path: root/coopgammad.c

/* See LICENSE file for copyright and license details. */
#include "arg.h"
#include "util.h"
#include "state.h"
#include "servers-master.h"
#include "servers-kernel.h"
#include "servers-crtc.h"
#include "servers-gamma.h"
#include "servers-coopgamma.h"

#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>


/**
 * Number put in front of the marshalled data
 * so the program an detect incompatible updates
 */
#define MARSHAL_VERSION  0


#ifndef GCC_ONLY
# if defined(__GNUC__) && !defined(__clang__)
#  define GCC_ONLY(...) __VA_ARGS__
# else
#  define GCC_ONLY(...) /* nothing */
# endif
#endif


/**
 * Lists all function recognised adjustment methods,
 * will call macro X with the code for the each
 * adjustment method as the first argument and
 * corresponding name as the second argument
 */
#define LIST_ADJUSTMENT_METHODS\
	X(LIBGAMMA_METHOD_DUMMY,                "dummy")\
	X(LIBGAMMA_METHOD_X_RANDR,              "randr")\
	X(LIBGAMMA_METHOD_X_VIDMODE,            "vidmode")\
	X(LIBGAMMA_METHOD_LINUX_DRM,            "drm")\
	X(LIBGAMMA_METHOD_W32_GDI,              "gdi")\
	X(LIBGAMMA_METHOD_QUARTZ_CORE_GRAPHICS, "quartz")


/**
 * Used by initialisation functions as their return type. If a
 * value not listed here is returned by such function, it is the
 * exit value the process shall exit with as soon as possible.
 */
enum init_status {
	/**
	 * Initialisation was successful
	 */
	INIT_SUCCESS = -1,

	/**
	 * Initialisation failed
	 */
	INIT_FAILURE = -2,

	/**
	 * Server is already running
	 */
	INIT_RUNNING = -3,
};


/**
 * The pathname of the PID file
 */
extern char *restrict pidpath;
char *restrict pidpath = NULL;

/**
 * The pathname of the socket
 */
extern char *restrict socketpath;
char *restrict socketpath = NULL;



/**
 * Called when the process receives
 * a signal telling it to re-execute
 * 
 * @param  signo  The received signal
 */
static void
sig_reexec(int signo)
{
	int saved_errno = errno;
	reexec = 1;
	signal(signo, sig_reexec);
	errno = saved_errno;
}


/**
 * Called when the process receives
 * a signal telling it to terminate
 * 
 * @param  signo  The received signal
 */
static void
sig_terminate(int signo)
{
	terminate = 1;
	(void) signo;
}


/**
 * Called when the process receives
 * a signal telling it to disconnect
 * from or reconnect to the site
 * 
 * @param  signo  The received signal
 */
static void
sig_connection(int signo)
{
	int saved_errno = errno;
	connection = signo - SIGRTMIN + 1;
	signal(signo, sig_connection);
	errno = saved_errno;
}


/**
 * Called when the process receives
 * a signal telling it to dump its
 * state to stderr
 * 
 * @param  signo  The received signal
 */
static void
sig_info(int signo)
{
	int saved_errno = errno;
	char *env;
	signal(signo, sig_info);
	env = getenv("COOPGAMMAD_PIDFILE_TOKEN");
	fprintf(stderr, "PID file token: %s\n", env ? env : "(null)");
	fprintf(stderr, "PID file: %s\n", pidpath ? pidpath : "(null)");
	fprintf(stderr, "Socket path: %s\n", socketpath ? socketpath : "(null)");
	state_dump();
	errno = saved_errno;
}


/**
 * Parse adjustment method name (or stringised number)
 * 
 * @param   arg  The adjustment method name (or stringised number)
 * @return       The adjustment method, -1 (negative) on error
 */
GCC_ONLY(__attribute__((__nonnull__)))
static int
get_method(const char *restrict arg)
{
#if LIBGAMMA_METHOD_MAX > 5
# warning libgamma has added more adjustment methods
#endif

	const char *restrict p;
  
#define X(C, N) if (!strcmp(arg, N)) return C;
	LIST_ADJUSTMENT_METHODS;
#undef X

	if (!*arg || (/* avoid overflow: */ strlen(arg) > 4))
		goto bad;
	for (p = arg; *p; p++)
		if ('0' > *p || *p > '9')
			goto bad;

	return atoi(arg);

bad:
	fprintf(stderr, "%s: unrecognised adjustment method name: %s\n", argv0, arg);
	errno = 0;
	return -1;
}


/**
 * Set up signal handlers
 * 
 * @return  Zero on success, -1 on error
 */
static int
set_up_signals(void)
{
	if (signal(SIGUSR1,      sig_reexec)     == SIG_ERR ||
	    signal(SIGUSR2,      sig_info)       == SIG_ERR ||
#if defined(SIGINFO)
	    signal(SIGINFO,      sig_info)       == SIG_ERR ||
#endif
	    signal(SIGTERM,      sig_terminate)  == SIG_ERR ||
	    signal(SIGRTMIN + 0, sig_connection) == SIG_ERR ||
	    signal(SIGRTMIN + 1, sig_connection) == SIG_ERR)
		return -1;
	return 0;
}


/**
 * Fork the process to the background
 * 
 * @param   keep_stderr  Keep stderr open?
 * @return               An `enum init_status` value or an exit value
 */
static enum init_status
daemonise(int keep_stderr)
{
	pid_t pid;
	int fd = -1, saved_errno;
	int notify_rw[2] = {-1, -1};
	char a_byte = 0;
	ssize_t got;

	if (pipe(notify_rw) < 0)
		goto fail;
	if (notify_rw[0] <= STDERR_FILENO)
		if ((notify_rw[0] = fcntl(notify_rw[0], F_DUPFD, STDERR_FILENO + 1)) < 0)
			goto fail;
	if (notify_rw[1] <= STDERR_FILENO)
		if ((notify_rw[1] = fcntl(notify_rw[1], F_DUPFD, STDERR_FILENO + 1)) < 0)
			goto fail;

	if ((pid = fork()) < 0)
		goto fail;
	if (pid > 0) {
		/* Original process (parent): */
		waitpid(pid, NULL, 0);
		close(notify_rw[1]), notify_rw[1] = -1;
		got = read(notify_rw[0], &a_byte, 1);
		if (got < 0)
			goto fail;
		close(notify_rw[0]);
		errno = 0;
		return got == 0 ? INIT_FAILURE : (enum init_status)0;
	}

	/* Intermediary process (child): */
	close(notify_rw[0]), notify_rw[0] = -1;
	if (setsid() < 0)
		goto fail;
	if ((pid = fork()) < 0)
		goto fail;
	if (pid > 0) {
		/* Intermediary process (parent): */
		return (enum init_status)0;
	}

	/* Daemon process (child): */

	/* Replace std* with /dev/null */
	fd = open("/dev/null", O_RDWR);
	if (fd < 0 ||
	    dup2(fd, STDIN_FILENO) < 0 ||
	    dup2(fd, STDOUT_FILENO) < 0 ||
	    (keep_stderr && dup2(fd, STDERR_FILENO) < 0))
		goto fail;
	if (fd > STDERR_FILENO)
		close(fd);
	fd = -1;
  
	/* Update PID file */
	fd = open(pidpath, O_WRONLY);
	if (fd < 0)
		goto fail;
	if (dprintf(fd, "%llu\n", (unsigned long long)getpid()) < 0)
		goto fail;
	close(fd);
	fd = -1;

	/* Notify */
	if (write(notify_rw[1], &a_byte, 1) <= 0)
		goto fail;
	close(notify_rw[1]);

	return INIT_SUCCESS;
fail:
	saved_errno = errno;
	if (fd >= 0)
		close(fd);
	if (notify_rw[0] >= 0)
		close(notify_rw[0]);
	if (notify_rw[1] >= 0)
		close(notify_rw[1]);
	errno = saved_errno;
	return INIT_FAILURE;
}


/**
 * Initialise the process
 * 
 * @param   foreground   Keep process in the foreground
 * @param   keep_stderr  Keep stderr open
 * @param   query        Was -q used, see `main` for description
 * @return               An `enum init_status` value or an exit value
 */
static enum init_status
initialise(int foreground, int keep_stderr, int query)
{
	struct rlimit rlimit;
	size_t i, n;
	sigset_t mask;
	int s;
	enum init_status r;

	/* Zero out some memory so it can be destroyed safely. */
	memset(&site, 0, sizeof(site));

	if (!query) {
		/* Close all file descriptors above stderr */
		if (getrlimit(RLIMIT_NOFILE, &rlimit) || rlimit.rlim_cur == RLIM_INFINITY)
			n = 4 << 10;
		else
			n = (size_t)(rlimit.rlim_cur);
		for (i = STDERR_FILENO + 1; i < n; i++)
			close((int)i);

		/* Set umask, reset signal handlers, and reset signal mask */
		umask(0);
		for (s = 1; s < _NSIG; s++)
			signal(s, SIG_DFL);
		if (sigfillset(&mask))
			perror(argv0);
		else
			sigprocmask(SIG_UNBLOCK, &mask, NULL);
	}

	/* Get method */
	if (method < 0 && libgamma_list_methods(&method, 1, 0) < 1)
		return fprintf(stderr, "%s: no adjustment method available\n", argv0), -1;

	/* Go no further if we are just interested in the adjustment method and site */
	if (query)
		return INIT_SUCCESS;

	/* Get site */
	if (initialise_site() < 0)
		goto fail;

	/* Get PID file and socket pathname */
	if (!(pidpath = get_pidfile_pathname()) ||
	    !(socketpath = get_socket_pathname()))
		goto fail;

	/* Create PID file */
	if ((r = create_pidfile(pidpath)) < 0) {
		free(pidpath);
		pidpath = NULL;
		if (r == -2)
			return INIT_RUNNING;
		goto fail;
	}

	/* Get partitions and CRTC:s */
	if (initialise_crtcs() < 0)
		goto fail;

	/* Get CRTC information */
	if (outputs_n && !(outputs = calloc(outputs_n, sizeof(*outputs))))
		goto fail;
	if (initialise_gamma_info() < 0)
		goto fail;

	/* Sort outputs */
	qsort(outputs, outputs_n, sizeof(*outputs), output_cmp_by_name);

	/* Load current gamma ramps */
	store_gamma();

	/* Preserve current gamma ramps at priority=0 if -p */
	if (preserve && preserve_gamma() < 0)
		goto fail;

	/* Create socket and start listening */
	if (create_socket(socketpath) < 0)
		goto fail;

	/* Get the real pathname of the process's binary, in case
	 * it is relative, so we can re-execute without problem. */
	if (*argv0 != '/' && strchr(argv0, '/') && !(argv0_real = realpath(argv0, NULL)))
		goto fail;

	/* Change directory to / to avoid blocking umounting */
	if (chdir("/") < 0)
		perror(argv0);

	/* Set up signal handlers */
	if (set_up_signals() < 0)
		goto fail;

	/* Place in the background unless -f */
	if (!foreground) {
		return daemonise(keep_stderr);
	} else {
		/* Signal the spawner that the service is ready */
		close(STDOUT_FILENO);
		/* Avoid potential catastrophes that would occur if a library
		 * that is being used was so mindless as to write to stdout. */
		if (dup2(STDERR_FILENO, STDOUT_FILENO) < 0)
			perror(argv0);
	}

	return INIT_SUCCESS;
fail:
	return INIT_FAILURE;
}


/**
 * Deinitialise the process
 * 
 * @param  full  Perform a full deinitialisation, shall be
 *               done iff the process is going to re-execute
 */
static void
destroy(int full)
{
	if (full) {
		disconnect_all();
		close_socket(socketpath);
		free(argv0_real);
		if (outputs && connected)
			restore_gamma();
	}
	state_destroy();
	free(socketpath);
	if (full && pidpath)
		unlink(pidpath);
	free(pidpath);
}


#if defined(__clang__)
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wcast-align"
#endif


/**
 * Marshal the state of the process
 * 
 * @param   buf  Output buffer for the marshalled data,
 *               `NULL` to only measure how large the
 *               buffer needs to be
 * @return       The number of marshalled bytes
 */
static size_t
marshal(void *restrict buf)
{
	size_t off = 0, n;
	char *restrict bs = buf;

	if (bs)
		*(int *)&bs[off] = MARSHAL_VERSION;
	off += sizeof(int);

	n = strlen(pidpath) + 1;
	if (bs)
		memcpy(&bs[off], pidpath, n);
	off += n;

	n = strlen(socketpath) + 1;
	if (bs)
		memcpy(&bs[off], socketpath, n);
	off += n;

	off += state_marshal(bs ? &bs[off] : NULL);

	return off;
}


/**
 * Unmarshal the state of the process
 * 
 * @param   buf  Buffer with the marshalled data
 * @return       The number of marshalled bytes, 0 on error
 */
GCC_ONLY(__attribute__((__nonnull__)))
static size_t
unmarshal(const void *restrict buf)
{
	size_t off = 0, n;
	const char *restrict bs = buf;

	if (*(const int *)&bs[off] != MARSHAL_VERSION) {
		fprintf(stderr, "%s: re-executing to incompatible version, sorry about that\n", argv0);
		errno = 0;
		return 0;
	}
	off += sizeof(int);

	n = strlen(&bs[off]) + 1;
	if (!(pidpath = memdup(&bs[off], n)))
		return 0;
	off += n;

	n = strlen(&bs[off]) + 1;
	if (!(socketpath = memdup(&bs[off], n)))
		return 0;
	off += n;

	off += n = state_unmarshal(&bs[off]);
	if (!n)
		return 0;

	return off;
}


#if defined(__clang__)
# pragma GCC diagnostic pop
#endif


/**
 * Do minimal initialisation, unmarshal the state of
 * the process and merge with new state
 * 
 * @param   statefile  The state file
 * @return             Zero on success, -1 on error
 */
GCC_ONLY(__attribute__((__nonnull__)))
static int
restore_state(const char *restrict statefile)
{
	void *marshalled = NULL;
	int fd = -1, saved_errno;
	size_t r, n;

	if (set_up_signals() < 0)
		goto fail;

	fd = open(statefile, O_RDONLY);
	if (fd < 0)
		goto fail;

	if (!(marshalled = nread(fd, &n)))
		goto fail;
	close(fd);
	fd = -1;
	unlink(statefile);
	statefile = NULL;

	r = unmarshal(marshalled);
	if (!r)
		goto fail;
	if (r != n) {
		fprintf(stderr, "%s: unmarshalled state file was %s than the unmarshalled state: read %zu of %zu bytes\n",
		        argv0, n > r ? "larger" : "smaller", r, n);
		errno = 0;
		goto fail;
	}
	free(marshalled);
	marshalled = NULL;

	if (connected) {
		connected = 0;
		if (reconnect() < 0)
			goto fail;
	}

	return 0;
fail:
	saved_errno = errno;
	if (fd >= 0)
		close(fd);
	free(marshalled);
	errno = saved_errno;
	return -1;
}


/**
 * Reexecute the server
 * 
 * Returns only on failure
 * 
 * @return  Pathname of file where the state is stored,
 *          `NULL` if the state is in tact
 */
static char *
reexecute(void)
{
	char *statefile = NULL;
	char *statebuffer = NULL;
	size_t buffer_size;
	int fd = -1, saved_errno;

	statefile = get_state_pathname();
	if (!statefile)
		goto fail;

	buffer_size = marshal(NULL);
	statebuffer = malloc(buffer_size);
	if (!statebuffer)
		goto fail;
	if (marshal(statebuffer) != buffer_size) {
		fprintf(stderr, "%s: internal error\n", argv0);
		errno = 0;
		goto fail;
	}

	fd = open(statefile, O_CREAT | O_TRUNC | O_WRONLY, S_IRUSR | S_IWUSR);
	if (fd < 0)
		goto fail;

	if (nwrite(fd, statebuffer, buffer_size) != buffer_size)
		goto fail;
	free(statebuffer);
	statebuffer = NULL;

	if (close(fd) < 0) {
		fd = -1;
		if (errno != EINTR)
			goto fail;
	}
	fd = -1;

	destroy(0);

	execlp(argv0_real ? argv0_real : argv0, argv0, "- ", statefile, NULL);
	free(argv0_real);
	argv0_real = NULL;
	return statefile;

fail:
	saved_errno = errno;
	free(statebuffer);
	if (fd >= 0)
		close(fd);
	if (statefile != NULL) {
		unlink(statefile);
		free(statefile);
	}
	errno = saved_errno;
	return NULL;
}


/**
 * Print the response for the -q option
 * 
 * @param   query  See -q for `main`, must be atleast 1
 * @return         Zero on success, -1 on error
 */
static int
print_method_and_site(int query)
{
	const char *restrict methodname = NULL;
	const char *const_sitename;
	char *p;

	if (query == 1) {
		switch (method) {
#define X(C, N) case C: methodname = N; break;
		LIST_ADJUSTMENT_METHODS;
#undef X
		default:
			if (printf("%i\n", method) < 0)
				return -1;
			break;
		}
		if (methodname)
			if (printf("%s\n", methodname) < 0)
				return -1;
	}

	if (!sitename)
		if ((const_sitename = libgamma_method_default_site(method)))
			if (!(sitename = memdup(const_sitename, strlen(const_sitename) + 1)))
				return -1;

	if (sitename) {
		switch (method) {
		case LIBGAMMA_METHOD_X_RANDR:
		case LIBGAMMA_METHOD_X_VIDMODE:
			if ((p = strrchr(sitename, ':')))
				if ((p = strchr(p, '.')))
					*p = '\0';
			break;
		default:
			break;
		}
	}

	if (sitename && query == 1)
		if (printf("%s\n", sitename) < 0)
			return -1;

	if (query == 2) {
		site.method = method;
		site.site = sitename;
		sitename = NULL;
		socketpath = get_socket_pathname();
		if (!socketpath)
			return -1;
		if (printf("%s\n", socketpath) < 0)
			return -1;
	}

	if (fflush(stdout))
		return -1;
	return 0;
}


/**
 * Print usage information and exit
 */
#if defined(__GNU__) || defined(__clang__)
__attribute__((__noreturn__))
#endif
static void
usage(void)
{
	fprintf(stderr, "usage: %s [-m method] [-s site] [-fkpq]\n", argv0);
	exit(1);
}


#if defined(__clang__)
# pragma GCC diagnostic ignored "-Wdocumentation-unknown-command"
#endif


/**
 * Must not be started without stdin, stdout, or stderr (may be /dev/null)
 * 
 * argv[0] must refer to the real command name or pathname,
 * otherwise, re-execute will not work
 * 
 * The process closes stdout when the socket has been created
 * 
 * @signal  SIGUSR1     Re-execute to updated process image
 * @signal  SIGUSR2     Dump the state of the process to standard error
 * @signal  SIGINFO     Ditto
 * @signal  SIGTERM     Terminate the process gracefully
 * @signal  SIGRTMIN+0  Disconnect from the site
 * @signal  SiGRTMIN+1  Reconnect to the site
 * 
 * @param   argc  The number of elements in `argv`
 * @param   argv  Command line arguments. Recognised options:
 *                  -s SITENAME
 *                    The site to which to connect
 *                  -m METHOD
 *                    Adjustment method name or adjustment method number
 *                  -p
 *                    Preserve current gamma ramps at priority 0
 *                  -f
 *                    Do not fork the process into the background
 *                  -k
 *                    Keep stderr open
 *                  -q
 *                    Print the select (possiblity default) adjustment
 *                    method on the first line in stdout, and the
 *                    selected (possibility defasult) site on the second
 *                    line in stdout, and exit. If the site name is `NULL`,
 *                    the second line is omitted. This is indented to
 *                    be used by clients to figure out to which instance
 *                    of the service it should connect. Use twice to
 *                    simply ge the socket pathname, an a terminating LF.
 *                    By combining -q and -m you can enumerate the name
 *                    of all recognised adjustment method, start from 0
 *                    and work up until a numerical adjustment method is
 *                    returned.
 * @return        0: Successful
 *                1: An error occurred
 *                2: Already running
 */
int
main(int argc, char *argv[])
{
	int rc = 1, foreground = 0, keep_stderr = 0, query = 0, r;
	char *statefile = NULL, *statefile_ = NULL;

	ARGBEGIN {
	case 's':
		sitename = EARGF(usage());
		/* To simplify re-exec: */
		sitename = memdup(sitename, strlen(sitename) + 1);
		if (!sitename)
			goto fail;
		break;
	case 'm':
		method = get_method(EARGF(usage()));
		if (method < 0)
			goto fail;
		break;
	case 'p': preserve    = 1;     break;
	case 'f': foreground  = 1;     break;
	case 'k': keep_stderr = 1;     break;
	case 'q': query = 1 + !!query; break;
	case ' ': /* Internal, do not document */
		statefile = statefile_ = EARGF(usage());
		break;
	default:
		usage();
	}
	ARGEND;

	if (argc > 0)
		usage();

restart:
	if (!statefile) {
		switch ((r = initialise(foreground, keep_stderr, query))) {
		case INIT_SUCCESS: break;
		case INIT_RUNNING: rc = 2;  /* fall through */
		case INIT_FAILURE: goto fail;
		default:           return r;
		}
	} else if (restore_state(statefile) < 0) {
		goto fail;
	} else {
		if (statefile != statefile_)
			free(statefile);
		unlink(statefile);
		statefile = NULL;
	}

	if (query) {
		if (print_method_and_site(query) < 0)
			goto fail;
		goto done;
	}

reenter_loop:
	if (main_loop() < 0)
		goto fail;

	if (reexec && !terminate) {
		statefile = reexecute();
		if (statefile) {
			perror(argv0);
			fprintf(stderr, "%s: restoring state without re-executing\n", argv0);
			reexec = 0;
			goto restart;
		}
		perror(argv0);
		fprintf(stderr, "%s: continuing without re-executing\n", argv0);
		reexec = 0;
		goto reenter_loop;
	}

done:
	rc = 0;
deinit:
	if (statefile)
		unlink(statefile);
	if (reexec)
		free(statefile);
	destroy(1);
	return rc;

fail:
	if (errno)
		perror(argv0);
	goto deinit;
}