gdb/fork-child.c

   1 /* Fork a Unix child process, and set up to debug it, for GDB.
   2    Copyright 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
   3    Contributed by Cygnus Support.
   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 2 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, write to the Free Software
  19 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  20
  21 #include "defs.h"
  22 #include <string.h>
  23 #include "frame.h"  /* required by inferior.h */
  24 #include "inferior.h"
  25 #include "target.h"
  26 #include "wait.h"
  27 #include "gdbcore.h"
  28 #include "terminal.h"
  29 #include "thread.h"
  30
  31 #include <signal.h>
  32
  33 #ifdef SET_STACK_LIMIT_HUGE
  34 #include <sys/time.h>
  35 #include <sys/resource.h>
  36
  37 extern int original_stack_limit;
  38 #endif /* SET_STACK_LIMIT_HUGE */
  39
  40 extern char **environ;
  41
  42 #ifndef SHELL_FILE
  43 #define SHELL_FILE "/bin/sh"
  44 #endif
  45
  46 /* Start an inferior Unix child process and sets inferior_pid to its pid.
  47    EXEC_FILE is the file to run.
  48    ALLARGS is a string containing the arguments to the program.
  49    ENV is the environment vector to pass.  SHELL_FILE is the shell file,
  50    or NULL if we should pick one.  Errors reported with error().  */
  51
  52 void
  53 fork_inferior (exec_file, allargs, env, traceme_fun, init_trace_fun,
  54                shell_file)
  55      char *exec_file;
  56      char *allargs;
  57      char **env;
  58      void (*traceme_fun) PARAMS ((void));
  59      void (*init_trace_fun) PARAMS ((int));
  60      char *shell_file;
  61 {
  62   int pid;
  63   char *shell_command;
  64   static char default_shell_file[] = SHELL_FILE;
  65   int len;
  66   /* Set debug_fork then attach to the child while it sleeps, to debug. */
  67   static int debug_fork = 0;
  68   /* This is set to the result of setpgrp, which if vforked, will be visible
  69      to you in the parent process.  It's only used by humans for debugging.  */
  70   static int debug_setpgrp = 657473;
  71   char **save_our_env;
  72
  73   /* If no exec file handed to us, get it from the exec-file command -- with
  74      a good, common error message if none is specified.  */
  75   if (exec_file == 0)
  76     exec_file = get_exec_file(1);
  77
  78   /* The user might want tilde-expansion, and in general probably wants
  79      the program to behave the same way as if run from
  80      his/her favorite shell.  So we let the shell run it for us.
  81      FIXME-maybe, we might want a "set shell" command so the user can change
  82      the shell from within GDB (if so, change callers which pass in a non-NULL
  83      shell_file too).  */
  84   if (shell_file == NULL)
  85     shell_file = getenv ("SHELL");
  86   if (shell_file == NULL)
  87     shell_file = default_shell_file;
  88
  89   /* Multiplying the length of exec_file by 4 is to account for the fact
  90      that it may expand when quoted; it is a worst-case number based on
  91      every character being '.  */
  92   len = 5 + 4 * strlen (exec_file) + 1 + strlen (allargs) + 1 + /*slop*/ 12;
  93   /* If desired, concat something onto the front of ALLARGS.
  94      SHELL_COMMAND is the result.  */
  95 #ifdef SHELL_COMMAND_CONCAT
  96   shell_command = (char *) alloca (strlen (SHELL_COMMAND_CONCAT) + len);
  97   strcpy (shell_command, SHELL_COMMAND_CONCAT);
  98 #else
  99   shell_command = (char *) alloca (len);
 100   shell_command[0] = '\0';
 101 #endif
 102   strcat (shell_command, "exec ");
 103
 104   /* Now add exec_file, quoting as necessary.  */
 105   {
 106     char *p;
 107     int need_to_quote;
 108
 109     /* Quoting in this style is said to work with all shells.  But csh
 110        on IRIX 4.0.1 can't deal with it.  So we only quote it if we need
 111        to.  */
 112     p = exec_file;
 113     while (1)
 114       {
 115         switch (*p)
 116           {
 117           case '\'':
 118           case '"':
 119           case '(':
 120           case ')':
 121           case '$':
 122           case '&':
 123           case ';':
 124           case '<':
 125           case '>':
 126           case ' ':
 127           case '\n':
 128           case '\t':
 129             need_to_quote = 1;
 130             goto end_scan;
 131
 132           case '\0':
 133             need_to_quote = 0;
 134             goto end_scan;
 135
 136           default:
 137             break;
 138           }
 139         ++p;
 140       }
 141   end_scan:
 142     if (need_to_quote)
 143       {
 144         strcat (shell_command, "'");
 145         for (p = exec_file; *p != '\0'; ++p)
 146           {
 147             if (*p == '\'')
 148               strcat (shell_command, "'\\''");
 149             else
 150               strncat (shell_command, p, 1);
 151           }
 152         strcat (shell_command, "'");
 153       }
 154     else
 155       strcat (shell_command, exec_file);
 156   }
 157
 158   strcat (shell_command, " ");
 159   strcat (shell_command, allargs);
 160
 161   /* exec is said to fail if the executable is open.  */
 162   close_exec_file ();
 163
 164   /* Retain a copy of our environment variables, since the child will
 165      replace the value of  environ  and if we're vforked, we have to
 166      restore it.  */
 167   save_our_env = environ;
 168
 169   /* Tell the terminal handling subsystem what tty we plan to run on;
 170      it will just record the information for later.  */
 171
 172   new_tty_prefork (inferior_io_terminal);
 173
 174   /* It is generally good practice to flush any possible pending stdio
 175      output prior to doing a fork, to avoid the possibility of both the
 176      parent and child flushing the same data after the fork. */
 177
 178   gdb_flush (gdb_stdout);
 179   gdb_flush (gdb_stderr);
 180
 181 #if defined(USG) && !defined(HAVE_VFORK)
 182   pid = fork ();
 183 #else
 184   if (debug_fork)
 185     pid = fork ();
 186   else
 187     pid = vfork ();
 188 #endif
 189
 190   if (pid < 0)
 191     perror_with_name ("vfork");
 192
 193   if (pid == 0)
 194     {
 195       if (debug_fork)
 196         sleep (debug_fork);
 197
 198       /* Run inferior in a separate process group.  */
 199       debug_setpgrp = gdb_setpgid ();
 200       if (debug_setpgrp == -1)
 201          perror("setpgrp failed in child");
 202
 203 #ifdef SET_STACK_LIMIT_HUGE
 204       /* Reset the stack limit back to what it was.  */
 205       {
 206         struct rlimit rlim;
 207
 208         getrlimit (RLIMIT_STACK, &rlim);
 209         rlim.rlim_cur = original_stack_limit;
 210         setrlimit (RLIMIT_STACK, &rlim);
 211       }
 212 #endif /* SET_STACK_LIMIT_HUGE */
 213
 214       /* Ask the tty subsystem to switch to the one we specified earlier
 215          (or to share the current terminal, if none was specified).  */
 216
 217       new_tty ();
 218
 219       /* Changing the signal handlers for the inferior after
 220          a vfork can also change them for the superior, so we don't mess
 221          with signals here.  See comments in
 222          initialize_signals for how we get the right signal handlers
 223          for the inferior.  */
 224
 225       /* "Trace me, Dr. Memory!" */
 226       (*traceme_fun) ();
 227
 228       /* There is no execlpe call, so we have to set the environment
 229          for our child in the global variable.  If we've vforked, this
 230          clobbers the parent, but environ is restored a few lines down
 231          in the parent.  By the way, yes we do need to look down the
 232          path to find $SHELL.  Rich Pixley says so, and I agree.  */
 233       environ = env;
 234       execlp (shell_file, shell_file, "-c", shell_command, (char *)0);
 235
 236       fprintf_unfiltered (gdb_stderr, "Cannot exec %s: %s.\n", shell_file,
 237                safe_strerror (errno));
 238       gdb_flush (gdb_stderr);
 239       _exit (0177);
 240     }
 241
 242   /* Restore our environment in case a vforked child clob'd it.  */
 243   environ = save_our_env;
 244
 245   init_thread_list();
 246
 247   inferior_pid = pid;           /* Needed for wait_for_inferior stuff below */
 248
 249   /* Now that we have a child process, make it our target, and
 250      initialize anything target-vector-specific that needs initializing.  */
 251   (*init_trace_fun)(pid);
 252
 253   /* We are now in the child process of interest, having exec'd the
 254      correct program, and are poised at the first instruction of the
 255      new program.  */
 256 #ifdef SOLIB_CREATE_INFERIOR_HOOK
 257   SOLIB_CREATE_INFERIOR_HOOK (pid);
 258 #endif
 259 }
 260
 261 /* Accept NTRAPS traps from the inferior.  */
 262
 263 void
 264 startup_inferior (ntraps)
 265      int ntraps;
 266 {
 267   int pending_execs = ntraps;
 268   int terminal_initted;
 269
 270   /* The process was started by the fork that created it,
 271      but it will have stopped one instruction after execing the shell.
 272      Here we must get it up to actual execution of the real program.  */
 273
 274   clear_proceed_status ();
 275
 276   init_wait_for_inferior ();
 277
 278   terminal_initted = 0;
 279
 280   while (1)
 281     {
 282       stop_soon_quietly = 1;    /* Make wait_for_inferior be quiet */
 283       wait_for_inferior ();
 284       if (stop_signal != TARGET_SIGNAL_TRAP)
 285         {
 286           /* Let shell child handle its own signals in its own way */
 287           /* FIXME, what if child has exit()ed?  Must exit loop somehow */
 288           resume (0, stop_signal);
 289         }
 290       else
 291         {
 292           /* We handle SIGTRAP, however; it means child did an exec.  */
 293           if (!terminal_initted)
 294             {
 295               /* Now that the child has exec'd we know it has already set its
 296                  process group.  On POSIX systems, tcsetpgrp will fail with
 297                  EPERM if we try it before the child's setpgid.  */
 298
 299               /* Set up the "saved terminal modes" of the inferior
 300                  based on what modes we are starting it with.  */
 301               target_terminal_init ();
 302
 303               /* Install inferior's terminal modes.  */
 304               target_terminal_inferior ();
 305
 306               terminal_initted = 1;
 307             }
 308           if (0 == --pending_execs)
 309             break;
 310           resume (0, TARGET_SIGNAL_0);          /* Just make it go on */
 311         }
 312     }
 313   stop_soon_quietly = 0;
 314 }