diff --git a/share/man/man4/linux.4 b/share/man/man4/linux.4 index b2d36158c622..b24e3dbc9f79 100644 --- a/share/man/man4/linux.4 +++ b/share/man/man4/linux.4 @@ -1,181 +1,187 @@ .\" Copyright (c) 2000 Sheldon Hearn .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" $FreeBSD$ .\" -.Dd May 6, 2021 +.Dd January 2, 2022 .Dt LINUX 4 .Os .Sh NAME .Nm linux .Nd Linux ABI support .Sh SYNOPSIS -To compile support for this ABI into an i386 kernel -place the following line in your -kernel configuration file: -.Bd -ragged -offset indent -.Cd "options COMPAT_LINUX" -.Ed -.Pp -for an amd64 kernel use: -.Bd -ragged -offset indent -.Cd "options COMPAT_LINUX32" -.Ed -.Pp -Alternatively, to load the ABI as a -module at boot time, place the following line in -.Xr loader.conf 5 : +To enable the Linux ABI at boot time, place the following line in +.Xr rc.conf 5 : .Bd -literal -offset indent -linux_load="YES" +linux_enable="YES" .Ed .Sh DESCRIPTION The .Nm module provides limited Linux ABI (application binary interface) compatibility, -making it possible to run many unmodified Linux applications and libraries +making it possible to run many unmodified Linux applications without the need for virtualization or emulation. Some of the facilities provided are: .Bl -bullet .It -An image activator -for correctly branded -.Xr elf 5 -executable images -.It -Special signal handling for activated images -.It Linux to native system call translation .It Linux-specific system calls +.It +Special signal handling for Linux processes +.It +Path translation mechanism +.It +Linux-specific virtual file systems .El .Pp -Note that dynamically linked Linux executables -will require a suitable environment in -.Pa /compat/linux . -This includes native Linux shared libraries, and Linux-specific virtual -filesystems. -To set it up, install the +The path translation mechanism makes Linux processes look up file paths +under +.Va emul_path +(defaulting to +.Pa /compat/linux ) +before +.Pa / . +For example, when Linux process attempts to open +.Pa /etc/passwd , +it will really access +.Pa /compat/linux/etc/passwd , +unless the latter does not exist. +This is used to make sure Linux processes load Linux shared libraries +instead of their similarly-named FreeBSD counterparts, and also +to provide alternative versions of certain other files and virtual +file systems. +.Pp +To install Linux shared libraries and system files into +.Pa /compat/linux , +use the .Pa emulators/linux_base-c7 -port or the linux_base-c7 -package, and add the following line to the +port or the +.Dv linux_base-c7 +package. +.Pp +To avoid mounting Linux-specific filesystems at startup, add the following +line to the .Xr rc.conf 5 file: .Pp -.Dl linux_enable="YES" -.Pp -To avoid mounting Linux-specific filesystems at startup, also add the following -line: -.Pp .Dl linux_mounts_enable="NO" .Sh SYSCTL VARIABLES The following variables are available as both .Xr sysctl 8 variables and .Xr loader 8 tunables: .Bl -tag -width indent .It Va compat.linux.debug Enable debugging messages. Set to 0 to silence them. Defaults to 3. A setting of 1 prints debug messages, tells about unimplemented stuff (only once). Set to 2 is like 1, but also prints messages about implemented but not tested stuff (only once). Setting it to 3 or higher is like 2, but no rate limiting of messages. .It Va compat.linux.default_openfiles Default soft openfiles resource limit for Linux applications. Set to -1 to disable the limit. Defaults to 1024. .It Va compat.linux.emul_path Path to the Linux run-time environment. Defaults to .Pa /compat/linux . .It Va compat.linux.osname Linux kernel operating system name. +Defaults to "Linux". .It Va compat.linux.osrelease Linux kernel operating system release. Changing this to something else is discouraged on non-development systems, because it may change the way Linux programs work. -Recent versions of GNU libc are known to use different syscalls depending +Some versions of GNU libc are known to use different syscalls depending on the value of this sysctl. .It Va compat.linux.oss_version Linux Open Sound System version. +Defaults to 198144. .It Va compat.linux.preserve_vstatus When set to 1, it prevents Linux applications from resetting the .Xr termios 4 VSTATUS setting. From a user perspective, this makes .Va SIGINFO work for Linux executables. Defaults to 0. .It Va compat.linux.setid_allowed Disable handling of set-user-ID and set-group-ID mode bits for the new process image file when image is to be executed under Linux ABI. When set, new Linux images always use credentials of the program -that issued +that issued the .Xr execve 2 call, regardless of the image file mode. +Defaults to 1. .Pp This might be reasonable or even required, because .Fx does not emulate Linux environment completely, and missed features could become holes. .El .Sh FILES .Bl -tag -width /compat/linux/dev/shm -compact .It Pa /compat/linux -minimal Linux run-time environment +Linux run-time environment .It Pa /compat/linux/dev device file system, see .Xr devfs 5 .It Pa /compat/linux/dev/fd file descriptor file system mounted with the .Cm linrdlnk option, see .Xr fdescfs 5 .It Pa /compat/linux/dev/shm in-memory file system, see .Xr tmpfs 5 .It Pa /compat/linux/proc Linux process file system, see .Xr linprocfs 5 .It Pa /compat/linux/sys Linux kernel objects file system, see .Xr linsysfs 5 .El .Sh SEE ALSO .Xr brandelf 1 , .Xr pty 4 , .Xr elf 5 , .Xr fdescfs 5 , .Xr linprocfs 5 , .Xr linsysfs 5 , .Xr tmpfs 5 .Sh HISTORY Linux ABI support first appeared in .Fx 2.1 . +Support for amd64 binaries first appeared in +.Fx 10.3 . +Support for arm64 binaries first appeared in +.Fx 12.0 . .Sh BUGS Support for some of the Linux-specific system calls and system call arguments is missing.