163 lines
5.2 KiB
Groff
163 lines
5.2 KiB
Groff
.\" Copyright (c) 2003 Matthew N. Dodd <winter@jurai.net>
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.\" All rights reserved.
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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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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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.\" $FreeBSD$
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.\"
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.Dd January 31, 2004
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.Dt LIBMAP.CONF 5
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.Os
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.Sh NAME
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.Nm libmap.conf
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.Nd "configuration file for dynamic object dependency mapping"
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.Sh DESCRIPTION
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The
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.Nm libmap
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functionality of
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.Xr ld-elf.so.1 1
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allows dynamic object dependencies to be mapped to arbitrary
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names.
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.Pp
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The configuration file consists of two whitespace separated columns; the
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left hand side containing the mapping candidate and the right hand
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side containing the mapping.
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Dependencies are matched against candidates and replaced with the mappings.
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.Pp
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Constrained mappings may be specified by enclosing the name of the
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executable or library in brackets.
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All mappings following a constraint will only be evaluated for that constraint.
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Constraints can be one of three types:
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.Bl -tag -width indent
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.It Exact
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The constraint is matched literally so that only an executable with an
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identical fully qualified pathname will match the constraint.
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This means that the executable
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.Pa /usr/bin/foo
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will not match a constraint for
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.Pa /usr/bin/./foo
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and vice-versa.
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This is the default constraint type.
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.It Basename
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A constraint with no path is matched against the basename of the
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executable.
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.Pa foo
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will match
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.Pa /bin/foo ,
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.Pa /usr/local/sbin/foo ,
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or any other executable named
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.Pa foo ,
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no matter what its path is.
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.It Directory
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A constraint with a trailing slash is prefix-matched against the full
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pathname of the executable.
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.Pa /usr/bin/
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will match any executable with a path starting with /usr/bin.
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.El
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.Pp
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Note that the executable path matched against is the
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.Fa path
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parameter in an
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.Fn exec*
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function call.
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The Directory or Exact constraints can only match when the executable
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is called with a full pathname.
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Most programs executed from a shell are run without a full path, via
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.Fn exec*p ,
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so the Basename constraint type is the most useful.
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.Pp
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WARNING!
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Constrained mappings must never appear first in the configuration file.
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While there is a way to specify the
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.Dq default
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constraint, its use is not recommended.
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.Pp
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The most common use at the date of writing is for allowing multiple
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.Tn POSIX
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threading libraries to be used on a system without relinking or
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changing symlinks.
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.Pp
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This mechanism has also been used to create shims to allow Linux
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shared libraries to be dynamically loaded into
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.Fx
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binaries.
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In this case, an Exact constraint is use for the Linux shared library,
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mapping libraries it depends on to a wrapper.
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The wrapper then defines any needed symbols for the Linux shared library
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and relies on its libraries not being mapped to provide actual
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implementations.
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It appears that only libraries loaded via
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.Xr dlopen 3
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will work correctly.
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The symbol version information in shared libraries is checked at
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link time, but at run time the version information is currently
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ignored.
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.Sh FILES
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.Bl -tag -width ".Pa /etc/libmap.conf" -compact
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.It Pa /etc/libmap.conf
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The libmap configuration file.
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.El
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.Sh EXAMPLES
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.Bd -literal
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# /etc/libmap.conf
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#
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# candidate mapping
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#
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libpthread.so.1 libpthread.so.1 # Everything uses 'libpthread'
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libpthread.so libpthread.so
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libc_r.so.5 libpthread.so.1 # Everything that uses 'libc_r'
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libc_r.so libpthread.so # now uses 'libpthread'
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[/tmp/mplayer] # Test version of mplayer uses libc_r
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libpthread.so.1 libc_r.so.5
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libpthread.so libc_r.so
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[mplayer] # All other mplayers use libpthread
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libpthread.so.1 libpthread.so.1
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libpthread.so libpthread.so
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[/usr/local/jdk1.4.1/] # All Java 1.4.1 programs use libthr
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# This works because "javavms" executes
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# programs with the full pathname
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libpthread.so.1 libthr.so.1
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libpthread.so libthr.so
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# Glue for Linux-only EPSON printer .so to be loaded into cups, etc.
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[/usr/local/lib/pips/libsc80c.so]
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libc.so.6 pluginwrapper/pips.so
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libdl.so.2 pluginwrapper/pips.so
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.Ed
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.Sh SEE ALSO
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.Xr ldd 1 ,
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.Xr rtld 1
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.Sh HISTORY
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The
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.Nm
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manual page and
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.Nm libmap
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functionality first appeared in
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.Fx 5.1 .
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.Sh AUTHORS
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This manual page was written by
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.An Matthew N. Dodd Aq winter@jurai.net .
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