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/* Low-level child interface to ptrace.
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Copyright (C) 1988-2022 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 3 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, see <http://www.gnu.org/licenses/>. */
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#include "defs.h"
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#include "command.h"
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#include "inferior.h"
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#include "terminal.h"
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#include "gdbcore.h"
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#include "regcache.h"
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#include "nat/gdb_ptrace.h"
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#include "gdbsupport/gdb_wait.h"
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#include <signal.h>
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#include "inf-ptrace.h"
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#include "inf-child.h"
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#include "gdbthread.h"
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#include "nat/fork-inferior.h"
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#include "utils.h"
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#include "gdbarch.h"
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static PTRACE_TYPE_RET
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gdb_ptrace (PTRACE_TYPE_ARG1 request, ptid_t ptid, PTRACE_TYPE_ARG3 addr,
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PTRACE_TYPE_ARG4 data)
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{
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#ifdef __NetBSD__
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return ptrace (request, ptid.pid (), addr, data);
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#else
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pid_t pid = get_ptrace_pid (ptid);
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return ptrace (request, pid, addr, data);
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#endif
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}
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/* The event pipe registered as a waitable file in the event loop. */
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event_pipe inf_ptrace_target::m_event_pipe;
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inf_ptrace_target::~inf_ptrace_target ()
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{}
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/* Prepare to be traced. */
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static void
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inf_ptrace_me (void)
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{
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/* "Trace me, Dr. Memory!" */
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if (ptrace (PT_TRACE_ME, 0, (PTRACE_TYPE_ARG3) 0, 0) < 0)
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trace_start_error_with_name ("ptrace");
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}
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/* Start a new inferior Unix child process. EXEC_FILE is the file to
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run, ALLARGS is a string containing the arguments to the program.
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ENV is the environment vector to pass. If FROM_TTY is non-zero, be
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chatty about it. */
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void
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inf_ptrace_target::create_inferior (const char *exec_file,
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const std::string &allargs,
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char **env, int from_tty)
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{
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inferior *inf = current_inferior ();
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/* Do not change either targets above or the same target if already present.
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The reason is the target stack is shared across multiple inferiors. */
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int ops_already_pushed = inf->target_is_pushed (this);
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target_unpush_up unpusher;
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if (! ops_already_pushed)
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{
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/* Clear possible core file with its process_stratum. */
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inf->push_target (this);
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unpusher.reset (this);
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}
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pid_t pid = fork_inferior (exec_file, allargs, env, inf_ptrace_me, NULL,
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NULL, NULL, NULL);
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ptid_t ptid (pid);
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/* We have something that executes now. We'll be running through
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the shell at this point (if startup-with-shell is true), but the
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pid shouldn't change. */
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thread_info *thr = add_thread_silent (this, ptid);
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switch_to_thread (thr);
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unpusher.release ();
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gdb_startup_inferior (pid, START_INFERIOR_TRAPS_EXPECTED);
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/* On some targets, there must be some explicit actions taken after
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the inferior has been started up. */
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post_startup_inferior (ptid);
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}
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/* Clean up a rotting corpse of an inferior after it died. */
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void
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inf_ptrace_target::mourn_inferior ()
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{
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int status;
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/* Wait just one more time to collect the inferior's exit status.
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Do not check whether this succeeds though, since we may be
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dealing with a process that we attached to. Such a process will
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only report its exit status to its original parent. */
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waitpid (inferior_ptid.pid (), &status, 0);
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inf_child_target::mourn_inferior ();
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}
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/* Attach to the process specified by ARGS. If FROM_TTY is non-zero,
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be chatty about it. */
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void
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inf_ptrace_target::attach (const char *args, int from_tty)
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{
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inferior *inf = current_inferior ();
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/* Do not change either targets above or the same target if already present.
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The reason is the target stack is shared across multiple inferiors. */
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int ops_already_pushed = inf->target_is_pushed (this);
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pid_t pid = parse_pid_to_attach (args);
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if (pid == getpid ()) /* Trying to masturbate? */
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error (_("I refuse to debug myself!"));
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target_unpush_up unpusher;
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if (! ops_already_pushed)
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{
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/* target_pid_to_str already uses the target. Also clear possible core
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file with its process_stratum. */
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inf->push_target (this);
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unpusher.reset (this);
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}
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target_announce_attach (from_tty, pid);
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#ifdef PT_ATTACH
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errno = 0;
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ptrace (PT_ATTACH, pid, (PTRACE_TYPE_ARG3)0, 0);
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if (errno != 0)
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perror_with_name (("ptrace"));
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#else
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error (_("This system does not support attaching to a process"));
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#endif
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inferior_appeared (inf, pid);
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inf->attach_flag = 1;
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/* Always add a main thread. If some target extends the ptrace
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target, it should decorate the ptid later with more info. */
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thread_info *thr = add_thread_silent (this, ptid_t (pid));
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switch_to_thread (thr);
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/* Don't consider the thread stopped until we've processed its
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initial SIGSTOP stop. */
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set_executing (this, thr->ptid, true);
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unpusher.release ();
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}
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/* Detach from the inferior. If FROM_TTY is non-zero, be chatty about it. */
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void
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inf_ptrace_target::detach (inferior *inf, int from_tty)
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{
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pid_t pid = inferior_ptid.pid ();
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target_announce_detach (from_tty);
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#ifdef PT_DETACH
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/* We'd better not have left any breakpoints in the program or it'll
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die when it hits one. Also note that this may only work if we
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previously attached to the inferior. It *might* work if we
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started the process ourselves. */
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errno = 0;
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ptrace (PT_DETACH, pid, (PTRACE_TYPE_ARG3)1, 0);
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if (errno != 0)
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perror_with_name (("ptrace"));
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#else
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error (_("This system does not support detaching from a process"));
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#endif
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detach_success (inf);
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}
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/* See inf-ptrace.h. */
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void
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inf_ptrace_target::detach_success (inferior *inf)
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{
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switch_to_no_thread ();
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detach_inferior (inf);
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maybe_unpush_target ();
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}
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/* Kill the inferior. */
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void
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inf_ptrace_target::kill ()
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{
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pid_t pid = inferior_ptid.pid ();
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int status;
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if (pid == 0)
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return;
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ptrace (PT_KILL, pid, (PTRACE_TYPE_ARG3)0, 0);
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waitpid (pid, &status, 0);
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target_mourn_inferior (inferior_ptid);
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}
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#ifndef __NetBSD__
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/* See inf-ptrace.h. */
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pid_t
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get_ptrace_pid (ptid_t ptid)
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{
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pid_t pid;
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/* If we have an LWPID to work with, use it. Otherwise, we're
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dealing with a non-threaded program/target. */
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pid = ptid.lwp ();
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if (pid == 0)
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pid = ptid.pid ();
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return pid;
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}
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#endif
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/* Resume execution of thread PTID, or all threads if PTID is -1. If
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STEP is nonzero, single-step it. If SIGNAL is nonzero, give it
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that signal. */
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void
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inf_ptrace_target::resume (ptid_t ptid, int step, enum gdb_signal signal)
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{
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PTRACE_TYPE_ARG1 request;
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if (minus_one_ptid == ptid)
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/* Resume all threads. Traditionally ptrace() only supports
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single-threaded processes, so simply resume the inferior. */
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ptid = ptid_t (inferior_ptid.pid ());
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if (catch_syscall_enabled () > 0)
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request = PT_SYSCALL;
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else
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request = PT_CONTINUE;
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if (step)
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{
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/* If this system does not support PT_STEP, a higher level
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function will have called the appropriate functions to transmute the
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step request into a continue request (by setting breakpoints on
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all possible successor instructions), so we don't have to
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worry about that here. */
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request = PT_STEP;
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}
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/* An address of (PTRACE_TYPE_ARG3)1 tells ptrace to continue from
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where it was. If GDB wanted it to start some other way, we have
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already written a new program counter value to the child. */
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errno = 0;
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gdb_ptrace (request, ptid, (PTRACE_TYPE_ARG3)1, gdb_signal_to_host (signal));
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if (errno != 0)
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perror_with_name (("ptrace"));
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}
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/* Wait for the child specified by PTID to do something. Return the
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process ID of the child, or MINUS_ONE_PTID in case of error; store
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the status in *OURSTATUS. */
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ptid_t
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inf_ptrace_target::wait (ptid_t ptid, struct target_waitstatus *ourstatus,
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target_wait_flags target_options)
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{
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pid_t pid;
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int options, status, save_errno;
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options = 0;
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if (target_options & TARGET_WNOHANG)
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options |= WNOHANG;
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do
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{
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set_sigint_trap ();
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do
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{
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pid = waitpid (ptid.pid (), &status, options);
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save_errno = errno;
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}
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while (pid == -1 && errno == EINTR);
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clear_sigint_trap ();
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if (pid == 0)
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{
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gdb_assert (target_options & TARGET_WNOHANG);
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ourstatus->set_ignore ();
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return minus_one_ptid;
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}
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if (pid == -1)
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{
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/* In async mode the SIGCHLD might have raced and triggered
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a check for an event that had already been reported. If
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the event was the exit of the only remaining child,
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waitpid() will fail with ECHILD. */
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if (ptid == minus_one_ptid && save_errno == ECHILD)
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{
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ourstatus->set_no_resumed ();
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return minus_one_ptid;
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}
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gdb_printf (gdb_stderr,
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_("Child process unexpectedly missing: %s.\n"),
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safe_strerror (save_errno));
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ourstatus->set_ignore ();
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return minus_one_ptid;
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}
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/* Ignore terminated detached child processes. */
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if (!WIFSTOPPED (status) && find_inferior_pid (this, pid) == nullptr)
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pid = -1;
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}
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while (pid == -1);
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*ourstatus = host_status_to_waitstatus (status);
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return ptid_t (pid);
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}
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/* Transfer data via ptrace into process PID's memory from WRITEBUF, or
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from process PID's memory into READBUF. Start at target address ADDR
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and transfer up to LEN bytes. Exactly one of READBUF and WRITEBUF must
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be non-null. Return the number of transferred bytes. */
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static ULONGEST
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inf_ptrace_peek_poke (ptid_t ptid, gdb_byte *readbuf,
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const gdb_byte *writebuf,
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ULONGEST addr, ULONGEST len)
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{
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ULONGEST n;
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unsigned int chunk;
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/* We transfer aligned words. Thus align ADDR down to a word
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boundary and determine how many bytes to skip at the
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beginning. */
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ULONGEST skip = addr & (sizeof (PTRACE_TYPE_RET) - 1);
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addr -= skip;
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for (n = 0;
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n < len;
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n += chunk, addr += sizeof (PTRACE_TYPE_RET), skip = 0)
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{
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/* Restrict to a chunk that fits in the current word. */
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chunk = std::min (sizeof (PTRACE_TYPE_RET) - skip, len - n);
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/* Use a union for type punning. */
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union
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{
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PTRACE_TYPE_RET word;
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gdb_byte byte[sizeof (PTRACE_TYPE_RET)];
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} buf;
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/* Read the word, also when doing a partial word write. */
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if (readbuf != NULL || chunk < sizeof (PTRACE_TYPE_RET))
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{
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errno = 0;
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buf.word = gdb_ptrace (PT_READ_I, ptid,
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(PTRACE_TYPE_ARG3)(uintptr_t) addr, 0);
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if (errno != 0)
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break;
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if (readbuf != NULL)
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memcpy (readbuf + n, buf.byte + skip, chunk);
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}
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if (writebuf != NULL)
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{
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memcpy (buf.byte + skip, writebuf + n, chunk);
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errno = 0;
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gdb_ptrace (PT_WRITE_D, ptid, (PTRACE_TYPE_ARG3)(uintptr_t) addr,
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buf.word);
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if (errno != 0)
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{
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/* Using the appropriate one (I or D) is necessary for
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Gould NP1, at least. */
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errno = 0;
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gdb_ptrace (PT_WRITE_I, ptid, (PTRACE_TYPE_ARG3)(uintptr_t) addr,
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buf.word);
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if (errno != 0)
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break;
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}
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}
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}
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return n;
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}
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/* Implement the to_xfer_partial target_ops method. */
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enum target_xfer_status
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inf_ptrace_target::xfer_partial (enum target_object object,
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const char *annex, gdb_byte *readbuf,
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const gdb_byte *writebuf,
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ULONGEST offset, ULONGEST len, ULONGEST *xfered_len)
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{
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ptid_t ptid = inferior_ptid;
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switch (object)
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{
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case TARGET_OBJECT_MEMORY:
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#ifdef PT_IO
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/* OpenBSD 3.1, NetBSD 1.6 and FreeBSD 5.0 have a new PT_IO
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request that promises to be much more efficient in reading
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and writing data in the traced process's address space. */
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{
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struct ptrace_io_desc piod;
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/* NOTE: We assume that there are no distinct address spaces
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|
for instruction and data. However, on OpenBSD 3.9 and
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later, PIOD_WRITE_D doesn't allow changing memory that's
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|
mapped read-only. Since most code segments will be
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read-only, using PIOD_WRITE_D will prevent us from
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inserting breakpoints, so we use PIOD_WRITE_I instead. */
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|
piod.piod_op = writebuf ? PIOD_WRITE_I : PIOD_READ_D;
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|
|
piod.piod_addr = writebuf ? (void *) writebuf : readbuf;
|
|
|
piod.piod_offs = (void *) (long) offset;
|
|
|
piod.piod_len = len;
|
|
|
|
|
|
errno = 0;
|
|
|
if (gdb_ptrace (PT_IO, ptid, (caddr_t)&piod, 0) == 0)
|
|
|
{
|
|
|
/* Return the actual number of bytes read or written. */
|
|
|
*xfered_len = piod.piod_len;
|
|
|
return (piod.piod_len == 0) ? TARGET_XFER_EOF : TARGET_XFER_OK;
|
|
|
}
|
|
|
/* If the PT_IO request is somehow not supported, fallback on
|
|
|
using PT_WRITE_D/PT_READ_D. Otherwise we will return zero
|
|
|
to indicate failure. */
|
|
|
if (errno != EINVAL)
|
|
|
return TARGET_XFER_EOF;
|
|
|
}
|
|
|
#endif
|
|
|
*xfered_len = inf_ptrace_peek_poke (ptid, readbuf, writebuf,
|
|
|
offset, len);
|
|
|
return *xfered_len != 0 ? TARGET_XFER_OK : TARGET_XFER_EOF;
|
|
|
|
|
|
case TARGET_OBJECT_UNWIND_TABLE:
|
|
|
return TARGET_XFER_E_IO;
|
|
|
|
|
|
case TARGET_OBJECT_AUXV:
|
|
|
#if defined (PT_IO) && defined (PIOD_READ_AUXV)
|
|
|
/* OpenBSD 4.5 has a new PIOD_READ_AUXV operation for the PT_IO
|
|
|
request that allows us to read the auxilliary vector. Other
|
|
|
BSD's may follow if they feel the need to support PIE. */
|
|
|
{
|
|
|
struct ptrace_io_desc piod;
|
|
|
|
|
|
if (writebuf)
|
|
|
return TARGET_XFER_E_IO;
|
|
|
piod.piod_op = PIOD_READ_AUXV;
|
|
|
piod.piod_addr = readbuf;
|
|
|
piod.piod_offs = (void *) (long) offset;
|
|
|
piod.piod_len = len;
|
|
|
|
|
|
errno = 0;
|
|
|
if (gdb_ptrace (PT_IO, ptid, (caddr_t)&piod, 0) == 0)
|
|
|
{
|
|
|
/* Return the actual number of bytes read or written. */
|
|
|
*xfered_len = piod.piod_len;
|
|
|
return (piod.piod_len == 0) ? TARGET_XFER_EOF : TARGET_XFER_OK;
|
|
|
}
|
|
|
}
|
|
|
#endif
|
|
|
return TARGET_XFER_E_IO;
|
|
|
|
|
|
case TARGET_OBJECT_WCOOKIE:
|
|
|
return TARGET_XFER_E_IO;
|
|
|
|
|
|
default:
|
|
|
return TARGET_XFER_E_IO;
|
|
|
}
|
|
|
}
|
|
|
|
|
|
/* Return non-zero if the thread specified by PTID is alive. */
|
|
|
|
|
|
bool
|
|
|
inf_ptrace_target::thread_alive (ptid_t ptid)
|
|
|
{
|
|
|
/* ??? Is kill the right way to do this? */
|
|
|
return (::kill (ptid.pid (), 0) != -1);
|
|
|
}
|
|
|
|
|
|
/* Print status information about what we're accessing. */
|
|
|
|
|
|
void
|
|
|
inf_ptrace_target::files_info ()
|
|
|
{
|
|
|
struct inferior *inf = current_inferior ();
|
|
|
|
|
|
gdb_printf (_("\tUsing the running image of %s %s.\n"),
|
|
|
inf->attach_flag ? "attached" : "child",
|
|
|
target_pid_to_str (inferior_ptid).c_str ());
|
|
|
}
|
|
|
|
|
|
std::string
|
|
|
inf_ptrace_target::pid_to_str (ptid_t ptid)
|
|
|
{
|
|
|
return normal_pid_to_str (ptid);
|
|
|
}
|
|
|
|
|
|
/* Implement the "close" target method. */
|
|
|
|
|
|
void
|
|
|
inf_ptrace_target::close ()
|
|
|
{
|
|
|
/* Unregister from the event loop. */
|
|
|
if (is_async_p ())
|
|
|
async (0);
|
|
|
|
|
|
inf_child_target::close ();
|
|
|
}
|