1998-01-09 09:54:27 +03:00
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.\" $NetBSD: 2.5.t,v 1.2 1998/01/09 06:54:53 perry Exp $
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.\"
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1997-10-17 13:49:00 +04:00
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.\" Copyright (c) 1983, 1993, 1994
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1994-06-19 04:07:16 +04:00
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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1997-10-17 13:49:00 +04:00
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.\" @(#)2.5.t 8.6 (Berkeley) 5/29/94
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1994-06-19 04:07:16 +04:00
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.\"
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1997-10-17 13:49:00 +04:00
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.Sh 2 "Process debugging
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.Sh 3 "Traditional debugging
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.LP
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Debuggers traditionally use the
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.Fn ptrace
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interface:
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.DS
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.Fd ptrace 4 "process trace
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ptrace(request, pid, addr, data);
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int request, pid, *addr, data;
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.DE
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This interface provides a means by which a parent process may
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control the execution of a child process,
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and examine and change its core image.
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Its primary use is for the implementation of breakpoint debugging.
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There are four arguments whose interpretation
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depends on a request argument.
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A process being traced behaves normally until it
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encounters a signal (whether internally generated like
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``illegal instruction'' or externally generated
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like ``interrupt'').
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Then the traced process enters a stopped state
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and its parent is notified via
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.Fn wait .
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When the child is in the stopped state,
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its core image can be examined and modified using
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.Fn ptrace .
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Another ptrace request can then cause the child either to terminate
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or to continue, possibly ignoring the signal.
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1994-06-19 04:07:16 +04:00
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.PP
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1997-10-17 13:49:00 +04:00
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A more general interface is also provided in 4.4BSD;
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the \fImount_procfs\fP filesystem attaches an instance of
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the process name space to the global filesystem name space.
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The conventional mount point is \fI/proc\fP.
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The root of the process filesystem contains an entry for each active
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process.
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These processes are visible as directories named by the process' ID.
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In addition, the special entry \fIcurproc\fP references the current
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process.
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Each directory contains several files, including a \fIctl\fP file.
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The debugger finds (or creates) the process that it wants to
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debug and then issues an attach command via the \fIctl\fP file.
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Further interaction can then be done with the process through
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the other files provided by the \fI/proc\fP filesystem.
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.Sh 3 "Kernel tracing
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.LP
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Another facility for debugging programs is provided by the
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.Fn ktrace
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interface:
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.DS
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.Fd ktrace 4 "process tracing
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ktrace(tracefile, ops, trpoints, pid);
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char *tracefile; int ops, trpoints, pid;
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.DE
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.Fn Ktrace
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does kernel trace logging for the specified processes.
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The kernel operations that are traced include system calls,
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pathname translations, signal processing, and I/O.
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This facility can be particularly useful to debug
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programs for which you do not have the source.
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.\"
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.\" We currently do not document the vtrace call
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.\" .Fd vtrace 2
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