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2090129c SDJ |
1 | /* Fork a Unix child process, and set up to debug it, for GDB and GDBserver. |
2 | ||
3 | Copyright (C) 1990-2017 Free Software Foundation, Inc. | |
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 | ||
20 | #include "common-defs.h" | |
21 | #include "fork-inferior.h" | |
22 | #include "target/waitstatus.h" | |
23 | #include "filestuff.h" | |
24 | #include "target/target.h" | |
25 | #include "common-inferior.h" | |
26 | #include "common-gdbthread.h" | |
27 | #include "signals-state-save-restore.h" | |
28 | #include <vector> | |
29 | ||
30 | extern char **environ; | |
31 | ||
32 | /* Default shell file to be used if 'startup-with-shell' is set but | |
33 | $SHELL is not. */ | |
34 | #define SHELL_FILE "/bin/sh" | |
35 | ||
36 | /* Build the argument vector for execv(3). */ | |
37 | ||
38 | class execv_argv | |
39 | { | |
40 | public: | |
41 | /* EXEC_FILE is the file to run. ALLARGS is a string containing the | |
42 | arguments to the program. If starting with a shell, SHELL_FILE | |
43 | is the shell to run. Otherwise, SHELL_FILE is NULL. */ | |
44 | execv_argv (const char *exec_file, const std::string &allargs, | |
45 | const char *shell_file); | |
46 | ||
47 | /* Return a pointer to the built argv, in the type expected by | |
48 | execv. The result is (only) valid for as long as this execv_argv | |
49 | object is live. We return a "char **" because that's the type | |
50 | that the execv functions expect. Note that it is guaranteed that | |
51 | the execv functions do not modify the argv[] array nor the | |
52 | strings to which the array point. */ | |
53 | char **argv () | |
54 | { | |
55 | return const_cast<char **> (&m_argv[0]); | |
56 | } | |
57 | ||
58 | private: | |
d6541620 | 59 | DISABLE_COPY_AND_ASSIGN (execv_argv); |
2090129c SDJ |
60 | |
61 | /* Helper methods for constructing the argument vector. */ | |
62 | ||
63 | /* Used when building an argv for a straight execv call, without | |
64 | going via the shell. */ | |
65 | void init_for_no_shell (const char *exec_file, | |
66 | const std::string &allargs); | |
67 | ||
68 | /* Used when building an argv for execing a shell that execs the | |
69 | child program. */ | |
70 | void init_for_shell (const char *exec_file, | |
71 | const std::string &allargs, | |
72 | const char *shell_file); | |
73 | ||
74 | /* The argument vector built. Holds non-owning pointers. Elements | |
75 | either point to the strings passed to the execv_argv ctor, or | |
76 | inside M_STORAGE. */ | |
77 | std::vector<const char *> m_argv; | |
78 | ||
79 | /* Storage. In the no-shell case, this contains a copy of the | |
80 | arguments passed to the ctor, split by '\0'. In the shell case, | |
81 | this contains the quoted shell command. I.e., SHELL_COMMAND in | |
82 | {"$SHELL" "-c", SHELL_COMMAND, NULL}. */ | |
83 | std::string m_storage; | |
84 | }; | |
85 | ||
86 | /* Create argument vector for straight call to execvp. Breaks up | |
87 | ALLARGS into an argument vector suitable for passing to execvp and | |
88 | stores it in M_ARGV. E.g., on "run a b c d" this routine would get | |
89 | as input the string "a b c d", and as output it would fill in | |
90 | M_ARGV with the four arguments "a", "b", "c", "d". Each argument | |
91 | in M_ARGV points to a substring of a copy of ALLARGS stored in | |
92 | M_STORAGE. */ | |
93 | ||
94 | void | |
95 | execv_argv::init_for_no_shell (const char *exec_file, | |
96 | const std::string &allargs) | |
97 | { | |
98 | ||
99 | /* Save/work with a copy stored in our storage. The pointers pushed | |
100 | to M_ARGV point directly into M_STORAGE, which is modified in | |
101 | place with the necessary NULL terminators. This avoids N heap | |
102 | allocations and string dups when 1 is sufficient. */ | |
103 | std::string &args_copy = m_storage = allargs; | |
104 | ||
105 | m_argv.push_back (exec_file); | |
106 | ||
107 | for (size_t cur_pos = 0; cur_pos < args_copy.size ();) | |
108 | { | |
109 | /* Skip whitespace-like chars. */ | |
110 | std::size_t pos = args_copy.find_first_not_of (" \t\n", cur_pos); | |
111 | ||
112 | if (pos != std::string::npos) | |
113 | cur_pos = pos; | |
114 | ||
115 | /* Find the position of the next separator. */ | |
116 | std::size_t next_sep = args_copy.find_first_of (" \t\n", cur_pos); | |
117 | ||
118 | if (next_sep == std::string::npos) | |
119 | { | |
120 | /* No separator found, which means this is the last | |
121 | argument. */ | |
122 | next_sep = args_copy.size (); | |
123 | } | |
124 | else | |
125 | { | |
126 | /* Replace the separator with a terminator. */ | |
127 | args_copy[next_sep++] = '\0'; | |
128 | } | |
129 | ||
130 | m_argv.push_back (&args_copy[cur_pos]); | |
131 | ||
132 | cur_pos = next_sep; | |
133 | } | |
134 | ||
135 | /* NULL-terminate the vector. */ | |
136 | m_argv.push_back (NULL); | |
137 | } | |
138 | ||
139 | /* When executing a command under the given shell, return true if the | |
140 | '!' character should be escaped when embedded in a quoted | |
141 | command-line argument. */ | |
142 | ||
143 | static bool | |
144 | escape_bang_in_quoted_argument (const char *shell_file) | |
145 | { | |
146 | size_t shell_file_len = strlen (shell_file); | |
147 | ||
148 | /* Bang should be escaped only in C Shells. For now, simply check | |
149 | that the shell name ends with 'csh', which covers at least csh | |
150 | and tcsh. This should be good enough for now. */ | |
151 | ||
152 | if (shell_file_len < 3) | |
153 | return false; | |
154 | ||
155 | if (shell_file[shell_file_len - 3] == 'c' | |
156 | && shell_file[shell_file_len - 2] == 's' | |
157 | && shell_file[shell_file_len - 1] == 'h') | |
158 | return true; | |
159 | ||
160 | return false; | |
161 | } | |
162 | ||
163 | /* See declaration. */ | |
164 | ||
165 | execv_argv::execv_argv (const char *exec_file, | |
166 | const std::string &allargs, | |
167 | const char *shell_file) | |
168 | { | |
169 | if (shell_file == NULL) | |
170 | init_for_no_shell (exec_file, allargs); | |
171 | else | |
172 | init_for_shell (exec_file, allargs, shell_file); | |
173 | } | |
174 | ||
175 | /* See declaration. */ | |
176 | ||
177 | void | |
178 | execv_argv::init_for_shell (const char *exec_file, | |
179 | const std::string &allargs, | |
180 | const char *shell_file) | |
181 | { | |
182 | const char *exec_wrapper = get_exec_wrapper (); | |
183 | ||
184 | /* We're going to call a shell. */ | |
185 | bool escape_bang = escape_bang_in_quoted_argument (shell_file); | |
186 | ||
187 | /* We need to build a new shell command string, and make argv point | |
188 | to it. So build it in the storage. */ | |
189 | std::string &shell_command = m_storage; | |
190 | ||
191 | shell_command = "exec "; | |
192 | ||
193 | /* Add any exec wrapper. That may be a program name with arguments, | |
194 | so the user must handle quoting. */ | |
195 | if (exec_wrapper != NULL) | |
196 | { | |
197 | shell_command += exec_wrapper; | |
198 | 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 csh | |
204 | on IRIX 4.0.1 can't deal with it. So we only quote it if we need | |
205 | to. */ | |
206 | bool need_to_quote; | |
207 | const char *p = exec_file; | |
208 | while (1) | |
209 | { | |
210 | switch (*p) | |
211 | { | |
212 | case '\'': | |
213 | case '!': | |
214 | case '"': | |
215 | case '(': | |
216 | case ')': | |
217 | case '$': | |
218 | case '&': | |
219 | case ';': | |
220 | case '<': | |
221 | case '>': | |
222 | case ' ': | |
223 | case '\n': | |
224 | case '\t': | |
225 | need_to_quote = true; | |
226 | goto end_scan; | |
227 | ||
228 | case '\0': | |
229 | need_to_quote = false; | |
230 | goto end_scan; | |
231 | ||
232 | default: | |
233 | break; | |
234 | } | |
235 | ++p; | |
236 | } | |
237 | end_scan: | |
238 | if (need_to_quote) | |
239 | { | |
240 | shell_command += '\''; | |
241 | for (p = exec_file; *p != '\0'; ++p) | |
242 | { | |
243 | if (*p == '\'') | |
244 | shell_command += "'\\''"; | |
245 | else if (*p == '!' && escape_bang) | |
246 | shell_command += "\\!"; | |
247 | else | |
248 | shell_command += *p; | |
249 | } | |
250 | shell_command += '\''; | |
251 | } | |
252 | else | |
253 | shell_command += exec_file; | |
254 | ||
255 | shell_command += ' ' + allargs; | |
256 | ||
257 | /* If we decided above to start up with a shell, we exec the shell. | |
258 | "-c" says to interpret the next arg as a shell command to | |
259 | execute, and this command is "exec <target-program> <args>". */ | |
260 | m_argv.reserve (4); | |
261 | m_argv.push_back (shell_file); | |
262 | m_argv.push_back ("-c"); | |
263 | m_argv.push_back (shell_command.c_str ()); | |
264 | m_argv.push_back (NULL); | |
265 | } | |
266 | ||
267 | /* Return the shell that must be used to startup the inferior. The | |
268 | first attempt is the environment variable SHELL; if it is not set, | |
269 | then we default to SHELL_FILE. */ | |
270 | ||
271 | static const char * | |
272 | get_startup_shell () | |
273 | { | |
274 | static const char *ret; | |
275 | ||
276 | ret = getenv ("SHELL"); | |
277 | if (ret == NULL) | |
278 | ret = SHELL_FILE; | |
279 | ||
280 | return ret; | |
281 | } | |
282 | ||
283 | /* See nat/fork-inferior.h. */ | |
284 | ||
285 | pid_t | |
286 | fork_inferior (const char *exec_file_arg, const std::string &allargs, | |
287 | char **env, void (*traceme_fun) (), | |
288 | void (*init_trace_fun) (int), void (*pre_trace_fun) (), | |
289 | const char *shell_file_arg, | |
290 | void (*exec_fun)(const char *file, char * const *argv, | |
291 | char * const *env)) | |
292 | { | |
293 | pid_t pid; | |
294 | /* Set debug_fork then attach to the child while it sleeps, to debug. */ | |
295 | int debug_fork = 0; | |
296 | const char *shell_file; | |
297 | const char *exec_file; | |
298 | char **save_our_env; | |
299 | int i; | |
300 | int save_errno; | |
301 | ||
302 | /* If no exec file handed to us, get it from the exec-file command | |
303 | -- with a good, common error message if none is specified. */ | |
304 | if (exec_file_arg == NULL) | |
305 | exec_file = get_exec_file (1); | |
306 | else | |
307 | exec_file = exec_file_arg; | |
308 | ||
309 | /* 'startup_with_shell' is declared in inferior.h and bound to the | |
310 | "set startup-with-shell" option. If 0, we'll just do a | |
311 | fork/exec, no shell, so don't bother figuring out what shell. */ | |
312 | if (startup_with_shell) | |
313 | { | |
314 | shell_file = shell_file_arg; | |
315 | ||
316 | /* Figure out what shell to start up the user program under. */ | |
317 | if (shell_file == NULL) | |
318 | shell_file = get_startup_shell (); | |
319 | ||
320 | gdb_assert (shell_file != NULL); | |
321 | } | |
322 | else | |
323 | shell_file = NULL; | |
324 | ||
325 | /* Build the argument vector. */ | |
326 | execv_argv child_argv (exec_file, allargs, shell_file); | |
327 | ||
328 | /* Retain a copy of our environment variables, since the child will | |
329 | replace the value of environ and if we're vforked, we have to | |
330 | restore it. */ | |
331 | save_our_env = environ; | |
332 | ||
333 | /* Perform any necessary actions regarding to TTY before the | |
334 | fork/vfork call. */ | |
335 | prefork_hook (allargs.c_str ()); | |
336 | ||
337 | /* It is generally good practice to flush any possible pending stdio | |
338 | output prior to doing a fork, to avoid the possibility of both | |
339 | the parent and child flushing the same data after the fork. */ | |
340 | gdb_flush_out_err (); | |
341 | ||
342 | /* If there's any initialization of the target layers that must | |
343 | happen to prepare to handle the child we're about fork, do it | |
344 | now... */ | |
345 | if (pre_trace_fun != NULL) | |
346 | (*pre_trace_fun) (); | |
347 | ||
348 | /* Create the child process. Since the child process is going to | |
349 | exec(3) shortly afterwards, try to reduce the overhead by | |
350 | calling vfork(2). However, if PRE_TRACE_FUN is non-null, it's | |
351 | likely that this optimization won't work since there's too much | |
352 | work to do between the vfork(2) and the exec(3). This is known | |
353 | to be the case on ttrace(2)-based HP-UX, where some handshaking | |
354 | between parent and child needs to happen between fork(2) and | |
355 | exec(2). However, since the parent is suspended in the vforked | |
356 | state, this doesn't work. Also note that the vfork(2) call might | |
357 | actually be a call to fork(2) due to the fact that autoconf will | |
358 | ``#define vfork fork'' on certain platforms. */ | |
359 | #if !(defined(__UCLIBC__) && defined(HAS_NOMMU)) | |
360 | if (pre_trace_fun || debug_fork) | |
361 | pid = fork (); | |
362 | else | |
363 | #endif | |
364 | pid = vfork (); | |
365 | ||
366 | if (pid < 0) | |
367 | perror_with_name (("vfork")); | |
368 | ||
369 | if (pid == 0) | |
370 | { | |
371 | /* Close all file descriptors except those that gdb inherited | |
372 | (usually 0/1/2), so they don't leak to the inferior. Note | |
373 | that this closes the file descriptors of all secondary | |
374 | UIs. */ | |
375 | close_most_fds (); | |
376 | ||
377 | if (debug_fork) | |
378 | sleep (debug_fork); | |
379 | ||
380 | /* Execute any necessary post-fork actions before we exec. */ | |
381 | postfork_child_hook (); | |
382 | ||
383 | /* Changing the signal handlers for the inferior after | |
384 | a vfork can also change them for the superior, so we don't mess | |
385 | with signals here. See comments in | |
386 | initialize_signals for how we get the right signal handlers | |
387 | for the inferior. */ | |
388 | ||
389 | /* "Trace me, Dr. Memory!" */ | |
390 | (*traceme_fun) (); | |
391 | ||
392 | /* The call above set this process (the "child") as debuggable | |
393 | by the original gdb process (the "parent"). Since processes | |
394 | (unlike people) can have only one parent, if you are debugging | |
395 | gdb itself (and your debugger is thus _already_ the | |
396 | controller/parent for this child), code from here on out is | |
397 | undebuggable. Indeed, you probably got an error message | |
398 | saying "not parent". Sorry; you'll have to use print | |
399 | statements! */ | |
400 | ||
401 | restore_original_signals_state (); | |
402 | ||
403 | /* There is no execlpe call, so we have to set the environment | |
404 | for our child in the global variable. If we've vforked, this | |
405 | clobbers the parent, but environ is restored a few lines down | |
406 | in the parent. By the way, yes we do need to look down the | |
407 | path to find $SHELL. Rich Pixley says so, and I agree. */ | |
408 | environ = env; | |
409 | ||
410 | char **argv = child_argv.argv (); | |
411 | ||
412 | if (exec_fun != NULL) | |
413 | (*exec_fun) (argv[0], &argv[0], env); | |
414 | else | |
415 | execvp (argv[0], &argv[0]); | |
416 | ||
417 | /* If we get here, it's an error. */ | |
418 | save_errno = errno; | |
419 | warning ("Cannot exec %s", argv[0]); | |
420 | ||
421 | for (i = 1; argv[i] != NULL; i++) | |
422 | warning (" %s", argv[i]); | |
423 | ||
424 | warning ("Error: %s\n", safe_strerror (save_errno)); | |
425 | ||
426 | _exit (0177); | |
427 | } | |
428 | ||
429 | /* Restore our environment in case a vforked child clob'd it. */ | |
430 | environ = save_our_env; | |
431 | ||
432 | postfork_hook (pid); | |
433 | ||
434 | /* Now that we have a child process, make it our target, and | |
435 | initialize anything target-vector-specific that needs | |
436 | initializing. */ | |
437 | if (init_trace_fun) | |
438 | (*init_trace_fun) (pid); | |
439 | ||
440 | /* We are now in the child process of interest, having exec'd the | |
441 | correct program, and are poised at the first instruction of the | |
442 | new program. */ | |
443 | return pid; | |
444 | } | |
445 | ||
446 | /* See nat/fork-inferior.h. */ | |
447 | ||
448 | ptid_t | |
449 | startup_inferior (pid_t pid, int ntraps, | |
450 | struct target_waitstatus *last_waitstatus, | |
451 | ptid_t *last_ptid) | |
452 | { | |
453 | int pending_execs = ntraps; | |
454 | int terminal_initted = 0; | |
455 | ptid_t resume_ptid; | |
456 | ||
457 | if (startup_with_shell) | |
458 | { | |
459 | /* One trap extra for exec'ing the shell. */ | |
460 | pending_execs++; | |
461 | } | |
462 | ||
463 | if (target_supports_multi_process ()) | |
464 | resume_ptid = pid_to_ptid (pid); | |
465 | else | |
466 | resume_ptid = minus_one_ptid; | |
467 | ||
468 | /* The process was started by the fork that created it, but it will | |
469 | have stopped one instruction after execing the shell. Here we | |
470 | must get it up to actual execution of the real program. */ | |
471 | if (get_exec_wrapper () != NULL) | |
472 | pending_execs++; | |
473 | ||
474 | while (1) | |
475 | { | |
476 | enum gdb_signal resume_signal = GDB_SIGNAL_0; | |
477 | ptid_t event_ptid; | |
478 | ||
479 | struct target_waitstatus ws; | |
480 | memset (&ws, 0, sizeof (ws)); | |
481 | event_ptid = target_wait (resume_ptid, &ws, 0); | |
482 | ||
483 | if (last_waitstatus != NULL) | |
484 | *last_waitstatus = ws; | |
485 | if (last_ptid != NULL) | |
486 | *last_ptid = event_ptid; | |
487 | ||
488 | if (ws.kind == TARGET_WAITKIND_IGNORE) | |
489 | /* The inferior didn't really stop, keep waiting. */ | |
490 | continue; | |
491 | ||
492 | switch (ws.kind) | |
493 | { | |
494 | case TARGET_WAITKIND_SPURIOUS: | |
495 | case TARGET_WAITKIND_LOADED: | |
496 | case TARGET_WAITKIND_FORKED: | |
497 | case TARGET_WAITKIND_VFORKED: | |
498 | case TARGET_WAITKIND_SYSCALL_ENTRY: | |
499 | case TARGET_WAITKIND_SYSCALL_RETURN: | |
500 | /* Ignore gracefully during startup of the inferior. */ | |
501 | switch_to_thread (event_ptid); | |
502 | break; | |
503 | ||
504 | case TARGET_WAITKIND_SIGNALLED: | |
505 | target_terminal_ours (); | |
506 | target_mourn_inferior (event_ptid); | |
507 | error (_("During startup program terminated with signal %s, %s."), | |
508 | gdb_signal_to_name (ws.value.sig), | |
509 | gdb_signal_to_string (ws.value.sig)); | |
510 | return resume_ptid; | |
511 | ||
512 | case TARGET_WAITKIND_EXITED: | |
513 | target_terminal_ours (); | |
514 | target_mourn_inferior (event_ptid); | |
515 | if (ws.value.integer) | |
516 | error (_("During startup program exited with code %d."), | |
517 | ws.value.integer); | |
518 | else | |
519 | error (_("During startup program exited normally.")); | |
520 | return resume_ptid; | |
521 | ||
522 | case TARGET_WAITKIND_EXECD: | |
523 | /* Handle EXEC signals as if they were SIGTRAP signals. */ | |
524 | xfree (ws.value.execd_pathname); | |
525 | resume_signal = GDB_SIGNAL_TRAP; | |
526 | switch_to_thread (event_ptid); | |
527 | break; | |
528 | ||
529 | case TARGET_WAITKIND_STOPPED: | |
530 | resume_signal = ws.value.sig; | |
531 | switch_to_thread (event_ptid); | |
532 | break; | |
533 | } | |
534 | ||
535 | if (resume_signal != GDB_SIGNAL_TRAP) | |
536 | { | |
537 | /* Let shell child handle its own signals in its own way. */ | |
538 | target_continue (resume_ptid, resume_signal); | |
539 | } | |
540 | else | |
541 | { | |
542 | /* We handle SIGTRAP, however; it means child did an exec. */ | |
543 | if (!terminal_initted) | |
544 | { | |
545 | /* Now that the child has exec'd we know it has already | |
546 | set its process group. On POSIX systems, tcsetpgrp | |
547 | will fail with EPERM if we try it before the child's | |
548 | setpgid. */ | |
549 | ||
550 | /* Set up the "saved terminal modes" of the inferior | |
551 | based on what modes we are starting it with. */ | |
552 | target_terminal_init (); | |
553 | ||
554 | /* Install inferior's terminal modes. */ | |
555 | target_terminal_inferior (); | |
556 | ||
557 | terminal_initted = 1; | |
558 | } | |
559 | ||
560 | if (--pending_execs == 0) | |
561 | break; | |
562 | ||
563 | /* Just make it go on. */ | |
564 | target_continue_no_signal (resume_ptid); | |
565 | } | |
566 | } | |
567 | ||
568 | return resume_ptid; | |
569 | } | |
570 | ||
571 | /* See nat/fork-inferior.h. */ | |
572 | ||
573 | void | |
574 | trace_start_error (const char *fmt, ...) | |
575 | { | |
576 | va_list ap; | |
577 | ||
578 | va_start (ap, fmt); | |
579 | warning ("Could not trace the inferior process.\nError: "); | |
580 | vwarning (fmt, ap); | |
581 | va_end (ap); | |
582 | ||
583 | gdb_flush_out_err (); | |
584 | _exit (0177); | |
585 | } | |
586 | ||
587 | /* See nat/fork-inferior.h. */ | |
588 | ||
589 | void | |
590 | trace_start_error_with_name (const char *string) | |
591 | { | |
592 | trace_start_error ("%s: %s", string, safe_strerror (errno)); | |
593 | } |