gdb/fork-child.c

   1 /* Fork a Unix child process, and set up to debug it, for GDB.
   2
   3    Copyright (C) 1990-2023 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 std::string exec_wrapper;
  37
  38 /* See gdbsupport/common-inferior.h.  */
  39
  40 const char *
  41 get_exec_wrapper ()
  42 {
  43   return !exec_wrapper.empty () ? exec_wrapper.c_str () : nullptr;
  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   gdb_assert (saved_ui == NULL);
  65   /* Retain a copy of our UI, since the child will replace this value
  66      and if we're vforked, we have to restore it.  */
  67   saved_ui = current_ui;
  68
  69   /* Tell the terminal handling subsystem what tty we plan to run on;
  70      it will just record the information for later.  */
  71   new_tty_prefork (current_inferior ()->tty ());
  72 }
  73
  74 /* See nat/fork-inferior.h.  */
  75
  76 void
  77 postfork_hook (pid_t pid)
  78 {
  79   inferior *inf = current_inferior ();
  80
  81   inferior_appeared (inf, pid);
  82
  83   gdb_assert (saved_ui != NULL);
  84   current_ui = saved_ui;
  85   saved_ui = NULL;
  86
  87   new_tty_postfork ();
  88 }
  89
  90 /* See nat/fork-inferior.h.  */
  91
  92 void
  93 postfork_child_hook ()
  94 {
  95   /* This is set to the result of setpgrp, which if vforked, will be
  96      visible to you in the parent process.  It's only used by humans
  97      for debugging.  */
  98   static int debug_setpgrp = 657473;
  99
 100   /* Make sure we switch to main_ui here in order to be able to
 101      use the gdb_printf/warning/error functions.  */
 102   current_ui = main_ui;
 103
 104   /* Create a new session for the inferior process, if necessary.
 105      It will also place the inferior in a separate process group.  */
 106   if (create_tty_session () <= 0)
 107     {
 108       /* No session was created, but we still want to run the inferior
 109          in a separate process group.  */
 110       debug_setpgrp = gdb_setpgid ();
 111       if (debug_setpgrp == -1)
 112         perror (_("setpgrp failed in child"));
 113     }
 114
 115   /* Ask the tty subsystem to switch to the one we specified
 116      earlier (or to share the current terminal, if none was
 117      specified).  */
 118   new_tty ();
 119 }
 120
 121 /* See inferior.h.  */
 122
 123 ptid_t
 124 gdb_startup_inferior (pid_t pid, int num_traps)
 125 {
 126   inferior *inf = current_inferior ();
 127   process_stratum_target *proc_target = inf->process_target ();
 128
 129   scoped_restore save_starting_up
 130     = make_scoped_restore (&inf->starting_up, true);
 131
 132   ptid_t ptid = startup_inferior (proc_target, pid, num_traps, NULL, NULL);
 133
 134   /* Mark all threads non-executing.  */
 135   set_executing (proc_target, ptid, false);
 136
 137   return ptid;
 138 }
 139
 140 /* Implement the "unset exec-wrapper" command.  */
 141
 142 static void
 143 unset_exec_wrapper_command (const char *args, int from_tty)
 144 {
 145   exec_wrapper.clear ();
 146 }
 147
 148 static void
 149 show_startup_with_shell (struct ui_file *file, int from_tty,
 150                          struct cmd_list_element *c, const char *value)
 151 {
 152   gdb_printf (file,
 153               _("Use of shell to start subprocesses is %s.\n"),
 154               value);
 155 }
 156
 157 void _initialize_fork_child ();
 158 void
 159 _initialize_fork_child ()
 160 {
 161   add_setshow_filename_cmd ("exec-wrapper", class_run, &exec_wrapper, _("\
 162 Set a wrapper for running programs.\n\
 163 The wrapper prepares the system and environment for the new program."),
 164                             _("\
 165 Show the wrapper for running programs."), NULL,
 166                             NULL, NULL,
 167                             &setlist, &showlist);
 168
 169   add_cmd ("exec-wrapper", class_run, unset_exec_wrapper_command,
 170            _("Disable use of an execution wrapper."),
 171            &unsetlist);
 172
 173   add_setshow_boolean_cmd ("startup-with-shell", class_support,
 174                            &startup_with_shell, _("\
 175 Set use of shell to start subprocesses.  The default is on."), _("\
 176 Show use of shell to start subprocesses."), NULL,
 177                            NULL,
 178                            show_startup_with_shell,
 179                            &setlist, &showlist);
 180 }