Mercurial > hg > octave-lojdl > gnulib-hg
annotate lib/savewd.c @ 7408:e23b1333a117
[lib/ChangeLog]
* fcntl_.h (O_NOFOLLOW): Don't depend on O_NOFOLLOW_IS_INEFFECTIVE;
we now test for that separately.
* fts.c (fts_safe_changedir): Inspect HAVE_WORKING_O_NOFOLLOW
rather than O_NOFOLLOW, when testing whether it's possible to
avoid a race condition reliably.
* savewd.c (savewd_chdir): Likewise.
[m4/ChangeLog]
* fcntl_h.m4 (gl_FCNTL_H): Define HAVE_WORKING_O_NOFOLLOW instead
of O_NOFOLLOW_IS_INEFFECTIVE. Define HAVE_WORKING_O_NOATIME if
O_NOATIME works.
| author | Paul Eggert <eggert@cs.ucla.edu> |
|---|---|
| date | Thu, 05 Oct 2006 21:38:10 +0000 |
| parents | 4a6efdc58ddb |
| children | 5166dec344af |
| rev | line source |
|---|---|
| 7315 | 1 /* Save and restore the working directory, possibly using a child process. |
| 2 | |
| 3 Copyright (C) 2006 Free Software Foundation, Inc. | |
| 4 | |
| 5 This program is free software; you can redistribute it and/or modify | |
| 6 it under the terms of the GNU General Public License as published by | |
| 7 the Free Software Foundation; either version 2, or (at your option) | |
| 8 any later version. | |
| 9 | |
| 10 This program is distributed in the hope that it will be useful, | |
| 11 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 13 GNU General Public License for more details. | |
| 14 | |
| 15 You should have received a copy of the GNU General Public License | |
| 16 along with this program; if not, write to the Free Software Foundation, | |
| 17 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ | |
| 18 | |
| 19 /* Written by Paul Eggert. */ | |
| 20 | |
| 21 #include <config.h> | |
| 22 | |
| 23 #include "savewd.h" | |
| 24 | |
| 25 #include <assert.h> | |
| 26 #include <errno.h> | |
| 27 #include <fcntl.h> | |
| 7375 | 28 #include <signal.h> |
| 7315 | 29 #include <stdbool.h> |
| 30 #include <sys/types.h> | |
| 31 #include <sys/wait.h> | |
| 32 #include <unistd.h> | |
| 33 | |
| 34 #include "exit.h" | |
| 35 #include "dirname.h" | |
| 36 #include "fcntl-safer.h" | |
| 37 | |
| 38 | |
| 39 /* Save the working directory into *WD, if it hasn't been saved | |
| 40 already. Return true if a child has been forked to do the real | |
| 41 work. */ | |
| 42 static bool | |
| 43 savewd_save (struct savewd *wd) | |
| 44 { | |
| 45 switch (wd->state) | |
| 46 { | |
| 47 case INITIAL_STATE: | |
| 48 /* Save the working directory, or prepare to fall back if possible. */ | |
| 49 { | |
| 50 int fd = open_safer (".", O_RDONLY); | |
| 51 if (0 <= fd) | |
| 52 { | |
| 53 wd->state = FD_STATE; | |
| 54 wd->val.fd = fd; | |
| 55 break; | |
| 56 } | |
| 57 if (errno != EACCES) | |
| 58 { | |
| 59 wd->state = ERROR_STATE; | |
| 60 wd->val.errnum = errno; | |
| 61 break; | |
| 62 } | |
| 63 } | |
| 64 wd->state = FORKING_STATE; | |
| 65 wd->val.child = -1; | |
| 66 /* Fall through. */ | |
| 67 case FORKING_STATE: | |
| 68 if (wd->val.child < 0) | |
| 69 { | |
| 70 /* "Save" the initial working directory by forking a new | |
| 71 subprocess that will attempt all the work from the chdir | |
| 72 until until the next savewd_restore. */ | |
| 73 wd->val.child = fork (); | |
| 74 if (wd->val.child != 0) | |
| 75 { | |
| 76 if (0 < wd->val.child) | |
| 77 return true; | |
| 78 wd->state = ERROR_STATE; | |
| 79 wd->val.errnum = errno; | |
| 80 } | |
| 81 } | |
| 82 break; | |
| 83 | |
| 84 case FD_STATE: | |
| 85 case FD_POST_CHDIR_STATE: | |
| 86 case ERROR_STATE: | |
| 87 case FINAL_STATE: | |
| 88 break; | |
| 89 | |
| 90 default: | |
| 91 assert (false); | |
| 92 } | |
| 93 | |
| 94 return false; | |
| 95 } | |
| 96 | |
| 97 int | |
| 98 savewd_chdir (struct savewd *wd, char const *dir, int options, | |
| 99 int open_result[2]) | |
| 100 { | |
| 101 int fd = -1; | |
| 102 int result = 0; | |
| 103 | |
| 104 /* Open the directory if requested, or if avoiding a race condition | |
| 105 is requested and possible. */ | |
| 7408 | 106 if (open_result |
| 107 || (options & (HAVE_WORKING_O_NOFOLLOW ? SAVEWD_CHDIR_NOFOLLOW : 0))) | |
| 7315 | 108 { |
| 109 fd = open (dir, | |
| 110 (O_RDONLY | O_DIRECTORY | O_NOCTTY | O_NONBLOCK | |
| 111 | (options & SAVEWD_CHDIR_NOFOLLOW ? O_NOFOLLOW : 0))); | |
| 112 | |
| 113 if (open_result) | |
| 114 { | |
| 115 open_result[0] = fd; | |
| 116 open_result[1] = errno; | |
| 117 } | |
| 118 | |
| 119 if (fd < 0 && (errno != EACCES || (options & SAVEWD_CHDIR_READABLE))) | |
| 120 result = -1; | |
| 121 } | |
| 122 | |
| 123 if (result == 0 && ! (0 <= fd && options & SAVEWD_CHDIR_SKIP_READABLE)) | |
| 124 { | |
| 125 if (savewd_save (wd)) | |
| 126 { | |
| 127 open_result = NULL; | |
| 128 result = -2; | |
| 129 } | |
| 130 else | |
| 131 { | |
| 132 result = (fd < 0 ? chdir (dir) : fchdir (fd)); | |
| 133 | |
| 134 if (result == 0) | |
| 135 switch (wd->state) | |
| 136 { | |
| 137 case FD_STATE: | |
| 138 wd->state = FD_POST_CHDIR_STATE; | |
| 139 break; | |
| 140 | |
| 141 case ERROR_STATE: | |
| 142 case FD_POST_CHDIR_STATE: | |
| 143 case FINAL_STATE: | |
| 144 break; | |
| 145 | |
| 146 case FORKING_STATE: | |
| 147 assert (wd->val.child == 0); | |
| 148 break; | |
| 149 | |
| 150 default: | |
| 151 assert (false); | |
| 152 } | |
| 153 } | |
| 154 } | |
| 155 | |
| 156 if (0 <= fd && ! open_result) | |
| 157 { | |
| 158 int e = errno; | |
| 159 close (fd); | |
| 160 errno = e; | |
| 161 } | |
| 162 | |
| 163 return result; | |
| 164 } | |
| 165 | |
| 166 int | |
| 167 savewd_restore (struct savewd *wd, int status) | |
| 168 { | |
| 169 switch (wd->state) | |
| 170 { | |
| 171 case INITIAL_STATE: | |
| 172 case FD_STATE: | |
| 173 /* The working directory is the desired directory, so there's no | |
| 174 work to do. */ | |
| 175 break; | |
| 176 | |
| 177 case FD_POST_CHDIR_STATE: | |
| 178 /* Restore the working directory using fchdir. */ | |
| 179 if (fchdir (wd->val.fd) == 0) | |
| 180 { | |
| 181 wd->state = FD_STATE; | |
| 182 break; | |
| 183 } | |
| 184 else | |
| 185 { | |
| 186 int chdir_errno = errno; | |
| 187 close (wd->val.fd); | |
| 188 wd->state = ERROR_STATE; | |
| 189 wd->val.errnum = chdir_errno; | |
| 190 } | |
| 191 /* Fall through. */ | |
| 192 case ERROR_STATE: | |
| 193 /* Report an error if asked to restore the working directory. */ | |
| 194 errno = wd->val.errnum; | |
| 195 return -1; | |
| 196 | |
| 197 case FORKING_STATE: | |
| 198 /* "Restore" the working directory by waiting for the subprocess | |
| 199 to finish. */ | |
| 200 { | |
| 201 pid_t child = wd->val.child; | |
| 202 if (child == 0) | |
| 203 _exit (status); | |
| 204 if (0 < child) | |
| 205 { | |
|
7317
251167cff509
* savewd.c (savewd_restore): Don't shadow: s/status/child_status/.
Jim Meyering <jim@meyering.net>
parents:
7315
diff
changeset
|
206 int child_status; |
|
251167cff509
* savewd.c (savewd_restore): Don't shadow: s/status/child_status/.
Jim Meyering <jim@meyering.net>
parents:
7315
diff
changeset
|
207 while (waitpid (child, &child_status, 0) < 0) |
| 7315 | 208 assert (errno == EINTR); |
| 209 wd->val.child = -1; | |
|
7317
251167cff509
* savewd.c (savewd_restore): Don't shadow: s/status/child_status/.
Jim Meyering <jim@meyering.net>
parents:
7315
diff
changeset
|
210 if (! WIFEXITED (child_status)) |
|
251167cff509
* savewd.c (savewd_restore): Don't shadow: s/status/child_status/.
Jim Meyering <jim@meyering.net>
parents:
7315
diff
changeset
|
211 raise (WTERMSIG (child_status)); |
|
251167cff509
* savewd.c (savewd_restore): Don't shadow: s/status/child_status/.
Jim Meyering <jim@meyering.net>
parents:
7315
diff
changeset
|
212 return WEXITSTATUS (child_status); |
| 7315 | 213 } |
| 214 } | |
| 215 break; | |
| 216 | |
| 217 default: | |
| 218 assert (false); | |
| 219 } | |
| 220 | |
| 221 return 0; | |
| 222 } | |
| 223 | |
| 224 void | |
| 225 savewd_finish (struct savewd *wd) | |
| 226 { | |
| 227 switch (wd->state) | |
| 228 { | |
| 229 case INITIAL_STATE: | |
| 230 case ERROR_STATE: | |
| 231 break; | |
| 232 | |
| 233 case FD_STATE: | |
| 234 case FD_POST_CHDIR_STATE: | |
| 235 close (wd->val.fd); | |
| 236 break; | |
| 237 | |
| 238 case FORKING_STATE: | |
| 239 assert (wd->val.child < 0); | |
| 240 break; | |
| 241 | |
| 242 default: | |
| 243 assert (false); | |
| 244 } | |
| 245 | |
| 246 wd->state = FINAL_STATE; | |
| 247 } | |
| 248 | |
| 249 /* Return true if the actual work is currently being done by a | |
| 250 subprocess. | |
| 251 | |
| 252 A true return means that the caller and the subprocess should | |
| 253 resynchronize later with savewd_restore, using only their own | |
| 254 memory to decide when to resynchronize; they should not consult the | |
| 255 file system to decide, because that might lead to race conditions. | |
| 256 This is why savewd_chdir is broken out into another function; | |
| 257 savewd_chdir's callers _can_ inspect the file system to decide | |
| 258 whether to call savewd_chdir. */ | |
| 259 static inline bool | |
| 260 savewd_delegating (struct savewd const *wd) | |
| 261 { | |
| 262 return wd->state == FORKING_STATE && 0 < wd->val.child; | |
| 263 } | |
| 264 | |
| 265 int | |
| 266 savewd_process_files (int n_files, char **file, | |
| 267 int (*act) (char *, struct savewd *, void *), | |
| 268 void *options) | |
| 269 { | |
| 270 int i = 0; | |
| 271 int last_relative; | |
| 272 int exit_status = EXIT_SUCCESS; | |
| 273 struct savewd wd; | |
| 274 savewd_init (&wd); | |
| 275 | |
| 276 for (last_relative = n_files - 1; 0 <= last_relative; last_relative--) | |
| 277 if (! IS_ABSOLUTE_FILE_NAME (file[last_relative])) | |
| 278 break; | |
| 279 | |
| 280 for (; i < last_relative; i++) | |
| 281 { | |
| 282 if (! savewd_delegating (&wd)) | |
| 283 { | |
| 284 int s = act (file[i], &wd, options); | |
| 285 if (exit_status < s) | |
| 286 exit_status = s; | |
| 287 } | |
| 288 | |
| 289 if (! IS_ABSOLUTE_FILE_NAME (file[i + 1])) | |
| 290 { | |
| 291 int r = savewd_restore (&wd, exit_status); | |
| 292 if (exit_status < r) | |
| 293 exit_status = r; | |
| 294 } | |
| 295 } | |
| 296 | |
| 297 savewd_finish (&wd); | |
| 298 | |
| 299 for (; i < n_files; i++) | |
| 300 { | |
| 301 int s = act (file[i], &wd, options); | |
| 302 if (exit_status < s) | |
| 303 exit_status = s; | |
| 304 } | |
| 305 | |
| 306 return exit_status; | |
| 307 } |