| 1 | /* Fork a Unix child process, and set up to debug it, for GDB. |
| 2 | |
| 3 | Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, |
| 4 | 2001, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc. |
| 5 | |
| 6 | Contributed by Cygnus Support. |
| 7 | |
| 8 | This file is part of GDB. |
| 9 | |
| 10 | This program is free software; you can redistribute it and/or modify |
| 11 | it under the terms of the GNU General Public License as published by |
| 12 | the Free Software Foundation; either version 3 of the License, or |
| 13 | (at your option) any later version. |
| 14 | |
| 15 | This program is distributed in the hope that it will be useful, |
| 16 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 18 | GNU General Public License for more details. |
| 19 | |
| 20 | You should have received a copy of the GNU General Public License |
| 21 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
| 22 | |
| 23 | #include "defs.h" |
| 24 | #include "gdb_string.h" |
| 25 | #include "frame.h" /* required by inferior.h */ |
| 26 | #include "inferior.h" |
| 27 | #include "target.h" |
| 28 | #include "gdb_wait.h" |
| 29 | #include "gdb_vfork.h" |
| 30 | #include "gdbcore.h" |
| 31 | #include "terminal.h" |
| 32 | #include "gdbthread.h" |
| 33 | #include "command.h" /* for dont_repeat () */ |
| 34 | #include "gdbcmd.h" |
| 35 | #include "solib.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; |
| 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 | cp = strchr (cp, ' '); |
| 71 | if (cp == NULL) |
| 72 | cp = strchr (cp, '\t'); |
| 73 | if (cp == NULL) |
| 74 | cp = strchr (cp, '\n'); |
| 75 | |
| 76 | /* No separators => end of string => break. */ |
| 77 | if (cp == NULL) |
| 78 | break; |
| 79 | |
| 80 | /* Replace the separator with a terminator. */ |
| 81 | *cp++ = '\0'; |
| 82 | } |
| 83 | |
| 84 | /* Null-terminate the vector. */ |
| 85 | *argv = NULL; |
| 86 | } |
| 87 | |
| 88 | /* When executing a command under the given shell, return non-zero if |
| 89 | the '!' character should be escaped when embedded in a quoted |
| 90 | command-line argument. */ |
| 91 | |
| 92 | static int |
| 93 | escape_bang_in_quoted_argument (const char *shell_file) |
| 94 | { |
| 95 | const int shell_file_len = strlen (shell_file); |
| 96 | |
| 97 | /* Bang should be escaped only in C Shells. For now, simply check |
| 98 | that the shell name ends with 'csh', which covers at least csh |
| 99 | and tcsh. This should be good enough for now. */ |
| 100 | |
| 101 | if (shell_file_len < 3) |
| 102 | return 0; |
| 103 | |
| 104 | if (shell_file[shell_file_len - 3] == 'c' |
| 105 | && shell_file[shell_file_len - 2] == 's' |
| 106 | && shell_file[shell_file_len - 1] == 'h') |
| 107 | return 1; |
| 108 | |
| 109 | return 0; |
| 110 | } |
| 111 | |
| 112 | /* Start an inferior Unix child process and sets inferior_ptid to its |
| 113 | pid. EXEC_FILE is the file to run. ALLARGS is a string containing |
| 114 | the arguments to the program. ENV is the environment vector to |
| 115 | pass. SHELL_FILE is the shell file, or NULL if we should pick |
| 116 | one. */ |
| 117 | |
| 118 | /* This function is NOT reentrant. Some of the variables have been |
| 119 | made static to ensure that they survive the vfork call. */ |
| 120 | |
| 121 | void |
| 122 | fork_inferior (char *exec_file_arg, char *allargs, char **env, |
| 123 | void (*traceme_fun) (void), void (*init_trace_fun) (int), |
| 124 | void (*pre_trace_fun) (void), char *shell_file_arg) |
| 125 | { |
| 126 | int pid; |
| 127 | char *shell_command; |
| 128 | static char default_shell_file[] = SHELL_FILE; |
| 129 | int len; |
| 130 | /* Set debug_fork then attach to the child while it sleeps, to debug. */ |
| 131 | static int debug_fork = 0; |
| 132 | /* This is set to the result of setpgrp, which if vforked, will be visible |
| 133 | to you in the parent process. It's only used by humans for debugging. */ |
| 134 | static int debug_setpgrp = 657473; |
| 135 | static char *shell_file; |
| 136 | static char *exec_file; |
| 137 | char **save_our_env; |
| 138 | int shell = 0; |
| 139 | static char **argv; |
| 140 | const char *inferior_io_terminal = get_inferior_io_terminal (); |
| 141 | |
| 142 | /* If no exec file handed to us, get it from the exec-file command |
| 143 | -- with a good, common error message if none is specified. */ |
| 144 | exec_file = exec_file_arg; |
| 145 | if (exec_file == 0) |
| 146 | exec_file = get_exec_file (1); |
| 147 | |
| 148 | /* STARTUP_WITH_SHELL is defined in inferior.h. If 0,e we'll just |
| 149 | do a fork/exec, no shell, so don't bother figuring out what |
| 150 | shell. */ |
| 151 | shell_file = shell_file_arg; |
| 152 | if (STARTUP_WITH_SHELL) |
| 153 | { |
| 154 | /* Figure out what shell to start up the user program under. */ |
| 155 | if (shell_file == NULL) |
| 156 | shell_file = getenv ("SHELL"); |
| 157 | if (shell_file == NULL) |
| 158 | shell_file = default_shell_file; |
| 159 | shell = 1; |
| 160 | } |
| 161 | |
| 162 | /* Multiplying the length of exec_file by 4 is to account for the |
| 163 | fact that it may expand when quoted; it is a worst-case number |
| 164 | based on every character being '. */ |
| 165 | len = 5 + 4 * strlen (exec_file) + 1 + strlen (allargs) + 1 + /*slop */ 12; |
| 166 | if (exec_wrapper) |
| 167 | len += strlen (exec_wrapper) + 1; |
| 168 | |
| 169 | shell_command = (char *) alloca (len); |
| 170 | shell_command[0] = '\0'; |
| 171 | |
| 172 | if (!shell) |
| 173 | { |
| 174 | /* We're going to call execvp. Create argument vector. |
| 175 | Calculate an upper bound on the length of the vector by |
| 176 | assuming that every other character is a separate |
| 177 | argument. */ |
| 178 | int argc = (strlen (allargs) + 1) / 2 + 2; |
| 179 | argv = (char **) xmalloc (argc * sizeof (*argv)); |
| 180 | argv[0] = exec_file; |
| 181 | breakup_args (allargs, &argv[1]); |
| 182 | } |
| 183 | else |
| 184 | { |
| 185 | /* We're going to call a shell. */ |
| 186 | |
| 187 | char *p; |
| 188 | int need_to_quote; |
| 189 | const int escape_bang = escape_bang_in_quoted_argument (shell_file); |
| 190 | |
| 191 | strcat (shell_command, "exec "); |
| 192 | |
| 193 | /* Add any exec wrapper. That may be a program name with arguments, so |
| 194 | the user must handle quoting. */ |
| 195 | if (exec_wrapper) |
| 196 | { |
| 197 | strcat (shell_command, exec_wrapper); |
| 198 | strcat (shell_command, " "); |
| 199 | } |
| 200 | |
| 201 | /* Now add exec_file, quoting as necessary. */ |
| 202 | |
| 203 | /* Quoting in this style is said to work with all shells. But |
| 204 | csh on IRIX 4.0.1 can't deal with it. So we only quote it if |
| 205 | we need to. */ |
| 206 | p = exec_file; |
| 207 | while (1) |
| 208 | { |
| 209 | switch (*p) |
| 210 | { |
| 211 | case '\'': |
| 212 | case '!': |
| 213 | case '"': |
| 214 | case '(': |
| 215 | case ')': |
| 216 | case '$': |
| 217 | case '&': |
| 218 | case ';': |
| 219 | case '<': |
| 220 | case '>': |
| 221 | case ' ': |
| 222 | case '\n': |
| 223 | case '\t': |
| 224 | need_to_quote = 1; |
| 225 | goto end_scan; |
| 226 | |
| 227 | case '\0': |
| 228 | need_to_quote = 0; |
| 229 | goto end_scan; |
| 230 | |
| 231 | default: |
| 232 | break; |
| 233 | } |
| 234 | ++p; |
| 235 | } |
| 236 | end_scan: |
| 237 | if (need_to_quote) |
| 238 | { |
| 239 | strcat (shell_command, "'"); |
| 240 | for (p = exec_file; *p != '\0'; ++p) |
| 241 | { |
| 242 | if (*p == '\'') |
| 243 | strcat (shell_command, "'\\''"); |
| 244 | else if (*p == '!' && escape_bang) |
| 245 | strcat (shell_command, "\\!"); |
| 246 | else |
| 247 | strncat (shell_command, p, 1); |
| 248 | } |
| 249 | strcat (shell_command, "'"); |
| 250 | } |
| 251 | else |
| 252 | strcat (shell_command, exec_file); |
| 253 | |
| 254 | strcat (shell_command, " "); |
| 255 | strcat (shell_command, allargs); |
| 256 | } |
| 257 | |
| 258 | /* On some systems an exec will fail if the executable is open. */ |
| 259 | close_exec_file (); |
| 260 | |
| 261 | /* Retain a copy of our environment variables, since the child will |
| 262 | replace the value of environ and if we're vforked, we have to |
| 263 | restore it. */ |
| 264 | save_our_env = environ; |
| 265 | |
| 266 | /* Tell the terminal handling subsystem what tty we plan to run on; |
| 267 | it will just record the information for later. */ |
| 268 | new_tty_prefork (inferior_io_terminal); |
| 269 | |
| 270 | /* It is generally good practice to flush any possible pending stdio |
| 271 | output prior to doing a fork, to avoid the possibility of both |
| 272 | the parent and child flushing the same data after the fork. */ |
| 273 | gdb_flush (gdb_stdout); |
| 274 | gdb_flush (gdb_stderr); |
| 275 | |
| 276 | /* If there's any initialization of the target layers that must |
| 277 | happen to prepare to handle the child we're about fork, do it |
| 278 | now... */ |
| 279 | if (pre_trace_fun != NULL) |
| 280 | (*pre_trace_fun) (); |
| 281 | |
| 282 | /* Create the child process. Since the child process is going to |
| 283 | exec(3) shortly afterwards, try to reduce the overhead by |
| 284 | calling vfork(2). However, if PRE_TRACE_FUN is non-null, it's |
| 285 | likely that this optimization won't work since there's too much |
| 286 | work to do between the vfork(2) and the exec(3). This is known |
| 287 | to be the case on ttrace(2)-based HP-UX, where some handshaking |
| 288 | between parent and child needs to happen between fork(2) and |
| 289 | exec(2). However, since the parent is suspended in the vforked |
| 290 | state, this doesn't work. Also note that the vfork(2) call might |
| 291 | actually be a call to fork(2) due to the fact that autoconf will |
| 292 | ``#define vfork fork'' on certain platforms. */ |
| 293 | if (pre_trace_fun || debug_fork) |
| 294 | pid = fork (); |
| 295 | else |
| 296 | pid = vfork (); |
| 297 | |
| 298 | if (pid < 0) |
| 299 | perror_with_name (("vfork")); |
| 300 | |
| 301 | if (pid == 0) |
| 302 | { |
| 303 | if (debug_fork) |
| 304 | sleep (debug_fork); |
| 305 | |
| 306 | /* Create a new session for the inferior process, if necessary. |
| 307 | It will also place the inferior in a separate process group. */ |
| 308 | if (create_tty_session () <= 0) |
| 309 | { |
| 310 | /* No session was created, but we still want to run the inferior |
| 311 | in a separate process group. */ |
| 312 | debug_setpgrp = gdb_setpgid (); |
| 313 | if (debug_setpgrp == -1) |
| 314 | perror ("setpgrp failed in child"); |
| 315 | } |
| 316 | |
| 317 | /* Ask the tty subsystem to switch to the one we specified |
| 318 | earlier (or to share the current terminal, if none was |
| 319 | specified). */ |
| 320 | new_tty (); |
| 321 | |
| 322 | /* Changing the signal handlers for the inferior after |
| 323 | a vfork can also change them for the superior, so we don't mess |
| 324 | with signals here. See comments in |
| 325 | initialize_signals for how we get the right signal handlers |
| 326 | for the inferior. */ |
| 327 | |
| 328 | /* "Trace me, Dr. Memory!" */ |
| 329 | (*traceme_fun) (); |
| 330 | |
| 331 | /* The call above set this process (the "child") as debuggable |
| 332 | by the original gdb process (the "parent"). Since processes |
| 333 | (unlike people) can have only one parent, if you are debugging |
| 334 | gdb itself (and your debugger is thus _already_ the |
| 335 | controller/parent for this child), code from here on out is |
| 336 | undebuggable. Indeed, you probably got an error message |
| 337 | saying "not parent". Sorry; you'll have to use print |
| 338 | statements! */ |
| 339 | |
| 340 | /* There is no execlpe call, so we have to set the environment |
| 341 | for our child in the global variable. If we've vforked, this |
| 342 | clobbers the parent, but environ is restored a few lines down |
| 343 | in the parent. By the way, yes we do need to look down the |
| 344 | path to find $SHELL. Rich Pixley says so, and I agree. */ |
| 345 | environ = env; |
| 346 | |
| 347 | /* If we decided above to start up with a shell, we exec the |
| 348 | shell, "-c" says to interpret the next arg as a shell command |
| 349 | to execute, and this command is "exec <target-program> |
| 350 | <args>". */ |
| 351 | if (shell) |
| 352 | { |
| 353 | execlp (shell_file, shell_file, "-c", shell_command, (char *) 0); |
| 354 | |
| 355 | /* If we get here, it's an error. */ |
| 356 | fprintf_unfiltered (gdb_stderr, "Cannot exec %s: %s.\n", shell_file, |
| 357 | safe_strerror (errno)); |
| 358 | gdb_flush (gdb_stderr); |
| 359 | _exit (0177); |
| 360 | } |
| 361 | else |
| 362 | { |
| 363 | /* Otherwise, we directly exec the target program with |
| 364 | execvp. */ |
| 365 | int i; |
| 366 | char *errstring; |
| 367 | |
| 368 | execvp (exec_file, argv); |
| 369 | |
| 370 | /* If we get here, it's an error. */ |
| 371 | errstring = safe_strerror (errno); |
| 372 | fprintf_unfiltered (gdb_stderr, "Cannot exec %s ", exec_file); |
| 373 | |
| 374 | i = 1; |
| 375 | while (argv[i] != NULL) |
| 376 | { |
| 377 | if (i != 1) |
| 378 | fprintf_unfiltered (gdb_stderr, " "); |
| 379 | fprintf_unfiltered (gdb_stderr, "%s", argv[i]); |
| 380 | i++; |
| 381 | } |
| 382 | fprintf_unfiltered (gdb_stderr, ".\n"); |
| 383 | #if 0 |
| 384 | /* This extra info seems to be useless. */ |
| 385 | fprintf_unfiltered (gdb_stderr, "Got error %s.\n", errstring); |
| 386 | #endif |
| 387 | gdb_flush (gdb_stderr); |
| 388 | _exit (0177); |
| 389 | } |
| 390 | } |
| 391 | |
| 392 | /* Restore our environment in case a vforked child clob'd it. */ |
| 393 | environ = save_our_env; |
| 394 | |
| 395 | init_thread_list (); |
| 396 | |
| 397 | /* Needed for wait_for_inferior stuff below. */ |
| 398 | inferior_ptid = pid_to_ptid (pid); |
| 399 | |
| 400 | /* Now that we have a child process, make it our target, and |
| 401 | initialize anything target-vector-specific that needs |
| 402 | initializing. */ |
| 403 | (*init_trace_fun) (pid); |
| 404 | |
| 405 | /* We are now in the child process of interest, having exec'd the |
| 406 | correct program, and are poised at the first instruction of the |
| 407 | new program. */ |
| 408 | } |
| 409 | |
| 410 | /* Accept NTRAPS traps from the inferior. */ |
| 411 | |
| 412 | void |
| 413 | startup_inferior (int ntraps) |
| 414 | { |
| 415 | int pending_execs = ntraps; |
| 416 | int terminal_initted = 0; |
| 417 | |
| 418 | /* The process was started by the fork that created it, but it will |
| 419 | have stopped one instruction after execing the shell. Here we |
| 420 | must get it up to actual execution of the real program. */ |
| 421 | |
| 422 | if (exec_wrapper) |
| 423 | pending_execs++; |
| 424 | |
| 425 | clear_proceed_status (); |
| 426 | |
| 427 | init_wait_for_inferior (); |
| 428 | |
| 429 | while (1) |
| 430 | { |
| 431 | /* Make wait_for_inferior be quiet. */ |
| 432 | stop_soon = STOP_QUIETLY; |
| 433 | wait_for_inferior (1); |
| 434 | if (stop_signal != TARGET_SIGNAL_TRAP) |
| 435 | { |
| 436 | /* Let shell child handle its own signals in its own way. |
| 437 | FIXME: what if child has exited? Must exit loop |
| 438 | somehow. */ |
| 439 | resume (0, stop_signal); |
| 440 | } |
| 441 | else |
| 442 | { |
| 443 | /* We handle SIGTRAP, however; it means child did an exec. */ |
| 444 | if (!terminal_initted) |
| 445 | { |
| 446 | /* Now that the child has exec'd we know it has already |
| 447 | set its process group. On POSIX systems, tcsetpgrp |
| 448 | will fail with EPERM if we try it before the child's |
| 449 | setpgid. */ |
| 450 | |
| 451 | /* Set up the "saved terminal modes" of the inferior |
| 452 | based on what modes we are starting it with. */ |
| 453 | target_terminal_init (); |
| 454 | |
| 455 | /* Install inferior's terminal modes. */ |
| 456 | target_terminal_inferior (); |
| 457 | |
| 458 | terminal_initted = 1; |
| 459 | } |
| 460 | |
| 461 | if (--pending_execs == 0) |
| 462 | break; |
| 463 | |
| 464 | resume (0, TARGET_SIGNAL_0); /* Just make it go on. */ |
| 465 | } |
| 466 | } |
| 467 | stop_soon = NO_STOP_QUIETLY; |
| 468 | } |
| 469 | |
| 470 | /* Implement the "unset exec-wrapper" command. */ |
| 471 | |
| 472 | static void |
| 473 | unset_exec_wrapper_command (char *args, int from_tty) |
| 474 | { |
| 475 | xfree (exec_wrapper); |
| 476 | exec_wrapper = NULL; |
| 477 | } |
| 478 | |
| 479 | void |
| 480 | _initialize_fork_child (void) |
| 481 | { |
| 482 | add_setshow_filename_cmd ("exec-wrapper", class_run, &exec_wrapper, _("\ |
| 483 | Set a wrapper for running programs.\n\ |
| 484 | The wrapper prepares the system and environment for the new program."), |
| 485 | _("\ |
| 486 | Show the wrapper for running programs."), NULL, |
| 487 | NULL, NULL, |
| 488 | &setlist, &showlist); |
| 489 | |
| 490 | add_cmd ("exec-wrapper", class_run, unset_exec_wrapper_command, |
| 491 | _("Disable use of an execution wrapper."), |
| 492 | &unsetlist); |
| 493 | } |