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2 * Copyright (c) 2008, 2009, 2010 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 /* Prepare to start a process whose command-line arguments are given by the
123 * null-terminated 'argv' array. Returns 0 if successful, otherwise a
124 * positive errno value. */
126 process_prestart(char **argv
)
132 /* Log the process to be started. */
133 if (VLOG_IS_DBG_ENABLED()) {
134 char *args
= process_escape_args(argv
);
135 VLOG_DBG("starting subprocess: %s", args
);
139 /* execvp() will search PATH too, but the error in that case is more
140 * obscure, since it is only reported post-fork. */
141 binary
= process_search_path(argv
[0]);
143 VLOG_ERR("%s not found in PATH", argv
[0]);
151 /* Creates and returns a new struct process with the specified 'name' and
154 * This is racy unless SIGCHLD is blocked (and has been blocked since before
155 * the fork()) that created the subprocess. */
156 static struct process
*
157 process_register(const char *name
, pid_t pid
)
162 assert(sigchld_is_blocked());
164 p
= xzalloc(sizeof *p
);
166 slash
= strrchr(name
, '/');
167 p
->name
= xstrdup(slash
? slash
+ 1 : name
);
170 list_push_back(&all_processes
, &p
->node
);
175 /* Starts a subprocess with the arguments in the null-terminated argv[] array.
176 * argv[0] is used as the name of the process. Searches the PATH environment
177 * variable to find the program to execute.
179 * All file descriptors are closed before executing the subprocess, except for
180 * fds 0, 1, and 2 and the 'n_keep_fds' fds listed in 'keep_fds'. Also, any of
181 * the 'n_null_fds' fds listed in 'null_fds' are replaced by /dev/null.
183 * Returns 0 if successful, otherwise a positive errno value indicating the
184 * error. If successful, '*pp' is assigned a new struct process that may be
185 * used to query the process's status. On failure, '*pp' is set to NULL. */
187 process_start(char **argv
,
188 const int keep_fds
[], size_t n_keep_fds
,
189 const int null_fds
[], size_t n_null_fds
,
197 COVERAGE_INC(process_start
);
198 error
= process_prestart(argv
);
203 block_sigchld(&oldsigs
);
206 unblock_sigchld(&oldsigs
);
207 VLOG_WARN("fork failed: %s", strerror(errno
));
210 /* Running in parent process. */
211 *pp
= process_register(argv
[0], pid
);
212 unblock_sigchld(&oldsigs
);
215 /* Running in child process. */
216 int fd_max
= get_max_fds();
220 unblock_sigchld(&oldsigs
);
221 for (fd
= 0; fd
< fd_max
; fd
++) {
222 if (is_member(fd
, null_fds
, n_null_fds
)) {
223 /* We can't use get_null_fd() here because we might have
224 * already closed its fd. */
225 int nullfd
= open("/dev/null", O_RDWR
);
228 } else if (fd
>= 3 && !is_member(fd
, keep_fds
, n_keep_fds
)) {
232 execvp(argv
[0], argv
);
233 fprintf(stderr
, "execvp(\"%s\") failed: %s\n",
234 argv
[0], strerror(errno
));
239 /* Destroys process 'p'. */
241 process_destroy(struct process
*p
)
246 block_sigchld(&oldsigs
);
247 list_remove(&p
->node
);
248 unblock_sigchld(&oldsigs
);
255 /* Sends signal 'signr' to process 'p'. Returns 0 if successful, otherwise a
256 * positive errno value. */
258 process_kill(const struct process
*p
, int signr
)
260 return (p
->exited
? ESRCH
261 : !kill(p
->pid
, signr
) ? 0
265 /* Returns the pid of process 'p'. */
267 process_pid(const struct process
*p
)
272 /* Returns the name of process 'p' (the name passed to process_start() with any
273 * leading directories stripped). */
275 process_name(const struct process
*p
)
280 /* Returns true if process 'p' has exited, false otherwise. */
282 process_exited(struct process
*p
)
287 char buf
[_POSIX_PIPE_BUF
];
288 ignore(read(fds
[0], buf
, sizeof buf
));
293 /* Returns process 'p''s exit status, as reported by waitpid(2).
294 * process_status(p) may be called only after process_exited(p) has returned
297 process_status(const struct process
*p
)
304 process_run(char **argv
,
305 const int keep_fds
[], size_t n_keep_fds
,
306 const int null_fds
[], size_t n_null_fds
,
312 COVERAGE_INC(process_run
);
313 retval
= process_start(argv
, keep_fds
, n_keep_fds
, null_fds
, n_null_fds
,
320 while (!process_exited(p
)) {
324 *status
= process_status(p
);
329 /* Given 'status', which is a process status in the form reported by waitpid(2)
330 * and returned by process_status(), returns a string describing how the
331 * process terminated. The caller is responsible for freeing the string when
332 * it is no longer needed. */
334 process_status_msg(int status
)
336 struct ds ds
= DS_EMPTY_INITIALIZER
;
337 if (WIFEXITED(status
)) {
338 ds_put_format(&ds
, "exit status %d", WEXITSTATUS(status
));
339 } else if (WIFSIGNALED(status
) || WIFSTOPPED(status
)) {
340 int signr
= WIFSIGNALED(status
) ? WTERMSIG(status
) : WSTOPSIG(status
);
341 const char *name
= NULL
;
342 #ifdef HAVE_STRSIGNAL
343 name
= strsignal(signr
);
345 ds_put_format(&ds
, "%s by signal %d",
346 WIFSIGNALED(status
) ? "killed" : "stopped", signr
);
348 ds_put_format(&ds
, " (%s)", name
);
351 ds_put_format(&ds
, "terminated abnormally (%x)", status
);
353 if (WCOREDUMP(status
)) {
354 ds_put_cstr(&ds
, ", core dumped");
359 /* Causes the next call to poll_block() to wake up when process 'p' has
362 process_wait(struct process
*p
)
365 poll_immediate_wake();
367 poll_fd_wait(fds
[0], POLLIN
);
372 process_search_path(const char *name
)
374 char *save_ptr
= NULL
;
378 if (strchr(name
, '/') || !getenv("PATH")) {
379 return stat(name
, &s
) == 0 ? xstrdup(name
) : NULL
;
382 path
= xstrdup(getenv("PATH"));
383 for (dir
= strtok_r(path
, ":", &save_ptr
); dir
;
384 dir
= strtok_r(NULL
, ":", &save_ptr
)) {
385 char *file
= xasprintf("%s/%s", dir
, name
);
386 if (stat(file
, &s
) == 0) {
396 /* process_run_capture() and supporting functions. */
404 stream_open(struct stream
*s
)
408 VLOG_WARN("failed to create pipe: %s", strerror(errno
));
411 set_nonblocking(s
->fds
[0]);
416 stream_read(struct stream
*s
)
427 error
= read_fully(s
->fds
[0], buffer
, sizeof buffer
, &n
);
428 ds_put_buffer(&s
->log
, buffer
, n
);
430 if (error
== EAGAIN
|| error
== EWOULDBLOCK
) {
434 VLOG_WARN("error reading subprocess pipe: %s",
439 } else if (s
->log
.length
> PROCESS_MAX_CAPTURE
) {
440 VLOG_WARN("subprocess output overflowed %d-byte buffer",
441 PROCESS_MAX_CAPTURE
);
450 stream_wait(struct stream
*s
)
452 if (s
->fds
[0] >= 0) {
453 poll_fd_wait(s
->fds
[0], POLLIN
);
458 stream_close(struct stream
*s
)
461 if (s
->fds
[0] >= 0) {
464 if (s
->fds
[1] >= 0) {
469 /* Starts the process whose arguments are given in the null-terminated array
470 * 'argv' and waits for it to exit. On success returns 0 and stores the
471 * process exit value (suitable for passing to process_status_msg()) in
472 * '*status'. On failure, returns a positive errno value and stores 0 in
475 * If 'stdout_log' is nonnull, then the subprocess's output to stdout (up to a
476 * limit of PROCESS_MAX_CAPTURE bytes) is captured in a memory buffer, which
477 * when this function returns 0 is stored as a null-terminated string in
478 * '*stdout_log'. The caller is responsible for freeing '*stdout_log' (by
479 * passing it to free()). When this function returns an error, '*stdout_log'
482 * If 'stderr_log' is nonnull, then it is treated like 'stdout_log' except
483 * that it captures the subprocess's output to stderr. */
485 process_run_capture(char **argv
, char **stdout_log
, char **stderr_log
,
488 struct stream s_stdout
, s_stderr
;
493 COVERAGE_INC(process_run_capture
);
501 error
= process_prestart(argv
);
506 error
= stream_open(&s_stdout
);
511 error
= stream_open(&s_stderr
);
513 stream_close(&s_stdout
);
517 block_sigchld(&oldsigs
);
522 unblock_sigchld(&oldsigs
);
523 VLOG_WARN("fork failed: %s", strerror(error
));
525 stream_close(&s_stdout
);
526 stream_close(&s_stderr
);
530 /* Running in parent process. */
533 p
= process_register(argv
[0], pid
);
534 unblock_sigchld(&oldsigs
);
536 close(s_stdout
.fds
[1]);
537 close(s_stderr
.fds
[1]);
538 while (!process_exited(p
)) {
539 stream_read(&s_stdout
);
540 stream_read(&s_stderr
);
542 stream_wait(&s_stdout
);
543 stream_wait(&s_stderr
);
547 stream_read(&s_stdout
);
548 stream_read(&s_stderr
);
551 *stdout_log
= ds_steal_cstr(&s_stdout
.log
);
554 *stderr_log
= ds_steal_cstr(&s_stderr
.log
);
557 stream_close(&s_stdout
);
558 stream_close(&s_stderr
);
560 *status
= process_status(p
);
564 /* Running in child process. */
569 unblock_sigchld(&oldsigs
);
571 dup2(get_null_fd(), 0);
572 dup2(s_stdout
.fds
[1], 1);
573 dup2(s_stderr
.fds
[1], 2);
575 max_fds
= get_max_fds();
576 for (i
= 3; i
< max_fds
; i
++) {
580 execvp(argv
[0], argv
);
581 fprintf(stderr
, "execvp(\"%s\") failed: %s\n",
582 argv
[0], strerror(errno
));
588 sigchld_handler(int signr UNUSED
)
592 COVERAGE_INC(process_sigchld
);
593 LIST_FOR_EACH (p
, struct process
, node
, &all_processes
) {
597 retval
= waitpid(p
->pid
, &status
, WNOHANG
);
598 } while (retval
== -1 && errno
== EINTR
);
599 if (retval
== p
->pid
) {
602 } else if (retval
< 0) {
603 /* XXX We want to log something but we're in a signal
610 ignore(write(fds
[1], "", 1));
614 is_member(int x
, const int *array
, size_t n
)
618 for (i
= 0; i
< n
; i
++) {
627 sigchld_is_blocked(void)
630 if (sigprocmask(SIG_SETMASK
, NULL
, &sigs
)) {
631 ovs_fatal(errno
, "sigprocmask");
633 return sigismember(&sigs
, SIGCHLD
);
637 block_sigchld(sigset_t
*oldsigs
)
640 sigemptyset(&sigchld
);
641 sigaddset(&sigchld
, SIGCHLD
);
642 if (sigprocmask(SIG_BLOCK
, &sigchld
, oldsigs
)) {
643 ovs_fatal(errno
, "sigprocmask");
648 unblock_sigchld(const sigset_t
*oldsigs
)
650 if (sigprocmask(SIG_SETMASK
, oldsigs
, NULL
)) {
651 ovs_fatal(errno
, "sigprocmask");