9c1e214f79
This fix is spiritually similar to r287442 and was discovered thanks to the KASSERT added in that revision. NT_PROCSTAT_VMMAP output length, when packing kinfo structs, is tied to the length of filenames corresponding to vnodes in the process' vm map via vn_fullpath. As vnodes may move during coredump, this is racy. We do not remove the race, only prevent it from causing coredump corruption. - Add a sysctl, kern.coredump_pack_vmmapinfo, to allow users to disable kinfo packing for PROCSTAT_VMMAP notes. This avoids VMMAP corruption and truncation, even if names change, at the cost of up to PATH_MAX bytes per mapped object. The new sysctl is documented in core.5. - Fix note_procstat_vmmap to self-limit in the second pass. This addresses corruption, at the cost of sometimes producing a truncated result. - Fix PROCSTAT_VMMAP consumers libutil (and libprocstat, via copy-paste) to grok the new zero padding. Reported by: pho (https://people.freebsd.org/~pho/stress/log/datamove4-2.txt) Relnotes: yes Sponsored by: EMC / Isilon Storage Division Differential Revision: https://reviews.freebsd.org/D3824
165 lines
5.4 KiB
Groff
165 lines
5.4 KiB
Groff
.\" Copyright (c) 1980, 1991, 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.
|
|
.\"
|
|
.\" @(#)core.5 8.3 (Berkeley) 12/11/93
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd October 5, 2015
|
|
.Dt CORE 5
|
|
.Os
|
|
.Sh NAME
|
|
.Nm core
|
|
.Nd memory image file format
|
|
.Sh SYNOPSIS
|
|
.In sys/param.h
|
|
.Sh DESCRIPTION
|
|
A small number of signals which cause abnormal termination of a process
|
|
also cause a record of the process's in-core state to be written
|
|
to disk for later examination by one of the available debuggers.
|
|
(See
|
|
.Xr sigaction 2 . )
|
|
This memory image is written to a file named by default
|
|
.Nm programname.core
|
|
in the working directory;
|
|
provided the terminated process had write permission in the directory,
|
|
and provided the abnormality did not cause
|
|
a system crash.
|
|
(In this event, the decision to save the core file is arbitrary, see
|
|
.Xr savecore 8 . )
|
|
.Pp
|
|
The maximum size of a core file is limited by
|
|
.Xr setrlimit 2 .
|
|
Files which would be larger than the limit are not created.
|
|
.Pp
|
|
The name of the file is controlled via the
|
|
.Xr sysctl 8
|
|
variable
|
|
.Va kern.corefile .
|
|
The contents of this variable describes a filename to store
|
|
the core image to.
|
|
This filename can be absolute, or relative (which
|
|
will resolve to the current working directory of the program
|
|
generating it).
|
|
.Pp
|
|
The following format specifiers may be used in the
|
|
.Va kern.corefile
|
|
sysctl to insert additional information into the resulting core file
|
|
name:
|
|
.Bl -tag -width "1234567890" -compact -offset "12345"
|
|
.It Em \&%H
|
|
Machine hostname.
|
|
.It Em \&%I
|
|
An index starting at zero until the sysctl
|
|
.Em debug.ncores
|
|
is reached.
|
|
This can be useful for limiting the number of corefiles
|
|
generated by a particular process.
|
|
.It Em \&%N
|
|
process name.
|
|
.It Em \&%P
|
|
processes PID.
|
|
.It Em \&%U
|
|
process UID.
|
|
.El
|
|
.Pp
|
|
The name defaults to
|
|
.Em \&%N.core ,
|
|
yielding the traditional
|
|
.Fx
|
|
behaviour.
|
|
.Pp
|
|
By default, a process that changes user or group credentials whether
|
|
real or effective will not create a corefile.
|
|
This behaviour can be
|
|
changed to generate a core dump by setting the
|
|
.Xr sysctl 8
|
|
variable
|
|
.Va kern.sugid_coredump
|
|
to 1.
|
|
.Pp
|
|
Corefiles can be compressed by the kernel if the following item
|
|
is included in the kernel configuration file:
|
|
.Bl -tag -width "1234567890" -compact -offset "12345"
|
|
.It options
|
|
GZIO
|
|
.El
|
|
.Pp
|
|
When the GZIO option is included, the following sysctls control whether core
|
|
files will be compressed:
|
|
.Bl -tag -width "kern.compress_user_cores_gzlevel" -compact -offset "12345"
|
|
.It Em kern.compress_user_cores_gzlevel
|
|
Gzip compression level.
|
|
Defaults to 6.
|
|
.It Em kern.compress_user_cores
|
|
Actually compress user cores.
|
|
Compressed core files will have a suffix of
|
|
.Ql .gz
|
|
appended to them.
|
|
.El
|
|
.Sh NOTES
|
|
Corefiles are written with open file descriptor information as an ELF note.
|
|
By default, file paths are packed to only use as much space as needed.
|
|
However, file paths can change at any time, including during core dump,
|
|
and this can result in truncated file descriptor data.
|
|
.Pp
|
|
All file descriptor information can be preserved by disabling packing.
|
|
This potentially wastes up to PATH_MAX bytes per open fd.
|
|
Packing is disabled with
|
|
.Dl sysctl kern.coredump_pack_fileinfo=0 .
|
|
.Pp
|
|
Similarly, corefiles are written with vmmap information as an ELF note, which
|
|
contains file paths.
|
|
By default, they are packed to only use as much space as
|
|
needed.
|
|
By the same mechanism as for the open files note, these paths can also
|
|
change at any time and result in a truncated note.
|
|
.Pp
|
|
All vmmap information can be preserved by disabling packing.
|
|
Like the file information, this potentially wastes up to PATH_MAX bytes per
|
|
mapped object.
|
|
Packing is disabled with
|
|
.Dl sysctl kern.coredump_pack_vmmapinfo=0 .
|
|
.Sh EXAMPLES
|
|
In order to store all core images in per-user private areas under
|
|
.Pa /var/coredumps ,
|
|
the following
|
|
.Xr sysctl 8
|
|
command can be used:
|
|
.Pp
|
|
.Dl sysctl kern.corefile=/var/coredumps/\&%U/\&%N.core
|
|
.Sh SEE ALSO
|
|
.Xr gdb 1 ,
|
|
.Xr kgdb 1 ,
|
|
.Xr setrlimit 2 ,
|
|
.Xr sigaction 2 ,
|
|
.Xr sysctl 8
|
|
.Sh HISTORY
|
|
A
|
|
.Nm
|
|
file format appeared in
|
|
.At v6 .
|