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886ae81fa3
Additionally, because of sysctl(3) use (which is generally good), behaviour for crash dumps differs slightly from behaviour for live kernels and this will probably never be fixed entirely, so weaken that claim. MFC after: 1 week
121 lines
4.0 KiB
Groff
121 lines
4.0 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 25, 2010
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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 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_getfiles 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_nlist 3 ,
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.Xr kvm_open 3 ,
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.Xr kvm_openfiles 3 ,
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.Xr kvm_read 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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