9da227510d
Imported with no changes, but not all parts are expected to be functional. The libc nlist functionality is enabled for the purpose of successful linking, although the nlist functionaly has not been tested on MINIX3 nor is it needed for how we use libkvm. In terms of function calls: kvm_getproc2, kvm_getargv2, kvm_getenvv2, and kvm_getlwps are expected to work, whereas kvm_getproc, kvm_getargv, kvm_getenvv, and kvm_getfiles are not. Change-Id: I7539209736f1771fc0b7db5e839d2df72f5ac615
238 lines
6.1 KiB
Groff
238 lines
6.1 KiB
Groff
.\" $NetBSD: kvm_open.3,v 1.18 2011/09/12 21:11:32 christos Exp $
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.\"
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.\" 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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.\" 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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.\" @(#)kvm_open.3 8.3 (Berkeley) 4/19/94
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.\"
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.Dd September 14, 2011
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.Dt KVM_OPEN 3
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.Os
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.Sh NAME
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.Nm kvm_open ,
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.Nm kvm_openfiles ,
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.Nm kvm_close
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.Nd initialize kernel virtual memory access
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.Sh LIBRARY
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.Lb libkvm
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.Sh SYNOPSIS
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.In fcntl.h
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.In kvm.h
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.Ft kvm_t *
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.Fn kvm_open "const char *execfile" "const char *corefile" "char *swapfile" "int flags" "const char *errstr"
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.Ft kvm_t *
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.Fn kvm_openfiles "const char *execfile" "const char *corefile" "char *swapfile" "int flags" "char *errbuf"
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.Ft int
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.Fn kvm_close "kvm_t *kd"
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.Sh DESCRIPTION
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The functions
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.Fn kvm_open
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and
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.Fn kvm_openfiles
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return a descriptor used to access kernel virtual memory
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via the
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.Xr kvm 3
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library routines.
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Both active kernels and crash dumps are accessible
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through this interface.
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.Pp
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.Fa execfile
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is the executable image of the kernel being examined.
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This file must contain a symbol table.
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If this argument is
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.Dv NULL ,
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the currently running system is assumed; in this case, the functions will
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attempt to use the
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.Xr ksyms 4
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device indicated by
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.Dv _PATH_KSYMS
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in
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.In paths.h ;
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if that fails, then they will use the file indicated by the
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.Xr sysctl 3
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variable
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.Va machdep.booted_kernel ,
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or (if the sysctl information is not available)
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the default kernel path indicated by
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.Dv _PATH_UNIX
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in
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.In paths.h .
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.Pp
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.Fa corefile
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is the kernel memory device file.
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It can be either
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.Pa /dev/mem
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or a crash dump core generated by
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.Xr savecore 8 .
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If
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.Fa corefile
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is
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.Dv NULL ,
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the default indicated by
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.Dv _PATH_MEM
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from
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.In paths.h
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is used.
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.Pp
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.Fa swapfile
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should indicate the swap device.
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If
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.Dv NULL ,
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.Dv _PATH_DRUM
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from
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.In paths.h
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is used.
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.Pp
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The
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.Fa flags
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argument indicates read/write access as in
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.Xr open 2
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and applies only to the core file.
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The only permitted flags from
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.Xr open 2
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are
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.Dv O_RDONLY ,
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.Dv O_WRONLY ,
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and
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.Dv O_RDWR .
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.Pp
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As a special case, a
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.Fa flags
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argument of
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.Dv KVM_NO_FILES
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will initialize the
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.Xr kvm 3
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library for use on active kernels only using
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.Xr sysctl 3
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for retrieving kernel data and ignores the
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.Fa execfile ,
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.Fa corefile
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and
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.Fa swapfile
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arguments.
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Only a small subset of the
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.Xr kvm 3
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library functions are available using this method.
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These are currently
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.Xr kvm_getproc2 3 ,
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.Xr kvm_getargv2 3
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and
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.Xr kvm_getenvv2 3 .
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.Pp
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There are two open routines which differ only with respect to
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the error mechanism.
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One provides backward compatibility with the SunOS kvm library, while the
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other provides an improved error reporting framework.
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.Pp
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The
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.Fn kvm_open
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function is the Sun kvm compatible open call.
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Here, the
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.Fa errstr
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argument indicates how errors should be handled.
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If it is
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.Dv NULL ,
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no errors are reported and the application cannot know the
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specific nature of the failed kvm call.
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If it is not
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.Dv NULL ,
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errors are printed to stderr with
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.Fa errstr
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prepended to the message, as in
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.Xr perror 3 .
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Normally, the name of the program is used here.
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The string is assumed to persist at least until the corresponding
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.Fn kvm_close
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call.
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.Pp
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The
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.Fn kvm_openfiles
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function provides
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.Bx
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style error reporting.
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Here, error messages are not printed out by the library.
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Instead, the application obtains the error message
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corresponding to the most recent kvm library call using
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.Fn kvm_geterr
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(see
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.Xr kvm_geterr 3 ) .
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The results are undefined if the most recent kvm call did not produce
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an error.
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Since
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.Fn kvm_geterr
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requires a kvm descriptor, but the open routines return
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.Dv NULL
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on failure,
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.Fn kvm_geterr
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cannot be used to get the error message if open fails.
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Thus,
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.Fn kvm_openfiles
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will place any error message in the
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.Fa errbuf
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argument.
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This buffer should be _POSIX2_LINE_MAX characters large (from
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.In limits.h ) .
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.Sh RETURN VALUES
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The
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.Fn kvm_open
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and
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.Fn kvm_openfiles
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functions both return a descriptor to be used
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in all subsequent kvm library calls.
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The library is fully re-entrant.
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On failure,
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.Dv NULL
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is returned, in which case
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.Fn kvm_openfiles
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writes the error message into
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.Fa errbuf .
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.Pp
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The
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.Fn kvm_close
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function returns 0 on success and -1 on failure.
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.Sh SEE ALSO
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.Xr open 2 ,
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.Xr kvm 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_getkernelname 3 ,
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.Xr kvm_getprocs 3 ,
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.Xr kvm_nlist 3 ,
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.Xr kvm_read 3 ,
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.Xr kvm_write 3
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.Sh BUGS
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There should not be two open calls.
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The ill-defined error semantics of the Sun library
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and the desire to have a backward-compatible library for
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.Bx
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left little choice.
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