freebsd-dev/usr.bin/gcore/gcore.1
Konstantin Belousov 73e8f06ac5 gcore: add option to dump core using kernel facility
-k switch causes gcore to use ptrace(PT_COREDUMP) instead of manually
reading process memory and constructing the core.

Reviewed by:	markj
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D29955
2021-05-03 19:18:26 +03:00

107 lines
3.3 KiB
Groff

.\" Copyright (c) 1983, 1990, 1992, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" @(#)gcore.1 8.2 (Berkeley) 4/18/94
.\" $FreeBSD$
.\"
.Dd April 24, 2021
.Dt GCORE 1
.Os
.Sh NAME
.Nm gcore
.Nd get core images of running process
.Sh SYNOPSIS
.Nm
.Op Fl f
.Op Fl k
.Op Fl c Ar core
.Op Ar executable
.Ar pid
.Sh DESCRIPTION
The
.Nm
utility creates a core image of the specified process,
suitable for use with
.Xr gdb 1 .
By default, the core is written to the file
.Dq Pa core.<pid> .
The process identifier,
.Ar pid ,
must be given on the command line.
.Pp
The following options are available:
.Bl -tag -width indent
.It Fl c
Write the core file to the specified file instead of
.Dq Pa core.<pid> .
.It Fl f
Dumps all available segments, excluding only malformed and undumpable
segments.
Unlike the default invocation, this flag dumps mappings of devices which
may invalidate the state of device transactions or trigger other unexpected
behavior.
As a result, this flag should only be used when the behavior of the
application and any devices it has mapped is fully understood and any side
effects can be controlled or tolerated.
.It Fl k
Use the
.Xr ptrace 2
.Dv PT_COREDUMP
kernel facility to write the core dump, instead of reading the process'
memory and constructing the dump file in
.Nm
itself.
This is faster, and the dump is written by the
same kernel code that writes core dumps upon fatal signals.
.El
.Sh FILES
.Bl -tag -width /var/log/messages -compact
.It Pa core.<pid>
the core image
.El
.Sh HISTORY
A
.Nm
utility appeared in
.Bx 4.2 .
.Sh BUGS
Because of the
.Xr ptrace 2
usage
.Nm
may not work with processes which are actively being investigated with
.Xr truss 1
or
.Xr gdb 1 .
Additionally, interruptable sleeps may exit with EINTR.
.Pp
The
.Nm
utility is not compatible with the original
.Bx 4.2
version.