2 * Copyright (c) 2008, 2009 Nicira Networks.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at:
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
29 #include "dynamic-string.h"
30 #include "fatal-signal.h"
32 #include "poll-loop.h"
33 #include "socket-util.h"
36 #define THIS_MODULE VLM_process
44 /* Modified by signal handler. */
49 /* Pipe used to signal child termination. */
53 static struct list all_processes = LIST_INITIALIZER(&all_processes);
55 static bool sigchld_is_blocked(void);
56 static void block_sigchld(sigset_t *);
57 static void unblock_sigchld(const sigset_t *);
58 static void sigchld_handler(int signr UNUSED);
59 static bool is_member(int x, const int *array, size_t);
61 /* Initializes the process subsystem (if it is not already initialized). Calls
62 * exit() if initialization fails.
64 * Calling this function is optional; it will be called automatically by
65 * process_start() if necessary. Calling it explicitly allows the client to
66 * prevent the process from exiting at an unexpected time. */
78 /* Create notification pipe. */
80 ovs_fatal(errno, "could not create pipe");
82 set_nonblocking(fds[0]);
83 set_nonblocking(fds[1]);
85 /* Set up child termination signal handler. */
86 memset(&sa, 0, sizeof sa);
87 sa.sa_handler = sigchld_handler;
88 sigemptyset(&sa.sa_mask);
89 sa.sa_flags = SA_NOCLDSTOP | SA_RESTART;
90 if (sigaction(SIGCHLD, &sa, NULL)) {
91 ovs_fatal(errno, "sigaction(SIGCHLD) failed");
96 process_escape_args(char **argv)
98 struct ds ds = DS_EMPTY_INITIALIZER;
100 for (argp = argv; *argp; argp++) {
101 const char *arg = *argp;
104 ds_put_char(&ds, ' ');
106 if (arg[strcspn(arg, " \t\r\n\v\\")]) {
107 ds_put_char(&ds, '"');
108 for (p = arg; *p; p++) {
109 if (*p == '\\' || *p == '\"') {
110 ds_put_char(&ds, '\\');
112 ds_put_char(&ds, *p);
114 ds_put_char(&ds, '"');
116 ds_put_cstr(&ds, arg);
122 /* Starts a subprocess with the arguments in the null-terminated argv[] array.
123 * argv[0] is used as the name of the process. Searches the PATH environment
124 * variable to find the program to execute.
126 * All file descriptors are closed before executing the subprocess, except for
127 * fds 0, 1, and 2 and the 'n_keep_fds' fds listed in 'keep_fds'. Also, any of
128 * the 'n_null_fds' fds listed in 'null_fds' are replaced by /dev/null.
130 * Returns 0 if successful, otherwise a positive errno value indicating the
131 * error. If successful, '*pp' is assigned a new struct process that may be
132 * used to query the process's status. On failure, '*pp' is set to NULL. */
134 process_start(char **argv,
135 const int keep_fds[], size_t n_keep_fds,
136 const int null_fds[], size_t n_null_fds,
145 COVERAGE_INC(process_start);
147 if (VLOG_IS_DBG_ENABLED()) {
148 char *args = process_escape_args(argv);
149 VLOG_DBG("starting subprocess: %s", args);
153 /* execvp() will search PATH too, but the error in that case is more
154 * obscure, since it is only reported post-fork. */
155 binary = process_search_path(argv[0]);
157 VLOG_ERR("%s not found in PATH", argv[0]);
162 block_sigchld(&oldsigs);
163 fatal_signal_block();
166 fatal_signal_unblock();
167 unblock_sigchld(&oldsigs);
168 VLOG_WARN("fork failed: %s", strerror(errno));
171 /* Running in parent process. */
175 p = xcalloc(1, sizeof *p);
177 slash = strrchr(argv[0], '/');
178 p->name = xstrdup(slash ? slash + 1 : argv[0]);
181 list_push_back(&all_processes, &p->node);
182 unblock_sigchld(&oldsigs);
183 fatal_signal_unblock();
188 /* Running in child process. */
189 int fd_max = get_max_fds();
193 fatal_signal_unblock();
194 unblock_sigchld(&oldsigs);
195 for (fd = 0; fd < fd_max; fd++) {
196 if (is_member(fd, null_fds, n_null_fds)) {
197 /* We can't use get_null_fd() here because we might have
198 * already closed its fd. */
199 int nullfd = open("/dev/null", O_RDWR);
202 } else if (fd >= 3 && !is_member(fd, keep_fds, n_keep_fds)) {
206 execvp(argv[0], argv);
207 fprintf(stderr, "execvp(\"%s\") failed: %s\n",
208 argv[0], strerror(errno));
213 /* Destroys process 'p'. */
215 process_destroy(struct process *p)
220 block_sigchld(&oldsigs);
221 list_remove(&p->node);
222 unblock_sigchld(&oldsigs);
229 /* Sends signal 'signr' to process 'p'. Returns 0 if successful, otherwise a
230 * positive errno value. */
232 process_kill(const struct process *p, int signr)
234 return (p->exited ? ESRCH
235 : !kill(p->pid, signr) ? 0
239 /* Returns the pid of process 'p'. */
241 process_pid(const struct process *p)
246 /* Returns the name of process 'p' (the name passed to process_start() with any
247 * leading directories stripped). */
249 process_name(const struct process *p)
254 /* Returns true if process 'p' has exited, false otherwise. */
256 process_exited(struct process *p)
261 char buf[_POSIX_PIPE_BUF];
262 read(fds[0], buf, sizeof buf);
267 /* Returns process 'p''s exit status, as reported by waitpid(2).
268 * process_status(p) may be called only after process_exited(p) has returned
271 process_status(const struct process *p)
278 process_run(char **argv,
279 const int keep_fds[], size_t n_keep_fds,
280 const int null_fds[], size_t n_null_fds,
286 COVERAGE_INC(process_run);
287 retval = process_start(argv, keep_fds, n_keep_fds, null_fds, n_null_fds,
294 while (!process_exited(p)) {
298 *status = process_status(p);
303 /* Given 'status', which is a process status in the form reported by waitpid(2)
304 * and returned by process_status(), returns a string describing how the
305 * process terminated. The caller is responsible for freeing the string when
306 * it is no longer needed. */
308 process_status_msg(int status)
310 struct ds ds = DS_EMPTY_INITIALIZER;
311 if (WIFEXITED(status)) {
312 ds_put_format(&ds, "exit status %d", WEXITSTATUS(status));
313 } else if (WIFSIGNALED(status) || WIFSTOPPED(status)) {
314 int signr = WIFSIGNALED(status) ? WTERMSIG(status) : WSTOPSIG(status);
315 const char *name = NULL;
316 #ifdef HAVE_STRSIGNAL
317 name = strsignal(signr);
319 ds_put_format(&ds, "%s by signal %d",
320 WIFSIGNALED(status) ? "killed" : "stopped", signr);
322 ds_put_format(&ds, " (%s)", name);
325 ds_put_format(&ds, "terminated abnormally (%x)", status);
327 if (WCOREDUMP(status)) {
328 ds_put_cstr(&ds, ", core dumped");
333 /* Causes the next call to poll_block() to wake up when process 'p' has
336 process_wait(struct process *p)
339 poll_immediate_wake();
341 poll_fd_wait(fds[0], POLLIN);
346 process_search_path(const char *name)
348 char *save_ptr = NULL;
352 if (strchr(name, '/') || !getenv("PATH")) {
353 return stat(name, &s) == 0 ? xstrdup(name) : NULL;
356 path = xstrdup(getenv("PATH"));
357 for (dir = strtok_r(path, ":", &save_ptr); dir;
358 dir = strtok_r(NULL, ":", &save_ptr)) {
359 char *file = xasprintf("%s/%s", dir, name);
360 if (stat(file, &s) == 0) {
371 sigchld_handler(int signr UNUSED)
375 COVERAGE_INC(process_sigchld);
376 LIST_FOR_EACH (p, struct process, node, &all_processes) {
380 retval = waitpid(p->pid, &status, WNOHANG);
381 } while (retval == -1 && errno == EINTR);
382 if (retval == p->pid) {
385 } else if (retval < 0) {
386 /* XXX We want to log something but we're in a signal
393 write(fds[1], "", 1);
397 is_member(int x, const int *array, size_t n)
401 for (i = 0; i < n; i++) {
410 block_sigchld(sigset_t *oldsigs)
413 sigemptyset(&sigchld);
414 sigaddset(&sigchld, SIGCHLD);
415 if (sigprocmask(SIG_BLOCK, &sigchld, oldsigs)) {
416 ovs_fatal(errno, "sigprocmask");
421 unblock_sigchld(const sigset_t *oldsigs)
423 if (sigprocmask(SIG_SETMASK, oldsigs, NULL)) {
424 ovs_fatal(errno, "sigprocmask");