core-d08ae9eff/libpromises/signals.c

/*
  Copyright 2021 Northern.tech AS

  This file is part of CFEngine 3 - written and maintained by Northern.tech AS.

  This program is free software; you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by the
  Free Software Foundation; version 3.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA

  To the extent this program is licensed as part of the Enterprise
  versions of CFEngine, the applicable Commercial Open Source License
  (COSL) may apply to this file if you as a licensee so wish it. See
  included file COSL.txt.
*/

#include <signals.h>
#include <cleanup.h>
#include <known_dirs.h>         /* GetStateDir() */
#include <file_lib.h>           /* FILE_SEPARATOR */

static bool PENDING_TERMINATION = false; /* GLOBAL_X */

static bool RELOAD_CONFIG = false; /* GLOBAL_X */
/********************************************************************/

bool IsPendingTermination(void)
{
    return PENDING_TERMINATION;
}

bool ReloadConfigRequested(void)
{
    return RELOAD_CONFIG;
}

void ClearRequestReloadConfig()
{
    RELOAD_CONFIG = false;
}

/********************************************************************/

static int SIGNAL_PIPE[2] = { -1, -1 }; /* GLOBAL_C */

static void CloseSignalPipe(void)
{
    int c = 2;
    while (c > 0)
    {
        c--;
        if (SIGNAL_PIPE[c] >= 0)
        {
            close(SIGNAL_PIPE[c]);
            SIGNAL_PIPE[c] = -1;
        }
    }
}

/**
 * Make a pipe that can be used to flag that a signal has arrived.
 * Using a pipe avoids race conditions, since it saves its values until emptied.
 * Use GetSignalPipe() to get the pipe.
 * Note that we use a real socket as the pipe, because Windows only supports
 * using select() with real sockets. This means also using send() and recv()
 * instead of write() and read().
 */
void MakeSignalPipe(void)
{
    if (socketpair(AF_UNIX, SOCK_STREAM, 0, SIGNAL_PIPE) != 0)
    {
        Log(LOG_LEVEL_CRIT, "Could not create internal communication pipe. Cannot continue. (socketpair: '%s')",
            GetErrorStr());
        DoCleanupAndExit(EXIT_FAILURE);
    }

    RegisterCleanupFunction(&CloseSignalPipe);

    for (int c = 0; c < 2; c++)
    {
#ifdef __MINGW32__
        u_long enable = 1;
        int ret = ioctlsocket(SIGNAL_PIPE[c], FIONBIO, &enable);
#define CNTLNAME "ioctlsocket"
#else /* Unix: */
        int ret = fcntl(SIGNAL_PIPE[c], F_SETFL, O_NONBLOCK);
#define CNTLNAME "fcntl"
#endif /* __MINGW32__ */

        if (ret != 0)
        {
            Log(LOG_LEVEL_CRIT,
                "Could not unblock internal communication pipe. "
                "Cannot continue. (" CNTLNAME ": '%s')",
                GetErrorStr());
            DoCleanupAndExit(EXIT_FAILURE);
        }
#undef CNTLNAME
    }
}

/**
 * Gets the signal pipe, which is non-blocking.
 * Each byte read corresponds to one arrived signal.
 * Note: Use recv() to read from the pipe, not read().
 */
int GetSignalPipe(void)
{
    return SIGNAL_PIPE[0];
}

static void SignalNotify(int signum)
{
    unsigned char sig = (unsigned char)signum;
    if (SIGNAL_PIPE[1] >= 0)
    {
        // send() is async-safe, according to POSIX.
        if (send(SIGNAL_PIPE[1], &sig, 1, 0) < 0)
        {
            // These signal contention. Everything else is an error.
            if (errno != EAGAIN
#ifndef __MINGW32__
                && errno != EWOULDBLOCK
#endif
                )
            {
                // This is not async safe, but if we get in here there's something really weird
                // going on.
                Log(LOG_LEVEL_CRIT, "Could not write to signal pipe. Unsafe to continue. (write: '%s')",
                    GetErrorStr());
                _exit(EXIT_FAILURE);
            }
        }
    }
}

void HandleSignalsForAgent(int signum)
{
    switch (signum)
    {
    case SIGTERM:
    case SIGINT:
        /* TODO don't exit from the signal handler, just set a flag. Reason is
         * that all the cleanup() hooks we register are not reentrant. */
        DoCleanupAndExit(0);
    case SIGBUS:
        /* SIGBUS almost certainly means a violation of mmap() area boundaries
         * or some mis-aligned memory access. IOW, an LMDB corruption. */
        {
            char filename[PATH_MAX] = { 0 }; /* trying to avoid memory allocation */
            xsnprintf(filename, PATH_MAX, "%s%c%s",
                      GetStateDir(), FILE_SEPARATOR, CF_DB_REPAIR_TRIGGER);
            int fd = open(filename, O_CREAT|O_RDWR, CF_PERMS_DEFAULT);
            if (fd != -1)
            {
                close(fd);
            }

            /* avoid calling complex logging functions */
            fprintf(stdout, "process killed by SIGBUS\n");

            /* else: we tried, nothing more to do in the limited environment of a
             * signal handler */
            _exit(1);
        }
        break;
    case SIGUSR1:
        LogSetGlobalLevel(LOG_LEVEL_DEBUG);
        break;
    case SIGUSR2:
        LogSetGlobalLevel(LOG_LEVEL_NOTICE);
        break;
    default:
        /* No action */
        break;
    }

    SignalNotify(signum);

/* Reset the signal handler */
    signal(signum, HandleSignalsForAgent);
}

/********************************************************************/

void HandleSignalsForDaemon(int signum)
{
    switch (signum)
    {
    case SIGTERM:
    case SIGINT:
    case SIGSEGV:
    case SIGKILL:
        PENDING_TERMINATION = true;
        break;
    case SIGBUS:
        /* SIGBUS almost certainly means a violation of mmap() area boundaries
         * or some mis-aligned memory access. IOW, an LMDB corruption. */
        {
            char filename[PATH_MAX] = { 0 }; /* trying to avoid memory allocation */
            xsnprintf(filename, PATH_MAX, "%s%c%s",
                      GetStateDir(), FILE_SEPARATOR, CF_DB_REPAIR_TRIGGER);
            int fd = open(filename, O_CREAT|O_RDWR, CF_PERMS_DEFAULT);
            if (fd != -1)
            {
                close(fd);
            }

            /* avoid calling complex logging functions */
            fprintf(stdout, "process killed by SIGBUS\n");

            /* else: we tried, nothing more to do in the limited environment of a
             * signal handler */
            _exit(1);
        }
        break;
    case SIGUSR1:
        LogSetGlobalLevel(LOG_LEVEL_DEBUG);
        break;
    case SIGUSR2:
        LogSetGlobalLevel(LOG_LEVEL_NOTICE);
        break;
    case SIGHUP:
        RELOAD_CONFIG = true;
        break;
    case SIGPIPE:
    default:
        /* No action */
        break;
    }

    /* Notify processes that use the signal pipe (cf-serverd). */
    SignalNotify(signum);

    /* Reset the signal handler. */
    signal(signum, HandleSignalsForDaemon);
}