7aad67e9ca
This libcall has been broken since (at least) r174989/8.0-RELEASE. Bump SHLIB_MAJOR for the change Differential Revision: https://reviews.freebsd.org/D6052 Relnotes: yes Reviewed by: jhb, markj Sponsored by: EMC / Isilon Storage Division
162 lines
4.9 KiB
Groff
162 lines
4.9 KiB
Groff
.\" Copyright (c) 1992, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software developed by the Computer Systems
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.\" Engineering group at Lawrence Berkeley Laboratory under DARPA contract
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.\" BG 91-66 and contributed to Berkeley.
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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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.\" 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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.\" @(#)kvm.3 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd April 30, 2016
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.Dt KVM 3
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.Os
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.Sh NAME
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.Nm kvm
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.Nd kernel memory interface
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.Sh LIBRARY
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.Lb libkvm
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.Sh DESCRIPTION
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The
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.Nm
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library provides a uniform interface for accessing kernel virtual memory
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images, including live systems and crash dumps.
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Access to live systems is via
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.Xr sysctl 3
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for some functions, and
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.Xr mem 4
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and
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.Xr kmem 4
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for other functions,
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while crash dumps can be examined via the core file generated by
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.Xr savecore 8 .
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The interface behaves similarly in both cases.
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Memory can be read and written, kernel symbol addresses can be
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looked up efficiently, and information about user processes can
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be gathered.
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.Pp
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The
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.Fn kvm_open
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function is first called to obtain a descriptor for all subsequent calls.
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.Sh COMPATIBILITY
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The kvm interface was first introduced in SunOS.
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A considerable
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number of programs have been developed that use this interface,
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making backward compatibility highly desirable.
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In most respects, the Sun kvm interface is consistent and clean.
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Accordingly, the generic portion of the interface (i.e.,
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.Fn kvm_open ,
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.Fn kvm_close ,
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.Fn kvm_read ,
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.Fn kvm_write ,
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and
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.Fn kvm_nlist )
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has been incorporated into the
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.Bx
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interface.
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Indeed, many kvm
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applications (i.e., debuggers and statistical monitors) use only
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this subset of the interface.
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.Pp
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The process interface was not kept.
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This is not a portability
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issue since any code that manipulates processes is inherently
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machine dependent.
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.Pp
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Finally, the Sun kvm error reporting semantics are poorly defined.
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The library can be configured either to print errors to
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.Dv stderr
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automatically,
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or to print no error messages at all.
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In the latter case, the nature of the error cannot be determined.
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To overcome this, the
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.Bx
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interface includes a
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routine,
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.Xr kvm_geterr 3 ,
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to return (not print out) the error message
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corresponding to the most recent error condition on the
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given descriptor.
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.Sh CROSS DEBUGGING
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The
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.Nm
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library supports inspection of crash dumps from non-native kernels.
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Only a limited subset of the kvm interface is supported for these dumps.
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To inspect a crash dump of a non-native kernel,
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the caller must provide a
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.Fa resolver
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function when opening a descriptor via
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.Fn kvm_open2 .
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In addition,
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the kvm interface defines an integer type
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.Pq Vt kvaddr_t
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that is large enough to hold all valid addresses of all supported
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architectures.
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The interface also defines a new namelist structure type
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.Pq Vt "struct kvm_nlist"
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for use with
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.Fn kvm_nlist2 .
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To avoid address truncation issues,
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the caller should use
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.Fn kvm_nlist2
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and
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.Fn kvm_read2
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in place of
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.Fn kvm_nlist
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and
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.Fn kvm_read ,
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respectively.
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Finally, only a limited subset of operations are supported for non-native
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crash dumps:
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.Fn kvm_close ,
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.Fn kvm_geterr
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.Fn kvm_open2 ,
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.Fn kvm_native ,
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.Fn kvm_nlist2 ,
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and
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.Fn kvm_read2 .
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.Sh SEE ALSO
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.Xr kvm_close 3 ,
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.Xr kvm_getargv 3 ,
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.Xr kvm_getenvv 3 ,
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.Xr kvm_geterr 3 ,
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.Xr kvm_getloadavg 3 ,
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.Xr kvm_getprocs 3 ,
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.Xr kvm_getswapinfo 3 ,
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.Xr kvm_native 3 ,
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.Xr kvm_nlist 3 ,
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.Xr kvm_nlist2 3 ,
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.Xr kvm_open 3 ,
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.Xr kvm_open2 3 ,
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.Xr kvm_openfiles 3 ,
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.Xr kvm_read 3 ,
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.Xr kvm_read2 3 ,
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.Xr kvm_write 3 ,
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.Xr sysctl 3 ,
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.Xr kmem 4 ,
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.Xr mem 4
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