rev 57914 : 8238380: java.base/unix/native/libjava/childproc.c "multiple definition" link errors with GCC10
Summary: Fixed libjava/childproc.o link errors caused by GCC10 default -fno-common
Reviewed-by: alanb
1 /*
2 * Copyright (c) 2013, 2019, 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 #include <dirent.h>
27 #include <errno.h>
28 #include <fcntl.h>
29 #include <stdio.h>
30 #include <stdlib.h>
31 #include <string.h>
32 #include <unistd.h>
33 #include <limits.h>
34
35 #include "childproc.h"
36
37 const char * const *parentPathv;
38
39 ssize_t
40 restartableWrite(int fd, const void *buf, size_t count)
41 {
42 ssize_t result;
43 RESTARTABLE(write(fd, buf, count), result);
44 return result;
45 }
46
47 int
48 restartableDup2(int fd_from, int fd_to)
49 {
50 int err;
51 RESTARTABLE(dup2(fd_from, fd_to), err);
52 return err;
53 }
54
55 int
56 closeSafely(int fd)
57 {
58 return (fd == -1) ? 0 : close(fd);
59 }
60
61 int
62 isAsciiDigit(char c)
63 {
64 return c >= '0' && c <= '9';
65 }
66
67 #if defined(_AIX)
68 /* AIX does not understand '/proc/self' - it requires the real process ID */
69 #define FD_DIR aix_fd_dir
70 #define DIR DIR64
71 #define dirent dirent64
72 #define opendir opendir64
73 #define readdir readdir64
74 #define closedir closedir64
75 #elif defined(_ALLBSD_SOURCE)
76 #define FD_DIR "/dev/fd"
77 #else
78 #define FD_DIR "/proc/self/fd"
79 #endif
80
81 int
82 closeDescriptors(void)
83 {
84 DIR *dp;
85 struct dirent *dirp;
86 int from_fd = FAIL_FILENO + 1;
87
88 /* We're trying to close all file descriptors, but opendir() might
89 * itself be implemented using a file descriptor, and we certainly
90 * don't want to close that while it's in use. We assume that if
91 * opendir() is implemented using a file descriptor, then it uses
92 * the lowest numbered file descriptor, just like open(). So we
93 * close a couple explicitly. */
94
95 close(from_fd); /* for possible use by opendir() */
96 close(from_fd + 1); /* another one for good luck */
97
98 #if defined(_AIX)
99 /* AIX does not understand '/proc/self' - it requires the real process ID */
100 char aix_fd_dir[32]; /* the pid has at most 19 digits */
101 snprintf(aix_fd_dir, 32, "/proc/%d/fd", getpid());
102 #endif
103
104 if ((dp = opendir(FD_DIR)) == NULL)
105 return 0;
106
107 while ((dirp = readdir(dp)) != NULL) {
108 int fd;
109 if (isAsciiDigit(dirp->d_name[0]) &&
110 (fd = strtol(dirp->d_name, NULL, 10)) >= from_fd + 2)
111 close(fd);
112 }
113
114 closedir(dp);
115
116 return 1;
117 }
118
119 int
120 moveDescriptor(int fd_from, int fd_to)
121 {
122 if (fd_from != fd_to) {
123 if ((restartableDup2(fd_from, fd_to) == -1) ||
124 (close(fd_from) == -1))
125 return -1;
126 }
127 return 0;
128 }
129
130 int
131 magicNumber() {
132 return 43110;
133 }
134
135 /*
136 * Reads nbyte bytes from file descriptor fd into buf,
137 * The read operation is retried in case of EINTR or partial reads.
138 *
139 * Returns number of bytes read (normally nbyte, but may be less in
140 * case of EOF). In case of read errors, returns -1 and sets errno.
141 */
142 ssize_t
143 readFully(int fd, void *buf, size_t nbyte)
144 {
145 ssize_t remaining = nbyte;
146 for (;;) {
147 ssize_t n = read(fd, buf, remaining);
148 if (n == 0) {
149 return nbyte - remaining;
150 } else if (n > 0) {
151 remaining -= n;
152 if (remaining <= 0)
153 return nbyte;
154 /* We were interrupted in the middle of reading the bytes.
155 * Unlikely, but possible. */
156 buf = (void *) (((char *)buf) + n);
157 } else if (errno == EINTR) {
158 /* Strange signals like SIGJVM1 are possible at any time.
159 * See http://www.dreamsongs.com/WorseIsBetter.html */
160 } else {
161 return -1;
162 }
163 }
164 }
165
166 void
167 initVectorFromBlock(const char**vector, const char* block, int count)
168 {
169 int i;
170 const char *p;
171 for (i = 0, p = block; i < count; i++) {
172 /* Invariant: p always points to the start of a C string. */
173 vector[i] = p;
174 while (*(p++));
175 }
176 vector[count] = NULL;
177 }
178
179 /**
180 * Exec FILE as a traditional Bourne shell script (i.e. one without #!).
181 * If we could do it over again, we would probably not support such an ancient
182 * misfeature, but compatibility wins over sanity. The original support for
183 * this was imported accidentally from execvp().
184 */
185 void
186 execve_as_traditional_shell_script(const char *file,
187 const char *argv[],
188 const char *const envp[])
189 {
190 /* Use the extra word of space provided for us in argv by caller. */
191 const char *argv0 = argv[0];
192 const char *const *end = argv;
193 while (*end != NULL)
194 ++end;
195 memmove(argv+2, argv+1, (end-argv) * sizeof(*end));
196 argv[0] = "/bin/sh";
197 argv[1] = file;
198 execve(argv[0], (char **) argv, (char **) envp);
199 /* Can't even exec /bin/sh? Big trouble, but let's soldier on... */
200 memmove(argv+1, argv+2, (end-argv) * sizeof(*end));
201 argv[0] = argv0;
202 }
203
204 /**
205 * Like execve(2), except that in case of ENOEXEC, FILE is assumed to
206 * be a shell script and the system default shell is invoked to run it.
207 */
208 void
209 execve_with_shell_fallback(int mode, const char *file,
210 const char *argv[],
211 const char *const envp[])
212 {
213 if (mode == MODE_CLONE || mode == MODE_VFORK) {
214 /* shared address space; be very careful. */
215 execve(file, (char **) argv, (char **) envp);
216 if (errno == ENOEXEC)
217 execve_as_traditional_shell_script(file, argv, envp);
218 } else {
219 /* unshared address space; we can mutate environ. */
220 environ = (char **) envp;
221 execvp(file, (char **) argv);
222 }
223 }
224
225 /**
226 * 'execvpe' should have been included in the Unix standards,
227 * and is a GNU extension in glibc 2.10.
228 *
229 * JDK_execvpe is identical to execvp, except that the child environment is
230 * specified via the 3rd argument instead of being inherited from environ.
231 */
232 void
233 JDK_execvpe(int mode, const char *file,
234 const char *argv[],
235 const char *const envp[])
236 {
237 if (envp == NULL || (char **) envp == environ) {
238 execvp(file, (char **) argv);
239 return;
240 }
241
242 if (*file == '\0') {
243 errno = ENOENT;
244 return;
245 }
246
247 if (strchr(file, '/') != NULL) {
248 execve_with_shell_fallback(mode, file, argv, envp);
249 } else {
250 /* We must search PATH (parent's, not child's) */
251 char expanded_file[PATH_MAX];
252 int filelen = strlen(file);
253 int sticky_errno = 0;
254 const char * const * dirs;
255 for (dirs = parentPathv; *dirs; dirs++) {
256 const char * dir = *dirs;
257 int dirlen = strlen(dir);
258 if (filelen + dirlen + 2 >= PATH_MAX) {
259 errno = ENAMETOOLONG;
260 continue;
261 }
262 memcpy(expanded_file, dir, dirlen);
263 if (expanded_file[dirlen - 1] != '/')
264 expanded_file[dirlen++] = '/';
265 memcpy(expanded_file + dirlen, file, filelen);
266 expanded_file[dirlen + filelen] = '\0';
267 execve_with_shell_fallback(mode, expanded_file, argv, envp);
268 /* There are 3 responses to various classes of errno:
269 * return immediately, continue (especially for ENOENT),
270 * or continue with "sticky" errno.
271 *
272 * From exec(3):
273 *
274 * If permission is denied for a file (the attempted
275 * execve returned EACCES), these functions will continue
276 * searching the rest of the search path. If no other
277 * file is found, however, they will return with the
278 * global variable errno set to EACCES.
279 */
280 switch (errno) {
281 case EACCES:
282 sticky_errno = errno;
283 /* FALLTHRU */
284 case ENOENT:
285 case ENOTDIR:
286 #ifdef ELOOP
287 case ELOOP:
288 #endif
289 #ifdef ESTALE
290 case ESTALE:
291 #endif
292 #ifdef ENODEV
293 case ENODEV:
294 #endif
295 #ifdef ETIMEDOUT
296 case ETIMEDOUT:
297 #endif
298 break; /* Try other directories in PATH */
299 default:
300 return;
301 }
302 }
303 if (sticky_errno != 0)
304 errno = sticky_errno;
305 }
306 }
307
308 /**
309 * Child process after a successful fork().
310 * This function must not return, and must be prepared for either all
311 * of its address space to be shared with its parent, or to be a copy.
312 * It must not modify global variables such as "environ".
313 */
314 int
315 childProcess(void *arg)
316 {
317 const ChildStuff* p = (const ChildStuff*) arg;
318 int fail_pipe_fd = p->fail[1];
319
320 if (p->sendAlivePing) {
321 /* Child shall signal aliveness to parent at the very first
322 * moment. */
323 int code = CHILD_IS_ALIVE;
324 restartableWrite(fail_pipe_fd, &code, sizeof(code));
325 }
326
327 /* Close the parent sides of the pipes.
328 Closing pipe fds here is redundant, since closeDescriptors()
329 would do it anyways, but a little paranoia is a good thing. */
330 if ((closeSafely(p->in[1]) == -1) ||
331 (closeSafely(p->out[0]) == -1) ||
332 (closeSafely(p->err[0]) == -1) ||
333 (closeSafely(p->childenv[0]) == -1) ||
334 (closeSafely(p->childenv[1]) == -1) ||
335 (closeSafely(p->fail[0]) == -1))
336 goto WhyCantJohnnyExec;
337
338 /* Give the child sides of the pipes the right fileno's. */
339 /* Note: it is possible for in[0] == 0 */
340 if ((moveDescriptor(p->in[0] != -1 ? p->in[0] : p->fds[0],
341 STDIN_FILENO) == -1) ||
342 (moveDescriptor(p->out[1]!= -1 ? p->out[1] : p->fds[1],
343 STDOUT_FILENO) == -1))
344 goto WhyCantJohnnyExec;
345
346 if (p->redirectErrorStream) {
347 if ((closeSafely(p->err[1]) == -1) ||
348 (restartableDup2(STDOUT_FILENO, STDERR_FILENO) == -1))
349 goto WhyCantJohnnyExec;
350 } else {
351 if (moveDescriptor(p->err[1] != -1 ? p->err[1] : p->fds[2],
352 STDERR_FILENO) == -1)
353 goto WhyCantJohnnyExec;
354 }
355
356 if (moveDescriptor(fail_pipe_fd, FAIL_FILENO) == -1)
357 goto WhyCantJohnnyExec;
358
359 /* We moved the fail pipe fd */
360 fail_pipe_fd = FAIL_FILENO;
361
362 /* close everything */
363 if (closeDescriptors() == 0) { /* failed, close the old way */
364 int max_fd = (int)sysconf(_SC_OPEN_MAX);
365 int fd;
366 for (fd = FAIL_FILENO + 1; fd < max_fd; fd++)
367 if (close(fd) == -1 && errno != EBADF)
368 goto WhyCantJohnnyExec;
369 }
370
371 /* change to the new working directory */
372 if (p->pdir != NULL && chdir(p->pdir) < 0)
373 goto WhyCantJohnnyExec;
374
375 if (fcntl(FAIL_FILENO, F_SETFD, FD_CLOEXEC) == -1)
376 goto WhyCantJohnnyExec;
377
378 JDK_execvpe(p->mode, p->argv[0], p->argv, p->envv);
379
380 WhyCantJohnnyExec:
381 /* We used to go to an awful lot of trouble to predict whether the
382 * child would fail, but there is no reliable way to predict the
383 * success of an operation without *trying* it, and there's no way
384 * to try a chdir or exec in the parent. Instead, all we need is a
385 * way to communicate any failure back to the parent. Easy; we just
386 * send the errno back to the parent over a pipe in case of failure.
387 * The tricky thing is, how do we communicate the *success* of exec?
388 * We use FD_CLOEXEC together with the fact that a read() on a pipe
389 * yields EOF when the write ends (we have two of them!) are closed.
390 */
391 {
392 int errnum = errno;
393 restartableWrite(fail_pipe_fd, &errnum, sizeof(errnum));
394 }
395 close(fail_pipe_fd);
396 _exit(-1);
397 return 0; /* Suppress warning "no return value from function" */
398 }
--- EOF ---