linux/fs/Kconfig.binfmt
David Hildenbrand 6208721f13 binfmt: remove support for em86 (alpha only)
We have a fairly specific alpha binary loader in Linux: running x86
(i386, i486) binaries via the em86 [1] emulator. As noted in the Kconfig
option, the same behavior can be achieved via binfmt_misc, for example,
more nowadays used for running qemu-user.

An example on how to get binfmt_misc running with em86 can be found in
Documentation/admin-guide/binfmt-misc.rst

The defconfig does not have CONFIG_BINFMT_EM86=y set. And doing a
	make defconfig && make olddefconfig
results in
	# CONFIG_BINFMT_EM86 is not set

... as we don't seem to have any supported Linux distirbution for alpha
anymore, there isn't really any "default" user of that feature anymore.

Searching for "CONFIG_BINFMT_EM86=y" reveals mostly discussions from
around 20 years ago, like [2] describing how to get netscape via em86
running via em86, or [3] discussing that running wine or installing
Win 3.11 through em86 would be a nice feature.

The latest binaries available for em86 are from 2000, version 2.2.1 [4] --
which translates to "unsupported"; further, em86 doesn't even work with
glibc-2.x but only with glibc-2.0 [4, 5]. These are clear signs that
there might not be too many em86 users out there, especially users
relying on modern Linux kernels.

Even though the code footprint is relatively small, let's just get rid
of this blast from the past that's effectively unused.

[1] http://ftp.dreamtime.org/pub/linux/Linux-Alpha/em86/v0.4/docs/em86.html
[2] https://static.lwn.net/1998/1119/a/alpha-netscape.html
[3] https://groups.google.com/g/linux.debian.alpha/c/AkGuQHeCe0Y
[4] http://zeniv.linux.org.uk/pub/linux/alpha/em86/v2.2-1/relnotes.2.2.1.html
[5] https://forum.teamspeak.com/archive/index.php/t-1477.html

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-api@vger.kernel.org
Cc: linux-alpha@vger.kernel.org
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Matt Turner <mattst88@gmail.com>
2021-07-25 22:33:03 -07:00

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# SPDX-License-Identifier: GPL-2.0-only
menu "Executable file formats"
config BINFMT_ELF
bool "Kernel support for ELF binaries"
depends on MMU
select ELFCORE
default y
help
ELF (Executable and Linkable Format) is a format for libraries and
executables used across different architectures and operating
systems. Saying Y here will enable your kernel to run ELF binaries
and enlarge it by about 13 KB. ELF support under Linux has now all
but replaced the traditional Linux a.out formats (QMAGIC and ZMAGIC)
because it is portable (this does *not* mean that you will be able
to run executables from different architectures or operating systems
however) and makes building run-time libraries very easy. Many new
executables are distributed solely in ELF format. You definitely
want to say Y here.
Information about ELF is contained in the ELF HOWTO available from
<http://www.tldp.org/docs.html#howto>.
If you find that after upgrading from Linux kernel 1.2 and saying Y
here, you still can't run any ELF binaries (they just crash), then
you'll have to install the newest ELF runtime libraries, including
ld.so (check the file <file:Documentation/Changes> for location and
latest version).
config COMPAT_BINFMT_ELF
def_bool y
depends on COMPAT && BINFMT_ELF
select ELFCORE
config ARCH_BINFMT_ELF_STATE
bool
config ARCH_HAVE_ELF_PROT
bool
config ARCH_USE_GNU_PROPERTY
bool
config BINFMT_ELF_FDPIC
bool "Kernel support for FDPIC ELF binaries"
default y if !BINFMT_ELF
depends on (ARM || (SUPERH && !MMU))
select ELFCORE
help
ELF FDPIC binaries are based on ELF, but allow the individual load
segments of a binary to be located in memory independently of each
other. This makes this format ideal for use in environments where no
MMU is available as it still permits text segments to be shared,
even if data segments are not.
It is also possible to run FDPIC ELF binaries on MMU linux also.
config ELFCORE
bool
help
This option enables kernel/elfcore.o.
config CORE_DUMP_DEFAULT_ELF_HEADERS
bool "Write ELF core dumps with partial segments"
default y
depends on BINFMT_ELF && ELF_CORE
help
ELF core dump files describe each memory mapping of the crashed
process, and can contain or omit the memory contents of each one.
The contents of an unmodified text mapping are omitted by default.
For an unmodified text mapping of an ELF object, including just
the first page of the file in a core dump makes it possible to
identify the build ID bits in the file, without paying the i/o
cost and disk space to dump all the text. However, versions of
GDB before 6.7 are confused by ELF core dump files in this format.
The core dump behavior can be controlled per process using
the /proc/PID/coredump_filter pseudo-file; this setting is
inherited. See Documentation/filesystems/proc.rst for details.
This config option changes the default setting of coredump_filter
seen at boot time. If unsure, say Y.
config BINFMT_SCRIPT
tristate "Kernel support for scripts starting with #!"
default y
help
Say Y here if you want to execute interpreted scripts starting with
#! followed by the path to an interpreter.
You can build this support as a module; however, until that module
gets loaded, you cannot run scripts. Thus, if you want to load this
module from an initramfs, the portion of the initramfs before loading
this module must consist of compiled binaries only.
Most systems will not boot if you say M or N here. If unsure, say Y.
config ARCH_HAS_BINFMT_FLAT
bool
config BINFMT_FLAT
bool "Kernel support for flat binaries"
depends on ARCH_HAS_BINFMT_FLAT
help
Support uClinux FLAT format binaries.
config BINFMT_FLAT_ARGVP_ENVP_ON_STACK
bool
config BINFMT_FLAT_OLD_ALWAYS_RAM
bool
config BINFMT_FLAT_NO_DATA_START_OFFSET
bool
config BINFMT_FLAT_OLD
bool "Enable support for very old legacy flat binaries"
depends on BINFMT_FLAT
help
Support decade old uClinux FLAT format binaries. Unless you know
you have some of those say N here.
config BINFMT_ZFLAT
bool "Enable ZFLAT support"
depends on BINFMT_FLAT
select ZLIB_INFLATE
help
Support FLAT format compressed binaries
config BINFMT_SHARED_FLAT
bool "Enable shared FLAT support"
depends on BINFMT_FLAT
help
Support FLAT shared libraries
config HAVE_AOUT
def_bool n
config BINFMT_AOUT
tristate "Kernel support for a.out and ECOFF binaries"
depends on HAVE_AOUT
help
A.out (Assembler.OUTput) is a set of formats for libraries and
executables used in the earliest versions of UNIX. Linux used
the a.out formats QMAGIC and ZMAGIC until they were replaced
with the ELF format.
The conversion to ELF started in 1995. This option is primarily
provided for historical interest and for the benefit of those
who need to run binaries from that era.
Most people should answer N here. If you think you may have
occasional use for this format, enable module support above
and answer M here to compile this support as a module called
binfmt_aout.
If any crucial components of your system (such as /sbin/init
or /lib/ld.so) are still in a.out format, you will have to
say Y here.
config OSF4_COMPAT
bool "OSF/1 v4 readv/writev compatibility"
depends on ALPHA && BINFMT_AOUT
help
Say Y if you are using OSF/1 binaries (like Netscape and Acrobat)
with v4 shared libraries freely available from Compaq. If you're
going to use shared libraries from Tru64 version 5.0 or later, say N.
config BINFMT_MISC
tristate "Kernel support for MISC binaries"
help
If you say Y here, it will be possible to plug wrapper-driven binary
formats into the kernel. You will like this especially when you use
programs that need an interpreter to run like Java, Python, .NET or
Emacs-Lisp. It's also useful if you often run DOS executables under
the Linux DOS emulator DOSEMU (read the DOSEMU-HOWTO, available from
<http://www.tldp.org/docs.html#howto>). Once you have
registered such a binary class with the kernel, you can start one of
those programs simply by typing in its name at a shell prompt; Linux
will automatically feed it to the correct interpreter.
You can do other nice things, too. Read the file
<file:Documentation/admin-guide/binfmt-misc.rst> to learn how to use this
feature, <file:Documentation/admin-guide/java.rst> for information about how
to include Java support. and <file:Documentation/admin-guide/mono.rst> for
information about how to include Mono-based .NET support.
To use binfmt_misc, you will need to mount it:
mount binfmt_misc -t binfmt_misc /proc/sys/fs/binfmt_misc
You may say M here for module support and later load the module when
you have use for it; the module is called binfmt_misc. If you
don't know what to answer at this point, say Y.
config COREDUMP
bool "Enable core dump support" if EXPERT
default y
help
This option enables support for performing core dumps. You almost
certainly want to say Y here. Not necessary on systems that never
need debugging or only ever run flawless code.
endmenu