPTH];
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unw_cursor_t cursor;
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unw_context_t uc;
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if (daemonize_fd == -1) {
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return;
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}
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dep = 0;
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unw_getcontext(&uc);
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unw_init_local(&cursor, &uc);
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while (dep < UNW_MAX_DEPTH && unw_step(&cursor)) {
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memset(unw_bt[dep].func, 0, UNW_MAX_FUNCN);
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unw_get_reg(&cursor, UNW_REG_IP, &unw_bt[dep].ip);
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unw_get_proc_name(&cursor, unw_bt[dep].func, UNW_MAX_FUNCN,
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&unw_bt[dep].offset);
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dep++;
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}
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if (monitor) {
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ignore(write(daemonize_fd, unw_bt,
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dep * sizeof(struct unw_backtrace)));
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} else {
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/* Since there is no monitor daemon running, write backtrace
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* in current process.
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*/
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char ip_str[16], offset_str[6];
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char line[64], fn_name[UNW_MAX_FUNCN];
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vlog_direct_write_to_log_file_unsafe(BACKTRACE_DUMP_MSG);
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for (int i = 0; i < dep; i++) {
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memset(line, 0, sizeof line);
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memset(fn_name, 0, sizeof fn_name);
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memset(offset_str, 0, sizeof offset_str);
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memset(ip_str, ' ', sizeof ip_str);
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ip_str[sizeof(ip_str) - 1] = 0;
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llong_to_hex_str(unw_bt[i].ip, ip_str);
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llong_to_hex_str(unw_bt[i].offset, offset_str);
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strcat(line, "0x");
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strcat(line, ip_str);
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strcat(line, "<");
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memcpy(fn_name, unw_bt[i].func, UNW_MAX_FUNCN - 1);
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strcat(line, fn_name);
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strcat(line, "+0x");
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strcat(line, offset_str);
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strcat(line, ">\n");
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vlog_direct_write_to_log_file_unsafe(line);
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}
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}
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}
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#elif HAVE_BACKTRACE
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/* Send the backtrace to monitor thread.
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*
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* Note that this runs in the signal handling context, any system
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* library functions used here must be async-signal-safe.
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* backtrace() is only signal safe if the "libgcc" or equivalent was loaded
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* before the signal handler. In order to keep it safe the fatal_signal_init()
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* should always call backtrace_capture which will ensure that "libgcc" or
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* equivlent is loaded.
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*/
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static inline void
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send_backtrace_to_monitor(void)
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{
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struct backtrace bt;
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backtrace_capture(&bt);
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if (monitor && daemonize_fd > -1) {
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ignore(write(daemonize_fd, &bt, sizeof bt));
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} else {
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int log_fd = vlog_get_log_file_fd_unsafe();
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if (log_fd < 0) {
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return;
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}
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vlog_direct_write_to_log_file_unsafe(BACKTRACE_DUMP_MSG);
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backtrace_symbols_fd(bt.frames, bt.n_frames, log_fd);
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}
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}
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#else
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static inline void
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send_backtrace_to_monitor(void) {
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/* Nothing. */
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}
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#endif
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/* Handles fatal signal number 'sig_nr'.
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*
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* Ordinarily this is the actual signal handler. When other code needs to
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* handle one of our signals, however, it can register for that signal and, if
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* and when necessary, call this function to do fatal signal processing for it
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* and terminate the process. Currently only timeval.c does this, for SIGALRM.
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* (It is not important whether the other code sets up its signal handler
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* before or after this file, because this file will only set up a signal
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* handler in the case where the signal has its default handling.) */
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void
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fatal_signal_handler(int sig_nr)
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{
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#ifndef _WIN32
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if (sig_nr == SIGSEGV) {
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signal(sig_nr, SIG_DFL); /* Set it back immediately. */
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send_backtrace_to_monitor();
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raise(sig_nr);
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}
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ignore(write(signal_fds[1], "", 1));
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#else
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SetEvent(wevent);
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#endif
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stored_sig_nr = sig_nr;
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}
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/* Check whether a fatal signal has occurred and, if so, call the fatal signal
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* hooks and exit.
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*
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* This function is called automatically by poll_block(), but specialized
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* programs that may not always call poll_block() on a regular basis should
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* also call it periodically. (Therefore, any function with "block" in its
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* name should call fatal_signal_run() each time it is called, either directly
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* or through poll_block(), because such functions can only used by specialized
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* programs that can afford to block outside their main loop around
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* poll_block().)
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*/
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void
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fatal_signal_run(void)
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{
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sig_atomic_t sig_nr;
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fatal_signal_init();
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sig_nr = stored_sig_nr;
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if (sig_nr != SIG_ATOMIC_MAX) {
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char namebuf[SIGNAL_NAME_BUFSIZE];
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ovs_mutex_lock(&mutex);
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#ifndef _WIN32
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VLOG_WARN("terminating with signal %d (%s)",
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(int)sig_nr, signal_name(sig_nr, namebuf, sizeof namebuf));
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#else
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VLOG_WARN("terminating with signal %d", (int)sig_nr);
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#endif
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call_hooks(sig_nr);
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fflush(stderr);
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/* Re-raise the signal with the default handling so that the program
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* termination status reflects that we were killed by this signal */
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signal(sig_nr, SIG_DFL);
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raise(sig_nr);
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ovs_mutex_unlock(&mutex);
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OVS_NOT_REACHED();
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}
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}
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void
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fatal_signal_wait(void)
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{
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fatal_signal_init();
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#ifdef _WIN32
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poll_wevent_wait(wevent);
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#else
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poll_fd_wait(signal_fds[0], POLLIN);
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#endif
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}
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void
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fatal_ignore_sigpipe(void)
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{
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#ifndef _WIN32
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signal(SIGPIPE, SIG_IGN);
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#endif
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}
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void
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fatal_signal_atexit_handler(void)
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{
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call_hooks(0);
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}
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static void
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call_hooks(int sig_nr)
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{
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static volatile sig_atomic_t recurse = 0;
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if (!recurse) {
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size_t i;
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recurse = 1;
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for (i = 0; i < n_hooks; i++) {
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struct hook *h = &hooks[i];
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if (sig_nr || h->run_at_exit) {
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h->hook_cb(h->aux);
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}
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}
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}
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}
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#ifdef _WIN32
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BOOL WINAPI ConsoleHandlerRoutine(DWORD dwCtrlType)
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{
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stored_sig_nr = SIGINT;
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SetEvent(wevent);
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return true;
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}
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#endif
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/* Files to delete on exit. */
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static struct sset files = SSET_INITIALIZER(&files);
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/* Has a hook function been registered with fatal_signal_add_hook() (and not
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* cleared by fatal_signal_fork())? */
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static bool added_hook;
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static void unlink_files(void *aux);
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static void cancel_files(void *aux);
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static void do_unlink_files(void);
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/* Registers 'file' to be unlinked when the program terminates via exit() or a
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* fatal signal. */
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void
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fatal_signal_add_file_to_unlink(const char *file)
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{
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fatal_signal_init();
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ovs_mutex_lock(&mutex);
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if (!added_hook) {
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added_hook = true;
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fatal_signal_add_hook(unlink_files, cancel_files, NULL, true);
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}
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sset_add(&files, file);
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ovs_mutex_unlock(&mutex);
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}
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/* Unregisters 'file' from being unlinked when the program terminates via
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* exit() or a fatal signal. */
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void
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fatal_signal_remove_file_to_unlink(const char *file)
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{
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fatal_signal_init();
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ovs_mutex_lock(&mutex);
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sset_find_and_delete(&files, file);
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ovs_mutex_unlock(&mutex);
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}
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/* Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'.
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* Returns 0 if successful, otherwise a positive errno value. */
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int
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fatal_signal_unlink_file_now(const char *file)
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{
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int error;
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fatal_signal_init();
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ovs_mutex_lock(&mutex);
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error = unlink(file) ? errno : 0;
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if (error) {
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VLOG_WARN("could not unlink \"%s\" (%s)", file, ovs_strerror(error));
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}
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fatal_signal_remove_file_to_unlink(file);
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ovs_mutex_unlock(&mutex);
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return error;
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}
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static void
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unlink_files(void *aux OVS_UNUSED)
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{
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do_unlink_files();
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}
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static void
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cancel_files(void *aux OVS_UNUSED)
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{
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sset_clear(&files);
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added_hook = false;
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}
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static void
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do_unlink_files(void)
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{
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const char *file;
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SSET_FOR_EACH (file, &files) {
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unlink(file);
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}
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}
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|
||
/* Clears all of the fatal signal hooks without executing them. If any of the
|
||
* hooks passed a 'cancel_cb' function to fatal_signal_add_hook(), then those
|
||
* functions will be called, allowing them to free resources, etc.
|
||
*
|
||
* Also re-creates wake-up events, so signals in one of the processes do not
|
||
* wake up the other one.
|
||
*
|
||
* Following a fork, one of the resulting processes can call this function to
|
||
* allow it to terminate without calling the hooks registered before calling
|
||
* this function. New hooks registered after calling this function will take
|
||
* effect normally. */
|
||
void
|
||
fatal_signal_fork(void)
|
||
{
|
||
size_t i;
|
||
|
||
assert_single_threaded();
|
||
|
||
fatal_signal_destroy_wakeup_events();
|
||
fatal_signal_create_wakeup_events();
|
||
|
||
for (i = 0; i < n_hooks; i++) {
|
||
struct hook *h = &hooks[i];
|
||
if (h->cancel_cb) {
|
||
h->cancel_cb(h->aux);
|
||
}
|
||
}
|
||
n_hooks = 0;
|
||
|
||
/* Raise any signals that we have already received with the default
|
||
* handler. */
|
||
if (stored_sig_nr != SIG_ATOMIC_MAX) {
|
||
raise(stored_sig_nr);
|
||
}
|
||
}
|
||
|
||
#ifndef _WIN32
|
||
/* Blocks all fatal signals and returns previous signal mask into
|
||
* 'prev_mask'. */
|
||
void
|
||
fatal_signal_block(sigset_t *prev_mask)
|
||
{
|
||
int i;
|
||
sigset_t block_mask;
|
||
|
||
sigemptyset(&block_mask);
|
||
for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) {
|
||
int sig_nr = fatal_signals[i];
|
||
sigaddset(&block_mask, sig_nr);
|
||
}
|
||
xpthread_sigmask(SIG_BLOCK, &block_mask, prev_mask);
|
||
}
|
||
#endif
|