gdb/fork-child.c

   1 /* Fork a Unix child process, and set up to debug it, for GDB.
   2
   3    Copyright (C) 1990-2024 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 "inferior.h"
  23 #include "cli/cli-cmds.h"
  24 #include "terminal.h"
  25 #include "gdbthread.h"
  26 #include "ui.h"
  27 #include "gdbsupport/job-control.h"
  28 #include "gdbsupport/filestuff.h"
  29 #include "nat/fork-inferior.h"
  30 #include "gdbsupport/common-inferior.h"
  31
  32 /* The exec-wrapper, if any, that will be used when starting the
  33    inferior.  */
  34
  35 static std::string exec_wrapper;
  36
  37 /* See gdbsupport/common-inferior.h.  */
  38
  39 const char *
  40 get_exec_wrapper ()
  41 {
  42   return !exec_wrapper.empty () ? exec_wrapper.c_str () : nullptr;
  43 }
  44
  45 /* See nat/fork-inferior.h.  */
  46
  47 void
  48 gdb_flush_out_err ()
  49 {
  50   gdb_flush (main_ui->m_gdb_stdout);
  51   gdb_flush (main_ui->m_gdb_stderr);
  52 }
  53
  54 /* The ui structure that will be saved on 'prefork_hook' and
  55    restored on 'postfork_hook'.  */
  56 static struct ui *saved_ui = NULL;
  57
  58 /* See nat/fork-inferior.h.  */
  59
  60 void
  61 prefork_hook (const char *args)
  62 {
  63   gdb_assert (saved_ui == NULL);
  64   /* Retain a copy of our UI, since the child will replace this value
  65      and if we're vforked, we have to restore it.  */
  66   saved_ui = current_ui;
  67
  68   /* Tell the terminal handling subsystem what tty we plan to run on;
  69      it will just record the information for later.  */
  70   new_tty_prefork (current_inferior ()->tty ());
  71 }
  72
  73 /* See nat/fork-inferior.h.  */
  74
  75 void
  76 postfork_hook (pid_t pid)
  77 {
  78   inferior *inf = current_inferior ();
  79
  80   inferior_appeared (inf, pid);
  81
  82   gdb_assert (saved_ui != NULL);
  83   current_ui = saved_ui;
  84   saved_ui = NULL;
  85
  86   new_tty_postfork ();
  87 }
  88
  89 /* See nat/fork-inferior.h.  */
  90
  91 void
  92 postfork_child_hook ()
  93 {
  94   /* This is set to the result of setpgrp, which if vforked, will be
  95      visible to you in the parent process.  It's only used by humans
  96      for debugging.  */
  97   static int debug_setpgrp = 657473;
  98
  99   /* Make sure we switch to main_ui here in order to be able to
 100      use the gdb_printf/warning/error functions.  */
 101   current_ui = main_ui;
 102
 103   /* Create a new session for the inferior process, if necessary.
 104      It will also place the inferior in a separate process group.  */
 105   if (create_tty_session () <= 0)
 106     {
 107       /* No session was created, but we still want to run the inferior
 108          in a separate process group.  */
 109       debug_setpgrp = gdb_setpgid ();
 110       if (debug_setpgrp == -1)
 111         perror (_("setpgrp failed in child"));
 112     }
 113
 114   /* Ask the tty subsystem to switch to the one we specified
 115      earlier (or to share the current terminal, if none was
 116      specified).  */
 117   new_tty ();
 118 }
 119
 120 /* See inferior.h.  */
 121
 122 ptid_t
 123 gdb_startup_inferior (pid_t pid, int num_traps)
 124 {
 125   inferior *inf = current_inferior ();
 126   process_stratum_target *proc_target = inf->process_target ();
 127
 128   scoped_restore save_starting_up
 129     = make_scoped_restore (&inf->starting_up, true);
 130
 131   ptid_t ptid = startup_inferior (proc_target, pid, num_traps, NULL, NULL);
 132
 133   /* Mark all threads non-executing.  */
 134   set_executing (proc_target, ptid, false);
 135
 136   return ptid;
 137 }
 138
 139 /* Implement the "unset exec-wrapper" command.  */
 140
 141 static void
 142 unset_exec_wrapper_command (const char *args, int from_tty)
 143 {
 144   exec_wrapper.clear ();
 145 }
 146
 147 static void
 148 show_startup_with_shell (struct ui_file *file, int from_tty,
 149                          struct cmd_list_element *c, const char *value)
 150 {
 151   gdb_printf (file,
 152               _("Use of shell to start subprocesses is %s.\n"),
 153               value);
 154 }
 155
 156 void _initialize_fork_child ();
 157 void
 158 _initialize_fork_child ()
 159 {
 160   add_setshow_filename_cmd ("exec-wrapper", class_run, &exec_wrapper, _("\
 161 Set a wrapper for running programs.\n\
 162 The wrapper prepares the system and environment for the new program."),
 163                             _("\
 164 Show the wrapper for running programs."), NULL,
 165                             NULL, NULL,
 166                             &setlist, &showlist);
 167
 168   add_cmd ("exec-wrapper", class_run, unset_exec_wrapper_command,
 169            _("Disable use of an execution wrapper."),
 170            &unsetlist);
 171
 172   add_setshow_boolean_cmd ("startup-with-shell", class_support,
 173                            &startup_with_shell, _("\
 174 Set use of shell to start subprocesses.  The default is on."), _("\
 175 Show use of shell to start subprocesses."), NULL,
 176                            NULL,
 177                            show_startup_with_shell,
 178                            &setlist, &showlist);
 179 }