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in kern_gzio.c. The old gzio interface was somewhat inflexible and has not worked properly since r272535: currently, the gzio functions are called with a range lock held on the output vnode, but kern_gzio.c does not pass the IO_RANGELOCKED flag to vn_rdwr() calls, resulting in deadlock when vn_rdwr() attempts to reacquire the range lock. Moreover, the new gzio interface can be used to implement kernel core compression. This change also modifies the kernel configuration options needed to enable userland core dump compression support: gzio is now an option rather than a device, and the COMPRESS_USER_CORES option is removed. Core dump compression is enabled using the kern.compress_user_cores sysctl/tunable. Differential Revision: https://reviews.freebsd.org/D1832 Reviewed by: rpaulo Discussed with: kib
142 lines
4.4 KiB
Groff
142 lines
4.4 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
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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. 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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.\" @(#)core.5 8.3 (Berkeley) 12/11/93
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.\" $FreeBSD$
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.\"
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.Dd March 8, 2015
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.Dt CORE 5
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.Os
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.Sh NAME
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.Nm core
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.Nd memory image file format
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.Sh SYNOPSIS
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.In sys/param.h
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.Sh DESCRIPTION
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A small number of signals which cause abnormal termination of a process
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also cause a record of the process's in-core state to be written
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to disk for later examination by one of the available debuggers.
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(See
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.Xr sigaction 2 . )
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This memory image is written to a file named by default
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.Nm programname.core
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in the working directory;
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provided the terminated process had write permission in the directory,
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and provided the abnormality did not cause
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a system crash.
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(In this event, the decision to save the core file is arbitrary, see
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.Xr savecore 8 . )
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.Pp
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The maximum size of a core file is limited by
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.Xr setrlimit 2 .
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Files which would be larger than the limit are not created.
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.Pp
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The name of the file is controlled via the
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.Xr sysctl 8
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variable
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.Va kern.corefile .
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The contents of this variable describes a filename to store
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the core image to.
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This filename can be absolute, or relative (which
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will resolve to the current working directory of the program
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generating it).
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.Pp
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The following format specifiers may be used in the
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.Va kern.corefile
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sysctl to insert additional information into the resulting core file
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name:
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.Bl -tag -width "1234567890" -compact -offset "12345"
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.It Em \&%H
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Machine hostname.
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.It Em \&%I
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An index starting at zero until the sysctl
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.Em debug.ncores
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is reached.
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This can be useful for limiting the number of corefiles
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generated by a particular process.
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.It Em \&%N
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process name.
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.It Em \&%P
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processes PID.
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.It Em \&%U
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process UID.
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.El
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.Pp
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The name defaults to
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.Em \&%N.core ,
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yielding the traditional
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.Fx
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behaviour.
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.Pp
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By default, a process that changes user or group credentials whether
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real or effective will not create a corefile.
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This behaviour can be
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changed to generate a core dump by setting the
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.Xr sysctl 8
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variable
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.Va kern.sugid_coredump
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to 1.
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.Pp
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Corefiles can be compressed by the kernel if the following item
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is included in the kernel configuration file:
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.Bl -tag -width "1234567890" -compact -offset "12345"
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.It options
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GZIO
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.El
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.Pp
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When the GZIO option is included, the following sysctls control whether core
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files will be compressed:
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.Bl -tag -width "kern.compress_user_cores_gzlevel" -compact -offset "12345"
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.It Em kern.compress_user_cores_gzlevel
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Gzip compression level.
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Defaults to 6.
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.It Em kern.compress_user_cores
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Actually compress user cores.
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Compressed core files will have a suffix of
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.Ql .gz
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appended to them.
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.El
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.Sh EXAMPLES
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In order to store all core images in per-user private areas under
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.Pa /var/coredumps ,
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the following
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.Xr sysctl 8
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command can be used:
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.Pp
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.Dl sysctl kern.corefile=/var/coredumps/\&%U/\&%N.core
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.Sh SEE ALSO
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.Xr gdb 1 ,
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.Xr kgdb 1 ,
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.Xr setrlimit 2 ,
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.Xr sigaction 2 ,
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.Xr sysctl 8
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.Sh HISTORY
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A
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.Nm
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file format appeared in
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.At v6 .
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