Blame tools/fpgad/daemonize.c

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// Copyright(c) 2017-2020, Intel Corporation
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//
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// Redistribution  and  use  in source  and  binary  forms,  with  or  without
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// modification, are permitted provided that the following conditions are met:
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//
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// * Redistributions of  source code  must retain the  above copyright notice,
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//   this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above copyright notice,
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//   this list of conditions and the following disclaimer in the documentation
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//   and/or other materials provided with the distribution.
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// * Neither the name  of Intel Corporation  nor the names of its contributors
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//   may be used to  endorse or promote  products derived  from this  software
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//   without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,  BUT NOT LIMITED TO,  THE
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// IMPLIED WARRANTIES OF  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED.  IN NO EVENT  SHALL THE COPYRIGHT OWNER  OR CONTRIBUTORS BE
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// LIABLE  FOR  ANY  DIRECT,  INDIRECT,  INCIDENTAL,  SPECIAL,  EXEMPLARY,  OR
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// CONSEQUENTIAL  DAMAGES  (INCLUDING,  BUT  NOT LIMITED  TO,  PROCUREMENT  OF
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// SUBSTITUTE GOODS OR SERVICES;  LOSS OF USE,  DATA, OR PROFITS;  OR BUSINESS
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// INTERRUPTION)  HOWEVER CAUSED  AND ON ANY THEORY  OF LIABILITY,  WHETHER IN
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// CONTRACT,  STRICT LIABILITY,  OR TORT  (INCLUDING NEGLIGENCE  OR OTHERWISE)
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,  EVEN IF ADVISED OF THE
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// POSSIBILITY OF SUCH DAMAGE.
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/*
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 * daemonize.c : routine to become a system daemon process.
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 */
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <signal.h>
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int daemonize(void (*hndlr)(int, siginfo_t *, void *), mode_t mask, const char *dir)
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{
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	pid_t pid;
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	pid_t sid;
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	int res;
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	int fd;
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	struct sigaction sa;
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	pid = fork();
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	if (pid < 0) // fork() failed.
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		return errno;
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	// 1) Orphan the child process so that it runs in the background.
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	if (pid > 0)
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		exit(0);
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	// 2) Become leader of a new session and process group leader of new process
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	// group. The process is now detached from its controlling terminal.
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	sid = setsid();
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	if (sid < 0)
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		return errno;
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	// 3) Establish signal handler.
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	memset(&sa, 0, sizeof(sa));
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	sa.sa_flags     = SA_SIGINFO | SA_RESETHAND;
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	sa.sa_sigaction = hndlr;
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	res = sigaction(SIGINT, &sa, NULL);
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	if (res < 0)
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		return errno;
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	res = sigaction(SIGTERM, &sa, NULL);
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	if (res < 0)
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		return errno;
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	// 4) Orphan the child again - the session leading process terminates.
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	// (only session leaders can request TTY).
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	pid = fork();
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	if (pid < 0) // fork() failed.
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		return errno;
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	if (pid > 0)
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		exit(0);
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	// 5) Set new file mode mask.
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	umask(mask);
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	// 6) change directory
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	res = chdir(dir);
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	if (res < 0)
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		return errno;
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	// 7) Close all open file descriptors
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	fd = sysconf(_SC_OPEN_MAX);
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	while (fd >= 0)
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		close(fd--);
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	return 0;
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}