ucm: add exec sequence command

This change renames the original exec command to shell which
is more appropriate. Implement a light version of the exec
command which calls directly the specified executable without
the shell interaction (man 3 system).

Signed-off-by: Jaroslav Kysela <perex@perex.cz>

src/ucm/Makefile.am

@@ -1,7 +1,7 @@
 EXTRA_LTLIBRARIES = libucm.la
 
 libucm_la_SOURCES = utils.c parser.c ucm_cond.c ucm_subs.c ucm_include.c \
-		    ucm_regex.c main.c
+		    ucm_regex.c ucm_exec.c main.c
 
 noinst_HEADERS = ucm_local.h
 

src/ucm/main.c

@@ -717,6 +717,14 @@ static int execute_sequence(snd_use_case_mgr_t *uc_mgr,
 			usleep(s->data.sleep);
 			break;
 		case SEQUENCE_ELEMENT_TYPE_EXEC:
+			err = uc_mgr_exec(s->data.exec);
+			if (err != 0) {
+				uc_error("exec '%s' failed (exit code %d)", s->data.exec, err);
+				goto __fail;
+			}
+			break;
+		case SEQUENCE_ELEMENT_TYPE_SHELL:
+shell_retry:
 			err = system(s->data.exec);
 			if (WIFSIGNALED(err)) {
 				err = -EINTR;
@@ -727,6 +735,8 @@ static int execute_sequence(snd_use_case_mgr_t *uc_mgr,
 					goto __fail;
 				}
 			} else if (err < 0) {
+				if (errno == EAGAIN)
+					goto shell_retry;
 				err = -errno;
 				goto __fail;
 			}

src/ucm/parser.c

@@ -910,6 +910,7 @@ cset:
 
 		if (strcmp(cmd, "exec") == 0) {
 			curr->type = SEQUENCE_ELEMENT_TYPE_EXEC;
+exec:
 			err = parse_string_substitute3(uc_mgr, n, &curr->data.exec);
 			if (err < 0) {
 				uc_error("error: exec requires a string!");
@@ -918,6 +919,11 @@ cset:
 			continue;
 		}
 
+		if (strcmp(cmd, "shell") == 0) {
+			curr->type = SEQUENCE_ELEMENT_TYPE_SHELL;
+			goto exec;
+		}
+
 		if (strcmp(cmd, "comment") == 0)
 			goto skip;
 

src/ucm/ucm_exec.c

@@ -0,0 +1,285 @@
+/*
+ *  Exec an external program
+ *  Copyright (C) 2021 Jaroslav Kysela
+ *
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Lesser General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2 of the License, or (at your option) any later version.
+ *
+ *  This library 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
+ *  Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public
+ *  License along with this library; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ *  Support for the verb/device/modifier core logic and API,
+ *  command line tool and file parser was kindly sponsored by
+ *  Texas Instruments Inc.
+ *  Support for multiple active modifiers and devices,
+ *  transition sequences, multiple client access and user defined use
+ *  cases was kindly sponsored by Wolfson Microelectronics PLC.
+ *
+ *  Copyright (C) 2021 Red Hat Inc.
+ *  Authors: Jaroslav Kysela <perex@perex.cz>
+ */
+
+#include "ucm_local.h"
+#include <sys/stat.h>
+#include <sys/wait.h>
+#include <dirent.h>
+
+static pthread_mutex_t fork_lock = PTHREAD_MUTEX_INITIALIZER;
+
+/*
+ * Search PATH for executable
+ */
+static int find_exec(const char *name, char *out, size_t len)
+{
+	int ret = 0;
+	char bin[PATH_MAX];
+	char *path, *tmp, *tmp2 = NULL;
+	DIR *dir;
+	struct dirent *de;
+	struct stat st;
+	if (name[0] == '/') {
+		if (lstat(name, &st))
+			return 0;
+		if (!S_ISREG(st.st_mode) || !(st.st_mode & S_IEXEC))
+			return 0;
+		snd_strlcpy(out, name, len);
+		return 1;
+	}
+	if (!(tmp = getenv("PATH")))
+		return 0;
+	path = alloca(strlen(tmp) + 1);
+	if (!path)
+		return 0;
+	strcpy(path, tmp);
+	tmp = strtok_r(path, ":", &tmp2);
+	while (tmp && !ret) {
+		if ((dir = opendir(tmp))) {
+			while ((de = readdir(dir))) {
+				if (strstr(de->d_name, name) != de->d_name)
+					continue;
+				snprintf(bin, sizeof(bin), "%s/%s", tmp,
+					 de->d_name);
+				if (lstat(bin, &st))
+					continue;
+				if (!S_ISREG(st.st_mode)
+				    || !(st.st_mode & S_IEXEC))
+					continue;
+				snd_strlcpy(out, bin, len);
+				return 1;
+			}
+			closedir(dir);
+		}
+		tmp = strtok_r(NULL, ":", &tmp2);
+	}
+	return ret;
+}
+
+static void free_args(char **argv)
+{
+	char **a;
+
+	for (a = argv; *a; a++)
+		free(*a);
+	free(argv);
+}
+
+static int parse_args(char ***argv, int argc, const char *cmd)
+{
+	char *s, *f;
+	int i = 0, l, eow;
+
+	if (!argv || !cmd)
+		return -1;
+
+	s = alloca(strlen(cmd) + 1);
+	if (!s)
+		return -1;
+	strcpy(s, cmd);
+	*argv = calloc(argc, sizeof(char *));
+
+	while (*s && i < argc - 1) {
+		while (*s == ' ')
+			s++;
+		f = s;
+		eow = 0;
+		while (*s) {
+			if (*s == '\\') {
+				l = *(s + 1);
+				if (l == 'b')
+					l = '\b';
+				else if (l == 'f')
+					l = '\f';
+				else if (l == 'n')
+					l = '\n';
+				else if (l == 'r')
+					l = '\r';
+				else if (l == 't')
+					l = '\t';
+				else
+					l = 0;
+				if (l) {
+					*s++ = l;
+					memmove(s, s + 1, strlen(s));
+				} else {
+					memmove(s, s + 1, strlen(s));
+					if (*s)
+						s++;
+				}
+			} else if (eow) {
+				if (*s == eow) {
+					memmove(s, s + 1, strlen(s));
+					eow = 0;
+				} else {
+					s++;
+				}
+			} else if (*s == '\'' || *s == '"') {
+				eow = *s;
+				memmove(s, s + 1, strlen(s));
+			} else if (*s == ' ') {
+				break;
+			} else {
+				s++;
+			}
+		}
+		if (f != s) {
+			if (*s) {
+				*(char *)s = '\0';
+				s++;
+			}
+			(*argv)[i] = strdup(f);
+			if ((*argv)[i] == NULL) {
+				free_args(*argv);
+				return -ENOMEM;
+			}
+			i++;
+		}
+	}
+	(*argv)[i] = NULL;
+	return 0;
+}
+
+/*
+ * execute a binary file
+ *
+ */
+int uc_mgr_exec(const char *prog)
+{
+	pid_t p, f, maxfd;
+	int err = 0, status;
+	char bin[PATH_MAX];
+	struct sigaction sa;
+	struct sigaction intr, quit;
+	sigset_t omask;
+	char **argv;
+
+	if (parse_args(&argv, 32, prog))
+		return -EINVAL;
+
+	prog = argv[0];
+	if (argv[0][0] != '/' && argv[0][0] != '.') {
+		if (!find_exec(argv[0], bin, sizeof(bin))) {
+			err = -ENOEXEC;
+			goto __error;
+		}
+		prog = bin;
+	}
+
+	maxfd = sysconf(_SC_OPEN_MAX);
+
+	/*
+	 * block SIGCHLD signal
+	 * ignore SIGINT and SIGQUIT in parent
+	 */
+
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_handler = SIG_IGN;
+	sigemptyset(&sa.sa_mask);
+	sigaddset(&sa.sa_mask, SIGCHLD);
+
+	pthread_mutex_lock(&fork_lock);
+
+	sigprocmask(SIG_BLOCK, &sa.sa_mask, &omask);
+
+	sigaction(SIGINT, &sa, &intr);
+	sigaction(SIGQUIT, &sa, &quit);
+
+	p = fork();
+
+	if (p == -1) {
+		err = -errno;
+		pthread_mutex_unlock(&fork_lock);
+		uc_error("Unable to fork() for \"%s\" -- %s", prog,
+			 strerror(errno));
+		goto __error;
+	}
+
+	if (p == 0) {
+		f = open("/dev/null", O_RDWR);
+		if (f == -1) {
+			uc_error("pid %d cannot open /dev/null for redirect %s -- %s",
+				 getpid(), prog, strerror(errno));
+			exit(1);
+		}
+
+		close(0);
+		close(1);
+		close(2);
+
+		dup2(f, 0);
+		dup2(f, 1);
+		dup2(f, 2);
+
+		close(f);
+
+		for (f = 3; f < maxfd; f++)
+			close(f);
+
+		/* install default handlers for the forked process */
+		signal(SIGINT, SIG_DFL);
+		signal(SIGQUIT, SIG_DFL);
+
+		execve(prog, argv, environ);
+		exit(1);
+	}
+
+	sigaction(SIGINT, &intr, NULL);
+	sigaction(SIGQUIT, &quit, NULL);
+	sigprocmask(SIG_SETMASK, &omask, NULL);
+
+	pthread_mutex_unlock(&fork_lock);
+
+	/* make the spawned process a session leader so killing the
+	   process group recursively kills any child process that
+	   might have been spawned */
+	setpgid(p, p);
+
+	while (1) {
+		f = waitpid(p, &status, 0);
+		if (f == -1) {
+			if (errno == EAGAIN)
+				continue;
+			err = -errno;
+			goto __error;
+		}
+		if (WIFSIGNALED(status)) {
+			err = -EINTR;
+			break;
+		}
+		if (WIFEXITED(status)) {
+			err = WEXITSTATUS(status);
+			break;
+		}
+	}
+
+ __error:
+	free_args(argv);
+	return err;
+}

src/ucm/ucm_local.h

@@ -49,12 +49,13 @@
 #define SEQUENCE_ELEMENT_TYPE_CSET		2
 #define SEQUENCE_ELEMENT_TYPE_SLEEP		3
 #define SEQUENCE_ELEMENT_TYPE_EXEC		4
-#define SEQUENCE_ELEMENT_TYPE_CSET_BIN_FILE	5
-#define SEQUENCE_ELEMENT_TYPE_CSET_TLV		6
-#define SEQUENCE_ELEMENT_TYPE_CSET_NEW		7
-#define SEQUENCE_ELEMENT_TYPE_CTL_REMOVE	8
-#define SEQUENCE_ELEMENT_TYPE_CMPT_SEQ		9
-#define SEQUENCE_ELEMENT_TYPE_SYSSET		10
+#define SEQUENCE_ELEMENT_TYPE_SHELL		5
+#define SEQUENCE_ELEMENT_TYPE_CSET_BIN_FILE	6
+#define SEQUENCE_ELEMENT_TYPE_CSET_TLV		7
+#define SEQUENCE_ELEMENT_TYPE_CSET_NEW		8
+#define SEQUENCE_ELEMENT_TYPE_CTL_REMOVE	9
+#define SEQUENCE_ELEMENT_TYPE_CMPT_SEQ		10
+#define SEQUENCE_ELEMENT_TYPE_SYSSET		11
 
 struct ucm_value {
         struct list_head list;
@@ -356,6 +357,8 @@ int uc_mgr_define_regex(snd_use_case_mgr_t *uc_mgr,
 			const char *name,
 			snd_config_t *eval);
 
+int uc_mgr_exec(const char *prog);
+
 /** The name of the environment variable containing the UCM directory */
 #define ALSA_CONFIG_UCM_VAR "ALSA_CONFIG_UCM"
 

src/ucm/utils.c

@@ -509,6 +509,7 @@ void uc_mgr_free_sequence_element(struct sequence_element *seq)
 		free(seq->data.sysw);
 		break;
 	case SEQUENCE_ELEMENT_TYPE_EXEC:
+	case SEQUENCE_ELEMENT_TYPE_SHELL:
 		free(seq->data.exec);
 		break;
 	default: