217 lines
6.6 KiB
Groff
217 lines
6.6 KiB
Groff
.\" Copyright (c) 2000 Mark Newton
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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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.Dd October 28, 2003
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.Dt SVR4 4 i386
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.Os
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.Sh NAME
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.Nm svr4
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.Nd System V Release 4 ABI support
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.Sh SYNOPSIS
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To link System V Release 4 (SVR4) ABI support into the kernel:
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.Cd options COMPAT_SVR4
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.Pp
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To load the SVR4 ABI support kernel module:
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.Dl kldload svr4
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.Sh DESCRIPTION
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The
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.Nm
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module provides limited
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System V Release 4 ABI (application binary interface) compatibility
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for userland applications.
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The module provides the following significant facilities:
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.Bl -bullet
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.It
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An image activator
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for correctly branded
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.Xr elf 5
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executable images
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.It
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Special signal handling for activated images
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.It
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SVR4 to native system call translation
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.It
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STREAMS network API emulation (via the
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.Xr streams 4
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loadable module, or by means of
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.Dl device streams
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in a kernel configuration file)
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.It
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Mappings between
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.Fx
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and SVR4
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.Xr ioctl 2
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calls, or, where no such mappings exist, reverse-engineered implementations
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of the SVR4 calls.
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.El
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.Pp
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It is important to note that the SVR4 ABI support
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it not provided through an emulator.
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Rather, a true (albeit limited) "clean room" reverse-engineered ABI
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implementation is provided.
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.Sh LIMITATIONS
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Because the provided ABI has been developed in ignorance of actual SVR4
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source code, there are bound to be unforeseen interactions between SVR4
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client applications and the emulated ABI which cause applications to
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malfunction.
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.Pp
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Additionally, some SVR4 operating systems do not adhere to the SVR4
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ELF standard.
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In particular, Solaris does not set the ELF interpreter field in the
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ELF header to a value which would allow the kernel to correctly
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identify a client executable as an SVR4 application.
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Thus, in certain instances it is necessary to use the
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.Xr brandelf 1
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utility to explicitly brand the executable, or to set the
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kern.fallback_elf_brand
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.Xr sysctl 8
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variable to define a "default" ABI for unbranded executables.
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Value ELFOSABI_SOLARIS represents Solaris; ELFOSABI_SYSV represents other
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SysVR4 operating systems.
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See
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.In sys/elf_common.h
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for ELFOSABI branding definitions, and
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.Xr brandelf 1
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for information on branding executables.
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.Pp
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The
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.Nm
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module can be linked into the kernel statically with the
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.Dv COMPAT_SVR4
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kernel configuration option
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or loaded as required.
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The following command will load the module
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if it is neither linked into the kernel
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nor already loaded as a module:
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.Bd -literal -offset indent
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if ! kldstat -v | grep -E 'svr4elf' > /dev/null; then
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kldload svr4 > /dev/null 2>&1
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fi
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.Ed
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.Pp
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The kernel
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will check for the presence of the
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.Xr streams 4
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module, and load it if necessary.
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.Pp
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Note that dynamically linked SVR4 executables
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will require a suitable environment in
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.Pa /compat/svr4 .
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.Pp
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For information on loading the
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.Nm
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kernel loadable module automatically on system startup,
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see
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.Xr rc.conf 5 .
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This information applies
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regardless of whether the
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.Nm
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module is statically linked into the kernel
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or loaded as a module.
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.Pp
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STREAMS emulation is limited but (largely) functional.
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Assuming the
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.Xr streams 4
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module is loaded, a STREAMS handle can be obtained by opening one of the
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relevant files in
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.Pa /dev
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or
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.Pa /compat/svr4/dev .
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Internally, the
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.Xr streams 4
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driver produces a socket descriptor and
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.Dq tags
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it with additional STREAMS
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state information before returning it to the client application.
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The
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.Nm
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environment uses the additional state information to recognize and
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manipulate emulated STREAMS handles when STREAMS-specific
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.Xr ioctl 2
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calls are executed.
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.Pp
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The subset of STREAMS functionality which is provided is small, probably
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little more than what is required to enable programs on the Solaris CD
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sets to run.
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.Sh BUGS
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Emulation of signal handlers is buggy.
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.Pp
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Emulated connectionless STREAMS fail to receive data from the network in
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some circumstances (but succeed in others -- probably due to particular
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ways of initializing them which the
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.Xr streams 4
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module is mishandling, and interaction between STREAMS and
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.Xr poll 2 ) .
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Connection-oriented STREAMS appear to be functional.
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.Pp
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Ironically, this SVR4 emulator does not (yet) support SVR4 semaphores or
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shared memory.
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.Pp
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.Xr ports 7
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to automatically create the
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.Pa /compat/svr4
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environment do not exist.
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.Xr tar 1
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archives containing pre-populated trees can be obtained from
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.Pa http://people.FreeBSD.org/~newton/freebsd-svr4/ .
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.Pp
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Extensive testing has only really been carried out with Solaris 2.x binaries,
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with anecdotal reports of limited success coming from testers with
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early-revision SCO media.
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In theory, the basic SVR4 ABI should be constant
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across the set of vendors who produce SVR4 operating systems, but in
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practice that's probably not the case.
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If necessary, future work can
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either implement additional
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.Xr kld 4
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modules which produce functionality which contains OS-dependent
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departures from the behaviour which has been implemented in this
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ABI implementation.
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Alternatively,
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.Xr sysctl 8
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variables could set the
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.Dq personality
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the environment should present to
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client applications.
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.Sh FILES
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.Bl -tag -width /sys/compat/svr4/syscalls.master -compact
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.It Pa /compat/svr4
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minimal SVR4 run-time environment
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.It Pa /sys/compat/svr4/syscalls.master
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mappings between SVR4 syscalls and
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.Nm
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module entrypoints.
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.El
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.Sh SEE ALSO
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.Xr brandelf 1 ,
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.Xr streams 4 ,
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.Xr elf 5
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.Sh HISTORY
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System V Release 4 ABI support first appeared in
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.Fx 4.0 .
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The ABI was ported from an equivalent facility present in
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.Nx 1.3
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written by Christos Zoulas.
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