1 /*
2 * Copyright (c) 1995, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 #undef _LARGEFILE64_SOURCE
27 #define _LARGEFILE64_SOURCE 1
28
29 #include "jni.h"
30 #include "jvm.h"
31 #include "jvm_md.h"
32 #include "jni_util.h"
33 #include "io_util.h"
34
35 /*
36 * Platform-specific support for java.lang.Process
37 */
38 #include <assert.h>
39 #include <stddef.h>
40 #include <stdlib.h>
41 #include <sys/types.h>
42 #include <ctype.h>
43 #include <sys/wait.h>
44 #include <signal.h>
45 #include <string.h>
46 #include <errno.h>
47 #include <dirent.h>
48 #include <unistd.h>
49 #include <fcntl.h>
50 #include <limits.h>
51
52 #ifdef __APPLE__
53 #include <crt_externs.h>
54 #define environ (*_NSGetEnviron())
55 #endif
56
57 /*
58 * There are 3 possible strategies we might use to "fork":
59 *
60 * - fork(2). Very portable and reliable but subject to
61 * failure due to overcommit (see the documentation on
62 * /proc/sys/vm/overcommit_memory in Linux proc(5)).
63 * This is the ancient problem of spurious failure whenever a large
64 * process starts a small subprocess.
65 *
66 * - vfork(). Using this is scary because all relevant man pages
67 * contain dire warnings, e.g. Linux vfork(2). But at least it's
68 * documented in the glibc docs and is standardized by XPG4.
69 * http://www.opengroup.org/onlinepubs/000095399/functions/vfork.html
70 * On Linux, one might think that vfork() would be implemented using
71 * the clone system call with flag CLONE_VFORK, but in fact vfork is
72 * a separate system call (which is a good sign, suggesting that
73 * vfork will continue to be supported at least on Linux).
74 * Another good sign is that glibc implements posix_spawn using
75 * vfork whenever possible. Note that we cannot use posix_spawn
76 * ourselves because there's no reliable way to close all inherited
77 * file descriptors.
78 *
79 * - clone() with flags CLONE_VM but not CLONE_THREAD. clone() is
80 * Linux-specific, but this ought to work - at least the glibc
81 * sources contain code to handle different combinations of CLONE_VM
82 * and CLONE_THREAD. However, when this was implemented, it
83 * appeared to fail on 32-bit i386 (but not 64-bit x86_64) Linux with
84 * the simple program
85 * Runtime.getRuntime().exec("/bin/true").waitFor();
86 * with:
87 * # Internal Error (os_linux_x86.cpp:683), pid=19940, tid=2934639536
88 * # Error: pthread_getattr_np failed with errno = 3 (ESRCH)
89 * We believe this is a glibc bug, reported here:
90 * http://sources.redhat.com/bugzilla/show_bug.cgi?id=10311
91 * but the glibc maintainers closed it as WONTFIX.
92 *
93 * Based on the above analysis, we are currently using vfork() on
94 * Linux and fork() on other Unix systems, but the code to use clone()
95 * remains.
96 */
97
98 #define START_CHILD_USE_CLONE 0 /* clone() currently disabled; see above. */
99
100 #ifndef START_CHILD_USE_CLONE
101 #ifdef __linux__
102 #define START_CHILD_USE_CLONE 1
103 #else
104 #define START_CHILD_USE_CLONE 0
105 #endif
106 #endif
107
108 /* By default, use vfork() on Linux. */
109 #ifndef START_CHILD_USE_VFORK
110 #ifdef __linux__
111 #define START_CHILD_USE_VFORK 1
112 #else
113 #define START_CHILD_USE_VFORK 0
114 #endif
115 #endif
116
117 #if START_CHILD_USE_CLONE
118 #include <sched.h>
119 #define START_CHILD_SYSTEM_CALL "clone"
120 #elif START_CHILD_USE_VFORK
121 #define START_CHILD_SYSTEM_CALL "vfork"
122 #else
123 #define START_CHILD_SYSTEM_CALL "fork"
124 #endif
125
126 #ifndef STDIN_FILENO
127 #define STDIN_FILENO 0
128 #endif
129
130 #ifndef STDOUT_FILENO
131 #define STDOUT_FILENO 1
132 #endif
133
134 #ifndef STDERR_FILENO
135 #define STDERR_FILENO 2
136 #endif
137
138 #ifndef SA_NOCLDSTOP
139 #define SA_NOCLDSTOP 0
140 #endif
141
142 #ifndef SA_RESTART
143 #define SA_RESTART 0
144 #endif
145
146 #define FAIL_FILENO (STDERR_FILENO + 1)
147
148 /* TODO: Refactor. */
149 #define RESTARTABLE(_cmd, _result) do { \
150 do { \
151 _result = _cmd; \
152 } while((_result == -1) && (errno == EINTR)); \
153 } while(0)
154
155 /* This is one of the rare times it's more portable to declare an
156 * external symbol explicitly, rather than via a system header.
157 * The declaration is standardized as part of UNIX98, but there is
158 * no standard (not even de-facto) header file where the
159 * declaration is to be found. See:
160 * http://www.opengroup.org/onlinepubs/009695399/functions/environ.html
161 * http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_02.html
162 *
163 * "All identifiers in this volume of IEEE Std 1003.1-2001, except
164 * environ, are defined in at least one of the headers" (!)
165 */
166 extern char **environ;
167
168
169 static void
170 setSIGCHLDHandler(JNIEnv *env)
171 {
172 /* There is a subtle difference between having the signal handler
173 * for SIGCHLD be SIG_DFL and SIG_IGN. We cannot obtain process
174 * termination information for child processes if the signal
175 * handler is SIG_IGN. It must be SIG_DFL.
176 *
177 * We used to set the SIGCHLD handler only on Linux, but it's
178 * safest to set it unconditionally.
179 *
180 * Consider what happens if java's parent process sets the SIGCHLD
181 * handler to SIG_IGN. Normally signal handlers are inherited by
182 * children, but SIGCHLD is a controversial case. Solaris appears
183 * to always reset it to SIG_DFL, but this behavior may be
184 * non-standard-compliant, and we shouldn't rely on it.
185 *
186 * References:
187 * http://www.opengroup.org/onlinepubs/7908799/xsh/exec.html
188 * http://www.pasc.org/interps/unofficial/db/p1003.1/pasc-1003.1-132.html
189 */
190 struct sigaction sa;
191 sa.sa_handler = SIG_DFL;
192 sigemptyset(&sa.sa_mask);
193 sa.sa_flags = SA_NOCLDSTOP | SA_RESTART;
194 if (sigaction(SIGCHLD, &sa, NULL) < 0)
195 JNU_ThrowInternalError(env, "Can't set SIGCHLD handler");
196 }
197
198 static void*
199 xmalloc(JNIEnv *env, size_t size)
200 {
201 void *p = malloc(size);
202 if (p == NULL)
203 JNU_ThrowOutOfMemoryError(env, NULL);
204 return p;
205 }
206
207 #define NEW(type, n) ((type *) xmalloc(env, (n) * sizeof(type)))
208
209 /**
210 * If PATH is not defined, the OS provides some default value.
211 * Unfortunately, there's no portable way to get this value.
212 * Fortunately, it's only needed if the child has PATH while we do not.
213 */
214 static const char*
215 defaultPath(void)
216 {
217 #ifdef __solaris__
218 /* These really are the Solaris defaults! */
219 return (geteuid() == 0 || getuid() == 0) ?
220 "/usr/xpg4/bin:/usr/ccs/bin:/usr/bin:/opt/SUNWspro/bin:/usr/sbin" :
221 "/usr/xpg4/bin:/usr/ccs/bin:/usr/bin:/opt/SUNWspro/bin:";
222 #else
223 return ":/bin:/usr/bin"; /* glibc */
224 #endif
225 }
226
227 static const char*
228 effectivePath(void)
229 {
230 const char *s = getenv("PATH");
231 return (s != NULL) ? s : defaultPath();
232 }
233
234 static int
235 countOccurrences(const char *s, char c)
236 {
237 int count;
238 for (count = 0; *s != '\0'; s++)
239 count += (*s == c);
240 return count;
241 }
242
243 static const char * const *
244 splitPath(JNIEnv *env, const char *path)
245 {
246 const char *p, *q;
247 char **pathv;
248 int i;
249 int k;
250 int count = countOccurrences(path, ':') + 1;
251
252 pathv = NEW(char*, count+1);
253 if (pathv == NULL)
254 return NULL;
255
256 pathv[count] = NULL;
257 for (p = path, i = 0; i < count; i++, p = q + 1) {
258 for (q = p; (*q != ':') && (*q != '\0'); q++);
259
260 if (q == p) /* empty PATH component => "." */
261 pathv[i] = "./";
262 else {
263 int addSlash = ((*(q - 1)) != '/');
264 pathv[i] = NEW(char, q - p + addSlash + 1);
265 if (pathv[i] == NULL)
266 goto cleanUpMemory;
267
268 memcpy(pathv[i], p, q - p);
269 if (addSlash)
270 pathv[i][q - p] = '/';
271 pathv[i][q - p + addSlash] = '\0';
272 }
273 }
274 return (const char * const *) pathv;
275
276 cleanUpMemory:
277 for (k = 0; k <= i; k++)
278 free(pathv[k]);
279 return NULL;
280 }
281
282 /**
283 * Cached value of JVM's effective PATH.
284 * (We don't support putenv("PATH=...") in native code)
285 */
286 static const char *parentPath;
287
288 /**
289 * Split, canonicalized version of parentPath
290 */
291 static const char * const *parentPathv;
292
293 static jfieldID field_exitcode;
294
295 JNIEXPORT void JNICALL
296 Java_java_lang_UNIXProcess_initIDs(JNIEnv *env, jclass clazz)
297 {
298 field_exitcode = (*env)->GetFieldID(env, clazz, "exitcode", "I");
299
300 parentPath = effectivePath();
301 parentPathv = splitPath(env, parentPath);
302
303 setSIGCHLDHandler(env);
304 }
305
306
307 #ifndef WIFEXITED
308 #define WIFEXITED(status) (((status)&0xFF) == 0)
309 #endif
310
311 #ifndef WEXITSTATUS
312 #define WEXITSTATUS(status) (((status)>>8)&0xFF)
313 #endif
314
315 #ifndef WIFSIGNALED
316 #define WIFSIGNALED(status) (((status)&0xFF) > 0 && ((status)&0xFF00) == 0)
317 #endif
318
319 #ifndef WTERMSIG
320 #define WTERMSIG(status) ((status)&0x7F)
321 #endif
322
323 /* Block until a child process exits and return its exit code.
324 Note, can only be called once for any given pid. */
325 JNIEXPORT jint JNICALL
326 Java_java_lang_UNIXProcess_waitForProcessExit(JNIEnv* env,
327 jobject junk,
328 jint pid)
329 {
330 /* We used to use waitid() on Solaris, waitpid() on Linux, but
331 * waitpid() is more standard, so use it on all POSIX platforms. */
332 int status;
333 /* Wait for the child process to exit. This returns immediately if
334 the child has already exited. */
335 while (waitpid(pid, &status, 0) < 0) {
336 switch (errno) {
337 case ECHILD: return 0;
338 case EINTR: break;
339 default: return -1;
340 }
341 }
342
343 if (WIFEXITED(status)) {
344 /*
345 * The child exited normally; get its exit code.
346 */
347 return WEXITSTATUS(status);
348 } else if (WIFSIGNALED(status)) {
349 /* The child exited because of a signal.
350 * The best value to return is 0x80 + signal number,
351 * because that is what all Unix shells do, and because
352 * it allows callers to distinguish between process exit and
353 * process death by signal.
354 * Unfortunately, the historical behavior on Solaris is to return
355 * the signal number, and we preserve this for compatibility. */
356 #ifdef __solaris__
357 return WTERMSIG(status);
358 #else
359 return 0x80 + WTERMSIG(status);
360 #endif
361 } else {
362 /*
363 * Unknown exit code; pass it through.
364 */
365 return status;
366 }
367 }
368
369 static ssize_t
370 restartableWrite(int fd, const void *buf, size_t count)
371 {
372 ssize_t result;
373 RESTARTABLE(write(fd, buf, count), result);
374 return result;
375 }
376
377 static int
378 restartableDup2(int fd_from, int fd_to)
379 {
380 int err;
381 RESTARTABLE(dup2(fd_from, fd_to), err);
382 return err;
383 }
384
385 static int
386 restartableClose(int fd)
387 {
388 int err;
389 RESTARTABLE(close(fd), err);
390 return err;
391 }
392
393 static int
394 closeSafely(int fd)
395 {
396 return (fd == -1) ? 0 : restartableClose(fd);
397 }
398
399 static int
400 isAsciiDigit(char c)
401 {
402 return c >= '0' && c <= '9';
403 }
404
405 #ifdef _ALLBSD_SOURCE
406 #define FD_DIR "/dev/fd"
407 #define dirent64 dirent
408 #define readdir64 readdir
409 #else
410 #define FD_DIR "/proc/self/fd"
411 #endif
412
413 static int
414 closeDescriptors(void)
415 {
416 DIR *dp;
417 struct dirent64 *dirp;
418 int from_fd = FAIL_FILENO + 1;
419
420 /* We're trying to close all file descriptors, but opendir() might
421 * itself be implemented using a file descriptor, and we certainly
422 * don't want to close that while it's in use. We assume that if
423 * opendir() is implemented using a file descriptor, then it uses
424 * the lowest numbered file descriptor, just like open(). So we
425 * close a couple explicitly. */
426
427 restartableClose(from_fd); /* for possible use by opendir() */
428 restartableClose(from_fd + 1); /* another one for good luck */
429
430 if ((dp = opendir(FD_DIR)) == NULL)
431 return 0;
432
433 /* We use readdir64 instead of readdir to work around Solaris bug
434 * 6395699: /proc/self/fd fails to report file descriptors >= 1024 on Solaris 9
435 */
436 while ((dirp = readdir64(dp)) != NULL) {
437 int fd;
438 if (isAsciiDigit(dirp->d_name[0]) &&
439 (fd = strtol(dirp->d_name, NULL, 10)) >= from_fd + 2)
440 restartableClose(fd);
441 }
442
443 closedir(dp);
444
445 return 1;
446 }
447
448 static int
449 moveDescriptor(int fd_from, int fd_to)
450 {
451 if (fd_from != fd_to) {
452 if ((restartableDup2(fd_from, fd_to) == -1) ||
453 (restartableClose(fd_from) == -1))
454 return -1;
455 }
456 return 0;
457 }
458
459 static const char *
460 getBytes(JNIEnv *env, jbyteArray arr)
461 {
462 return arr == NULL ? NULL :
463 (const char*) (*env)->GetByteArrayElements(env, arr, NULL);
464 }
465
466 static void
467 releaseBytes(JNIEnv *env, jbyteArray arr, const char* parr)
468 {
469 if (parr != NULL)
470 (*env)->ReleaseByteArrayElements(env, arr, (jbyte*) parr, JNI_ABORT);
471 }
472
473 static void
474 initVectorFromBlock(const char**vector, const char* block, int count)
475 {
476 int i;
477 const char *p;
478 for (i = 0, p = block; i < count; i++) {
479 /* Invariant: p always points to the start of a C string. */
480 vector[i] = p;
481 while (*(p++));
482 }
483 vector[count] = NULL;
484 }
485
486 static void
487 throwIOException(JNIEnv *env, int errnum, const char *defaultDetail)
488 {
489 static const char * const format = "error=%d, %s";
490 const char *detail = defaultDetail;
491 char *errmsg;
492 jstring s;
493
494 if (errnum != 0) {
495 const char *s = strerror(errnum);
496 if (strcmp(s, "Unknown error") != 0)
497 detail = s;
498 }
499 /* ASCII Decimal representation uses 2.4 times as many bits as binary. */
500 errmsg = NEW(char, strlen(format) + strlen(detail) + 3 * sizeof(errnum));
501 if (errmsg == NULL)
502 return;
503
504 sprintf(errmsg, format, errnum, detail);
505 s = JNU_NewStringPlatform(env, errmsg);
506 if (s != NULL) {
507 jobject x = JNU_NewObjectByName(env, "java/io/IOException",
508 "(Ljava/lang/String;)V", s);
509 if (x != NULL)
510 (*env)->Throw(env, x);
511 }
512 free(errmsg);
513 }
514
515 #ifdef DEBUG_PROCESS
516 /* Debugging process code is difficult; where to write debug output? */
517 static void
518 debugPrint(char *format, ...)
519 {
520 FILE *tty = fopen("/dev/tty", "w");
521 va_list ap;
522 va_start(ap, format);
523 vfprintf(tty, format, ap);
524 va_end(ap);
525 fclose(tty);
526 }
527 #endif /* DEBUG_PROCESS */
528
529 /**
530 * Exec FILE as a traditional Bourne shell script (i.e. one without #!).
531 * If we could do it over again, we would probably not support such an ancient
532 * misfeature, but compatibility wins over sanity. The original support for
533 * this was imported accidentally from execvp().
534 */
535 static void
536 execve_as_traditional_shell_script(const char *file,
537 const char *argv[],
538 const char *const envp[])
539 {
540 /* Use the extra word of space provided for us in argv by caller. */
541 const char *argv0 = argv[0];
542 const char *const *end = argv;
543 while (*end != NULL)
544 ++end;
545 memmove(argv+2, argv+1, (end-argv) * sizeof (*end));
546 argv[0] = "/bin/sh";
547 argv[1] = file;
548 execve(argv[0], (char **) argv, (char **) envp);
549 /* Can't even exec /bin/sh? Big trouble, but let's soldier on... */
550 memmove(argv+1, argv+2, (end-argv) * sizeof (*end));
551 argv[0] = argv0;
552 }
553
554 /**
555 * Like execve(2), except that in case of ENOEXEC, FILE is assumed to
556 * be a shell script and the system default shell is invoked to run it.
557 */
558 static void
559 execve_with_shell_fallback(const char *file,
560 const char *argv[],
561 const char *const envp[])
562 {
563 #if START_CHILD_USE_CLONE || START_CHILD_USE_VFORK
564 /* shared address space; be very careful. */
565 execve(file, (char **) argv, (char **) envp);
566 if (errno == ENOEXEC)
567 execve_as_traditional_shell_script(file, argv, envp);
568 #else
569 /* unshared address space; we can mutate environ. */
570 environ = (char **) envp;
571 execvp(file, (char **) argv);
572 #endif
573 }
574
575 /**
576 * 'execvpe' should have been included in the Unix standards,
577 * and is a GNU extension in glibc 2.10.
578 *
579 * JDK_execvpe is identical to execvp, except that the child environment is
580 * specified via the 3rd argument instead of being inherited from environ.
581 */
582 static void
583 JDK_execvpe(const char *file,
584 const char *argv[],
585 const char *const envp[])
586 {
587 if (envp == NULL || (char **) envp == environ) {
588 execvp(file, (char **) argv);
589 return;
590 }
591
592 if (*file == '\0') {
593 errno = ENOENT;
594 return;
595 }
596
597 if (strchr(file, '/') != NULL) {
598 execve_with_shell_fallback(file, argv, envp);
599 } else {
600 /* We must search PATH (parent's, not child's) */
601 char expanded_file[PATH_MAX];
602 int filelen = strlen(file);
603 int sticky_errno = 0;
604 const char * const * dirs;
605 for (dirs = parentPathv; *dirs; dirs++) {
606 const char * dir = *dirs;
607 int dirlen = strlen(dir);
608 if (filelen + dirlen + 1 >= PATH_MAX) {
609 errno = ENAMETOOLONG;
610 continue;
611 }
612 memcpy(expanded_file, dir, dirlen);
613 memcpy(expanded_file + dirlen, file, filelen);
614 expanded_file[dirlen + filelen] = '\0';
615 execve_with_shell_fallback(expanded_file, argv, envp);
616 /* There are 3 responses to various classes of errno:
617 * return immediately, continue (especially for ENOENT),
618 * or continue with "sticky" errno.
619 *
620 * From exec(3):
621 *
622 * If permission is denied for a file (the attempted
623 * execve returned EACCES), these functions will continue
624 * searching the rest of the search path. If no other
625 * file is found, however, they will return with the
626 * global variable errno set to EACCES.
627 */
628 switch (errno) {
629 case EACCES:
630 sticky_errno = errno;
631 /* FALLTHRU */
632 case ENOENT:
633 case ENOTDIR:
634 #ifdef ELOOP
635 case ELOOP:
636 #endif
637 #ifdef ESTALE
638 case ESTALE:
639 #endif
640 #ifdef ENODEV
641 case ENODEV:
642 #endif
643 #ifdef ETIMEDOUT
644 case ETIMEDOUT:
645 #endif
646 break; /* Try other directories in PATH */
647 default:
648 return;
649 }
650 }
651 if (sticky_errno != 0)
652 errno = sticky_errno;
653 }
654 }
655
656 /*
657 * Reads nbyte bytes from file descriptor fd into buf,
658 * The read operation is retried in case of EINTR or partial reads.
659 *
660 * Returns number of bytes read (normally nbyte, but may be less in
661 * case of EOF). In case of read errors, returns -1 and sets errno.
662 */
663 static ssize_t
664 readFully(int fd, void *buf, size_t nbyte)
665 {
666 ssize_t remaining = nbyte;
667 for (;;) {
668 ssize_t n = read(fd, buf, remaining);
669 if (n == 0) {
670 return nbyte - remaining;
671 } else if (n > 0) {
672 remaining -= n;
673 if (remaining <= 0)
674 return nbyte;
675 /* We were interrupted in the middle of reading the bytes.
676 * Unlikely, but possible. */
677 buf = (void *) (((char *)buf) + n);
678 } else if (errno == EINTR) {
679 /* Strange signals like SIGJVM1 are possible at any time.
680 * See http://www.dreamsongs.com/WorseIsBetter.html */
681 } else {
682 return -1;
683 }
684 }
685 }
686
687 typedef struct _ChildStuff
688 {
689 int in[2];
690 int out[2];
691 int err[2];
692 int fail[2];
693 int fds[3];
694 const char **argv;
695 const char **envv;
696 const char *pdir;
697 jboolean redirectErrorStream;
698 #if START_CHILD_USE_CLONE
699 void *clone_stack;
700 #endif
701 } ChildStuff;
702
703 static void
704 copyPipe(int from[2], int to[2])
705 {
706 to[0] = from[0];
707 to[1] = from[1];
708 }
709
710 /**
711 * Child process after a successful fork() or clone().
712 * This function must not return, and must be prepared for either all
713 * of its address space to be shared with its parent, or to be a copy.
714 * It must not modify global variables such as "environ".
715 */
716 static int
717 childProcess(void *arg)
718 {
719 const ChildStuff* p = (const ChildStuff*) arg;
720
721 /* Close the parent sides of the pipes.
722 Closing pipe fds here is redundant, since closeDescriptors()
723 would do it anyways, but a little paranoia is a good thing. */
724 if ((closeSafely(p->in[1]) == -1) ||
725 (closeSafely(p->out[0]) == -1) ||
726 (closeSafely(p->err[0]) == -1) ||
727 (closeSafely(p->fail[0]) == -1))
728 goto WhyCantJohnnyExec;
729
730 /* Give the child sides of the pipes the right fileno's. */
731 /* Note: it is possible for in[0] == 0 */
732 if ((moveDescriptor(p->in[0] != -1 ? p->in[0] : p->fds[0],
733 STDIN_FILENO) == -1) ||
734 (moveDescriptor(p->out[1]!= -1 ? p->out[1] : p->fds[1],
735 STDOUT_FILENO) == -1))
736 goto WhyCantJohnnyExec;
737
738 if (p->redirectErrorStream) {
739 if ((closeSafely(p->err[1]) == -1) ||
740 (restartableDup2(STDOUT_FILENO, STDERR_FILENO) == -1))
741 goto WhyCantJohnnyExec;
742 } else {
743 if (moveDescriptor(p->err[1] != -1 ? p->err[1] : p->fds[2],
744 STDERR_FILENO) == -1)
745 goto WhyCantJohnnyExec;
746 }
747
748 if (moveDescriptor(p->fail[1], FAIL_FILENO) == -1)
749 goto WhyCantJohnnyExec;
750
751 /* close everything */
752 if (closeDescriptors() == 0) { /* failed, close the old way */
753 int max_fd = (int)sysconf(_SC_OPEN_MAX);
754 int fd;
755 for (fd = FAIL_FILENO + 1; fd < max_fd; fd++)
756 if (restartableClose(fd) == -1 && errno != EBADF)
757 goto WhyCantJohnnyExec;
758 }
759
760 /* change to the new working directory */
761 if (p->pdir != NULL && chdir(p->pdir) < 0)
762 goto WhyCantJohnnyExec;
763
764 if (fcntl(FAIL_FILENO, F_SETFD, FD_CLOEXEC) == -1)
765 goto WhyCantJohnnyExec;
766
767 JDK_execvpe(p->argv[0], p->argv, p->envv);
768
769 WhyCantJohnnyExec:
770 /* We used to go to an awful lot of trouble to predict whether the
771 * child would fail, but there is no reliable way to predict the
772 * success of an operation without *trying* it, and there's no way
773 * to try a chdir or exec in the parent. Instead, all we need is a
774 * way to communicate any failure back to the parent. Easy; we just
775 * send the errno back to the parent over a pipe in case of failure.
776 * The tricky thing is, how do we communicate the *success* of exec?
777 * We use FD_CLOEXEC together with the fact that a read() on a pipe
778 * yields EOF when the write ends (we have two of them!) are closed.
779 */
780 {
781 int errnum = errno;
782 restartableWrite(FAIL_FILENO, &errnum, sizeof(errnum));
783 }
784 restartableClose(FAIL_FILENO);
785 _exit(-1);
786 return 0; /* Suppress warning "no return value from function" */
787 }
788
789 /**
790 * Start a child process running function childProcess.
791 * This function only returns in the parent.
792 * We are unusually paranoid; use of clone/vfork is
793 * especially likely to tickle gcc/glibc bugs.
794 */
795 #ifdef __attribute_noinline__ /* See: sys/cdefs.h */
796 __attribute_noinline__
797 #endif
798 static pid_t
799 startChild(ChildStuff *c) {
800 #if START_CHILD_USE_CLONE
801 #define START_CHILD_CLONE_STACK_SIZE (64 * 1024)
802 /*
803 * See clone(2).
804 * Instead of worrying about which direction the stack grows, just
805 * allocate twice as much and start the stack in the middle.
806 */
807 if ((c->clone_stack = malloc(2 * START_CHILD_CLONE_STACK_SIZE)) == NULL)
808 /* errno will be set to ENOMEM */
809 return -1;
810 return clone(childProcess,
811 c->clone_stack + START_CHILD_CLONE_STACK_SIZE,
812 CLONE_VFORK | CLONE_VM | SIGCHLD, c);
813 #else
814 #if START_CHILD_USE_VFORK
815 /*
816 * We separate the call to vfork into a separate function to make
817 * very sure to keep stack of child from corrupting stack of parent,
818 * as suggested by the scary gcc warning:
819 * warning: variable 'foo' might be clobbered by 'longjmp' or 'vfork'
820 */
821 volatile pid_t resultPid = vfork();
822 #else
823 /*
824 * From Solaris fork(2): In Solaris 10, a call to fork() is
825 * identical to a call to fork1(); only the calling thread is
826 * replicated in the child process. This is the POSIX-specified
827 * behavior for fork().
828 */
829 pid_t resultPid = fork();
830 #endif
831 if (resultPid == 0)
832 childProcess(c);
833 assert(resultPid != 0); /* childProcess never returns */
834 return resultPid;
835 #endif /* ! START_CHILD_USE_CLONE */
836 }
837
838 JNIEXPORT jint JNICALL
839 Java_java_lang_UNIXProcess_forkAndExec(JNIEnv *env,
840 jobject process,
841 jbyteArray prog,
842 jbyteArray argBlock, jint argc,
843 jbyteArray envBlock, jint envc,
844 jbyteArray dir,
845 jintArray std_fds,
846 jboolean redirectErrorStream)
847 {
848 int errnum;
849 int resultPid = -1;
850 int in[2], out[2], err[2], fail[2];
851 jint *fds = NULL;
852 const char *pprog = NULL;
853 const char *pargBlock = NULL;
854 const char *penvBlock = NULL;
855 ChildStuff *c;
856
857 in[0] = in[1] = out[0] = out[1] = err[0] = err[1] = fail[0] = fail[1] = -1;
858
859 if ((c = NEW(ChildStuff, 1)) == NULL) return -1;
860 c->argv = NULL;
861 c->envv = NULL;
862 c->pdir = NULL;
863 #if START_CHILD_USE_CLONE
864 c->clone_stack = NULL;
865 #endif
866
867 /* Convert prog + argBlock into a char ** argv.
868 * Add one word room for expansion of argv for use by
869 * execve_as_traditional_shell_script.
870 */
871 assert(prog != NULL && argBlock != NULL);
872 if ((pprog = getBytes(env, prog)) == NULL) goto Catch;
873 if ((pargBlock = getBytes(env, argBlock)) == NULL) goto Catch;
874 if ((c->argv = NEW(const char *, argc + 3)) == NULL) goto Catch;
875 c->argv[0] = pprog;
876 initVectorFromBlock(c->argv+1, pargBlock, argc);
877
878 if (envBlock != NULL) {
879 /* Convert envBlock into a char ** envv */
880 if ((penvBlock = getBytes(env, envBlock)) == NULL) goto Catch;
881 if ((c->envv = NEW(const char *, envc + 1)) == NULL) goto Catch;
882 initVectorFromBlock(c->envv, penvBlock, envc);
883 }
884
885 if (dir != NULL) {
886 if ((c->pdir = getBytes(env, dir)) == NULL) goto Catch;
887 }
888
889 assert(std_fds != NULL);
890 fds = (*env)->GetIntArrayElements(env, std_fds, NULL);
891 if (fds == NULL) goto Catch;
892
893 if ((fds[0] == -1 && pipe(in) < 0) ||
894 (fds[1] == -1 && pipe(out) < 0) ||
895 (fds[2] == -1 && pipe(err) < 0) ||
896 (pipe(fail) < 0)) {
897 throwIOException(env, errno, "Bad file descriptor");
898 goto Catch;
899 }
900 c->fds[0] = fds[0];
901 c->fds[1] = fds[1];
902 c->fds[2] = fds[2];
903
904 copyPipe(in, c->in);
905 copyPipe(out, c->out);
906 copyPipe(err, c->err);
907 copyPipe(fail, c->fail);
908
909 c->redirectErrorStream = redirectErrorStream;
910
911 resultPid = startChild(c);
912 assert(resultPid != 0);
913
914 if (resultPid < 0) {
915 throwIOException(env, errno, START_CHILD_SYSTEM_CALL " failed");
916 goto Catch;
917 }
918
919 restartableClose(fail[1]); fail[1] = -1; /* See: WhyCantJohnnyExec */
920
921 switch (readFully(fail[0], &errnum, sizeof(errnum))) {
922 case 0: break; /* Exec succeeded */
923 case sizeof(errnum):
924 waitpid(resultPid, NULL, 0);
925 throwIOException(env, errnum, "Exec failed");
926 goto Catch;
927 default:
928 throwIOException(env, errno, "Read failed");
929 goto Catch;
930 }
931
932 fds[0] = (in [1] != -1) ? in [1] : -1;
933 fds[1] = (out[0] != -1) ? out[0] : -1;
934 fds[2] = (err[0] != -1) ? err[0] : -1;
935
936 Finally:
937 #if START_CHILD_USE_CLONE
938 free(c->clone_stack);
939 #endif
940
941 /* Always clean up the child's side of the pipes */
942 closeSafely(in [0]);
943 closeSafely(out[1]);
944 closeSafely(err[1]);
945
946 /* Always clean up fail descriptors */
947 closeSafely(fail[0]);
948 closeSafely(fail[1]);
949
950 releaseBytes(env, prog, pprog);
951 releaseBytes(env, argBlock, pargBlock);
952 releaseBytes(env, envBlock, penvBlock);
953 releaseBytes(env, dir, c->pdir);
954
955 free(c->argv);
956 free(c->envv);
957 free(c);
958
959 if (fds != NULL)
960 (*env)->ReleaseIntArrayElements(env, std_fds, fds, 0);
961
962 return resultPid;
963
964 Catch:
965 /* Clean up the parent's side of the pipes in case of failure only */
966 closeSafely(in [1]);
967 closeSafely(out[0]);
968 closeSafely(err[0]);
969 goto Finally;
970 }
971
972 JNIEXPORT void JNICALL
973 Java_java_lang_UNIXProcess_destroyProcess(JNIEnv *env,
974 jobject junk,
975 jint pid,
976 jboolean force)
977 {
978 int sig = (force == JNI_TRUE) ? SIGKILL : SIGTERM;
979 kill(pid, sig);
980 }