/*

 * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at:

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#include <config.h>

#include "backtrace.h"

#include "fatal-signal.h"

#include <errno.h>

#include <signal.h>

#include <stdbool.h>

#include <stdio.h>

#include <stdint.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include "ovs-thread.h"

#include "openvswitch/poll-loop.h"

#include "openvswitch/shash.h"

#include "sset.h"

#include "signals.h"

#include "socket-util.h"

#include "util.h"

#include "openvswitch/vlog.h"

#include "openvswitch/type-props.h"

#if defined(HAVE_UNWIND) || defined(HAVE_BACKTRACE)

#include "daemon-private.h"

#endif

#ifdef HAVE_BACKTRACE

#include <execinfo.h>

#endif

#ifndef SIG_ATOMIC_MAX

#define SIG_ATOMIC_MAX TYPE_MAXIMUM(sig_atomic_t)

#endif

VLOG_DEFINE_THIS_MODULE(fatal_signal);

/* Signals to catch. */

static const int fatal_signals[] = { SIGTERM, SIGINT, SIGHUP, SIGALRM,

                                     SIGSEGV };

/* Hooks to call upon catching a signal */

struct hook {

    void (*hook_cb)(void *aux);

    void (*cancel_cb)(void *aux);

    void *aux;

    bool run_at_exit;

};

#define MAX_HOOKS 32

static struct hook hooks[MAX_HOOKS];

static size_t n_hooks;

static int signal_fds[2];

static volatile sig_atomic_t stored_sig_nr = SIG_ATOMIC_MAX;

static struct ovs_mutex mutex;

static void call_hooks(int sig_nr)

    OVS_REQUIRES(mutex);

/* Sets up a pipe or event handle that will be used to wake up the current

 * process after signal is received, so it can be processed outside of the

 * signal handler context in fatal_signal_run(). */

static void

fatal_signal_create_wakeup_events(void)

{

    xpipe_nonblocking(signal_fds);

}

static void

fatal_signal_destroy_wakeup_events(void)

{

    close(signal_fds[0]);

    signal_fds[0] = -1;

    close(signal_fds[1]);

    signal_fds[1] = -1;

}

/* Initializes the fatal signal handling module.  Calling this function is

 * optional, because calling any other function in the module will also

 * initialize it.  However, in a multithreaded program, the module must be

 * initialized while the process is still single-threaded. */

void

fatal_signal_init(void)

{

    static bool inited = false;

    if (!inited) {

        size_t i;

        assert_single_threaded();

        inited = true;

        ovs_mutex_init_recursive(&mutex);

        /* The dummy backtrace is needed.

         * See comment for send_backtrace_to_monitor(). */

        struct backtrace dummy_bt;

        backtrace_capture(&dummy_bt);

        fatal_signal_create_wakeup_events();

        for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) {

            int sig_nr = fatal_signals[i];

            struct sigaction old_sa;

            xsigaction(sig_nr, NULL, &old_sa);

            if (old_sa.sa_handler == SIG_DFL

                && signal(sig_nr, fatal_signal_handler) == SIG_ERR) {

                VLOG_FATAL("signal failed (%s)", ovs_strerror(errno));

            }

        }

        atexit(fatal_signal_atexit_handler);

    }

}

/* Registers 'hook_cb' to be called from inside poll_block() following a fatal

 * signal.  'hook_cb' does not need to be async-signal-safe.  In a

 * multithreaded program 'hook_cb' might be called from any thread, with

 * threads other than the one running 'hook_cb' in unknown states.

 *

 * If 'run_at_exit' is true, 'hook_cb' is also called during normal process

 * termination, e.g. when exit() is called or when main() returns.

 *

 * If the current process forks, fatal_signal_fork() may be called to clear the

 * parent process's fatal signal hooks, so that 'hook_cb' is only called when

 * the child terminates, not when the parent does.  When fatal_signal_fork() is

 * called, it calls the 'cancel_cb' function if it is nonnull, passing 'aux',

 * to notify that the hook has been canceled.  This allows the hook to free

 * memory, etc. */

void

fatal_signal_add_hook(void (*hook_cb)(void *aux), void (*cancel_cb)(void *aux),

                      void *aux, bool run_at_exit)

{

    fatal_signal_init();

    ovs_mutex_lock(&mutex);

    ovs_assert(n_hooks < MAX_HOOKS);

    hooks[n_hooks].hook_cb = hook_cb;

    hooks[n_hooks].cancel_cb = cancel_cb;

    hooks[n_hooks].aux = aux;

    hooks[n_hooks].run_at_exit = run_at_exit;

    n_hooks++;

    ovs_mutex_unlock(&mutex);

}

#ifdef HAVE_UNWIND

/* Convert unsigned long long to string.  This is needed because

 * using snprintf() is not async signal safe. */

static inline int

llong_to_hex_str(unsigned long long value, char *str)

{

    int i = 0, res;

    if (value / 16 > 0) {

        i = llong_to_hex_str(value / 16, str);

    }

    res = value % 16;

    str[i] = "0123456789abcdef"[res];

    return i + 1;

}

/* Send the backtrace buffer to monitor thread.

 *

 * Note that this runs in the signal handling context, any system

 * library functions used here must be async-signal-safe.

 */

static inline void

send_backtrace_to_monitor(void)

{

    /* volatile added to prevent a "clobbered" error on ppc64le with gcc */

    volatile int dep;

    struct unw_backtrace unw_bt[UNW_MAX_DEPTH];

    unw_cursor_t cursor;

    unw_context_t uc;

    if (daemonize_fd == -1) {

        return;

    }

    dep = 0;

    unw_getcontext(&uc);

    unw_init_local(&cursor, &uc);

    while (dep < UNW_MAX_DEPTH && unw_step(&cursor)) {

        memset(unw_bt[dep].func, 0, UNW_MAX_FUNCN);

        unw_get_reg(&cursor, UNW_REG_IP, &unw_bt[dep].ip);

        unw_get_proc_name(&cursor, unw_bt[dep].func, UNW_MAX_FUNCN,

                          &unw_bt[dep].offset);

        dep++;

    }

    if (monitor) {

        ovs_ignore(write(daemonize_fd, unw_bt,

                         dep * sizeof(struct unw_backtrace)));

    } else {

        /* Since there is no monitor daemon running, write backtrace

         * in current process.

         */

        char ip_str[16], offset_str[6];

        char line[64], fn_name[UNW_MAX_FUNCN];

        vlog_direct_write_to_log_file_unsafe(BACKTRACE_DUMP_MSG);

        for (int i = 0; i < dep; i++) {

            memset(line, 0, sizeof line);

            memset(fn_name, 0, sizeof fn_name);

            memset(offset_str, 0, sizeof offset_str);

            memset(ip_str, ' ', sizeof ip_str);

            ip_str[sizeof(ip_str) - 1] = 0;

            llong_to_hex_str(unw_bt[i].ip, ip_str);

            llong_to_hex_str(unw_bt[i].offset, offset_str);

            strcat(line, "0x");

            strcat(line, ip_str);

            strcat(line, "<");

            memcpy(fn_name, unw_bt[i].func, UNW_MAX_FUNCN - 1);

            strcat(line, fn_name);

            strcat(line, "+0x");

            strcat(line, offset_str);

            strcat(line, ">\n");

            vlog_direct_write_to_log_file_unsafe(line);

        }

    }

}

#elif HAVE_BACKTRACE

/* Send the backtrace to monitor thread.

 *

 * Note that this runs in the signal handling context, any system

 * library functions used here must be async-signal-safe.

 * backtrace() is only signal safe if the "libgcc" or equivalent was loaded

 * before the signal handler. In order to keep it safe the fatal_signal_init()

 * should always call backtrace_capture which will ensure that "libgcc" or

 * equivlent is loaded.

 */

static inline void

send_backtrace_to_monitor(void)

{

    struct backtrace bt;

    backtrace_capture(&bt);

    if (monitor && daemonize_fd > -1) {

        ovs_ignore(write(daemonize_fd, &bt, sizeof bt));

    } else {

        int log_fd = vlog_get_log_file_fd_unsafe();

        if (log_fd < 0) {

            return;

        }

        vlog_direct_write_to_log_file_unsafe(BACKTRACE_DUMP_MSG);

        backtrace_symbols_fd(bt.frames, bt.n_frames, log_fd);

    }

}

#else

static inline void

send_backtrace_to_monitor(void) {

    /* Nothing. */

}

#endif

/* Handles fatal signal number 'sig_nr'.

 *

 * Ordinarily this is the actual signal handler.  When other code needs to

 * handle one of our signals, however, it can register for that signal and, if

 * and when necessary, call this function to do fatal signal processing for it

 * and terminate the process.  Currently only timeval.c does this, for SIGALRM.

 * (It is not important whether the other code sets up its signal handler

 * before or after this file, because this file will only set up a signal

 * handler in the case where the signal has its default handling.)  */

void

fatal_signal_handler(int sig_nr)

{

    if (sig_nr == SIGSEGV) {

        signal(sig_nr, SIG_DFL); /* Set it back immediately. */

        send_backtrace_to_monitor();

        raise(sig_nr);

    }

    ovs_ignore(write(signal_fds[1], "", 1));

    stored_sig_nr = sig_nr;

}

/* Check whether a fatal signal has occurred and, if so, call the fatal signal

 * hooks and exit.

 *

 * This function is called automatically by poll_block(), but specialized

 * programs that may not always call poll_block() on a regular basis should

 * also call it periodically.  (Therefore, any function with "block" in its

 * name should call fatal_signal_run() each time it is called, either directly

 * or through poll_block(), because such functions can only used by specialized

 * programs that can afford to block outside their main loop around

 * poll_block().)

 */

void

fatal_signal_run(void)

{

    sig_atomic_t sig_nr;

    fatal_signal_init();

    sig_nr = stored_sig_nr;

    if (sig_nr != SIG_ATOMIC_MAX) {

        char namebuf[SIGNAL_NAME_BUFSIZE];

        ovs_mutex_lock(&mutex);

        VLOG_WARN("terminating with signal %d (%s)",

                  (int)sig_nr, signal_name(sig_nr, namebuf, sizeof namebuf));

        call_hooks(sig_nr);

        fflush(stderr);

        /* Re-raise the signal with the default handling so that the program

         * termination status reflects that we were killed by this signal */

        signal(sig_nr, SIG_DFL);

        raise(sig_nr);

        ovs_mutex_unlock(&mutex);

        OVS_NOT_REACHED();

    }

}

void

fatal_signal_wait(void)

{

    fatal_signal_init();

    poll_fd_wait(signal_fds[0], POLLIN);

}

void

fatal_ignore_sigpipe(void)

{

    signal(SIGPIPE, SIG_IGN);

}

void

fatal_signal_atexit_handler(void)

{

    ovs_mutex_lock(&mutex);

    call_hooks(0);

    ovs_mutex_unlock(&mutex);

}

static void

call_hooks(int sig_nr)

    OVS_REQUIRES(mutex)

{

    static volatile sig_atomic_t recurse = 0;

    if (!recurse) {

        size_t i;

        recurse = 1;

        for (i = 0; i < n_hooks; i++) {

            struct hook *h = &hooks[i];

            if (sig_nr || h->run_at_exit) {

                h->hook_cb(h->aux);

            }

        }

    }

}

/* Files to delete on exit. */

static struct sset files = SSET_INITIALIZER(&files);

/* Has a hook function been registered with fatal_signal_add_hook() (and not

 * cleared by fatal_signal_fork())? */

static bool added_hook;

static void unlink_files(void *aux);

static void cancel_files(void *aux);

static void do_unlink_files(void);

/* Registers 'file' to be unlinked when the program terminates via exit() or a

 * fatal signal. */

void

fatal_signal_add_file_to_unlink(const char *file)

{

    fatal_signal_init();

    ovs_mutex_lock(&mutex);

    if (!added_hook) {

        added_hook = true;

        fatal_signal_add_hook(unlink_files, cancel_files, NULL, true);

    }

    sset_add(&files, file);

    ovs_mutex_unlock(&mutex);

}

/* Unregisters 'file' from being unlinked when the program terminates via

 * exit() or a fatal signal. */

void

fatal_signal_remove_file_to_unlink(const char *file)

{

    fatal_signal_init();

    ovs_mutex_lock(&mutex);

    sset_find_and_delete(&files, file);

    ovs_mutex_unlock(&mutex);

}

/* Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'.

 * Returns 0 if successful, otherwise a positive errno value. */

int

fatal_signal_unlink_file_now(const char *file)

{

    int error;

    fatal_signal_init();

    ovs_mutex_lock(&mutex);

    error = unlink(file) ? errno : 0;

    if (error) {

        VLOG_WARN("could not unlink \"%s\" (%s)", file, ovs_strerror(error));

    }

    fatal_signal_remove_file_to_unlink(file);

    ovs_mutex_unlock(&mutex);

    return error;

}

static void

unlink_files(void *aux OVS_UNUSED)

{

    do_unlink_files();

}

static void

cancel_files(void *aux OVS_UNUSED)

{

    sset_clear(&files);

    added_hook = false;

}

static void

do_unlink_files(void)

{

    const char *file;

    SSET_FOR_EACH (file, &files) {

        unlink(file);

    }

}

/* 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);

    }

}

/* 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);

}