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[/] [openrisc/] [trunk/] [gnu-src/] [gdb-6.8/] [gdb/] [fork-child.c] - Blame information for rev 294

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1 24 jeremybenn
/* 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 "solib.h"
35
 
36
#include <signal.h>
37
 
38
/* This just gets used as a default if we can't find SHELL.  */
39
#define SHELL_FILE "/bin/sh"
40
 
41
extern char **environ;
42
 
43
/* Break up SCRATCH into an argument vector suitable for passing to
44
   execvp and store it in ARGV.  E.g., on "run a b c d" this routine
45
   would get as input the string "a b c d", and as output it would
46
   fill in ARGV with the four arguments "a", "b", "c", "d".  */
47
 
48
static void
49
breakup_args (char *scratch, char **argv)
50
{
51
  char *cp = scratch;
52
 
53
  for (;;)
54
    {
55
      /* Scan past leading separators */
56
      while (*cp == ' ' || *cp == '\t' || *cp == '\n')
57
        cp++;
58
 
59
      /* Break if at end of string.  */
60
      if (*cp == '\0')
61
        break;
62
 
63
      /* Take an arg.  */
64
      *argv++ = cp;
65
 
66
      /* Scan for next arg separator.  */
67
      cp = strchr (cp, ' ');
68
      if (cp == NULL)
69
        cp = strchr (cp, '\t');
70
      if (cp == NULL)
71
        cp = strchr (cp, '\n');
72
 
73
      /* No separators => end of string => break.  */
74
      if (cp == NULL)
75
        break;
76
 
77
      /* Replace the separator with a terminator.  */
78
      *cp++ = '\0';
79
    }
80
 
81
  /* Null-terminate the vector.  */
82
  *argv = NULL;
83
}
84
 
85
/* When executing a command under the given shell, return non-zero if
86
   the '!' character should be escaped when embedded in a quoted
87
   command-line argument.  */
88
 
89
static int
90
escape_bang_in_quoted_argument (const char *shell_file)
91
{
92
  const int shell_file_len = strlen (shell_file);
93
 
94
  /* Bang should be escaped only in C Shells.  For now, simply check
95
     that the shell name ends with 'csh', which covers at least csh
96
     and tcsh.  This should be good enough for now.  */
97
 
98
  if (shell_file_len < 3)
99
    return 0;
100
 
101
  if (shell_file[shell_file_len - 3] == 'c'
102
      && shell_file[shell_file_len - 2] == 's'
103
      && shell_file[shell_file_len - 1] == 'h')
104
    return 1;
105
 
106
  return 0;
107
}
108
 
109
/* Start an inferior Unix child process and sets inferior_ptid to its
110
   pid.  EXEC_FILE is the file to run.  ALLARGS is a string containing
111
   the arguments to the program.  ENV is the environment vector to
112
   pass.  SHELL_FILE is the shell file, or NULL if we should pick
113
   one.  */
114
 
115
/* This function is NOT reentrant.  Some of the variables have been
116
   made static to ensure that they survive the vfork call.  */
117
 
118
void
119
fork_inferior (char *exec_file_arg, char *allargs, char **env,
120
               void (*traceme_fun) (void), void (*init_trace_fun) (int),
121
               void (*pre_trace_fun) (void), char *shell_file_arg)
122
{
123
  int pid;
124
  char *shell_command;
125
  static char default_shell_file[] = SHELL_FILE;
126
  int len;
127
  /* Set debug_fork then attach to the child while it sleeps, to debug. */
128
  static int debug_fork = 0;
129
  /* This is set to the result of setpgrp, which if vforked, will be visible
130
     to you in the parent process.  It's only used by humans for debugging.  */
131
  static int debug_setpgrp = 657473;
132
  static char *shell_file;
133
  static char *exec_file;
134
  char **save_our_env;
135
  int shell = 0;
136
  static char **argv;
137
  const char *inferior_io_terminal = get_inferior_io_terminal ();
138
 
139
  /* If no exec file handed to us, get it from the exec-file command
140
     -- with a good, common error message if none is specified.  */
141
  exec_file = exec_file_arg;
142
  if (exec_file == 0)
143
    exec_file = get_exec_file (1);
144
 
145
  /* STARTUP_WITH_SHELL is defined in inferior.h.  If 0,e we'll just
146
    do a fork/exec, no shell, so don't bother figuring out what
147
    shell.  */
148
  shell_file = shell_file_arg;
149
  if (STARTUP_WITH_SHELL)
150
    {
151
      /* Figure out what shell to start up the user program under.  */
152
      if (shell_file == NULL)
153
        shell_file = getenv ("SHELL");
154
      if (shell_file == NULL)
155
        shell_file = default_shell_file;
156
      shell = 1;
157
    }
158
 
159
  /* Multiplying the length of exec_file by 4 is to account for the
160
     fact that it may expand when quoted; it is a worst-case number
161
     based on every character being '.  */
162
  len = 5 + 4 * strlen (exec_file) + 1 + strlen (allargs) + 1 + /*slop */ 12;
163
  shell_command = (char *) alloca (len);
164
  shell_command[0] = '\0';
165
 
166
  if (!shell)
167
    {
168
      /* We're going to call execvp.  Create argument vector.
169
         Calculate an upper bound on the length of the vector by
170
         assuming that every other character is a separate
171
         argument.  */
172
      int argc = (strlen (allargs) + 1) / 2 + 2;
173
      argv = (char **) xmalloc (argc * sizeof (*argv));
174
      argv[0] = exec_file;
175
      breakup_args (allargs, &argv[1]);
176
    }
177
  else
178
    {
179
      /* We're going to call a shell.  */
180
 
181
      /* Now add exec_file, quoting as necessary.  */
182
 
183
      char *p;
184
      int need_to_quote;
185
      const int escape_bang = escape_bang_in_quoted_argument (shell_file);
186
 
187
      strcat (shell_command, "exec ");
188
 
189
      /* Quoting in this style is said to work with all shells.  But
190
         csh on IRIX 4.0.1 can't deal with it.  So we only quote it if
191
         we need to.  */
192
      p = exec_file;
193
      while (1)
194
        {
195
          switch (*p)
196
            {
197
            case '\'':
198
            case '!':
199
            case '"':
200
            case '(':
201
            case ')':
202
            case '$':
203
            case '&':
204
            case ';':
205
            case '<':
206
            case '>':
207
            case ' ':
208
            case '\n':
209
            case '\t':
210
              need_to_quote = 1;
211
              goto end_scan;
212
 
213
            case '\0':
214
              need_to_quote = 0;
215
              goto end_scan;
216
 
217
            default:
218
              break;
219
            }
220
          ++p;
221
        }
222
    end_scan:
223
      if (need_to_quote)
224
        {
225
          strcat (shell_command, "'");
226
          for (p = exec_file; *p != '\0'; ++p)
227
            {
228
              if (*p == '\'')
229
                strcat (shell_command, "'\\''");
230
              else if (*p == '!' && escape_bang)
231
                strcat (shell_command, "\\!");
232
              else
233
                strncat (shell_command, p, 1);
234
            }
235
          strcat (shell_command, "'");
236
        }
237
      else
238
        strcat (shell_command, exec_file);
239
 
240
      strcat (shell_command, " ");
241
      strcat (shell_command, allargs);
242
    }
243
 
244
  /* On some systems an exec will fail if the executable is open.  */
245
  close_exec_file ();
246
 
247
  /* Retain a copy of our environment variables, since the child will
248
     replace the value of environ and if we're vforked, we have to
249
     restore it.  */
250
  save_our_env = environ;
251
 
252
  /* Tell the terminal handling subsystem what tty we plan to run on;
253
     it will just record the information for later.  */
254
  new_tty_prefork (inferior_io_terminal);
255
 
256
  /* It is generally good practice to flush any possible pending stdio
257
     output prior to doing a fork, to avoid the possibility of both
258
     the parent and child flushing the same data after the fork. */
259
  gdb_flush (gdb_stdout);
260
  gdb_flush (gdb_stderr);
261
 
262
  /* If there's any initialization of the target layers that must
263
     happen to prepare to handle the child we're about fork, do it
264
     now...  */
265
  if (pre_trace_fun != NULL)
266
    (*pre_trace_fun) ();
267
 
268
  /* Create the child process.  Since the child process is going to
269
     exec(3) shortly afterwards, try to reduce the overhead by
270
     calling vfork(2).  However, if PRE_TRACE_FUN is non-null, it's
271
     likely that this optimization won't work since there's too much
272
     work to do between the vfork(2) and the exec(3).  This is known
273
     to be the case on ttrace(2)-based HP-UX, where some handshaking
274
     between parent and child needs to happen between fork(2) and
275
     exec(2).  However, since the parent is suspended in the vforked
276
     state, this doesn't work.  Also note that the vfork(2) call might
277
     actually be a call to fork(2) due to the fact that autoconf will
278
     ``#define vfork fork'' on certain platforms.  */
279
  if (pre_trace_fun || debug_fork)
280
    pid = fork ();
281
  else
282
    pid = vfork ();
283
 
284
  if (pid < 0)
285
    perror_with_name (("vfork"));
286
 
287
  if (pid == 0)
288
    {
289
      if (debug_fork)
290
        sleep (debug_fork);
291
 
292
      /* Run inferior in a separate process group.  */
293
      debug_setpgrp = gdb_setpgid ();
294
      if (debug_setpgrp == -1)
295
        perror ("setpgrp failed in child");
296
 
297
      /* Ask the tty subsystem to switch to the one we specified
298
         earlier (or to share the current terminal, if none was
299
         specified).  */
300
      new_tty ();
301
 
302
      /* Changing the signal handlers for the inferior after
303
         a vfork can also change them for the superior, so we don't mess
304
         with signals here.  See comments in
305
         initialize_signals for how we get the right signal handlers
306
         for the inferior.  */
307
 
308
      /* "Trace me, Dr. Memory!" */
309
      (*traceme_fun) ();
310
 
311
      /* The call above set this process (the "child") as debuggable
312
        by the original gdb process (the "parent").  Since processes
313
        (unlike people) can have only one parent, if you are debugging
314
        gdb itself (and your debugger is thus _already_ the
315
        controller/parent for this child), code from here on out is
316
        undebuggable.  Indeed, you probably got an error message
317
        saying "not parent".  Sorry; you'll have to use print
318
        statements!  */
319
 
320
      /* There is no execlpe call, so we have to set the environment
321
         for our child in the global variable.  If we've vforked, this
322
         clobbers the parent, but environ is restored a few lines down
323
         in the parent.  By the way, yes we do need to look down the
324
         path to find $SHELL.  Rich Pixley says so, and I agree.  */
325
      environ = env;
326
 
327
      /* If we decided above to start up with a shell, we exec the
328
         shell, "-c" says to interpret the next arg as a shell command
329
         to execute, and this command is "exec <target-program>
330
         <args>".  */
331
      if (shell)
332
        {
333
          execlp (shell_file, shell_file, "-c", shell_command, (char *) 0);
334
 
335
          /* If we get here, it's an error.  */
336
          fprintf_unfiltered (gdb_stderr, "Cannot exec %s: %s.\n", shell_file,
337
                              safe_strerror (errno));
338
          gdb_flush (gdb_stderr);
339
          _exit (0177);
340
        }
341
      else
342
        {
343
          /* Otherwise, we directly exec the target program with
344
             execvp.  */
345
          int i;
346
          char *errstring;
347
 
348
          execvp (exec_file, argv);
349
 
350
          /* If we get here, it's an error.  */
351
          errstring = safe_strerror (errno);
352
          fprintf_unfiltered (gdb_stderr, "Cannot exec %s ", exec_file);
353
 
354
          i = 1;
355
          while (argv[i] != NULL)
356
            {
357
              if (i != 1)
358
                fprintf_unfiltered (gdb_stderr, " ");
359
              fprintf_unfiltered (gdb_stderr, "%s", argv[i]);
360
              i++;
361
            }
362
          fprintf_unfiltered (gdb_stderr, ".\n");
363
#if 0
364
          /* This extra info seems to be useless.  */
365
          fprintf_unfiltered (gdb_stderr, "Got error %s.\n", errstring);
366
#endif
367
          gdb_flush (gdb_stderr);
368
          _exit (0177);
369
        }
370
    }
371
 
372
  /* Restore our environment in case a vforked child clob'd it.  */
373
  environ = save_our_env;
374
 
375
  init_thread_list ();
376
 
377
  /* Needed for wait_for_inferior stuff below.  */
378
  inferior_ptid = pid_to_ptid (pid);
379
 
380
  /* Now that we have a child process, make it our target, and
381
     initialize anything target-vector-specific that needs
382
     initializing.  */
383
  (*init_trace_fun) (pid);
384
 
385
  /* We are now in the child process of interest, having exec'd the
386
     correct program, and are poised at the first instruction of the
387
     new program.  */
388
}
389
 
390
/* Accept NTRAPS traps from the inferior.  */
391
 
392
void
393
startup_inferior (int ntraps)
394
{
395
  int pending_execs = ntraps;
396
  int terminal_initted = 0;
397
 
398
  /* The process was started by the fork that created it, but it will
399
     have stopped one instruction after execing the shell.  Here we
400
     must get it up to actual execution of the real program.  */
401
 
402
  clear_proceed_status ();
403
 
404
  init_wait_for_inferior ();
405
 
406
  inferior_ignoring_leading_exec_events =
407
    target_reported_exec_events_per_exec_call () - 1;
408
 
409
  while (1)
410
    {
411
      /* Make wait_for_inferior be quiet. */
412
      stop_soon = STOP_QUIETLY;
413
      wait_for_inferior (1);
414
      if (stop_signal != TARGET_SIGNAL_TRAP)
415
        {
416
          /* Let shell child handle its own signals in its own way.
417
             FIXME: what if child has exited?  Must exit loop
418
             somehow.  */
419
          resume (0, stop_signal);
420
        }
421
      else
422
        {
423
          /* We handle SIGTRAP, however; it means child did an exec.  */
424
          if (!terminal_initted)
425
            {
426
              /* Now that the child has exec'd we know it has already
427
                 set its process group.  On POSIX systems, tcsetpgrp
428
                 will fail with EPERM if we try it before the child's
429
                 setpgid.  */
430
 
431
              /* Set up the "saved terminal modes" of the inferior
432
                 based on what modes we are starting it with.  */
433
              target_terminal_init ();
434
 
435
              /* Install inferior's terminal modes.  */
436
              target_terminal_inferior ();
437
 
438
              terminal_initted = 1;
439
            }
440
 
441
          if (--pending_execs == 0)
442
            break;
443
 
444
          resume (0, TARGET_SIGNAL_0);   /* Just make it go on.  */
445
        }
446
    }
447
  stop_soon = NO_STOP_QUIETLY;
448
}

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