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2090129c SDJ |
1 | /* Fork a Unix child process, and set up to debug it, for GDB and GDBserver. |
2 | ||
42a4f53d | 3 | Copyright (C) 1990-2019 Free Software Foundation, Inc. |
2090129c SDJ |
4 | |
5 | This file is part of GDB. | |
6 | ||
7 | This program is free software; you can redistribute it and/or modify | |
8 | it under the terms of the GNU General Public License as published by | |
9 | the Free Software Foundation; either version 3 of the License, or | |
10 | (at your option) any later version. | |
11 | ||
12 | This program is distributed in the hope that it will be useful, | |
13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | GNU General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU General Public License | |
18 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ | |
19 | ||
268a13a5 | 20 | #include "gdbsupport/common-defs.h" |
2090129c SDJ |
21 | #include "fork-inferior.h" |
22 | #include "target/waitstatus.h" | |
268a13a5 | 23 | #include "gdbsupport/filestuff.h" |
2090129c | 24 | #include "target/target.h" |
268a13a5 TT |
25 | #include "gdbsupport/common-inferior.h" |
26 | #include "gdbsupport/common-gdbthread.h" | |
27 | #include "gdbsupport/pathstuff.h" | |
28 | #include "gdbsupport/signals-state-save-restore.h" | |
29 | #include "gdbsupport/gdb_tilde_expand.h" | |
2090129c SDJ |
30 | #include <vector> |
31 | ||
32 | extern char **environ; | |
33 | ||
2090129c SDJ |
34 | /* Build the argument vector for execv(3). */ |
35 | ||
36 | class execv_argv | |
37 | { | |
38 | public: | |
39 | /* EXEC_FILE is the file to run. ALLARGS is a string containing the | |
40 | arguments to the program. If starting with a shell, SHELL_FILE | |
41 | is the shell to run. Otherwise, SHELL_FILE is NULL. */ | |
42 | execv_argv (const char *exec_file, const std::string &allargs, | |
43 | const char *shell_file); | |
44 | ||
45 | /* Return a pointer to the built argv, in the type expected by | |
46 | execv. The result is (only) valid for as long as this execv_argv | |
47 | object is live. We return a "char **" because that's the type | |
48 | that the execv functions expect. Note that it is guaranteed that | |
49 | the execv functions do not modify the argv[] array nor the | |
50 | strings to which the array point. */ | |
51 | char **argv () | |
52 | { | |
53 | return const_cast<char **> (&m_argv[0]); | |
54 | } | |
55 | ||
56 | private: | |
d6541620 | 57 | DISABLE_COPY_AND_ASSIGN (execv_argv); |
2090129c SDJ |
58 | |
59 | /* Helper methods for constructing the argument vector. */ | |
60 | ||
61 | /* Used when building an argv for a straight execv call, without | |
62 | going via the shell. */ | |
63 | void init_for_no_shell (const char *exec_file, | |
64 | const std::string &allargs); | |
65 | ||
66 | /* Used when building an argv for execing a shell that execs the | |
67 | child program. */ | |
68 | void init_for_shell (const char *exec_file, | |
69 | const std::string &allargs, | |
70 | const char *shell_file); | |
71 | ||
72 | /* The argument vector built. Holds non-owning pointers. Elements | |
73 | either point to the strings passed to the execv_argv ctor, or | |
74 | inside M_STORAGE. */ | |
75 | std::vector<const char *> m_argv; | |
76 | ||
77 | /* Storage. In the no-shell case, this contains a copy of the | |
78 | arguments passed to the ctor, split by '\0'. In the shell case, | |
79 | this contains the quoted shell command. I.e., SHELL_COMMAND in | |
80 | {"$SHELL" "-c", SHELL_COMMAND, NULL}. */ | |
81 | std::string m_storage; | |
82 | }; | |
83 | ||
84 | /* Create argument vector for straight call to execvp. Breaks up | |
85 | ALLARGS into an argument vector suitable for passing to execvp and | |
86 | stores it in M_ARGV. E.g., on "run a b c d" this routine would get | |
87 | as input the string "a b c d", and as output it would fill in | |
88 | M_ARGV with the four arguments "a", "b", "c", "d". Each argument | |
89 | in M_ARGV points to a substring of a copy of ALLARGS stored in | |
90 | M_STORAGE. */ | |
91 | ||
92 | void | |
93 | execv_argv::init_for_no_shell (const char *exec_file, | |
94 | const std::string &allargs) | |
95 | { | |
96 | ||
97 | /* Save/work with a copy stored in our storage. The pointers pushed | |
98 | to M_ARGV point directly into M_STORAGE, which is modified in | |
99 | place with the necessary NULL terminators. This avoids N heap | |
100 | allocations and string dups when 1 is sufficient. */ | |
101 | std::string &args_copy = m_storage = allargs; | |
102 | ||
103 | m_argv.push_back (exec_file); | |
104 | ||
105 | for (size_t cur_pos = 0; cur_pos < args_copy.size ();) | |
106 | { | |
107 | /* Skip whitespace-like chars. */ | |
108 | std::size_t pos = args_copy.find_first_not_of (" \t\n", cur_pos); | |
109 | ||
110 | if (pos != std::string::npos) | |
111 | cur_pos = pos; | |
112 | ||
113 | /* Find the position of the next separator. */ | |
114 | std::size_t next_sep = args_copy.find_first_of (" \t\n", cur_pos); | |
115 | ||
116 | if (next_sep == std::string::npos) | |
117 | { | |
118 | /* No separator found, which means this is the last | |
119 | argument. */ | |
120 | next_sep = args_copy.size (); | |
121 | } | |
122 | else | |
123 | { | |
124 | /* Replace the separator with a terminator. */ | |
125 | args_copy[next_sep++] = '\0'; | |
126 | } | |
127 | ||
128 | m_argv.push_back (&args_copy[cur_pos]); | |
129 | ||
130 | cur_pos = next_sep; | |
131 | } | |
132 | ||
133 | /* NULL-terminate the vector. */ | |
134 | m_argv.push_back (NULL); | |
135 | } | |
136 | ||
137 | /* When executing a command under the given shell, return true if the | |
138 | '!' character should be escaped when embedded in a quoted | |
139 | command-line argument. */ | |
140 | ||
141 | static bool | |
142 | escape_bang_in_quoted_argument (const char *shell_file) | |
143 | { | |
144 | size_t shell_file_len = strlen (shell_file); | |
145 | ||
146 | /* Bang should be escaped only in C Shells. For now, simply check | |
147 | that the shell name ends with 'csh', which covers at least csh | |
148 | and tcsh. This should be good enough for now. */ | |
149 | ||
150 | if (shell_file_len < 3) | |
151 | return false; | |
152 | ||
153 | if (shell_file[shell_file_len - 3] == 'c' | |
154 | && shell_file[shell_file_len - 2] == 's' | |
155 | && shell_file[shell_file_len - 1] == 'h') | |
156 | return true; | |
157 | ||
158 | return false; | |
159 | } | |
160 | ||
161 | /* See declaration. */ | |
162 | ||
163 | execv_argv::execv_argv (const char *exec_file, | |
164 | const std::string &allargs, | |
165 | const char *shell_file) | |
166 | { | |
167 | if (shell_file == NULL) | |
168 | init_for_no_shell (exec_file, allargs); | |
169 | else | |
170 | init_for_shell (exec_file, allargs, shell_file); | |
171 | } | |
172 | ||
173 | /* See declaration. */ | |
174 | ||
175 | void | |
176 | execv_argv::init_for_shell (const char *exec_file, | |
177 | const std::string &allargs, | |
178 | const char *shell_file) | |
179 | { | |
180 | const char *exec_wrapper = get_exec_wrapper (); | |
181 | ||
182 | /* We're going to call a shell. */ | |
183 | bool escape_bang = escape_bang_in_quoted_argument (shell_file); | |
184 | ||
185 | /* We need to build a new shell command string, and make argv point | |
186 | to it. So build it in the storage. */ | |
187 | std::string &shell_command = m_storage; | |
188 | ||
189 | shell_command = "exec "; | |
190 | ||
191 | /* Add any exec wrapper. That may be a program name with arguments, | |
192 | so the user must handle quoting. */ | |
193 | if (exec_wrapper != NULL) | |
194 | { | |
195 | shell_command += exec_wrapper; | |
196 | shell_command += ' '; | |
197 | } | |
198 | ||
199 | /* Now add exec_file, quoting as necessary. */ | |
200 | ||
201 | /* Quoting in this style is said to work with all shells. But csh | |
202 | on IRIX 4.0.1 can't deal with it. So we only quote it if we need | |
203 | to. */ | |
204 | bool need_to_quote; | |
205 | const char *p = exec_file; | |
206 | while (1) | |
207 | { | |
208 | switch (*p) | |
209 | { | |
210 | case '\'': | |
211 | case '!': | |
212 | case '"': | |
213 | case '(': | |
214 | case ')': | |
215 | case '$': | |
216 | case '&': | |
217 | case ';': | |
218 | case '<': | |
219 | case '>': | |
220 | case ' ': | |
221 | case '\n': | |
222 | case '\t': | |
223 | need_to_quote = true; | |
224 | goto end_scan; | |
225 | ||
226 | case '\0': | |
227 | need_to_quote = false; | |
228 | goto end_scan; | |
229 | ||
230 | default: | |
231 | break; | |
232 | } | |
233 | ++p; | |
234 | } | |
235 | end_scan: | |
236 | if (need_to_quote) | |
237 | { | |
238 | shell_command += '\''; | |
239 | for (p = exec_file; *p != '\0'; ++p) | |
240 | { | |
241 | if (*p == '\'') | |
242 | shell_command += "'\\''"; | |
243 | else if (*p == '!' && escape_bang) | |
244 | shell_command += "\\!"; | |
245 | else | |
246 | shell_command += *p; | |
247 | } | |
248 | shell_command += '\''; | |
249 | } | |
250 | else | |
251 | shell_command += exec_file; | |
252 | ||
253 | shell_command += ' ' + allargs; | |
254 | ||
255 | /* If we decided above to start up with a shell, we exec the shell. | |
256 | "-c" says to interpret the next arg as a shell command to | |
257 | execute, and this command is "exec <target-program> <args>". */ | |
258 | m_argv.reserve (4); | |
259 | m_argv.push_back (shell_file); | |
260 | m_argv.push_back ("-c"); | |
261 | m_argv.push_back (shell_command.c_str ()); | |
262 | m_argv.push_back (NULL); | |
263 | } | |
264 | ||
2090129c SDJ |
265 | /* See nat/fork-inferior.h. */ |
266 | ||
267 | pid_t | |
268 | fork_inferior (const char *exec_file_arg, const std::string &allargs, | |
269 | char **env, void (*traceme_fun) (), | |
270 | void (*init_trace_fun) (int), void (*pre_trace_fun) (), | |
271 | const char *shell_file_arg, | |
272 | void (*exec_fun)(const char *file, char * const *argv, | |
273 | char * const *env)) | |
274 | { | |
275 | pid_t pid; | |
276 | /* Set debug_fork then attach to the child while it sleeps, to debug. */ | |
277 | int debug_fork = 0; | |
278 | const char *shell_file; | |
279 | const char *exec_file; | |
280 | char **save_our_env; | |
281 | int i; | |
282 | int save_errno; | |
d092c5a2 SDJ |
283 | const char *inferior_cwd; |
284 | std::string expanded_inferior_cwd; | |
2090129c SDJ |
285 | |
286 | /* If no exec file handed to us, get it from the exec-file command | |
287 | -- with a good, common error message if none is specified. */ | |
288 | if (exec_file_arg == NULL) | |
289 | exec_file = get_exec_file (1); | |
290 | else | |
291 | exec_file = exec_file_arg; | |
292 | ||
293 | /* 'startup_with_shell' is declared in inferior.h and bound to the | |
294 | "set startup-with-shell" option. If 0, we'll just do a | |
295 | fork/exec, no shell, so don't bother figuring out what shell. */ | |
296 | if (startup_with_shell) | |
297 | { | |
298 | shell_file = shell_file_arg; | |
299 | ||
300 | /* Figure out what shell to start up the user program under. */ | |
301 | if (shell_file == NULL) | |
974e6844 | 302 | shell_file = get_shell (); |
2090129c SDJ |
303 | |
304 | gdb_assert (shell_file != NULL); | |
305 | } | |
306 | else | |
307 | shell_file = NULL; | |
308 | ||
309 | /* Build the argument vector. */ | |
310 | execv_argv child_argv (exec_file, allargs, shell_file); | |
311 | ||
312 | /* Retain a copy of our environment variables, since the child will | |
313 | replace the value of environ and if we're vforked, we have to | |
314 | restore it. */ | |
315 | save_our_env = environ; | |
316 | ||
317 | /* Perform any necessary actions regarding to TTY before the | |
318 | fork/vfork call. */ | |
319 | prefork_hook (allargs.c_str ()); | |
320 | ||
321 | /* It is generally good practice to flush any possible pending stdio | |
322 | output prior to doing a fork, to avoid the possibility of both | |
323 | the parent and child flushing the same data after the fork. */ | |
324 | gdb_flush_out_err (); | |
325 | ||
d092c5a2 SDJ |
326 | /* Check if the user wants to set a different working directory for |
327 | the inferior. */ | |
328 | inferior_cwd = get_inferior_cwd (); | |
329 | ||
330 | if (inferior_cwd != NULL) | |
331 | { | |
332 | /* Expand before forking because between fork and exec, the child | |
333 | process may only execute async-signal-safe operations. */ | |
334 | expanded_inferior_cwd = gdb_tilde_expand (inferior_cwd); | |
335 | inferior_cwd = expanded_inferior_cwd.c_str (); | |
336 | } | |
337 | ||
2090129c SDJ |
338 | /* If there's any initialization of the target layers that must |
339 | happen to prepare to handle the child we're about fork, do it | |
340 | now... */ | |
341 | if (pre_trace_fun != NULL) | |
342 | (*pre_trace_fun) (); | |
343 | ||
344 | /* Create the child process. Since the child process is going to | |
345 | exec(3) shortly afterwards, try to reduce the overhead by | |
346 | calling vfork(2). However, if PRE_TRACE_FUN is non-null, it's | |
347 | likely that this optimization won't work since there's too much | |
348 | work to do between the vfork(2) and the exec(3). This is known | |
349 | to be the case on ttrace(2)-based HP-UX, where some handshaking | |
350 | between parent and child needs to happen between fork(2) and | |
351 | exec(2). However, since the parent is suspended in the vforked | |
352 | state, this doesn't work. Also note that the vfork(2) call might | |
353 | actually be a call to fork(2) due to the fact that autoconf will | |
354 | ``#define vfork fork'' on certain platforms. */ | |
355 | #if !(defined(__UCLIBC__) && defined(HAS_NOMMU)) | |
356 | if (pre_trace_fun || debug_fork) | |
357 | pid = fork (); | |
358 | else | |
359 | #endif | |
360 | pid = vfork (); | |
361 | ||
362 | if (pid < 0) | |
363 | perror_with_name (("vfork")); | |
364 | ||
365 | if (pid == 0) | |
366 | { | |
367 | /* Close all file descriptors except those that gdb inherited | |
368 | (usually 0/1/2), so they don't leak to the inferior. Note | |
369 | that this closes the file descriptors of all secondary | |
370 | UIs. */ | |
371 | close_most_fds (); | |
372 | ||
d092c5a2 SDJ |
373 | /* Change to the requested working directory if the user |
374 | requested it. */ | |
375 | if (inferior_cwd != NULL) | |
376 | { | |
377 | if (chdir (inferior_cwd) < 0) | |
378 | trace_start_error_with_name (inferior_cwd); | |
379 | } | |
380 | ||
2090129c SDJ |
381 | if (debug_fork) |
382 | sleep (debug_fork); | |
383 | ||
384 | /* Execute any necessary post-fork actions before we exec. */ | |
385 | postfork_child_hook (); | |
386 | ||
387 | /* Changing the signal handlers for the inferior after | |
388 | a vfork can also change them for the superior, so we don't mess | |
389 | with signals here. See comments in | |
390 | initialize_signals for how we get the right signal handlers | |
391 | for the inferior. */ | |
392 | ||
393 | /* "Trace me, Dr. Memory!" */ | |
394 | (*traceme_fun) (); | |
395 | ||
396 | /* The call above set this process (the "child") as debuggable | |
397 | by the original gdb process (the "parent"). Since processes | |
398 | (unlike people) can have only one parent, if you are debugging | |
399 | gdb itself (and your debugger is thus _already_ the | |
400 | controller/parent for this child), code from here on out is | |
401 | undebuggable. Indeed, you probably got an error message | |
402 | saying "not parent". Sorry; you'll have to use print | |
403 | statements! */ | |
404 | ||
405 | restore_original_signals_state (); | |
406 | ||
407 | /* There is no execlpe call, so we have to set the environment | |
408 | for our child in the global variable. If we've vforked, this | |
409 | clobbers the parent, but environ is restored a few lines down | |
410 | in the parent. By the way, yes we do need to look down the | |
411 | path to find $SHELL. Rich Pixley says so, and I agree. */ | |
412 | environ = env; | |
413 | ||
414 | char **argv = child_argv.argv (); | |
415 | ||
416 | if (exec_fun != NULL) | |
417 | (*exec_fun) (argv[0], &argv[0], env); | |
418 | else | |
419 | execvp (argv[0], &argv[0]); | |
420 | ||
421 | /* If we get here, it's an error. */ | |
422 | save_errno = errno; | |
423 | warning ("Cannot exec %s", argv[0]); | |
424 | ||
425 | for (i = 1; argv[i] != NULL; i++) | |
426 | warning (" %s", argv[i]); | |
427 | ||
422186a9 | 428 | warning ("Error: %s", safe_strerror (save_errno)); |
2090129c SDJ |
429 | |
430 | _exit (0177); | |
431 | } | |
432 | ||
433 | /* Restore our environment in case a vforked child clob'd it. */ | |
434 | environ = save_our_env; | |
435 | ||
436 | postfork_hook (pid); | |
437 | ||
438 | /* Now that we have a child process, make it our target, and | |
439 | initialize anything target-vector-specific that needs | |
440 | initializing. */ | |
441 | if (init_trace_fun) | |
442 | (*init_trace_fun) (pid); | |
443 | ||
444 | /* We are now in the child process of interest, having exec'd the | |
445 | correct program, and are poised at the first instruction of the | |
446 | new program. */ | |
447 | return pid; | |
448 | } | |
449 | ||
450 | /* See nat/fork-inferior.h. */ | |
451 | ||
452 | ptid_t | |
453 | startup_inferior (pid_t pid, int ntraps, | |
454 | struct target_waitstatus *last_waitstatus, | |
455 | ptid_t *last_ptid) | |
456 | { | |
457 | int pending_execs = ntraps; | |
458 | int terminal_initted = 0; | |
459 | ptid_t resume_ptid; | |
460 | ||
461 | if (startup_with_shell) | |
462 | { | |
463 | /* One trap extra for exec'ing the shell. */ | |
464 | pending_execs++; | |
465 | } | |
466 | ||
467 | if (target_supports_multi_process ()) | |
f2907e49 | 468 | resume_ptid = ptid_t (pid); |
2090129c SDJ |
469 | else |
470 | resume_ptid = minus_one_ptid; | |
471 | ||
472 | /* The process was started by the fork that created it, but it will | |
473 | have stopped one instruction after execing the shell. Here we | |
474 | must get it up to actual execution of the real program. */ | |
475 | if (get_exec_wrapper () != NULL) | |
476 | pending_execs++; | |
477 | ||
478 | while (1) | |
479 | { | |
480 | enum gdb_signal resume_signal = GDB_SIGNAL_0; | |
481 | ptid_t event_ptid; | |
482 | ||
483 | struct target_waitstatus ws; | |
484 | memset (&ws, 0, sizeof (ws)); | |
485 | event_ptid = target_wait (resume_ptid, &ws, 0); | |
486 | ||
487 | if (last_waitstatus != NULL) | |
488 | *last_waitstatus = ws; | |
489 | if (last_ptid != NULL) | |
490 | *last_ptid = event_ptid; | |
491 | ||
492 | if (ws.kind == TARGET_WAITKIND_IGNORE) | |
493 | /* The inferior didn't really stop, keep waiting. */ | |
494 | continue; | |
495 | ||
496 | switch (ws.kind) | |
497 | { | |
498 | case TARGET_WAITKIND_SPURIOUS: | |
499 | case TARGET_WAITKIND_LOADED: | |
500 | case TARGET_WAITKIND_FORKED: | |
501 | case TARGET_WAITKIND_VFORKED: | |
502 | case TARGET_WAITKIND_SYSCALL_ENTRY: | |
503 | case TARGET_WAITKIND_SYSCALL_RETURN: | |
504 | /* Ignore gracefully during startup of the inferior. */ | |
505 | switch_to_thread (event_ptid); | |
506 | break; | |
507 | ||
508 | case TARGET_WAITKIND_SIGNALLED: | |
223ffa71 | 509 | target_terminal::ours (); |
2090129c SDJ |
510 | target_mourn_inferior (event_ptid); |
511 | error (_("During startup program terminated with signal %s, %s."), | |
512 | gdb_signal_to_name (ws.value.sig), | |
513 | gdb_signal_to_string (ws.value.sig)); | |
514 | return resume_ptid; | |
515 | ||
516 | case TARGET_WAITKIND_EXITED: | |
223ffa71 | 517 | target_terminal::ours (); |
2090129c SDJ |
518 | target_mourn_inferior (event_ptid); |
519 | if (ws.value.integer) | |
520 | error (_("During startup program exited with code %d."), | |
521 | ws.value.integer); | |
522 | else | |
523 | error (_("During startup program exited normally.")); | |
524 | return resume_ptid; | |
525 | ||
526 | case TARGET_WAITKIND_EXECD: | |
527 | /* Handle EXEC signals as if they were SIGTRAP signals. */ | |
528 | xfree (ws.value.execd_pathname); | |
529 | resume_signal = GDB_SIGNAL_TRAP; | |
530 | switch_to_thread (event_ptid); | |
531 | break; | |
532 | ||
533 | case TARGET_WAITKIND_STOPPED: | |
534 | resume_signal = ws.value.sig; | |
535 | switch_to_thread (event_ptid); | |
536 | break; | |
537 | } | |
538 | ||
539 | if (resume_signal != GDB_SIGNAL_TRAP) | |
540 | { | |
541 | /* Let shell child handle its own signals in its own way. */ | |
542 | target_continue (resume_ptid, resume_signal); | |
543 | } | |
544 | else | |
545 | { | |
546 | /* We handle SIGTRAP, however; it means child did an exec. */ | |
547 | if (!terminal_initted) | |
548 | { | |
549 | /* Now that the child has exec'd we know it has already | |
550 | set its process group. On POSIX systems, tcsetpgrp | |
551 | will fail with EPERM if we try it before the child's | |
552 | setpgid. */ | |
553 | ||
554 | /* Set up the "saved terminal modes" of the inferior | |
555 | based on what modes we are starting it with. */ | |
223ffa71 | 556 | target_terminal::init (); |
2090129c SDJ |
557 | |
558 | /* Install inferior's terminal modes. */ | |
223ffa71 | 559 | target_terminal::inferior (); |
2090129c SDJ |
560 | |
561 | terminal_initted = 1; | |
562 | } | |
563 | ||
564 | if (--pending_execs == 0) | |
565 | break; | |
566 | ||
567 | /* Just make it go on. */ | |
568 | target_continue_no_signal (resume_ptid); | |
569 | } | |
570 | } | |
571 | ||
572 | return resume_ptid; | |
573 | } | |
574 | ||
575 | /* See nat/fork-inferior.h. */ | |
576 | ||
577 | void | |
578 | trace_start_error (const char *fmt, ...) | |
579 | { | |
580 | va_list ap; | |
581 | ||
582 | va_start (ap, fmt); | |
583 | warning ("Could not trace the inferior process.\nError: "); | |
584 | vwarning (fmt, ap); | |
585 | va_end (ap); | |
586 | ||
587 | gdb_flush_out_err (); | |
588 | _exit (0177); | |
589 | } | |
590 | ||
591 | /* See nat/fork-inferior.h. */ | |
592 | ||
593 | void | |
594 | trace_start_error_with_name (const char *string) | |
595 | { | |
596 | trace_start_error ("%s: %s", string, safe_strerror (errno)); | |
597 | } |