1.\" Copyright (c) 2000 Sheldon Hearn 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd August 1, 2017 28.Dt LINUX 4 29.Os 30.Sh NAME 31.Nm linux 32.Nd Linux ABI support 33.Sh SYNOPSIS 34To compile support for this ABI into an i386 kernel 35place the following line in your 36kernel configuration file: 37.Bd -ragged -offset indent 38.Cd "options COMPAT_LINUX" 39.Ed 40.Pp 41for an amd64 kernel use: 42.Bd -ragged -offset indent 43.Cd "options COMPAT_LINUX32" 44.Ed 45.Pp 46Alternatively, to load the ABI as a 47module at boot time, place the following line in 48.Xr loader.conf 5 : 49.Bd -literal -offset indent 50linux_load="YES" 51.Ed 52.Sh DESCRIPTION 53The 54.Nm 55module provides limited 56Linux ABI (application binary interface) compatibility 57for userland applications. 58The module provides the following significant facilities: 59.Bl -bullet 60.It 61An image activator 62for correctly branded 63.Xr elf 5 64executable images 65.It 66Special signal handling for activated images 67.It 68Linux to native system call translation 69.El 70.Pp 71It is important to note that the Linux ABI support 72it not provided through an emulator. 73Rather, a true (albeit limited) ABI implementation is provided. 74.Pp 75The following 76.Xr sysctl 8 77tunable variables are available: 78.Bl -tag -width compat.linux.oss_version 79.It compat.linux.osname 80Linux kernel operating system name. 81.It compat.linux.osrelease 82Linux kernel operating system release. 83Changing this to something else is discouraged on non-development systems, 84because it may change the way Linux programs work. 85Recent versions of GNU libc are known to use different syscalls depending 86on the value of this sysctl. 87.It compat.linux.oss_version 88Linux Open Sound System version. 89.El 90.Pp 91The 92.Nm 93module can be linked into the kernel statically with the 94.Dv COMPAT_LINUX 95kernel configuration option 96or loaded as required. 97The following command will load the module 98if it is neither linked into the kernel 99nor already loaded as a module: 100.Bd -literal -offset indent 101if ! kldstat -v | grep -E 'linux(aout|elf)' > /dev/null; then 102 kldload linux > /dev/null 2>&1 103fi 104.Ed 105.Pp 106Note that dynamically linked Linux executables 107will require a suitable environment in 108.Pa /compat/linux . 109Specifically, the Linux run-time linker's hints files 110should be correctly initialized. 111For this reason, it is common to execute the following commands 112to prepare the system to correctly run Linux executables: 113.Bd -literal -offset indent 114if [ -x /compat/linux/sbin/ldconfig ]; then 115 /compat/linux/sbin/ldconfig -r /compat/linux 116fi 117.Ed 118.Pp 119For information on loading the 120.Nm 121kernel loadable module automatically on system startup, 122see 123.Xr rc.conf 5 . 124This information applies 125regardless of whether the 126.Nm 127module is statically linked into the kernel 128or loaded as a module. 129.Sh FILES 130.Bl -tag -width /compat/linux/dev/fd -compact 131.It Pa /compat/linux 132minimal Linux run-time environment 133.It Pa /compat/linux/dev/fd 134limited Linux file-descriptor file system 135.It Pa /compat/linux/proc 136limited Linux process file system 137.It Pa /compat/linux/sys 138limited Linux system file system 139.El 140.Sh SEE ALSO 141.Xr brandelf 1 , 142.Xr elf 5 , 143.Xr fdescfs 5 , 144.Xr linprocfs 5 , 145.Xr linsysfs 5 146.Sh HISTORY 147Linux ABI support first appeared in 148.Fx 2.1 . 149