| 1 | /* Fork a Unix child process, and set up to debug it, for GDB. |
| 2 | |
| 3 | Copyright (C) 1990-2013 Free Software Foundation, Inc. |
| 4 | |
| 5 | Contributed by Cygnus Support. |
| 6 | |
| 7 | This file is part of GDB. |
| 8 | |
| 9 | This program is free software; you can redistribute it and/or modify |
| 10 | it under the terms of the GNU General Public License as published by |
| 11 | the Free Software Foundation; either version 3 of the License, or |
| 12 | (at your option) any later version. |
| 13 | |
| 14 | This program is distributed in the hope that it will be useful, |
| 15 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 16 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 17 | GNU General Public License for more details. |
| 18 | |
| 19 | You should have received a copy of the GNU General Public License |
| 20 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
| 21 | |
| 22 | #include "defs.h" |
| 23 | #include <string.h> |
| 24 | #include "inferior.h" |
| 25 | #include "terminal.h" |
| 26 | #include "target.h" |
| 27 | #include "gdb_wait.h" |
| 28 | #include "gdb_vfork.h" |
| 29 | #include "gdbcore.h" |
| 30 | #include "terminal.h" |
| 31 | #include "gdbthread.h" |
| 32 | #include "command.h" /* for dont_repeat () */ |
| 33 | #include "gdbcmd.h" |
| 34 | #include "solib.h" |
| 35 | #include "filestuff.h" |
| 36 | |
| 37 | #include <signal.h> |
| 38 | |
| 39 | /* This just gets used as a default if we can't find SHELL. */ |
| 40 | #define SHELL_FILE "/bin/sh" |
| 41 | |
| 42 | extern char **environ; |
| 43 | |
| 44 | static char *exec_wrapper; |
| 45 | |
| 46 | /* Break up SCRATCH into an argument vector suitable for passing to |
| 47 | execvp and store it in ARGV. E.g., on "run a b c d" this routine |
| 48 | would get as input the string "a b c d", and as output it would |
| 49 | fill in ARGV with the four arguments "a", "b", "c", "d". */ |
| 50 | |
| 51 | static void |
| 52 | breakup_args (char *scratch, char **argv) |
| 53 | { |
| 54 | char *cp = scratch, *tmp; |
| 55 | |
| 56 | for (;;) |
| 57 | { |
| 58 | /* Scan past leading separators */ |
| 59 | while (*cp == ' ' || *cp == '\t' || *cp == '\n') |
| 60 | cp++; |
| 61 | |
| 62 | /* Break if at end of string. */ |
| 63 | if (*cp == '\0') |
| 64 | break; |
| 65 | |
| 66 | /* Take an arg. */ |
| 67 | *argv++ = cp; |
| 68 | |
| 69 | /* Scan for next arg separator. */ |
| 70 | tmp = strchr (cp, ' '); |
| 71 | if (tmp == NULL) |
| 72 | tmp = strchr (cp, '\t'); |
| 73 | if (tmp == NULL) |
| 74 | tmp = strchr (cp, '\n'); |
| 75 | |
| 76 | /* No separators => end of string => break. */ |
| 77 | if (tmp == NULL) |
| 78 | break; |
| 79 | cp = tmp; |
| 80 | |
| 81 | /* Replace the separator with a terminator. */ |
| 82 | *cp++ = '\0'; |
| 83 | } |
| 84 | |
| 85 | /* Null-terminate the vector. */ |
| 86 | *argv = NULL; |
| 87 | } |
| 88 | |
| 89 | /* When executing a command under the given shell, return non-zero if |
| 90 | the '!' character should be escaped when embedded in a quoted |
| 91 | command-line argument. */ |
| 92 | |
| 93 | static int |
| 94 | escape_bang_in_quoted_argument (const char *shell_file) |
| 95 | { |
| 96 | const int shell_file_len = strlen (shell_file); |
| 97 | |
| 98 | /* Bang should be escaped only in C Shells. For now, simply check |
| 99 | that the shell name ends with 'csh', which covers at least csh |
| 100 | and tcsh. This should be good enough for now. */ |
| 101 | |
| 102 | if (shell_file_len < 3) |
| 103 | return 0; |
| 104 | |
| 105 | if (shell_file[shell_file_len - 3] == 'c' |
| 106 | && shell_file[shell_file_len - 2] == 's' |
| 107 | && shell_file[shell_file_len - 1] == 'h') |
| 108 | return 1; |
| 109 | |
| 110 | return 0; |
| 111 | } |
| 112 | |
| 113 | /* Start an inferior Unix child process and sets inferior_ptid to its |
| 114 | pid. EXEC_FILE is the file to run. ALLARGS is a string containing |
| 115 | the arguments to the program. ENV is the environment vector to |
| 116 | pass. SHELL_FILE is the shell file, or NULL if we should pick |
| 117 | one. EXEC_FUN is the exec(2) function to use, or NULL for the default |
| 118 | one. */ |
| 119 | |
| 120 | /* This function is NOT reentrant. Some of the variables have been |
| 121 | made static to ensure that they survive the vfork call. */ |
| 122 | |
| 123 | int |
| 124 | fork_inferior (char *exec_file_arg, char *allargs, char **env, |
| 125 | void (*traceme_fun) (void), void (*init_trace_fun) (int), |
| 126 | void (*pre_trace_fun) (void), char *shell_file_arg, |
| 127 | void (*exec_fun)(const char *file, char * const *argv, |
| 128 | char * const *env)) |
| 129 | { |
| 130 | int pid; |
| 131 | static char default_shell_file[] = SHELL_FILE; |
| 132 | /* Set debug_fork then attach to the child while it sleeps, to debug. */ |
| 133 | static int debug_fork = 0; |
| 134 | /* This is set to the result of setpgrp, which if vforked, will be visible |
| 135 | to you in the parent process. It's only used by humans for debugging. */ |
| 136 | static int debug_setpgrp = 657473; |
| 137 | static char *shell_file; |
| 138 | static char *exec_file; |
| 139 | char **save_our_env; |
| 140 | int shell = 0; |
| 141 | static char **argv; |
| 142 | const char *inferior_io_terminal = get_inferior_io_terminal (); |
| 143 | struct inferior *inf; |
| 144 | int i; |
| 145 | int save_errno; |
| 146 | |
| 147 | /* If no exec file handed to us, get it from the exec-file command |
| 148 | -- with a good, common error message if none is specified. */ |
| 149 | exec_file = exec_file_arg; |
| 150 | if (exec_file == 0) |
| 151 | exec_file = get_exec_file (1); |
| 152 | |
| 153 | /* 'startup_with_shell' is declared in inferior.h and bound to the |
| 154 | "set startup-with-shell" option. If 0, we'll just do a |
| 155 | fork/exec, no shell, so don't bother figuring out what shell. */ |
| 156 | shell_file = shell_file_arg; |
| 157 | if (startup_with_shell) |
| 158 | { |
| 159 | /* Figure out what shell to start up the user program under. */ |
| 160 | if (shell_file == NULL) |
| 161 | shell_file = getenv ("SHELL"); |
| 162 | if (shell_file == NULL) |
| 163 | shell_file = default_shell_file; |
| 164 | shell = 1; |
| 165 | } |
| 166 | |
| 167 | if (!shell) |
| 168 | { |
| 169 | /* We're going to call execvp. Create argument vector. |
| 170 | Calculate an upper bound on the length of the vector by |
| 171 | assuming that every other character is a separate |
| 172 | argument. */ |
| 173 | int argc = (strlen (allargs) + 1) / 2 + 2; |
| 174 | |
| 175 | argv = (char **) alloca (argc * sizeof (*argv)); |
| 176 | argv[0] = exec_file; |
| 177 | breakup_args (allargs, &argv[1]); |
| 178 | } |
| 179 | else |
| 180 | { |
| 181 | /* We're going to call a shell. */ |
| 182 | char *shell_command; |
| 183 | int len; |
| 184 | char *p; |
| 185 | int need_to_quote; |
| 186 | const int escape_bang = escape_bang_in_quoted_argument (shell_file); |
| 187 | |
| 188 | /* Multiplying the length of exec_file by 4 is to account for the |
| 189 | fact that it may expand when quoted; it is a worst-case number |
| 190 | based on every character being '. */ |
| 191 | len = 5 + 4 * strlen (exec_file) + 1 + strlen (allargs) + 1 + /*slop */ 12; |
| 192 | if (exec_wrapper) |
| 193 | len += strlen (exec_wrapper) + 1; |
| 194 | |
| 195 | shell_command = (char *) alloca (len); |
| 196 | shell_command[0] = '\0'; |
| 197 | |
| 198 | strcat (shell_command, "exec "); |
| 199 | |
| 200 | /* Add any exec wrapper. That may be a program name with arguments, so |
| 201 | the user must handle quoting. */ |
| 202 | if (exec_wrapper) |
| 203 | { |
| 204 | strcat (shell_command, exec_wrapper); |
| 205 | strcat (shell_command, " "); |
| 206 | } |
| 207 | |
| 208 | /* Now add exec_file, quoting as necessary. */ |
| 209 | |
| 210 | /* Quoting in this style is said to work with all shells. But |
| 211 | csh on IRIX 4.0.1 can't deal with it. So we only quote it if |
| 212 | we need to. */ |
| 213 | p = exec_file; |
| 214 | while (1) |
| 215 | { |
| 216 | switch (*p) |
| 217 | { |
| 218 | case '\'': |
| 219 | case '!': |
| 220 | case '"': |
| 221 | case '(': |
| 222 | case ')': |
| 223 | case '$': |
| 224 | case '&': |
| 225 | case ';': |
| 226 | case '<': |
| 227 | case '>': |
| 228 | case ' ': |
| 229 | case '\n': |
| 230 | case '\t': |
| 231 | need_to_quote = 1; |
| 232 | goto end_scan; |
| 233 | |
| 234 | case '\0': |
| 235 | need_to_quote = 0; |
| 236 | goto end_scan; |
| 237 | |
| 238 | default: |
| 239 | break; |
| 240 | } |
| 241 | ++p; |
| 242 | } |
| 243 | end_scan: |
| 244 | if (need_to_quote) |
| 245 | { |
| 246 | strcat (shell_command, "'"); |
| 247 | for (p = exec_file; *p != '\0'; ++p) |
| 248 | { |
| 249 | if (*p == '\'') |
| 250 | strcat (shell_command, "'\\''"); |
| 251 | else if (*p == '!' && escape_bang) |
| 252 | strcat (shell_command, "\\!"); |
| 253 | else |
| 254 | strncat (shell_command, p, 1); |
| 255 | } |
| 256 | strcat (shell_command, "'"); |
| 257 | } |
| 258 | else |
| 259 | strcat (shell_command, exec_file); |
| 260 | |
| 261 | strcat (shell_command, " "); |
| 262 | strcat (shell_command, allargs); |
| 263 | |
| 264 | /* If we decided above to start up with a shell, we exec the |
| 265 | shell, "-c" says to interpret the next arg as a shell command |
| 266 | to execute, and this command is "exec <target-program> |
| 267 | <args>". */ |
| 268 | argv = (char **) alloca (4 * sizeof (char *)); |
| 269 | argv[0] = shell_file; |
| 270 | argv[1] = "-c"; |
| 271 | argv[2] = shell_command; |
| 272 | argv[3] = (char *) 0; |
| 273 | } |
| 274 | |
| 275 | /* Retain a copy of our environment variables, since the child will |
| 276 | replace the value of environ and if we're vforked, we have to |
| 277 | restore it. */ |
| 278 | save_our_env = environ; |
| 279 | |
| 280 | /* Tell the terminal handling subsystem what tty we plan to run on; |
| 281 | it will just record the information for later. */ |
| 282 | new_tty_prefork (inferior_io_terminal); |
| 283 | |
| 284 | /* It is generally good practice to flush any possible pending stdio |
| 285 | output prior to doing a fork, to avoid the possibility of both |
| 286 | the parent and child flushing the same data after the fork. */ |
| 287 | gdb_flush (gdb_stdout); |
| 288 | gdb_flush (gdb_stderr); |
| 289 | |
| 290 | /* If there's any initialization of the target layers that must |
| 291 | happen to prepare to handle the child we're about fork, do it |
| 292 | now... */ |
| 293 | if (pre_trace_fun != NULL) |
| 294 | (*pre_trace_fun) (); |
| 295 | |
| 296 | /* Create the child process. Since the child process is going to |
| 297 | exec(3) shortly afterwards, try to reduce the overhead by |
| 298 | calling vfork(2). However, if PRE_TRACE_FUN is non-null, it's |
| 299 | likely that this optimization won't work since there's too much |
| 300 | work to do between the vfork(2) and the exec(3). This is known |
| 301 | to be the case on ttrace(2)-based HP-UX, where some handshaking |
| 302 | between parent and child needs to happen between fork(2) and |
| 303 | exec(2). However, since the parent is suspended in the vforked |
| 304 | state, this doesn't work. Also note that the vfork(2) call might |
| 305 | actually be a call to fork(2) due to the fact that autoconf will |
| 306 | ``#define vfork fork'' on certain platforms. */ |
| 307 | if (pre_trace_fun || debug_fork) |
| 308 | pid = fork (); |
| 309 | else |
| 310 | pid = vfork (); |
| 311 | |
| 312 | if (pid < 0) |
| 313 | perror_with_name (("vfork")); |
| 314 | |
| 315 | if (pid == 0) |
| 316 | { |
| 317 | close_most_fds (); |
| 318 | |
| 319 | if (debug_fork) |
| 320 | sleep (debug_fork); |
| 321 | |
| 322 | /* Create a new session for the inferior process, if necessary. |
| 323 | It will also place the inferior in a separate process group. */ |
| 324 | if (create_tty_session () <= 0) |
| 325 | { |
| 326 | /* No session was created, but we still want to run the inferior |
| 327 | in a separate process group. */ |
| 328 | debug_setpgrp = gdb_setpgid (); |
| 329 | if (debug_setpgrp == -1) |
| 330 | perror (_("setpgrp failed in child")); |
| 331 | } |
| 332 | |
| 333 | /* Ask the tty subsystem to switch to the one we specified |
| 334 | earlier (or to share the current terminal, if none was |
| 335 | specified). */ |
| 336 | new_tty (); |
| 337 | |
| 338 | /* Changing the signal handlers for the inferior after |
| 339 | a vfork can also change them for the superior, so we don't mess |
| 340 | with signals here. See comments in |
| 341 | initialize_signals for how we get the right signal handlers |
| 342 | for the inferior. */ |
| 343 | |
| 344 | /* "Trace me, Dr. Memory!" */ |
| 345 | (*traceme_fun) (); |
| 346 | |
| 347 | /* The call above set this process (the "child") as debuggable |
| 348 | by the original gdb process (the "parent"). Since processes |
| 349 | (unlike people) can have only one parent, if you are debugging |
| 350 | gdb itself (and your debugger is thus _already_ the |
| 351 | controller/parent for this child), code from here on out is |
| 352 | undebuggable. Indeed, you probably got an error message |
| 353 | saying "not parent". Sorry; you'll have to use print |
| 354 | statements! */ |
| 355 | |
| 356 | /* There is no execlpe call, so we have to set the environment |
| 357 | for our child in the global variable. If we've vforked, this |
| 358 | clobbers the parent, but environ is restored a few lines down |
| 359 | in the parent. By the way, yes we do need to look down the |
| 360 | path to find $SHELL. Rich Pixley says so, and I agree. */ |
| 361 | environ = env; |
| 362 | |
| 363 | if (exec_fun != NULL) |
| 364 | (*exec_fun) (argv[0], argv, env); |
| 365 | else |
| 366 | execvp (argv[0], argv); |
| 367 | |
| 368 | /* If we get here, it's an error. */ |
| 369 | save_errno = errno; |
| 370 | fprintf_unfiltered (gdb_stderr, "Cannot exec %s", exec_file); |
| 371 | for (i = 1; argv[i] != NULL; i++) |
| 372 | fprintf_unfiltered (gdb_stderr, " %s", argv[i]); |
| 373 | fprintf_unfiltered (gdb_stderr, ".\n"); |
| 374 | fprintf_unfiltered (gdb_stderr, "Error: %s\n", |
| 375 | safe_strerror (save_errno)); |
| 376 | gdb_flush (gdb_stderr); |
| 377 | _exit (0177); |
| 378 | } |
| 379 | |
| 380 | /* Restore our environment in case a vforked child clob'd it. */ |
| 381 | environ = save_our_env; |
| 382 | |
| 383 | if (!have_inferiors ()) |
| 384 | init_thread_list (); |
| 385 | |
| 386 | inf = current_inferior (); |
| 387 | |
| 388 | inferior_appeared (inf, pid); |
| 389 | |
| 390 | /* Needed for wait_for_inferior stuff below. */ |
| 391 | inferior_ptid = pid_to_ptid (pid); |
| 392 | |
| 393 | new_tty_postfork (); |
| 394 | |
| 395 | /* We have something that executes now. We'll be running through |
| 396 | the shell at this point, but the pid shouldn't change. Targets |
| 397 | supporting MT should fill this task's ptid with more data as soon |
| 398 | as they can. */ |
| 399 | add_thread_silent (inferior_ptid); |
| 400 | |
| 401 | /* Now that we have a child process, make it our target, and |
| 402 | initialize anything target-vector-specific that needs |
| 403 | initializing. */ |
| 404 | if (init_trace_fun) |
| 405 | (*init_trace_fun) (pid); |
| 406 | |
| 407 | /* We are now in the child process of interest, having exec'd the |
| 408 | correct program, and are poised at the first instruction of the |
| 409 | new program. */ |
| 410 | return pid; |
| 411 | } |
| 412 | |
| 413 | /* Accept NTRAPS traps from the inferior. */ |
| 414 | |
| 415 | void |
| 416 | startup_inferior (int ntraps) |
| 417 | { |
| 418 | int pending_execs = ntraps; |
| 419 | int terminal_initted = 0; |
| 420 | ptid_t resume_ptid; |
| 421 | |
| 422 | if (startup_with_shell) |
| 423 | { |
| 424 | /* One trap extra for exec'ing the shell. */ |
| 425 | pending_execs++; |
| 426 | } |
| 427 | |
| 428 | if (target_supports_multi_process ()) |
| 429 | resume_ptid = pid_to_ptid (ptid_get_pid (inferior_ptid)); |
| 430 | else |
| 431 | resume_ptid = minus_one_ptid; |
| 432 | |
| 433 | /* The process was started by the fork that created it, but it will |
| 434 | have stopped one instruction after execing the shell. Here we |
| 435 | must get it up to actual execution of the real program. */ |
| 436 | |
| 437 | if (exec_wrapper) |
| 438 | pending_execs++; |
| 439 | |
| 440 | while (1) |
| 441 | { |
| 442 | enum gdb_signal resume_signal = GDB_SIGNAL_0; |
| 443 | ptid_t event_ptid; |
| 444 | |
| 445 | struct target_waitstatus ws; |
| 446 | memset (&ws, 0, sizeof (ws)); |
| 447 | event_ptid = target_wait (resume_ptid, &ws, 0); |
| 448 | |
| 449 | if (ws.kind == TARGET_WAITKIND_IGNORE) |
| 450 | /* The inferior didn't really stop, keep waiting. */ |
| 451 | continue; |
| 452 | |
| 453 | switch (ws.kind) |
| 454 | { |
| 455 | case TARGET_WAITKIND_SPURIOUS: |
| 456 | case TARGET_WAITKIND_LOADED: |
| 457 | case TARGET_WAITKIND_FORKED: |
| 458 | case TARGET_WAITKIND_VFORKED: |
| 459 | case TARGET_WAITKIND_SYSCALL_ENTRY: |
| 460 | case TARGET_WAITKIND_SYSCALL_RETURN: |
| 461 | /* Ignore gracefully during startup of the inferior. */ |
| 462 | switch_to_thread (event_ptid); |
| 463 | break; |
| 464 | |
| 465 | case TARGET_WAITKIND_SIGNALLED: |
| 466 | target_terminal_ours (); |
| 467 | target_mourn_inferior (); |
| 468 | error (_("During startup program terminated with signal %s, %s."), |
| 469 | gdb_signal_to_name (ws.value.sig), |
| 470 | gdb_signal_to_string (ws.value.sig)); |
| 471 | return; |
| 472 | |
| 473 | case TARGET_WAITKIND_EXITED: |
| 474 | target_terminal_ours (); |
| 475 | target_mourn_inferior (); |
| 476 | if (ws.value.integer) |
| 477 | error (_("During startup program exited with code %d."), |
| 478 | ws.value.integer); |
| 479 | else |
| 480 | error (_("During startup program exited normally.")); |
| 481 | return; |
| 482 | |
| 483 | case TARGET_WAITKIND_EXECD: |
| 484 | /* Handle EXEC signals as if they were SIGTRAP signals. */ |
| 485 | xfree (ws.value.execd_pathname); |
| 486 | resume_signal = GDB_SIGNAL_TRAP; |
| 487 | switch_to_thread (event_ptid); |
| 488 | break; |
| 489 | |
| 490 | case TARGET_WAITKIND_STOPPED: |
| 491 | resume_signal = ws.value.sig; |
| 492 | switch_to_thread (event_ptid); |
| 493 | break; |
| 494 | } |
| 495 | |
| 496 | if (resume_signal != GDB_SIGNAL_TRAP) |
| 497 | { |
| 498 | /* Let shell child handle its own signals in its own way. */ |
| 499 | target_resume (resume_ptid, 0, resume_signal); |
| 500 | } |
| 501 | else |
| 502 | { |
| 503 | /* We handle SIGTRAP, however; it means child did an exec. */ |
| 504 | if (!terminal_initted) |
| 505 | { |
| 506 | /* Now that the child has exec'd we know it has already |
| 507 | set its process group. On POSIX systems, tcsetpgrp |
| 508 | will fail with EPERM if we try it before the child's |
| 509 | setpgid. */ |
| 510 | |
| 511 | /* Set up the "saved terminal modes" of the inferior |
| 512 | based on what modes we are starting it with. */ |
| 513 | target_terminal_init (); |
| 514 | |
| 515 | /* Install inferior's terminal modes. */ |
| 516 | target_terminal_inferior (); |
| 517 | |
| 518 | terminal_initted = 1; |
| 519 | } |
| 520 | |
| 521 | if (--pending_execs == 0) |
| 522 | break; |
| 523 | |
| 524 | /* Just make it go on. */ |
| 525 | target_resume (resume_ptid, 0, GDB_SIGNAL_0); |
| 526 | } |
| 527 | } |
| 528 | |
| 529 | /* Mark all threads non-executing. */ |
| 530 | set_executing (resume_ptid, 0); |
| 531 | } |
| 532 | |
| 533 | /* Implement the "unset exec-wrapper" command. */ |
| 534 | |
| 535 | static void |
| 536 | unset_exec_wrapper_command (char *args, int from_tty) |
| 537 | { |
| 538 | xfree (exec_wrapper); |
| 539 | exec_wrapper = NULL; |
| 540 | } |
| 541 | |
| 542 | static void |
| 543 | show_startup_with_shell (struct ui_file *file, int from_tty, |
| 544 | struct cmd_list_element *c, const char *value) |
| 545 | { |
| 546 | fprintf_filtered (file, |
| 547 | _("Use of shell to start subprocesses is %s.\n"), |
| 548 | value); |
| 549 | } |
| 550 | |
| 551 | /* Provide a prototype to silence -Wmissing-prototypes. */ |
| 552 | extern initialize_file_ftype _initialize_fork_child; |
| 553 | |
| 554 | void |
| 555 | _initialize_fork_child (void) |
| 556 | { |
| 557 | add_setshow_filename_cmd ("exec-wrapper", class_run, &exec_wrapper, _("\ |
| 558 | Set a wrapper for running programs.\n\ |
| 559 | The wrapper prepares the system and environment for the new program."), |
| 560 | _("\ |
| 561 | Show the wrapper for running programs."), NULL, |
| 562 | NULL, NULL, |
| 563 | &setlist, &showlist); |
| 564 | |
| 565 | add_cmd ("exec-wrapper", class_run, unset_exec_wrapper_command, |
| 566 | _("Disable use of an execution wrapper."), |
| 567 | &unsetlist); |
| 568 | |
| 569 | add_setshow_boolean_cmd ("startup-with-shell", class_support, |
| 570 | &startup_with_shell, _("\ |
| 571 | Set use of shell to start subprocesses. The default is on."), _("\ |
| 572 | Show use of shell to start subprocesses."), NULL, |
| 573 | NULL, |
| 574 | show_startup_with_shell, |
| 575 | &setlist, &showlist); |
| 576 | } |