b084ee9dfc
Linux specific things to the native fdescfs file system.
Unlike FreeBSD, the Linux fdescfs is a directory containing a symbolic
links to the actual files, which the process has open.
A readlink(2) call on this file returns a full path in case of regular file
or a string in a special format (type:[inode], anon_inode:<file-type>, etc..).
As well as in a FreeBSD, opening the file in the Linux fdescfs directory is
equivalent to duplicating the corresponding file descriptor.
Here we have mutually exclusive requirements:
- in case of readlink(2) call fdescfs lookup() method should return VLNK
vnode otherwise our kern_readlink() fail with EINVAL error;
- in the other calls fdescfs lookup() method should return non VLNK vnode.
For what new vnode v_flag VV_READLINK was added, which is set if fdescfs has beed
mounted with linrdlnk option an modified kern_readlinkat() to properly handle it.
For now For Linux ABI compatibility mount fdescfs volume with linrdlnk option:
mount -t fdescfs -o linrdlnk null /compat/linux/dev/fd
Reviewed by: kib@
MFC after: 1 week
Relnotes: yes
149 lines
4.4 KiB
Groff
149 lines
4.4 KiB
Groff
.\" Copyright (c) 2000 Sheldon Hearn
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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 August 1, 2017
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.Dt LINUX 4
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.Os
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.Sh NAME
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.Nm linux
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.Nd Linux ABI support
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.Sh SYNOPSIS
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To compile support for this ABI into an i386 kernel
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place the following line in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "options COMPAT_LINUX"
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.Ed
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.Pp
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for an amd64 kernel use:
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.Bd -ragged -offset indent
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.Cd "options COMPAT_LINUX32"
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.Ed
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.Pp
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Alternatively, to load the ABI as a
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module at boot time, place the following line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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linux_load="YES"
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.Ed
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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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Linux 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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Linux to native system call translation
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.El
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.Pp
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It is important to note that the Linux ABI support
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it not provided through an emulator.
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Rather, a true (albeit limited) ABI implementation is provided.
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.Pp
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The following
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.Xr sysctl 8
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tunable variables are available:
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.Bl -tag -width compat.linux.oss_version
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.It compat.linux.osname
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Linux kernel operating system name.
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.It compat.linux.osrelease
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Linux kernel operating system release.
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Changing this to something else is discouraged on non-development systems,
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because it may change the way Linux programs work.
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Recent versions of GNU libc are known to use different syscalls depending
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on the value of this sysctl.
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.It compat.linux.oss_version
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Linux Open Sound System version.
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.El
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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_LINUX
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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 'linux(aout|elf)' > /dev/null; then
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kldload linux > /dev/null 2>&1
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fi
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.Ed
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.Pp
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Note that dynamically linked Linux executables
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will require a suitable environment in
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.Pa /compat/linux .
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Specifically, the Linux run-time linker's hints files
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should be correctly initialized.
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For this reason, it is common to execute the following commands
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to prepare the system to correctly run Linux executables:
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.Bd -literal -offset indent
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if [ -x /compat/linux/sbin/ldconfig ]; then
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/compat/linux/sbin/ldconfig -r /compat/linux
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fi
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.Ed
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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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.Sh FILES
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.Bl -tag -width /compat/linux/dev/fd -compact
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.It Pa /compat/linux
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minimal Linux run-time environment
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.It Pa /compat/linux/dev/fd
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limited Linux file-descriptor file system
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.It Pa /compat/linux/proc
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limited Linux process file system
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.It Pa /compat/linux/sys
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limited Linux system file system
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.El
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.Sh SEE ALSO
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.Xr brandelf 1 ,
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.Xr elf 5 ,
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.Xr fdescfs 5 ,
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.Xr linprocfs 5 ,
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.Xr linsysfs 5
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.Sh HISTORY
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Linux ABI support first appeared in
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.Fx 2.1 .
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