gdb/fork-child.c

   1 /* Fork a Unix child process, and set up to debug it, for GDB.
   2
   3    Copyright (C) 1990-2020 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 #include "inferior.h"
  24 #include "gdbcmd.h"
  25 #include "terminal.h"
  26 #include "gdbthread.h"
  27 #include "top.h"
  28 #include "gdbsupport/job-control.h"
  29 #include "gdbsupport/filestuff.h"
  30 #include "nat/fork-inferior.h"
  31 #include "gdbsupport/common-inferior.h"
  32
  33 /* The exec-wrapper, if any, that will be used when starting the
  34    inferior.  */
  35
  36 static char *exec_wrapper = NULL;
  37
  38 /* See gdbsupport/common-inferior.h.  */
  39
  40 const char *
  41 get_exec_wrapper ()
  42 {
  43   return exec_wrapper;
  44 }
  45
  46 /* See nat/fork-inferior.h.  */
  47
  48 void
  49 gdb_flush_out_err ()
  50 {
  51   gdb_flush (main_ui->m_gdb_stdout);
  52   gdb_flush (main_ui->m_gdb_stderr);
  53 }
  54
  55 /* The ui structure that will be saved on 'prefork_hook' and
  56    restored on 'postfork_hook'.  */
  57 static struct ui *saved_ui = NULL;
  58
  59 /* See nat/fork-inferior.h.  */
  60
  61 void
  62 prefork_hook (const char *args)
  63 {
  64   const char *inferior_io_terminal = get_inferior_io_terminal ();
  65
  66   gdb_assert (saved_ui == NULL);
  67   /* Retain a copy of our UI, since the child will replace this value
  68      and if we're vforked, we have to restore it.  */
  69   saved_ui = current_ui;
  70
  71   /* Tell the terminal handling subsystem what tty we plan to run on;
  72      it will just record the information for later.  */
  73   new_tty_prefork (inferior_io_terminal);
  74 }
  75
  76 /* See nat/fork-inferior.h.  */
  77
  78 void
  79 postfork_hook (pid_t pid)
  80 {
  81   inferior *inf = current_inferior ();
  82
  83   inferior_appeared (inf, pid);
  84
  85   /* Needed for wait_for_inferior stuff.  */
  86   inferior_ptid = ptid_t (pid);
  87
  88   gdb_assert (saved_ui != NULL);
  89   current_ui = saved_ui;
  90   saved_ui = NULL;
  91
  92   new_tty_postfork ();
  93 }
  94
  95 /* See nat/fork-inferior.h.  */
  96
  97 void
  98 postfork_child_hook ()
  99 {
 100   /* This is set to the result of setpgrp, which if vforked, will be
 101      visible to you in the parent process.  It's only used by humans
 102      for debugging.  */
 103   static int debug_setpgrp = 657473;
 104
 105   /* Make sure we switch to main_ui here in order to be able to
 106      use the fprintf_unfiltered/warning/error functions.  */
 107   current_ui = main_ui;
 108
 109   /* Create a new session for the inferior process, if necessary.
 110      It will also place the inferior in a separate process group.  */
 111   if (create_tty_session () <= 0)
 112     {
 113       /* No session was created, but we still want to run the inferior
 114          in a separate process group.  */
 115       debug_setpgrp = gdb_setpgid ();
 116       if (debug_setpgrp == -1)
 117         perror (_("setpgrp failed in child"));
 118     }
 119
 120   /* Ask the tty subsystem to switch to the one we specified
 121      earlier (or to share the current terminal, if none was
 122      specified).  */
 123   new_tty ();
 124 }
 125
 126 /* See inferior.h.  */
 127
 128 ptid_t
 129 gdb_startup_inferior (pid_t pid, int num_traps)
 130 {
 131   inferior *inf = current_inferior ();
 132   process_stratum_target *proc_target = inf->process_target ();
 133
 134   ptid_t ptid = startup_inferior (proc_target, pid, num_traps, NULL, NULL);
 135
 136   /* Mark all threads non-executing.  */
 137   set_executing (proc_target, ptid, false);
 138
 139   return ptid;
 140 }
 141
 142 /* Implement the "unset exec-wrapper" command.  */
 143
 144 static void
 145 unset_exec_wrapper_command (const char *args, int from_tty)
 146 {
 147   xfree (exec_wrapper);
 148   exec_wrapper = NULL;
 149 }
 150
 151 static void
 152 show_startup_with_shell (struct ui_file *file, int from_tty,
 153                          struct cmd_list_element *c, const char *value)
 154 {
 155   fprintf_filtered (file,
 156                     _("Use of shell to start subprocesses is %s.\n"),
 157                     value);
 158 }
 159
 160 void _initialize_fork_child ();
 161 void
 162 _initialize_fork_child ()
 163 {
 164   add_setshow_filename_cmd ("exec-wrapper", class_run, &exec_wrapper, _("\
 165 Set a wrapper for running programs.\n\
 166 The wrapper prepares the system and environment for the new program."),
 167                             _("\
 168 Show the wrapper for running programs."), NULL,
 169                             NULL, NULL,
 170                             &setlist, &showlist);
 171
 172   add_cmd ("exec-wrapper", class_run, unset_exec_wrapper_command,
 173            _("Disable use of an execution wrapper."),
 174            &unsetlist);
 175
 176   add_setshow_boolean_cmd ("startup-with-shell", class_support,
 177                            &startup_with_shell, _("\
 178 Set use of shell to start subprocesses.  The default is on."), _("\
 179 Show use of shell to start subprocesses."), NULL,
 180                            NULL,
 181                            show_startup_with_shell,
 182                            &setlist, &showlist);
 183 }