1 /* 2 * Copyright (c) 1995, 2008, 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 count = countOccurrences(path, ':') + 1; 250 251 pathv = NEW(char*, count+1); 252 pathv[count] = NULL; 253 for (p = path, i = 0; i < count; i++, p = q + 1) { 254 for (q = p; (*q != ':') && (*q != '\0'); q++) 255 ; 256 if (q == p) /* empty PATH component => "." */ 257 pathv[i] = "./"; 258 else { 259 int addSlash = ((*(q - 1)) != '/'); 260 pathv[i] = NEW(char, q - p + addSlash + 1); 261 memcpy(pathv[i], p, q - p); 262 if (addSlash) 263 pathv[i][q - p] = '/'; 264 pathv[i][q - p + addSlash] = '\0'; 265 } 266 } 267 return (const char * const *) pathv; 268 } 269 270 /** 271 * Cached value of JVM's effective PATH. 272 * (We don't support putenv("PATH=...") in native code) 273 */ 274 static const char *parentPath; 275 276 /** 277 * Split, canonicalized version of parentPath 278 */ 279 static const char * const *parentPathv; 280 281 static jfieldID field_exitcode; 282 283 JNIEXPORT void JNICALL 284 Java_java_lang_UNIXProcess_initIDs(JNIEnv *env, jclass clazz) 285 { 286 field_exitcode = (*env)->GetFieldID(env, clazz, "exitcode", "I"); 287 288 parentPath = effectivePath(); 289 parentPathv = splitPath(env, parentPath); 290 291 setSIGCHLDHandler(env); 292 } 293 294 295 #ifndef WIFEXITED 296 #define WIFEXITED(status) (((status)&0xFF) == 0) 297 #endif 298 299 #ifndef WEXITSTATUS 300 #define WEXITSTATUS(status) (((status)>>8)&0xFF) 301 #endif 302 303 #ifndef WIFSIGNALED 304 #define WIFSIGNALED(status) (((status)&0xFF) > 0 && ((status)&0xFF00) == 0) 305 #endif 306 307 #ifndef WTERMSIG 308 #define WTERMSIG(status) ((status)&0x7F) 309 #endif 310 311 /* Block until a child process exits and return its exit code. 312 Note, can only be called once for any given pid. */ 313 JNIEXPORT jint JNICALL 314 Java_java_lang_UNIXProcess_waitForProcessExit(JNIEnv* env, 315 jobject junk, 316 jint pid) 317 { 318 /* We used to use waitid() on Solaris, waitpid() on Linux, but 319 * waitpid() is more standard, so use it on all POSIX platforms. */ 320 int status; 321 /* Wait for the child process to exit. This returns immediately if 322 the child has already exited. */ 323 while (waitpid(pid, &status, 0) < 0) { 324 switch (errno) { 325 case ECHILD: return 0; 326 case EINTR: break; 327 default: return -1; 328 } 329 } 330 331 if (WIFEXITED(status)) { 332 /* 333 * The child exited normally; get its exit code. 334 */ 335 return WEXITSTATUS(status); 336 } else if (WIFSIGNALED(status)) { 337 /* The child exited because of a signal. 338 * The best value to return is 0x80 + signal number, 339 * because that is what all Unix shells do, and because 340 * it allows callers to distinguish between process exit and 341 * process death by signal. 342 * Unfortunately, the historical behavior on Solaris is to return 343 * the signal number, and we preserve this for compatibility. */ 344 #ifdef __solaris__ 345 return WTERMSIG(status); 346 #else 347 return 0x80 + WTERMSIG(status); 348 #endif 349 } else { 350 /* 351 * Unknown exit code; pass it through. 352 */ 353 return status; 354 } 355 } 356 357 static ssize_t 358 restartableWrite(int fd, const void *buf, size_t count) 359 { 360 ssize_t result; 361 RESTARTABLE(write(fd, buf, count), result); 362 return result; 363 } 364 365 static int 366 restartableDup2(int fd_from, int fd_to) 367 { 368 int err; 369 RESTARTABLE(dup2(fd_from, fd_to), err); 370 return err; 371 } 372 373 static int 374 restartableClose(int fd) 375 { 376 int err; 377 RESTARTABLE(close(fd), err); 378 return err; 379 } 380 381 static int 382 closeSafely(int fd) 383 { 384 return (fd == -1) ? 0 : restartableClose(fd); 385 } 386 387 static int 388 isAsciiDigit(char c) 389 { 390 return c >= '0' && c <= '9'; 391 } 392 393 #ifdef _ALLBSD_SOURCE 394 #define FD_DIR "/dev/fd" 395 #define dirent64 dirent 396 #define readdir64 readdir 397 #else 398 #define FD_DIR "/proc/self/fd" 399 #endif 400 401 static int 402 closeDescriptors(void) 403 { 404 DIR *dp; 405 struct dirent64 *dirp; 406 int from_fd = FAIL_FILENO + 1; 407 408 /* We're trying to close all file descriptors, but opendir() might 409 * itself be implemented using a file descriptor, and we certainly 410 * don't want to close that while it's in use. We assume that if 411 * opendir() is implemented using a file descriptor, then it uses 412 * the lowest numbered file descriptor, just like open(). So we 413 * close a couple explicitly. */ 414 415 restartableClose(from_fd); /* for possible use by opendir() */ 416 restartableClose(from_fd + 1); /* another one for good luck */ 417 418 if ((dp = opendir(FD_DIR)) == NULL) 419 return 0; 420 421 /* We use readdir64 instead of readdir to work around Solaris bug 422 * 6395699: /proc/self/fd fails to report file descriptors >= 1024 on Solaris 9 423 */ 424 while ((dirp = readdir64(dp)) != NULL) { 425 int fd; 426 if (isAsciiDigit(dirp->d_name[0]) && 427 (fd = strtol(dirp->d_name, NULL, 10)) >= from_fd + 2) 428 restartableClose(fd); 429 } 430 431 closedir(dp); 432 433 return 1; 434 } 435 436 static int 437 moveDescriptor(int fd_from, int fd_to) 438 { 439 if (fd_from != fd_to) { 440 if ((restartableDup2(fd_from, fd_to) == -1) || 441 (restartableClose(fd_from) == -1)) 442 return -1; 443 } 444 return 0; 445 } 446 447 static const char * 448 getBytes(JNIEnv *env, jbyteArray arr) 449 { 450 return arr == NULL ? NULL : 451 (const char*) (*env)->GetByteArrayElements(env, arr, NULL); 452 } 453 454 static void 455 releaseBytes(JNIEnv *env, jbyteArray arr, const char* parr) 456 { 457 if (parr != NULL) 458 (*env)->ReleaseByteArrayElements(env, arr, (jbyte*) parr, JNI_ABORT); 459 } 460 461 static void 462 initVectorFromBlock(const char**vector, const char* block, int count) 463 { 464 int i; 465 const char *p; 466 for (i = 0, p = block; i < count; i++) { 467 /* Invariant: p always points to the start of a C string. */ 468 vector[i] = p; 469 while (*(p++)); 470 } 471 vector[count] = NULL; 472 } 473 474 static void 475 throwIOException(JNIEnv *env, int errnum, const char *defaultDetail) 476 { 477 static const char * const format = "error=%d, %s"; 478 const char *detail = defaultDetail; 479 char *errmsg; 480 jstring s; 481 482 if (errnum != 0) { 483 const char *s = strerror(errnum); 484 if (strcmp(s, "Unknown error") != 0) 485 detail = s; 486 } 487 /* ASCII Decimal representation uses 2.4 times as many bits as binary. */ 488 errmsg = NEW(char, strlen(format) + strlen(detail) + 3 * sizeof(errnum)); 489 sprintf(errmsg, format, errnum, detail); 490 s = JNU_NewStringPlatform(env, errmsg); 491 if (s != NULL) { 492 jobject x = JNU_NewObjectByName(env, "java/io/IOException", 493 "(Ljava/lang/String;)V", s); 494 if (x != NULL) 495 (*env)->Throw(env, x); 496 } 497 free(errmsg); 498 } 499 500 #ifdef DEBUG_PROCESS 501 /* Debugging process code is difficult; where to write debug output? */ 502 static void 503 debugPrint(char *format, ...) 504 { 505 FILE *tty = fopen("/dev/tty", "w"); 506 va_list ap; 507 va_start(ap, format); 508 vfprintf(tty, format, ap); 509 va_end(ap); 510 fclose(tty); 511 } 512 #endif /* DEBUG_PROCESS */ 513 514 /** 515 * Exec FILE as a traditional Bourne shell script (i.e. one without #!). 516 * If we could do it over again, we would probably not support such an ancient 517 * misfeature, but compatibility wins over sanity. The original support for 518 * this was imported accidentally from execvp(). 519 */ 520 static void 521 execve_as_traditional_shell_script(const char *file, 522 const char *argv[], 523 const char *const envp[]) 524 { 525 /* Use the extra word of space provided for us in argv by caller. */ 526 const char *argv0 = argv[0]; 527 const char *const *end = argv; 528 while (*end != NULL) 529 ++end; 530 memmove(argv+2, argv+1, (end-argv) * sizeof (*end)); 531 argv[0] = "/bin/sh"; 532 argv[1] = file; 533 execve(argv[0], (char **) argv, (char **) envp); 534 /* Can't even exec /bin/sh? Big trouble, but let's soldier on... */ 535 memmove(argv+1, argv+2, (end-argv) * sizeof (*end)); 536 argv[0] = argv0; 537 } 538 539 /** 540 * Like execve(2), except that in case of ENOEXEC, FILE is assumed to 541 * be a shell script and the system default shell is invoked to run it. 542 */ 543 static void 544 execve_with_shell_fallback(const char *file, 545 const char *argv[], 546 const char *const envp[]) 547 { 548 #if START_CHILD_USE_CLONE || START_CHILD_USE_VFORK 549 /* shared address space; be very careful. */ 550 execve(file, (char **) argv, (char **) envp); 551 if (errno == ENOEXEC) 552 execve_as_traditional_shell_script(file, argv, envp); 553 #else 554 /* unshared address space; we can mutate environ. */ 555 environ = (char **) envp; 556 execvp(file, (char **) argv); 557 #endif 558 } 559 560 /** 561 * 'execvpe' should have been included in the Unix standards, 562 * and is a GNU extension in glibc 2.10. 563 * 564 * JDK_execvpe is identical to execvp, except that the child environment is 565 * specified via the 3rd argument instead of being inherited from environ. 566 */ 567 static void 568 JDK_execvpe(const char *file, 569 const char *argv[], 570 const char *const envp[]) 571 { 572 if (envp == NULL || (char **) envp == environ) { 573 execvp(file, (char **) argv); 574 return; 575 } 576 577 if (*file == '\0') { 578 errno = ENOENT; 579 return; 580 } 581 582 if (strchr(file, '/') != NULL) { 583 execve_with_shell_fallback(file, argv, envp); 584 } else { 585 /* We must search PATH (parent's, not child's) */ 586 char expanded_file[PATH_MAX]; 587 int filelen = strlen(file); 588 int sticky_errno = 0; 589 const char * const * dirs; 590 for (dirs = parentPathv; *dirs; dirs++) { 591 const char * dir = *dirs; 592 int dirlen = strlen(dir); 593 if (filelen + dirlen + 1 >= PATH_MAX) { 594 errno = ENAMETOOLONG; 595 continue; 596 } 597 memcpy(expanded_file, dir, dirlen); 598 memcpy(expanded_file + dirlen, file, filelen); 599 expanded_file[dirlen + filelen] = '\0'; 600 execve_with_shell_fallback(expanded_file, argv, envp); 601 /* There are 3 responses to various classes of errno: 602 * return immediately, continue (especially for ENOENT), 603 * or continue with "sticky" errno. 604 * 605 * From exec(3): 606 * 607 * If permission is denied for a file (the attempted 608 * execve returned EACCES), these functions will continue 609 * searching the rest of the search path. If no other 610 * file is found, however, they will return with the 611 * global variable errno set to EACCES. 612 */ 613 switch (errno) { 614 case EACCES: 615 sticky_errno = errno; 616 /* FALLTHRU */ 617 case ENOENT: 618 case ENOTDIR: 619 #ifdef ELOOP 620 case ELOOP: 621 #endif 622 #ifdef ESTALE 623 case ESTALE: 624 #endif 625 #ifdef ENODEV 626 case ENODEV: 627 #endif 628 #ifdef ETIMEDOUT 629 case ETIMEDOUT: 630 #endif 631 break; /* Try other directories in PATH */ 632 default: 633 return; 634 } 635 } 636 if (sticky_errno != 0) 637 errno = sticky_errno; 638 } 639 } 640 641 /* 642 * Reads nbyte bytes from file descriptor fd into buf, 643 * The read operation is retried in case of EINTR or partial reads. 644 * 645 * Returns number of bytes read (normally nbyte, but may be less in 646 * case of EOF). In case of read errors, returns -1 and sets errno. 647 */ 648 static ssize_t 649 readFully(int fd, void *buf, size_t nbyte) 650 { 651 ssize_t remaining = nbyte; 652 for (;;) { 653 ssize_t n = read(fd, buf, remaining); 654 if (n == 0) { 655 return nbyte - remaining; 656 } else if (n > 0) { 657 remaining -= n; 658 if (remaining <= 0) 659 return nbyte; 660 /* We were interrupted in the middle of reading the bytes. 661 * Unlikely, but possible. */ 662 buf = (void *) (((char *)buf) + n); 663 } else if (errno == EINTR) { 664 /* Strange signals like SIGJVM1 are possible at any time. 665 * See http://www.dreamsongs.com/WorseIsBetter.html */ 666 } else { 667 return -1; 668 } 669 } 670 } 671 672 typedef struct _ChildStuff 673 { 674 int in[2]; 675 int out[2]; 676 int err[2]; 677 int fail[2]; 678 int fds[3]; 679 const char **argv; 680 const char **envv; 681 const char *pdir; 682 jboolean redirectErrorStream; 683 #if START_CHILD_USE_CLONE 684 void *clone_stack; 685 #endif 686 } ChildStuff; 687 688 static void 689 copyPipe(int from[2], int to[2]) 690 { 691 to[0] = from[0]; 692 to[1] = from[1]; 693 } 694 695 /** 696 * Child process after a successful fork() or clone(). 697 * This function must not return, and must be prepared for either all 698 * of its address space to be shared with its parent, or to be a copy. 699 * It must not modify global variables such as "environ". 700 */ 701 static int 702 childProcess(void *arg) 703 { 704 const ChildStuff* p = (const ChildStuff*) arg; 705 706 /* Close the parent sides of the pipes. 707 Closing pipe fds here is redundant, since closeDescriptors() 708 would do it anyways, but a little paranoia is a good thing. */ 709 if ((closeSafely(p->in[1]) == -1) || 710 (closeSafely(p->out[0]) == -1) || 711 (closeSafely(p->err[0]) == -1) || 712 (closeSafely(p->fail[0]) == -1)) 713 goto WhyCantJohnnyExec; 714 715 /* Give the child sides of the pipes the right fileno's. */ 716 /* Note: it is possible for in[0] == 0 */ 717 if ((moveDescriptor(p->in[0] != -1 ? p->in[0] : p->fds[0], 718 STDIN_FILENO) == -1) || 719 (moveDescriptor(p->out[1]!= -1 ? p->out[1] : p->fds[1], 720 STDOUT_FILENO) == -1)) 721 goto WhyCantJohnnyExec; 722 723 if (p->redirectErrorStream) { 724 if ((closeSafely(p->err[1]) == -1) || 725 (restartableDup2(STDOUT_FILENO, STDERR_FILENO) == -1)) 726 goto WhyCantJohnnyExec; 727 } else { 728 if (moveDescriptor(p->err[1] != -1 ? p->err[1] : p->fds[2], 729 STDERR_FILENO) == -1) 730 goto WhyCantJohnnyExec; 731 } 732 733 if (moveDescriptor(p->fail[1], FAIL_FILENO) == -1) 734 goto WhyCantJohnnyExec; 735 736 /* close everything */ 737 if (closeDescriptors() == 0) { /* failed, close the old way */ 738 int max_fd = (int)sysconf(_SC_OPEN_MAX); 739 int fd; 740 for (fd = FAIL_FILENO + 1; fd < max_fd; fd++) 741 if (restartableClose(fd) == -1 && errno != EBADF) 742 goto WhyCantJohnnyExec; 743 } 744 745 /* change to the new working directory */ 746 if (p->pdir != NULL && chdir(p->pdir) < 0) 747 goto WhyCantJohnnyExec; 748 749 if (fcntl(FAIL_FILENO, F_SETFD, FD_CLOEXEC) == -1) 750 goto WhyCantJohnnyExec; 751 752 JDK_execvpe(p->argv[0], p->argv, p->envv); 753 754 WhyCantJohnnyExec: 755 /* We used to go to an awful lot of trouble to predict whether the 756 * child would fail, but there is no reliable way to predict the 757 * success of an operation without *trying* it, and there's no way 758 * to try a chdir or exec in the parent. Instead, all we need is a 759 * way to communicate any failure back to the parent. Easy; we just 760 * send the errno back to the parent over a pipe in case of failure. 761 * The tricky thing is, how do we communicate the *success* of exec? 762 * We use FD_CLOEXEC together with the fact that a read() on a pipe 763 * yields EOF when the write ends (we have two of them!) are closed. 764 */ 765 { 766 int errnum = errno; 767 restartableWrite(FAIL_FILENO, &errnum, sizeof(errnum)); 768 } 769 restartableClose(FAIL_FILENO); 770 _exit(-1); 771 return 0; /* Suppress warning "no return value from function" */ 772 } 773 774 /** 775 * Start a child process running function childProcess. 776 * This function only returns in the parent. 777 * We are unusually paranoid; use of clone/vfork is 778 * especially likely to tickle gcc/glibc bugs. 779 */ 780 #ifdef __attribute_noinline__ /* See: sys/cdefs.h */ 781 __attribute_noinline__ 782 #endif 783 static pid_t 784 startChild(ChildStuff *c) { 785 #if START_CHILD_USE_CLONE 786 #define START_CHILD_CLONE_STACK_SIZE (64 * 1024) 787 /* 788 * See clone(2). 789 * Instead of worrying about which direction the stack grows, just 790 * allocate twice as much and start the stack in the middle. 791 */ 792 if ((c->clone_stack = malloc(2 * START_CHILD_CLONE_STACK_SIZE)) == NULL) 793 /* errno will be set to ENOMEM */ 794 return -1; 795 return clone(childProcess, 796 c->clone_stack + START_CHILD_CLONE_STACK_SIZE, 797 CLONE_VFORK | CLONE_VM | SIGCHLD, c); 798 #else 799 #if START_CHILD_USE_VFORK 800 /* 801 * We separate the call to vfork into a separate function to make 802 * very sure to keep stack of child from corrupting stack of parent, 803 * as suggested by the scary gcc warning: 804 * warning: variable 'foo' might be clobbered by 'longjmp' or 'vfork' 805 */ 806 volatile pid_t resultPid = vfork(); 807 #else 808 /* 809 * From Solaris fork(2): In Solaris 10, a call to fork() is 810 * identical to a call to fork1(); only the calling thread is 811 * replicated in the child process. This is the POSIX-specified 812 * behavior for fork(). 813 */ 814 pid_t resultPid = fork(); 815 #endif 816 if (resultPid == 0) 817 childProcess(c); 818 assert(resultPid != 0); /* childProcess never returns */ 819 return resultPid; 820 #endif /* ! START_CHILD_USE_CLONE */ 821 } 822 823 JNIEXPORT jint JNICALL 824 Java_java_lang_UNIXProcess_forkAndExec(JNIEnv *env, 825 jobject process, 826 jbyteArray prog, 827 jbyteArray argBlock, jint argc, 828 jbyteArray envBlock, jint envc, 829 jbyteArray dir, 830 jintArray std_fds, 831 jboolean redirectErrorStream) 832 { 833 int errnum; 834 int resultPid = -1; 835 int in[2], out[2], err[2], fail[2]; 836 jint *fds = NULL; 837 const char *pprog = NULL; 838 const char *pargBlock = NULL; 839 const char *penvBlock = NULL; 840 ChildStuff *c; 841 842 in[0] = in[1] = out[0] = out[1] = err[0] = err[1] = fail[0] = fail[1] = -1; 843 844 if ((c = NEW(ChildStuff, 1)) == NULL) return -1; 845 c->argv = NULL; 846 c->envv = NULL; 847 c->pdir = NULL; 848 #if START_CHILD_USE_CLONE 849 c->clone_stack = NULL; 850 #endif 851 852 /* Convert prog + argBlock into a char ** argv. 853 * Add one word room for expansion of argv for use by 854 * execve_as_traditional_shell_script. 855 */ 856 assert(prog != NULL && argBlock != NULL); 857 if ((pprog = getBytes(env, prog)) == NULL) goto Catch; 858 if ((pargBlock = getBytes(env, argBlock)) == NULL) goto Catch; 859 if ((c->argv = NEW(const char *, argc + 3)) == NULL) goto Catch; 860 c->argv[0] = pprog; 861 initVectorFromBlock(c->argv+1, pargBlock, argc); 862 863 if (envBlock != NULL) { 864 /* Convert envBlock into a char ** envv */ 865 if ((penvBlock = getBytes(env, envBlock)) == NULL) goto Catch; 866 if ((c->envv = NEW(const char *, envc + 1)) == NULL) goto Catch; 867 initVectorFromBlock(c->envv, penvBlock, envc); 868 } 869 870 if (dir != NULL) { 871 if ((c->pdir = getBytes(env, dir)) == NULL) goto Catch; 872 } 873 874 assert(std_fds != NULL); 875 fds = (*env)->GetIntArrayElements(env, std_fds, NULL); 876 if (fds == NULL) goto Catch; 877 878 if ((fds[0] == -1 && pipe(in) < 0) || 879 (fds[1] == -1 && pipe(out) < 0) || 880 (fds[2] == -1 && pipe(err) < 0) || 881 (pipe(fail) < 0)) { 882 throwIOException(env, errno, "Bad file descriptor"); 883 goto Catch; 884 } 885 c->fds[0] = fds[0]; 886 c->fds[1] = fds[1]; 887 c->fds[2] = fds[2]; 888 889 copyPipe(in, c->in); 890 copyPipe(out, c->out); 891 copyPipe(err, c->err); 892 copyPipe(fail, c->fail); 893 894 c->redirectErrorStream = redirectErrorStream; 895 896 resultPid = startChild(c); 897 assert(resultPid != 0); 898 899 if (resultPid < 0) { 900 throwIOException(env, errno, START_CHILD_SYSTEM_CALL " failed"); 901 goto Catch; 902 } 903 904 restartableClose(fail[1]); fail[1] = -1; /* See: WhyCantJohnnyExec */ 905 906 switch (readFully(fail[0], &errnum, sizeof(errnum))) { 907 case 0: break; /* Exec succeeded */ 908 case sizeof(errnum): 909 waitpid(resultPid, NULL, 0); 910 throwIOException(env, errnum, "Exec failed"); 911 goto Catch; 912 default: 913 throwIOException(env, errno, "Read failed"); 914 goto Catch; 915 } 916 917 fds[0] = (in [1] != -1) ? in [1] : -1; 918 fds[1] = (out[0] != -1) ? out[0] : -1; 919 fds[2] = (err[0] != -1) ? err[0] : -1; 920 921 Finally: 922 #if START_CHILD_USE_CLONE 923 free(c->clone_stack); 924 #endif 925 926 /* Always clean up the child's side of the pipes */ 927 closeSafely(in [0]); 928 closeSafely(out[1]); 929 closeSafely(err[1]); 930 931 /* Always clean up fail descriptors */ 932 closeSafely(fail[0]); 933 closeSafely(fail[1]); 934 935 releaseBytes(env, prog, pprog); 936 releaseBytes(env, argBlock, pargBlock); 937 releaseBytes(env, envBlock, penvBlock); 938 releaseBytes(env, dir, c->pdir); 939 940 free(c->argv); 941 free(c->envv); 942 free(c); 943 944 if (fds != NULL) 945 (*env)->ReleaseIntArrayElements(env, std_fds, fds, 0); 946 947 return resultPid; 948 949 Catch: 950 /* Clean up the parent's side of the pipes in case of failure only */ 951 closeSafely(in [1]); 952 closeSafely(out[0]); 953 closeSafely(err[0]); 954 goto Finally; 955 } 956 957 JNIEXPORT void JNICALL 958 Java_java_lang_UNIXProcess_destroyProcess(JNIEnv *env, jobject junk, jint pid) 959 { 960 kill(pid, SIGTERM); 961 }