gdb/fork-child.c

   1 /* Fork a Unix child process, and set up to debug it, for GDB.
   2
   3    Copyright (C) 1990-2019 Free Software Foundation, Inc.
   4
   5    Contributed by Cygnus Support.
   6
   7    This file is part of GDB.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 3 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  21
  22 #include "defs.h"
  23
  24 /* Local non-gdb includes.  */
  25 #include "common/common-inferior.h"
  26 #include "common/filestuff.h"
  27 #include "common/job-control.h"
  28 #include "gdbcmd.h"
  29 #include "gdbthread.h"
  30 #include "inferior.h"
  31 #include "nat/fork-inferior.h"
  32 #include "terminal.h"
  33 #include "top.h"
  34
  35 /* The exec-wrapper, if any, that will be used when starting the
  36    inferior.  */
  37
  38 static char *exec_wrapper = NULL;
  39
  40 /* See common/common-inferior.h.  */
  41
  42 const char *
  43 get_exec_wrapper ()
  44 {
  45   return exec_wrapper;
  46 }
  47
  48 /* See nat/fork-inferior.h.  */
  49
  50 void
  51 gdb_flush_out_err ()
  52 {
  53   gdb_flush (main_ui->m_gdb_stdout);
  54   gdb_flush (main_ui->m_gdb_stderr);
  55 }
  56
  57 /* The ui structure that will be saved on 'prefork_hook' and
  58    restored on 'postfork_hook'.  */
  59 static struct ui *saved_ui = NULL;
  60
  61 /* See nat/fork-inferior.h.  */
  62
  63 void
  64 prefork_hook (const char *args)
  65 {
  66   const char *inferior_io_terminal = get_inferior_io_terminal ();
  67
  68   gdb_assert (saved_ui == NULL);
  69   /* Retain a copy of our UI, since the child will replace this value
  70      and if we're vforked, we have to restore it.  */
  71   saved_ui = current_ui;
  72
  73   /* Tell the terminal handling subsystem what tty we plan to run on;
  74      it will just record the information for later.  */
  75   new_tty_prefork (inferior_io_terminal);
  76 }
  77
  78 /* See nat/fork-inferior.h.  */
  79
  80 void
  81 postfork_hook (pid_t pid)
  82 {
  83   inferior *inf = current_inferior ();
  84
  85   inferior_appeared (inf, pid);
  86
  87   /* Needed for wait_for_inferior stuff.  */
  88   inferior_ptid = ptid_t (pid);
  89
  90   gdb_assert (saved_ui != NULL);
  91   current_ui = saved_ui;
  92   saved_ui = NULL;
  93
  94   new_tty_postfork ();
  95 }
  96
  97 /* See nat/fork-inferior.h.  */
  98
  99 void
 100 postfork_child_hook ()
 101 {
 102   /* This is set to the result of setpgrp, which if vforked, will be
 103      visible to you in the parent process.  It's only used by humans
 104      for debugging.  */
 105   static int debug_setpgrp = 657473;
 106
 107   /* Make sure we switch to main_ui here in order to be able to
 108      use the fprintf_unfiltered/warning/error functions.  */
 109   current_ui = main_ui;
 110
 111   /* Create a new session for the inferior process, if necessary.
 112      It will also place the inferior in a separate process group.  */
 113   if (create_tty_session () <= 0)
 114     {
 115       /* No session was created, but we still want to run the inferior
 116          in a separate process group.  */
 117       debug_setpgrp = gdb_setpgid ();
 118       if (debug_setpgrp == -1)
 119         perror (_("setpgrp failed in child"));
 120     }
 121
 122   /* Ask the tty subsystem to switch to the one we specified
 123      earlier (or to share the current terminal, if none was
 124      specified).  */
 125   new_tty ();
 126 }
 127
 128 /* See inferior.h.  */
 129
 130 ptid_t
 131 gdb_startup_inferior (pid_t pid, int num_traps)
 132 {
 133   ptid_t ptid = startup_inferior (pid, num_traps, NULL, NULL);
 134
 135   /* Mark all threads non-executing.  */
 136   set_executing (ptid, 0);
 137
 138   return ptid;
 139 }
 140
 141 /* Implement the "unset exec-wrapper" command.  */
 142
 143 static void
 144 unset_exec_wrapper_command (const char *args, int from_tty)
 145 {
 146   xfree (exec_wrapper);
 147   exec_wrapper = NULL;
 148 }
 149
 150 static void
 151 show_startup_with_shell (struct ui_file *file, int from_tty,
 152                          struct cmd_list_element *c, const char *value)
 153 {
 154   fprintf_filtered (file,
 155                     _("Use of shell to start subprocesses is %s.\n"),
 156                     value);
 157 }
 158
 159 void
 160 _initialize_fork_child (void)
 161 {
 162   add_setshow_filename_cmd ("exec-wrapper", class_run, &exec_wrapper, _("\
 163 Set a wrapper for running programs.\n\
 164 The wrapper prepares the system and environment for the new program."),
 165                             _("\
 166 Show the wrapper for running programs."), NULL,
 167                             NULL, NULL,
 168                             &setlist, &showlist);
 169
 170   add_cmd ("exec-wrapper", class_run, unset_exec_wrapper_command,
 171            _("Disable use of an execution wrapper."),
 172            &unsetlist);
 173
 174   add_setshow_boolean_cmd ("startup-with-shell", class_support,
 175                            &startup_with_shell, _("\
 176 Set use of shell to start subprocesses.  The default is on."), _("\
 177 Show use of shell to start subprocesses."), NULL,
 178                            NULL,
 179                            show_startup_with_shell,
 180                            &setlist, &showlist);
 181 }