gdbserver/fork-child.cc

   1 /* Fork a Unix child process, and set up to debug it, for GDBserver.
   2    Copyright (C) 1989-2024 Free Software Foundation, Inc.
   3
   4    This file is part of GDB.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  18
  19 #include "gdbsupport/job-control.h"
  20 #include "gdbsupport/scoped_restore.h"
  21 #include "nat/fork-inferior.h"
  22 #ifdef HAVE_SIGNAL_H
  23 #include <signal.h>
  24 #endif
  25
  26 #ifdef SIGTTOU
  27 /* A file descriptor for the controlling terminal.  */
  28 static int terminal_fd;
  29
  30 /* TERMINAL_FD's original foreground group.  */
  31 static pid_t old_foreground_pgrp;
  32
  33 /* Hand back terminal ownership to the original foreground group.  */
  34
  35 static void
  36 restore_old_foreground_pgrp (void)
  37 {
  38   tcsetpgrp (terminal_fd, old_foreground_pgrp);
  39 }
  40 #endif
  41
  42 /* See nat/fork-inferior.h.  */
  43
  44 void
  45 prefork_hook (const char *args)
  46 {
  47   client_state &cs = get_client_state ();
  48   threads_debug_printf ("args: %s", args);
  49
  50 #ifdef SIGTTOU
  51   signal (SIGTTOU, SIG_DFL);
  52   signal (SIGTTIN, SIG_DFL);
  53 #endif
  54
  55   /* Clear this so the backend doesn't get confused, thinking
  56      CONT_THREAD died, and it needs to resume all threads.  */
  57   cs.cont_thread = null_ptid;
  58 }
  59
  60 /* See nat/fork-inferior.h.  */
  61
  62 void
  63 postfork_hook (pid_t pid)
  64 {
  65 }
  66
  67 /* See nat/fork-inferior.h.  */
  68
  69 void
  70 postfork_child_hook ()
  71 {
  72   /* This is set to the result of setpgrp, which if vforked, will be
  73      visible to you in the parent process.  It's only used by humans
  74      for debugging.  */
  75   static int debug_setpgrp = 657473;
  76
  77   debug_setpgrp = gdb_setpgid ();
  78   if (debug_setpgrp == -1)
  79     perror (_("setpgrp failed in child"));
  80 }
  81
  82 /* See nat/fork-inferior.h.  */
  83
  84 void
  85 gdb_flush_out_err ()
  86 {
  87   fflush (stdout);
  88   fflush (stderr);
  89 }
  90
  91 /* See server.h.  */
  92
  93 void
  94 post_fork_inferior (int pid, const char *program)
  95 {
  96   client_state &cs = get_client_state ();
  97 #ifdef SIGTTOU
  98   signal (SIGTTOU, SIG_IGN);
  99   signal (SIGTTIN, SIG_IGN);
 100   terminal_fd = fileno (stderr);
 101   old_foreground_pgrp = tcgetpgrp (terminal_fd);
 102   tcsetpgrp (terminal_fd, pid);
 103   atexit (restore_old_foreground_pgrp);
 104 #endif
 105
 106   process_info *proc = find_process_pid (pid);
 107
 108   /* If the inferior fails to start, startup_inferior mourns the
 109      process (which deletes it), and then throws an error.  This means
 110      that on exception return, we don't need or want to clear this
 111      flag back, as PROC won't exist anymore.  Thus, we don't use a
 112      scoped_restore.  */
 113   proc->starting_up = true;
 114
 115   startup_inferior (the_target, pid,
 116                     START_INFERIOR_TRAPS_EXPECTED,
 117                     &cs.last_status, &cs.last_ptid);
 118
 119   /* If we get here, the process was successfully started.  */
 120   proc->starting_up = false;
 121
 122   current_thread->last_resume_kind = resume_stop;
 123   current_thread->last_status = cs.last_status;
 124   signal_pid = pid;
 125   target_post_create_inferior ();
 126   fprintf (stderr, "Process %s created; pid = %d\n", program, pid);
 127   fflush (stderr);
 128 }