gdbserver/fork-child.cc

   1 /* Fork a Unix child process, and set up to debug it, for GDBserver.
   2    Copyright (C) 1989-2023 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 "server.h"
  20 #include "gdbsupport/job-control.h"
  21 #include "gdbsupport/scoped_restore.h"
  22 #include "nat/fork-inferior.h"
  23 #ifdef HAVE_SIGNAL_H
  24 #include <signal.h>
  25 #endif
  26
  27 #ifdef SIGTTOU
  28 /* A file descriptor for the controlling terminal.  */
  29 static int terminal_fd;
  30
  31 /* TERMINAL_FD's original foreground group.  */
  32 static pid_t old_foreground_pgrp;
  33
  34 /* Hand back terminal ownership to the original foreground group.  */
  35
  36 static void
  37 restore_old_foreground_pgrp (void)
  38 {
  39   tcsetpgrp (terminal_fd, old_foreground_pgrp);
  40 }
  41 #endif
  42
  43 /* See nat/fork-inferior.h.  */
  44
  45 void
  46 prefork_hook (const char *args)
  47 {
  48   client_state &cs = get_client_state ();
  49   threads_debug_printf ("args: %s", args);
  50
  51 #ifdef SIGTTOU
  52   signal (SIGTTOU, SIG_DFL);
  53   signal (SIGTTIN, SIG_DFL);
  54 #endif
  55
  56   /* Clear this so the backend doesn't get confused, thinking
  57      CONT_THREAD died, and it needs to resume all threads.  */
  58   cs.cont_thread = null_ptid;
  59 }
  60
  61 /* See nat/fork-inferior.h.  */
  62
  63 void
  64 postfork_hook (pid_t pid)
  65 {
  66 }
  67
  68 /* See nat/fork-inferior.h.  */
  69
  70 void
  71 postfork_child_hook ()
  72 {
  73   /* This is set to the result of setpgrp, which if vforked, will be
  74      visible to you in the parent process.  It's only used by humans
  75      for debugging.  */
  76   static int debug_setpgrp = 657473;
  77
  78   debug_setpgrp = gdb_setpgid ();
  79   if (debug_setpgrp == -1)
  80     perror (_("setpgrp failed in child"));
  81 }
  82
  83 /* See nat/fork-inferior.h.  */
  84
  85 void
  86 gdb_flush_out_err ()
  87 {
  88   fflush (stdout);
  89   fflush (stderr);
  90 }
  91
  92 /* See server.h.  */
  93
  94 void
  95 post_fork_inferior (int pid, const char *program)
  96 {
  97   client_state &cs = get_client_state ();
  98 #ifdef SIGTTOU
  99   signal (SIGTTOU, SIG_IGN);
 100   signal (SIGTTIN, SIG_IGN);
 101   terminal_fd = fileno (stderr);
 102   old_foreground_pgrp = tcgetpgrp (terminal_fd);
 103   tcsetpgrp (terminal_fd, pid);
 104   atexit (restore_old_foreground_pgrp);
 105 #endif
 106
 107   process_info *proc = find_process_pid (pid);
 108
 109   /* If the inferior fails to start, startup_inferior mourns the
 110      process (which deletes it), and then throws an error.  This means
 111      that on exception return, we don't need or want to clear this
 112      flag back, as PROC won't exist anymore.  Thus, we don't use a
 113      scoped_restore.  */
 114   proc->starting_up = true;
 115
 116   startup_inferior (the_target, pid,
 117                     START_INFERIOR_TRAPS_EXPECTED,
 118                     &cs.last_status, &cs.last_ptid);
 119
 120   /* If we get here, the process was successfully started.  */
 121   proc->starting_up = false;
 122
 123   current_thread->last_resume_kind = resume_stop;
 124   current_thread->last_status = cs.last_status;
 125   signal_pid = pid;
 126   target_post_create_inferior ();
 127   fprintf (stderr, "Process %s created; pid = %d\n", program, pid);
 128   fflush (stderr);
 129 }