| 1 | /* Fork a Unix child process, and set up to debug it, for GDB. |
| 2 | Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, |
| 3 | 2001 Free Software Foundation, Inc. |
| 4 | Contributed by Cygnus Support. |
| 5 | |
| 6 | This file is part of GDB. |
| 7 | |
| 8 | This program is free software; you can redistribute it and/or modify |
| 9 | it under the terms of the GNU General Public License as published by |
| 10 | the Free Software Foundation; either version 2 of the License, or |
| 11 | (at your option) any later version. |
| 12 | |
| 13 | This program is distributed in the hope that it will be useful, |
| 14 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 16 | GNU General Public License for more details. |
| 17 | |
| 18 | You should have received a copy of the GNU General Public License |
| 19 | along with this program; if not, write to the Free Software |
| 20 | Foundation, Inc., 59 Temple Place - Suite 330, |
| 21 | Boston, MA 02111-1307, USA. */ |
| 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 | |
| 35 | #include <signal.h> |
| 36 | |
| 37 | /* This just gets used as a default if we can't find SHELL */ |
| 38 | #ifndef SHELL_FILE |
| 39 | #define SHELL_FILE "/bin/sh" |
| 40 | #endif |
| 41 | |
| 42 | extern char **environ; |
| 43 | |
| 44 | /* This function breaks up an argument string into an argument |
| 45 | * vector suitable for passing to execvp(). |
| 46 | * E.g., on "run a b c d" this routine would get as input |
| 47 | * the string "a b c d", and as output it would fill in argv with |
| 48 | * the four arguments "a", "b", "c", "d". |
| 49 | */ |
| 50 | static void |
| 51 | breakup_args (char *scratch, char **argv) |
| 52 | { |
| 53 | char *cp = scratch; |
| 54 | |
| 55 | for (;;) |
| 56 | { |
| 57 | |
| 58 | /* Scan past leading separators */ |
| 59 | while (*cp == ' ' || *cp == '\t' || *cp == '\n') |
| 60 | { |
| 61 | cp++; |
| 62 | } |
| 63 | |
| 64 | /* Break if at end of string */ |
| 65 | if (*cp == '\0') |
| 66 | break; |
| 67 | |
| 68 | /* Take an arg */ |
| 69 | *argv++ = cp; |
| 70 | |
| 71 | /* Scan for next arg separator */ |
| 72 | cp = strchr (cp, ' '); |
| 73 | if (cp == NULL) |
| 74 | cp = strchr (cp, '\t'); |
| 75 | if (cp == NULL) |
| 76 | cp = strchr (cp, '\n'); |
| 77 | |
| 78 | /* No separators => end of string => break */ |
| 79 | if (cp == NULL) |
| 80 | break; |
| 81 | |
| 82 | /* Replace the separator with a terminator */ |
| 83 | *cp++ = '\0'; |
| 84 | } |
| 85 | |
| 86 | /* execv requires a null-terminated arg vector */ |
| 87 | *argv = NULL; |
| 88 | |
| 89 | } |
| 90 | |
| 91 | |
| 92 | /* Start an inferior Unix child process and sets inferior_pid to its pid. |
| 93 | EXEC_FILE is the file to run. |
| 94 | ALLARGS is a string containing the arguments to the program. |
| 95 | ENV is the environment vector to pass. SHELL_FILE is the shell file, |
| 96 | or NULL if we should pick one. Errors reported with error(). */ |
| 97 | |
| 98 | void |
| 99 | fork_inferior (char *exec_file, char *allargs, char **env, |
| 100 | void (*traceme_fun) (void), void (*init_trace_fun) (int), |
| 101 | void (*pre_trace_fun) (void), char *shell_file) |
| 102 | { |
| 103 | int pid; |
| 104 | char *shell_command; |
| 105 | static char default_shell_file[] = SHELL_FILE; |
| 106 | int len; |
| 107 | /* Set debug_fork then attach to the child while it sleeps, to debug. */ |
| 108 | static int debug_fork = 0; |
| 109 | /* This is set to the result of setpgrp, which if vforked, will be visible |
| 110 | to you in the parent process. It's only used by humans for debugging. */ |
| 111 | static int debug_setpgrp = 657473; |
| 112 | char **save_our_env; |
| 113 | int shell = 0; |
| 114 | char **argv; |
| 115 | |
| 116 | /* If no exec file handed to us, get it from the exec-file command -- with |
| 117 | a good, common error message if none is specified. */ |
| 118 | if (exec_file == 0) |
| 119 | exec_file = get_exec_file (1); |
| 120 | |
| 121 | /* STARTUP_WITH_SHELL is defined in inferior.h. |
| 122 | * If 0, we'll just do a fork/exec, no shell, so don't |
| 123 | * bother figuring out what shell. |
| 124 | */ |
| 125 | if (STARTUP_WITH_SHELL) |
| 126 | { |
| 127 | /* Figure out what shell to start up the user program under. */ |
| 128 | if (shell_file == NULL) |
| 129 | shell_file = getenv ("SHELL"); |
| 130 | if (shell_file == NULL) |
| 131 | shell_file = default_shell_file; |
| 132 | shell = 1; |
| 133 | } |
| 134 | |
| 135 | /* Multiplying the length of exec_file by 4 is to account for the fact |
| 136 | that it may expand when quoted; it is a worst-case number based on |
| 137 | every character being '. */ |
| 138 | len = 5 + 4 * strlen (exec_file) + 1 + strlen (allargs) + 1 + /*slop */ 12; |
| 139 | /* If desired, concat something onto the front of ALLARGS. |
| 140 | SHELL_COMMAND is the result. */ |
| 141 | #ifdef SHELL_COMMAND_CONCAT |
| 142 | shell_command = (char *) alloca (strlen (SHELL_COMMAND_CONCAT) + len); |
| 143 | strcpy (shell_command, SHELL_COMMAND_CONCAT); |
| 144 | #else |
| 145 | shell_command = (char *) alloca (len); |
| 146 | shell_command[0] = '\0'; |
| 147 | #endif |
| 148 | |
| 149 | if (!shell) |
| 150 | { |
| 151 | /* We're going to call execvp. Create argv */ |
| 152 | /* Largest case: every other character is a separate arg */ |
| 153 | argv = (char **) xmalloc (((strlen (allargs) + 1) / (unsigned) 2 + 2) * sizeof (*argv)); |
| 154 | argv[0] = exec_file; |
| 155 | breakup_args (allargs, &argv[1]); |
| 156 | |
| 157 | } |
| 158 | else |
| 159 | { |
| 160 | |
| 161 | /* We're going to call a shell */ |
| 162 | |
| 163 | /* Now add exec_file, quoting as necessary. */ |
| 164 | |
| 165 | char *p; |
| 166 | int need_to_quote; |
| 167 | |
| 168 | strcat (shell_command, "exec "); |
| 169 | |
| 170 | /* Quoting in this style is said to work with all shells. But csh |
| 171 | on IRIX 4.0.1 can't deal with it. So we only quote it if we need |
| 172 | to. */ |
| 173 | p = exec_file; |
| 174 | while (1) |
| 175 | { |
| 176 | switch (*p) |
| 177 | { |
| 178 | case '\'': |
| 179 | case '"': |
| 180 | case '(': |
| 181 | case ')': |
| 182 | case '$': |
| 183 | case '&': |
| 184 | case ';': |
| 185 | case '<': |
| 186 | case '>': |
| 187 | case ' ': |
| 188 | case '\n': |
| 189 | case '\t': |
| 190 | need_to_quote = 1; |
| 191 | goto end_scan; |
| 192 | |
| 193 | case '\0': |
| 194 | need_to_quote = 0; |
| 195 | goto end_scan; |
| 196 | |
| 197 | default: |
| 198 | break; |
| 199 | } |
| 200 | ++p; |
| 201 | } |
| 202 | end_scan: |
| 203 | if (need_to_quote) |
| 204 | { |
| 205 | strcat (shell_command, "'"); |
| 206 | for (p = exec_file; *p != '\0'; ++p) |
| 207 | { |
| 208 | if (*p == '\'') |
| 209 | strcat (shell_command, "'\\''"); |
| 210 | else |
| 211 | strncat (shell_command, p, 1); |
| 212 | } |
| 213 | strcat (shell_command, "'"); |
| 214 | } |
| 215 | else |
| 216 | strcat (shell_command, exec_file); |
| 217 | |
| 218 | strcat (shell_command, " "); |
| 219 | strcat (shell_command, allargs); |
| 220 | |
| 221 | } |
| 222 | |
| 223 | /* exec is said to fail if the executable is open. */ |
| 224 | close_exec_file (); |
| 225 | |
| 226 | /* Retain a copy of our environment variables, since the child will |
| 227 | replace the value of environ and if we're vforked, we have to |
| 228 | restore it. */ |
| 229 | save_our_env = environ; |
| 230 | |
| 231 | /* Tell the terminal handling subsystem what tty we plan to run on; |
| 232 | it will just record the information for later. */ |
| 233 | |
| 234 | new_tty_prefork (inferior_io_terminal); |
| 235 | |
| 236 | /* It is generally good practice to flush any possible pending stdio |
| 237 | output prior to doing a fork, to avoid the possibility of both the |
| 238 | parent and child flushing the same data after the fork. */ |
| 239 | |
| 240 | gdb_flush (gdb_stdout); |
| 241 | gdb_flush (gdb_stderr); |
| 242 | |
| 243 | /* If there's any initialization of the target layers that must happen |
| 244 | to prepare to handle the child we're about fork, do it now... |
| 245 | */ |
| 246 | if (pre_trace_fun != NULL) |
| 247 | (*pre_trace_fun) (); |
| 248 | |
| 249 | if (debug_fork) |
| 250 | pid = fork (); |
| 251 | else |
| 252 | pid = vfork (); |
| 253 | |
| 254 | if (pid < 0) |
| 255 | perror_with_name ("vfork"); |
| 256 | |
| 257 | if (pid == 0) |
| 258 | { |
| 259 | if (debug_fork) |
| 260 | sleep (debug_fork); |
| 261 | |
| 262 | /* Run inferior in a separate process group. */ |
| 263 | debug_setpgrp = gdb_setpgid (); |
| 264 | if (debug_setpgrp == -1) |
| 265 | perror ("setpgrp failed in child"); |
| 266 | |
| 267 | /* Ask the tty subsystem to switch to the one we specified earlier |
| 268 | (or to share the current terminal, if none was specified). */ |
| 269 | |
| 270 | new_tty (); |
| 271 | |
| 272 | /* Changing the signal handlers for the inferior after |
| 273 | a vfork can also change them for the superior, so we don't mess |
| 274 | with signals here. See comments in |
| 275 | initialize_signals for how we get the right signal handlers |
| 276 | for the inferior. */ |
| 277 | |
| 278 | /* "Trace me, Dr. Memory!" */ |
| 279 | (*traceme_fun) (); |
| 280 | /* The call above set this process (the "child") as debuggable |
| 281 | * by the original gdb process (the "parent"). Since processes |
| 282 | * (unlike people) can have only one parent, if you are |
| 283 | * debugging gdb itself (and your debugger is thus _already_ the |
| 284 | * controller/parent for this child), code from here on out |
| 285 | * is undebuggable. Indeed, you probably got an error message |
| 286 | * saying "not parent". Sorry--you'll have to use print statements! |
| 287 | */ |
| 288 | |
| 289 | /* There is no execlpe call, so we have to set the environment |
| 290 | for our child in the global variable. If we've vforked, this |
| 291 | clobbers the parent, but environ is restored a few lines down |
| 292 | in the parent. By the way, yes we do need to look down the |
| 293 | path to find $SHELL. Rich Pixley says so, and I agree. */ |
| 294 | environ = env; |
| 295 | |
| 296 | /* If we decided above to start up with a shell, |
| 297 | * we exec the shell, |
| 298 | * "-c" says to interpret the next arg as a shell command |
| 299 | * to execute, and this command is "exec <target-program> <args>". |
| 300 | * "-f" means "fast startup" to the c-shell, which means |
| 301 | * don't do .cshrc file. Doing .cshrc may cause fork/exec |
| 302 | * events which will confuse debugger start-up code. |
| 303 | */ |
| 304 | if (shell) |
| 305 | { |
| 306 | execlp (shell_file, shell_file, "-c", shell_command, (char *) 0); |
| 307 | |
| 308 | /* If we get here, it's an error */ |
| 309 | fprintf_unfiltered (gdb_stderr, "Cannot exec %s: %s.\n", shell_file, |
| 310 | safe_strerror (errno)); |
| 311 | gdb_flush (gdb_stderr); |
| 312 | _exit (0177); |
| 313 | } |
| 314 | else |
| 315 | { |
| 316 | /* Otherwise, we directly exec the target program with execvp. */ |
| 317 | int i; |
| 318 | char *errstring; |
| 319 | |
| 320 | execvp (exec_file, argv); |
| 321 | |
| 322 | /* If we get here, it's an error */ |
| 323 | errstring = safe_strerror (errno); |
| 324 | fprintf_unfiltered (gdb_stderr, "Cannot exec %s ", exec_file); |
| 325 | |
| 326 | i = 1; |
| 327 | while (argv[i] != NULL) |
| 328 | { |
| 329 | if (i != 1) |
| 330 | fprintf_unfiltered (gdb_stderr, " "); |
| 331 | fprintf_unfiltered (gdb_stderr, "%s", argv[i]); |
| 332 | i++; |
| 333 | } |
| 334 | fprintf_unfiltered (gdb_stderr, ".\n"); |
| 335 | /* This extra info seems to be useless |
| 336 | fprintf_unfiltered (gdb_stderr, "Got error %s.\n", errstring); |
| 337 | */ |
| 338 | gdb_flush (gdb_stderr); |
| 339 | _exit (0177); |
| 340 | } |
| 341 | } |
| 342 | |
| 343 | /* Restore our environment in case a vforked child clob'd it. */ |
| 344 | environ = save_our_env; |
| 345 | |
| 346 | init_thread_list (); |
| 347 | |
| 348 | inferior_pid = pid; /* Needed for wait_for_inferior stuff below */ |
| 349 | |
| 350 | /* Now that we have a child process, make it our target, and |
| 351 | initialize anything target-vector-specific that needs initializing. */ |
| 352 | |
| 353 | (*init_trace_fun) (pid); |
| 354 | |
| 355 | /* We are now in the child process of interest, having exec'd the |
| 356 | correct program, and are poised at the first instruction of the |
| 357 | new program. */ |
| 358 | |
| 359 | /* Allow target dependent code to play with the new process. This might be |
| 360 | used to have target-specific code initialize a variable in the new process |
| 361 | prior to executing the first instruction. */ |
| 362 | TARGET_CREATE_INFERIOR_HOOK (pid); |
| 363 | |
| 364 | #ifdef SOLIB_CREATE_INFERIOR_HOOK |
| 365 | SOLIB_CREATE_INFERIOR_HOOK (pid); |
| 366 | #endif |
| 367 | } |
| 368 | |
| 369 | /* An inferior Unix process CHILD_PID has been created by a call to |
| 370 | fork() (or variants like vfork). It is presently stopped, and waiting |
| 371 | to be resumed. clone_and_follow_inferior will fork the debugger, |
| 372 | and that clone will "follow" (attach to) CHILD_PID. The original copy |
| 373 | of the debugger will not touch CHILD_PID again. |
| 374 | |
| 375 | Also, the original debugger will set FOLLOWED_CHILD FALSE, while the |
| 376 | clone will set it TRUE. |
| 377 | */ |
| 378 | void |
| 379 | clone_and_follow_inferior (int child_pid, int *followed_child) |
| 380 | { |
| 381 | extern int auto_solib_add; |
| 382 | |
| 383 | int debugger_pid; |
| 384 | int status; |
| 385 | char pid_spelling[100]; /* Arbitrary but sufficient length. */ |
| 386 | |
| 387 | /* This semaphore is used to coordinate the two debuggers' handoff |
| 388 | of CHILD_PID. The original debugger will detach from CHILD_PID, |
| 389 | and then the clone debugger will attach to it. (It must be done |
| 390 | this way because on some targets, only one process at a time can |
| 391 | trace another. Thus, the original debugger must relinquish its |
| 392 | tracing rights before the clone can pick them up.) |
| 393 | */ |
| 394 | #define SEM_TALK (1) |
| 395 | #define SEM_LISTEN (0) |
| 396 | int handoff_semaphore[2]; /* Original "talks" to [1], clone "listens" to [0] */ |
| 397 | int talk_value = 99; |
| 398 | int listen_value; |
| 399 | |
| 400 | /* Set debug_fork then attach to the child while it sleeps, to debug. */ |
| 401 | static int debug_fork = 0; |
| 402 | |
| 403 | /* It is generally good practice to flush any possible pending stdio |
| 404 | output prior to doing a fork, to avoid the possibility of both the |
| 405 | parent and child flushing the same data after the fork. */ |
| 406 | |
| 407 | gdb_flush (gdb_stdout); |
| 408 | gdb_flush (gdb_stderr); |
| 409 | |
| 410 | /* Open the semaphore pipes. |
| 411 | */ |
| 412 | status = pipe (handoff_semaphore); |
| 413 | if (status < 0) |
| 414 | error ("error getting pipe for handoff semaphore"); |
| 415 | |
| 416 | /* Clone the debugger. */ |
| 417 | #ifdef HAVE_VFORK |
| 418 | if (debug_fork) |
| 419 | debugger_pid = fork (); |
| 420 | else |
| 421 | debugger_pid = vfork (); |
| 422 | #else |
| 423 | debugger_pid = fork (); |
| 424 | #endif |
| 425 | |
| 426 | if (debugger_pid < 0) |
| 427 | perror_with_name ("fork"); |
| 428 | |
| 429 | /* Are we the original debugger? If so, we must relinquish all claims |
| 430 | to CHILD_PID. */ |
| 431 | if (debugger_pid != 0) |
| 432 | { |
| 433 | char signal_spelling[100]; /* Arbitrary but sufficient length */ |
| 434 | |
| 435 | /* Detach from CHILD_PID. Deliver a "stop" signal when we do, though, |
| 436 | so that it remains stopped until the clone debugger can attach |
| 437 | to it. |
| 438 | */ |
| 439 | detach_breakpoints (child_pid); |
| 440 | |
| 441 | sprintf (signal_spelling, "%d", target_signal_to_host (TARGET_SIGNAL_STOP)); |
| 442 | target_require_detach (child_pid, signal_spelling, 1); |
| 443 | |
| 444 | /* Notify the clone debugger that it should attach to CHILD_PID. */ |
| 445 | write (handoff_semaphore[SEM_TALK], &talk_value, sizeof (talk_value)); |
| 446 | |
| 447 | *followed_child = 0; |
| 448 | } |
| 449 | |
| 450 | /* We're the child. */ |
| 451 | else |
| 452 | { |
| 453 | if (debug_fork) |
| 454 | sleep (debug_fork); |
| 455 | |
| 456 | /* The child (i.e., the cloned debugger) must now attach to |
| 457 | CHILD_PID. inferior_pid is presently set to the parent process |
| 458 | of the fork, while CHILD_PID should be the child process of the |
| 459 | fork. |
| 460 | |
| 461 | Wait until the original debugger relinquishes control of CHILD_PID, |
| 462 | though. |
| 463 | */ |
| 464 | read (handoff_semaphore[SEM_LISTEN], &listen_value, sizeof (listen_value)); |
| 465 | |
| 466 | /* Note that we DON'T want to actually detach from inferior_pid, |
| 467 | because that would allow it to run free. The original |
| 468 | debugger wants to retain control of the process. So, we |
| 469 | just reset inferior_pid to CHILD_PID, and then ensure that all |
| 470 | breakpoints are really set in CHILD_PID. |
| 471 | */ |
| 472 | target_mourn_inferior (); |
| 473 | |
| 474 | /* Ask the tty subsystem to switch to the one we specified earlier |
| 475 | (or to share the current terminal, if none was specified). */ |
| 476 | |
| 477 | new_tty (); |
| 478 | |
| 479 | dont_repeat (); |
| 480 | sprintf (pid_spelling, "%d", child_pid); |
| 481 | target_require_attach (pid_spelling, 1); |
| 482 | |
| 483 | /* Perform any necessary cleanup, after attachment. (This form |
| 484 | of attaching can behave differently on some targets than the |
| 485 | standard method, where a process formerly not under debugger |
| 486 | control was suddenly attached to..) |
| 487 | */ |
| 488 | target_post_follow_inferior_by_clone (); |
| 489 | |
| 490 | *followed_child = 1; |
| 491 | } |
| 492 | |
| 493 | /* Discard the handoff sempahore. */ |
| 494 | (void) close (handoff_semaphore[SEM_LISTEN]); |
| 495 | (void) close (handoff_semaphore[SEM_TALK]); |
| 496 | } |
| 497 | |
| 498 | /* Accept NTRAPS traps from the inferior. */ |
| 499 | |
| 500 | void |
| 501 | startup_inferior (int ntraps) |
| 502 | { |
| 503 | int pending_execs = ntraps; |
| 504 | int terminal_initted; |
| 505 | |
| 506 | /* The process was started by the fork that created it, |
| 507 | but it will have stopped one instruction after execing the shell. |
| 508 | Here we must get it up to actual execution of the real program. */ |
| 509 | |
| 510 | clear_proceed_status (); |
| 511 | |
| 512 | init_wait_for_inferior (); |
| 513 | |
| 514 | terminal_initted = 0; |
| 515 | |
| 516 | if (STARTUP_WITH_SHELL) |
| 517 | inferior_ignoring_startup_exec_events = ntraps; |
| 518 | else |
| 519 | inferior_ignoring_startup_exec_events = 0; |
| 520 | inferior_ignoring_leading_exec_events = |
| 521 | target_reported_exec_events_per_exec_call () - 1; |
| 522 | |
| 523 | #ifdef STARTUP_INFERIOR |
| 524 | STARTUP_INFERIOR (pending_execs); |
| 525 | #else |
| 526 | while (1) |
| 527 | { |
| 528 | stop_soon_quietly = 1; /* Make wait_for_inferior be quiet */ |
| 529 | wait_for_inferior (); |
| 530 | if (stop_signal != TARGET_SIGNAL_TRAP) |
| 531 | { |
| 532 | /* Let shell child handle its own signals in its own way */ |
| 533 | /* FIXME, what if child has exit()ed? Must exit loop somehow */ |
| 534 | resume (0, stop_signal); |
| 535 | } |
| 536 | else |
| 537 | { |
| 538 | /* We handle SIGTRAP, however; it means child did an exec. */ |
| 539 | if (!terminal_initted) |
| 540 | { |
| 541 | /* Now that the child has exec'd we know it has already set its |
| 542 | process group. On POSIX systems, tcsetpgrp will fail with |
| 543 | EPERM if we try it before the child's setpgid. */ |
| 544 | |
| 545 | /* Set up the "saved terminal modes" of the inferior |
| 546 | based on what modes we are starting it with. */ |
| 547 | target_terminal_init (); |
| 548 | |
| 549 | /* Install inferior's terminal modes. */ |
| 550 | target_terminal_inferior (); |
| 551 | |
| 552 | terminal_initted = 1; |
| 553 | } |
| 554 | |
| 555 | pending_execs = pending_execs - 1; |
| 556 | if (0 == pending_execs) |
| 557 | break; |
| 558 | |
| 559 | resume (0, TARGET_SIGNAL_0); /* Just make it go on */ |
| 560 | } |
| 561 | } |
| 562 | #endif /* STARTUP_INFERIOR */ |
| 563 | stop_soon_quietly = 0; |
| 564 | } |