522 lines
14 KiB
C
522 lines
14 KiB
C
/* GNU/Linux native-dependent code common to multiple platforms.
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Copyright (C) 2003, 2004 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#include "defs.h"
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#include "inferior.h"
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#include "target.h"
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#include "gdb_wait.h"
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#include <sys/ptrace.h>
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#include "linux-nat.h"
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/* If the system headers did not provide the constants, hard-code the normal
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values. */
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#ifndef PTRACE_EVENT_FORK
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#define PTRACE_SETOPTIONS 0x4200
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#define PTRACE_GETEVENTMSG 0x4201
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/* options set using PTRACE_SETOPTIONS */
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#define PTRACE_O_TRACESYSGOOD 0x00000001
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#define PTRACE_O_TRACEFORK 0x00000002
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#define PTRACE_O_TRACEVFORK 0x00000004
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#define PTRACE_O_TRACECLONE 0x00000008
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#define PTRACE_O_TRACEEXEC 0x00000010
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#define PTRACE_O_TRACEVFORKDONE 0x00000020
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#define PTRACE_O_TRACEEXIT 0x00000040
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/* Wait extended result codes for the above trace options. */
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#define PTRACE_EVENT_FORK 1
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#define PTRACE_EVENT_VFORK 2
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#define PTRACE_EVENT_CLONE 3
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#define PTRACE_EVENT_EXEC 4
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#define PTRACE_EVENT_VFORKDONE 5
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#define PTRACE_EVENT_EXIT 6
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#endif /* PTRACE_EVENT_FORK */
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/* We can't always assume that this flag is available, but all systems
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with the ptrace event handlers also have __WALL, so it's safe to use
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here. */
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#ifndef __WALL
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#define __WALL 0x40000000 /* Wait for any child. */
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#endif
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extern struct target_ops child_ops;
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static int linux_parent_pid;
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struct simple_pid_list
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{
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int pid;
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struct simple_pid_list *next;
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};
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struct simple_pid_list *stopped_pids;
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/* This variable is a tri-state flag: -1 for unknown, 0 if PTRACE_O_TRACEFORK
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can not be used, 1 if it can. */
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static int linux_supports_tracefork_flag = -1;
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/* If we have PTRACE_O_TRACEFORK, this flag indicates whether we also have
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PTRACE_O_TRACEVFORKDONE. */
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static int linux_supports_tracevforkdone_flag = -1;
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/* Trivial list manipulation functions to keep track of a list of
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new stopped processes. */
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static void
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add_to_pid_list (struct simple_pid_list **listp, int pid)
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{
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struct simple_pid_list *new_pid = xmalloc (sizeof (struct simple_pid_list));
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new_pid->pid = pid;
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new_pid->next = *listp;
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*listp = new_pid;
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}
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static int
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pull_pid_from_list (struct simple_pid_list **listp, int pid)
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{
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struct simple_pid_list **p;
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for (p = listp; *p != NULL; p = &(*p)->next)
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if ((*p)->pid == pid)
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{
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struct simple_pid_list *next = (*p)->next;
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xfree (*p);
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*p = next;
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return 1;
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}
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return 0;
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}
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void
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linux_record_stopped_pid (int pid)
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{
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add_to_pid_list (&stopped_pids, pid);
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}
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/* A helper function for linux_test_for_tracefork, called after fork (). */
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static void
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linux_tracefork_child (void)
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{
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int ret;
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ptrace (PTRACE_TRACEME, 0, 0, 0);
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kill (getpid (), SIGSTOP);
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fork ();
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exit (0);
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}
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/* Determine if PTRACE_O_TRACEFORK can be used to follow fork events. We
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create a child process, attach to it, use PTRACE_SETOPTIONS to enable
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fork tracing, and let it fork. If the process exits, we assume that
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we can't use TRACEFORK; if we get the fork notification, and we can
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extract the new child's PID, then we assume that we can. */
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static void
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linux_test_for_tracefork (void)
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{
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int child_pid, ret, status;
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long second_pid;
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child_pid = fork ();
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if (child_pid == -1)
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perror_with_name ("linux_test_for_tracefork: fork");
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if (child_pid == 0)
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linux_tracefork_child ();
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ret = waitpid (child_pid, &status, 0);
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if (ret == -1)
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perror_with_name ("linux_test_for_tracefork: waitpid");
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else if (ret != child_pid)
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error ("linux_test_for_tracefork: waitpid: unexpected result %d.", ret);
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if (! WIFSTOPPED (status))
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error ("linux_test_for_tracefork: waitpid: unexpected status %d.", status);
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linux_supports_tracefork_flag = 0;
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ret = ptrace (PTRACE_SETOPTIONS, child_pid, 0, PTRACE_O_TRACEFORK);
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if (ret != 0)
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{
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ptrace (PTRACE_KILL, child_pid, 0, 0);
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waitpid (child_pid, &status, 0);
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return;
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}
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/* Check whether PTRACE_O_TRACEVFORKDONE is available. */
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ret = ptrace (PTRACE_SETOPTIONS, child_pid, 0,
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PTRACE_O_TRACEFORK | PTRACE_O_TRACEVFORKDONE);
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linux_supports_tracevforkdone_flag = (ret == 0);
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ptrace (PTRACE_CONT, child_pid, 0, 0);
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ret = waitpid (child_pid, &status, 0);
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if (ret == child_pid && WIFSTOPPED (status)
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&& status >> 16 == PTRACE_EVENT_FORK)
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{
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second_pid = 0;
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ret = ptrace (PTRACE_GETEVENTMSG, child_pid, 0, &second_pid);
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if (ret == 0 && second_pid != 0)
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{
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int second_status;
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linux_supports_tracefork_flag = 1;
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waitpid (second_pid, &second_status, 0);
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ptrace (PTRACE_DETACH, second_pid, 0, 0);
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}
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}
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if (WIFSTOPPED (status))
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{
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ptrace (PTRACE_DETACH, child_pid, 0, 0);
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waitpid (child_pid, &status, 0);
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}
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}
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/* Return non-zero iff we have tracefork functionality available.
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This function also sets linux_supports_tracefork_flag. */
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static int
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linux_supports_tracefork (void)
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{
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if (linux_supports_tracefork_flag == -1)
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linux_test_for_tracefork ();
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return linux_supports_tracefork_flag;
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}
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static int
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linux_supports_tracevforkdone (void)
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{
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if (linux_supports_tracefork_flag == -1)
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linux_test_for_tracefork ();
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return linux_supports_tracevforkdone_flag;
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}
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void
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linux_enable_event_reporting (ptid_t ptid)
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{
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int pid = ptid_get_pid (ptid);
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int options;
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if (! linux_supports_tracefork ())
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return;
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options = PTRACE_O_TRACEFORK | PTRACE_O_TRACEVFORK | PTRACE_O_TRACEEXEC
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| PTRACE_O_TRACECLONE;
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if (linux_supports_tracevforkdone ())
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options |= PTRACE_O_TRACEVFORKDONE;
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/* Do not enable PTRACE_O_TRACEEXIT until GDB is more prepared to support
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read-only process state. */
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ptrace (PTRACE_SETOPTIONS, pid, 0, options);
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}
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void
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child_post_attach (int pid)
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{
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linux_enable_event_reporting (pid_to_ptid (pid));
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}
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void
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linux_child_post_startup_inferior (ptid_t ptid)
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{
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linux_enable_event_reporting (ptid);
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}
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#ifndef LINUX_CHILD_POST_STARTUP_INFERIOR
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void
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child_post_startup_inferior (ptid_t ptid)
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{
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linux_child_post_startup_inferior (ptid);
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}
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#endif
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int
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child_follow_fork (int follow_child)
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{
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ptid_t last_ptid;
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struct target_waitstatus last_status;
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int has_vforked;
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int parent_pid, child_pid;
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get_last_target_status (&last_ptid, &last_status);
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has_vforked = (last_status.kind == TARGET_WAITKIND_VFORKED);
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parent_pid = ptid_get_pid (last_ptid);
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child_pid = last_status.value.related_pid;
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if (! follow_child)
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{
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/* We're already attached to the parent, by default. */
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/* Before detaching from the child, remove all breakpoints from
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it. (This won't actually modify the breakpoint list, but will
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physically remove the breakpoints from the child.) */
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/* If we vforked this will remove the breakpoints from the parent
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also, but they'll be reinserted below. */
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detach_breakpoints (child_pid);
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fprintf_filtered (gdb_stdout,
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"Detaching after fork from child process %d.\n",
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child_pid);
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ptrace (PTRACE_DETACH, child_pid, 0, 0);
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if (has_vforked)
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{
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if (linux_supports_tracevforkdone ())
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{
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int status;
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ptrace (PTRACE_CONT, parent_pid, 0, 0);
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waitpid (parent_pid, &status, __WALL);
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if ((status >> 16) != PTRACE_EVENT_VFORKDONE)
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warning ("Unexpected waitpid result %06x when waiting for "
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"vfork-done", status);
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}
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else
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{
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/* We can't insert breakpoints until the child has
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finished with the shared memory region. We need to
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wait until that happens. Ideal would be to just
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call:
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- ptrace (PTRACE_SYSCALL, parent_pid, 0, 0);
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- waitpid (parent_pid, &status, __WALL);
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However, most architectures can't handle a syscall
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being traced on the way out if it wasn't traced on
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the way in.
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We might also think to loop, continuing the child
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until it exits or gets a SIGTRAP. One problem is
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that the child might call ptrace with PTRACE_TRACEME.
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There's no simple and reliable way to figure out when
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the vforked child will be done with its copy of the
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shared memory. We could step it out of the syscall,
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two instructions, let it go, and then single-step the
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parent once. When we have hardware single-step, this
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would work; with software single-step it could still
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be made to work but we'd have to be able to insert
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single-step breakpoints in the child, and we'd have
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to insert -just- the single-step breakpoint in the
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parent. Very awkward.
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In the end, the best we can do is to make sure it
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runs for a little while. Hopefully it will be out of
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range of any breakpoints we reinsert. Usually this
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is only the single-step breakpoint at vfork's return
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point. */
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usleep (10000);
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}
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/* Since we vforked, breakpoints were removed in the parent
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too. Put them back. */
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reattach_breakpoints (parent_pid);
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}
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}
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else
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{
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char child_pid_spelling[40];
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/* Needed to keep the breakpoint lists in sync. */
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if (! has_vforked)
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detach_breakpoints (child_pid);
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/* Before detaching from the parent, remove all breakpoints from it. */
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remove_breakpoints ();
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fprintf_filtered (gdb_stdout,
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"Attaching after fork to child process %d.\n",
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child_pid);
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/* If we're vforking, we may want to hold on to the parent until
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the child exits or execs. At exec time we can remove the old
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breakpoints from the parent and detach it; at exit time we
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could do the same (or even, sneakily, resume debugging it - the
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child's exec has failed, or something similar).
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This doesn't clean up "properly", because we can't call
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target_detach, but that's OK; if the current target is "child",
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then it doesn't need any further cleanups, and lin_lwp will
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generally not encounter vfork (vfork is defined to fork
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in libpthread.so).
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The holding part is very easy if we have VFORKDONE events;
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but keeping track of both processes is beyond GDB at the
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moment. So we don't expose the parent to the rest of GDB.
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Instead we quietly hold onto it until such time as we can
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safely resume it. */
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if (has_vforked)
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linux_parent_pid = parent_pid;
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else
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target_detach (NULL, 0);
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inferior_ptid = pid_to_ptid (child_pid);
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push_target (&child_ops);
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/* Reset breakpoints in the child as appropriate. */
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follow_inferior_reset_breakpoints ();
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}
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return 0;
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}
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ptid_t
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linux_handle_extended_wait (int pid, int status,
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struct target_waitstatus *ourstatus)
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{
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int event = status >> 16;
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if (event == PTRACE_EVENT_FORK || event == PTRACE_EVENT_VFORK
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|| event == PTRACE_EVENT_CLONE)
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{
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unsigned long new_pid;
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int ret;
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ptrace (PTRACE_GETEVENTMSG, pid, 0, &new_pid);
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/* If we haven't already seen the new PID stop, wait for it now. */
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if (! pull_pid_from_list (&stopped_pids, new_pid))
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{
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/* The new child has a pending SIGSTOP. We can't affect it until it
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hits the SIGSTOP, but we're already attached. */
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do {
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ret = waitpid (new_pid, &status,
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(event == PTRACE_EVENT_CLONE) ? __WCLONE : 0);
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} while (ret == -1 && errno == EINTR);
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if (ret == -1)
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perror_with_name ("waiting for new child");
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else if (ret != new_pid)
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internal_error (__FILE__, __LINE__,
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"wait returned unexpected PID %d", ret);
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else if (!WIFSTOPPED (status) || WSTOPSIG (status) != SIGSTOP)
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internal_error (__FILE__, __LINE__,
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"wait returned unexpected status 0x%x", status);
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}
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if (event == PTRACE_EVENT_FORK)
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ourstatus->kind = TARGET_WAITKIND_FORKED;
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else if (event == PTRACE_EVENT_VFORK)
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ourstatus->kind = TARGET_WAITKIND_VFORKED;
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else
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ourstatus->kind = TARGET_WAITKIND_SPURIOUS;
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ourstatus->value.related_pid = new_pid;
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return inferior_ptid;
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}
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if (event == PTRACE_EVENT_EXEC)
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{
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ourstatus->kind = TARGET_WAITKIND_EXECD;
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ourstatus->value.execd_pathname
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= xstrdup (child_pid_to_exec_file (pid));
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if (linux_parent_pid)
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{
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detach_breakpoints (linux_parent_pid);
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ptrace (PTRACE_DETACH, linux_parent_pid, 0, 0);
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linux_parent_pid = 0;
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}
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return inferior_ptid;
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}
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internal_error (__FILE__, __LINE__,
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"unknown ptrace event %d", event);
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}
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int
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child_insert_fork_catchpoint (int pid)
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{
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if (! linux_supports_tracefork ())
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error ("Your system does not support fork catchpoints.");
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return 0;
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}
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int
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child_insert_vfork_catchpoint (int pid)
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{
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if (!linux_supports_tracefork ())
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error ("Your system does not support vfork catchpoints.");
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return 0;
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}
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int
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child_insert_exec_catchpoint (int pid)
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{
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if (!linux_supports_tracefork ())
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error ("Your system does not support exec catchpoints.");
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return 0;
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}
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void
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kill_inferior (void)
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{
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int status;
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int pid = PIDGET (inferior_ptid);
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struct target_waitstatus last;
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ptid_t last_ptid;
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int ret;
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if (pid == 0)
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return;
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/* If we're stopped while forking and we haven't followed yet, kill the
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other task. We need to do this first because the parent will be
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sleeping if this is a vfork. */
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get_last_target_status (&last_ptid, &last);
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if (last.kind == TARGET_WAITKIND_FORKED
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|| last.kind == TARGET_WAITKIND_VFORKED)
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{
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ptrace (PT_KILL, last.value.related_pid);
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ptrace_wait (null_ptid, &status);
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}
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/* Kill the current process. */
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ptrace (PT_KILL, pid, (PTRACE_ARG3_TYPE) 0, 0);
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ret = ptrace_wait (null_ptid, &status);
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/* We might get a SIGCHLD instead of an exit status. This is
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aggravated by the first kill above - a child has just died. */
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while (ret == pid && WIFSTOPPED (status))
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{
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ptrace (PT_KILL, pid, (PTRACE_ARG3_TYPE) 0, 0);
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ret = ptrace_wait (null_ptid, &status);
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}
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target_mourn_inferior ();
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}
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