ab35544b83
- Add a kvaddr_type to represent kernel virtual addresses instead of unsigned long. - Add a struct kvm_nlist which is a stripped down version of struct nlist that uses kvaddr_t for n_value. - Add a kvm_native() routine that returns true if an open kvm descriptor is for a native kernel and memory image. - Add a kvm_open2() function similar to kvm_openfiles(). It drops the unused 'swapfile' argument and adds a new function pointer argument for a symbol resolving function. Native kernels still use _fdnlist() from libc to resolve symbols if a resolver function is not supplied, but cross kernels require a resolver. - Add a kvm_nlist2() function similar to kvm_nlist() except that it uses struct kvm_nlist instead of struct nlist. - Add a kvm_read2() function similar to kvm_read() except that it uses kvaddr_t instead of unsigned long for the kernel virtual address. - Add a new kvm_arch switch of routines needed by a vmcore backend. Each backend is responsible for implementing kvm_read2() for a given vmcore format. - Use libelf to read headers from ELF kernels and cores (except for powerpc cores). - Add internal helper routines for the common page offset hash table used by the minidump backends. - Port all of the existing kvm backends to implement a kvm_arch switch and to be cross-friendly by using private constants instead of ones that vary by platform (e.g. PAGE_SIZE). Static assertions are present when a given backend is compiled natively to ensure the private constants match the real ones. - Enable all of the existing vmcore backends on all platforms. This means that libkvm on any platform should be able to perform KVA translation and read data from a vmcore of any platform. Tested on: amd64, i386, sparc64 (marius) Differential Revision: https://reviews.freebsd.org/D3341
253 lines
6.4 KiB
Groff
253 lines
6.4 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_open.3 8.3 (Berkeley) 4/19/94
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.\" $FreeBSD$
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.\"
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.Dd November 27, 2015
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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_open2 ,
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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" "const char *swapfile" "int flags" "const char *errstr"
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.Ft kvm_t *
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.Fo kvm_open2
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.Fa "const char *execfile"
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.Fa "const char *corefile"
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.Fa "int flags"
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.Fa "char *errbuf"
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.Fa "int (*resolver)(const char *name, kvaddr_t *addr)"
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.Fc
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.Ft kvm_t *
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.Fn kvm_openfiles "const char *execfile" "const char *corefile" "const 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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.Fn kvm_open2 ,
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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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The
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.Fa execfile
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argument 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,
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as determined from
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.Xr getbootfile 3 .
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.Pp
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The
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.Fa corefile
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argument 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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It can also be set to a special value
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.Pa /dev/null
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by utilities like
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.Xr ps 1
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that do not directly access kernel memory.
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.Pp
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The
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.Fa swapfile
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argument is currently unused.
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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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Only
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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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are permitted.
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.Pp
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The
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.Nm kvm
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library provides two different error reporting mechanisms.
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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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The mechanism used by a descriptor is determined by the function used to
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open the descriptor.
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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
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.Dv stderr
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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_open2
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and
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.Fn kvm_openfiles
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functions provide
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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_open2
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and
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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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<limits.h>).
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.Pp
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The
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.Fa resolver
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argument points to a function used by the
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.Nm kvm
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library to map symbol names to kernel virtual addresses.
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When the
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.Fa resolver
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function is called,
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.Fa name
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specifies the requested symbol name.
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If the function is able to resolve the name to an address,
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the address should be set in
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.Fa *addr
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and the function should return zero.
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If the function is not able to resolve the name to an address,
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it should return a non-zero value.
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When opening a native kernel image,
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.Fa resolver
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may be set to
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.Dv NULL
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to use an internal function to resolve symbol names.
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Non-native kernel images
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.Pq such as when cross-debugging a crash dump
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require a valid
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.Fa resolver .
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.Sh RETURN VALUES
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The
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.Fn kvm_open ,
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.Fn kvm_open2 ,
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and
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.Fn kvm_openfiles
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functions 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_open2
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and
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.Fn kvm_openfiles
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write 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_getprocs 3 ,
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.Xr kvm_native 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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.Xr kmem 4 ,
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.Xr mem 4
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.Sh BUGS
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There should not be three open calls.
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The ill-defined error semantics
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of the Sun library and the desire to have a backward-compatible library
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for
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.Bx
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left little choice.
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