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Date: Wed, 21 Apr 2021 09:54:31 +0200
From: Christian Brauner <christian.brauner@...ntu.com>
To: David Hildenbrand <david@...hat.com>,
John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Cc: linux-kernel@...r.kernel.org,
Alexander Viro <viro@...iv.linux.org.uk>,
Richard Henderson <rth@...ddle.net>,
Ivan Kokshaysky <ink@...assic.park.msu.ru>,
Matt Turner <mattst88@...il.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jonathan Corbet <corbet@....net>,
linux-fsdevel@...r.kernel.org, linux-api@...r.kernel.org,
linux-alpha@...r.kernel.org
Subject: Re: [PATCH v1] binfmt: remove support for em86 (alpha only)
On Tue, Apr 20, 2021 at 07:56:31PM +0200, David Hildenbrand wrote:
> 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@...iv.linux.org.uk>
> Cc: Richard Henderson <rth@...ddle.net>
> Cc: Ivan Kokshaysky <ink@...assic.park.msu.ru>
> Cc: Matt Turner <mattst88@...il.com>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Jonathan Corbet <corbet@....net>
> Cc: linux-fsdevel@...r.kernel.org
> Cc: linux-api@...r.kernel.org
> Cc: linux-alpha@...r.kernel.org
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
The only Alpha machines in active use I know of are here in Berlin at
the FU so adding Adrian in case they care but I don't think so and this
seems like a good cleanup:
Acked-by: Christian Brauner <christian.brauner@...ntu.com>
> fs/Kconfig.binfmt | 15 -------
> fs/Makefile | 1 -
> fs/binfmt_em86.c | 110 ----------------------------------------------
> 3 files changed, 126 deletions(-)
> delete mode 100644 fs/binfmt_em86.c
>
> diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
> index c6f1c8c1934e..8720e0a30005 100644
> --- a/fs/Kconfig.binfmt
> +++ b/fs/Kconfig.binfmt
> @@ -165,21 +165,6 @@ config OSF4_COMPAT
> 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_EM86
> - tristate "Kernel support for Linux/Intel ELF binaries"
> - depends on ALPHA
> - help
> - Say Y here if you want to be able to execute Linux/Intel ELF
> - binaries just like native Alpha binaries on your Alpha machine. For
> - this to work, you need to have the emulator /usr/bin/em86 in place.
> -
> - You can get the same functionality by saying N here and saying Y to
> - "Kernel support for MISC binaries".
> -
> - You may answer M to compile the emulation support as a module and
> - later load the module when you want to use a Linux/Intel binary. The
> - module will be called binfmt_em86. If unsure, say Y.
> -
> config BINFMT_MISC
> tristate "Kernel support for MISC binaries"
> help
> diff --git a/fs/Makefile b/fs/Makefile
> index 3215fe205256..c92e403c53f8 100644
> --- a/fs/Makefile
> +++ b/fs/Makefile
> @@ -39,7 +39,6 @@ obj-$(CONFIG_FS_ENCRYPTION) += crypto/
> obj-$(CONFIG_FS_VERITY) += verity/
> obj-$(CONFIG_FILE_LOCKING) += locks.o
> obj-$(CONFIG_BINFMT_AOUT) += binfmt_aout.o
> -obj-$(CONFIG_BINFMT_EM86) += binfmt_em86.o
> obj-$(CONFIG_BINFMT_MISC) += binfmt_misc.o
> obj-$(CONFIG_BINFMT_SCRIPT) += binfmt_script.o
> obj-$(CONFIG_BINFMT_ELF) += binfmt_elf.o
> diff --git a/fs/binfmt_em86.c b/fs/binfmt_em86.c
> deleted file mode 100644
> index 06b9b9fddf70..000000000000
> --- a/fs/binfmt_em86.c
> +++ /dev/null
> @@ -1,110 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0-only
> -/*
> - * linux/fs/binfmt_em86.c
> - *
> - * Based on linux/fs/binfmt_script.c
> - * Copyright (C) 1996 Martin von Löwis
> - * original #!-checking implemented by tytso.
> - *
> - * em86 changes Copyright (C) 1997 Jim Paradis
> - */
> -
> -#include <linux/module.h>
> -#include <linux/string.h>
> -#include <linux/stat.h>
> -#include <linux/binfmts.h>
> -#include <linux/elf.h>
> -#include <linux/init.h>
> -#include <linux/fs.h>
> -#include <linux/file.h>
> -#include <linux/errno.h>
> -
> -
> -#define EM86_INTERP "/usr/bin/em86"
> -#define EM86_I_NAME "em86"
> -
> -static int load_em86(struct linux_binprm *bprm)
> -{
> - const char *i_name, *i_arg;
> - char *interp;
> - struct file * file;
> - int retval;
> - struct elfhdr elf_ex;
> -
> - /* Make sure this is a Linux/Intel ELF executable... */
> - elf_ex = *((struct elfhdr *)bprm->buf);
> -
> - if (memcmp(elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
> - return -ENOEXEC;
> -
> - /* First of all, some simple consistency checks */
> - if ((elf_ex.e_type != ET_EXEC && elf_ex.e_type != ET_DYN) ||
> - (!((elf_ex.e_machine == EM_386) || (elf_ex.e_machine == EM_486))) ||
> - !bprm->file->f_op->mmap) {
> - return -ENOEXEC;
> - }
> -
> - /* Need to be able to load the file after exec */
> - if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
> - return -ENOENT;
> -
> - /* Unlike in the script case, we don't have to do any hairy
> - * parsing to find our interpreter... it's hardcoded!
> - */
> - interp = EM86_INTERP;
> - i_name = EM86_I_NAME;
> - i_arg = NULL; /* We reserve the right to add an arg later */
> -
> - /*
> - * Splice in (1) the interpreter's name for argv[0]
> - * (2) (optional) argument to interpreter
> - * (3) filename of emulated file (replace argv[0])
> - *
> - * This is done in reverse order, because of how the
> - * user environment and arguments are stored.
> - */
> - remove_arg_zero(bprm);
> - retval = copy_string_kernel(bprm->filename, bprm);
> - if (retval < 0) return retval;
> - bprm->argc++;
> - if (i_arg) {
> - retval = copy_string_kernel(i_arg, bprm);
> - if (retval < 0) return retval;
> - bprm->argc++;
> - }
> - retval = copy_string_kernel(i_name, bprm);
> - if (retval < 0) return retval;
> - bprm->argc++;
> -
> - /*
> - * OK, now restart the process with the interpreter's inode.
> - * Note that we use open_exec() as the name is now in kernel
> - * space, and we don't need to copy it.
> - */
> - file = open_exec(interp);
> - if (IS_ERR(file))
> - return PTR_ERR(file);
> -
> - bprm->interpreter = file;
> - return 0;
> -}
> -
> -static struct linux_binfmt em86_format = {
> - .module = THIS_MODULE,
> - .load_binary = load_em86,
> -};
> -
> -static int __init init_em86_binfmt(void)
> -{
> - register_binfmt(&em86_format);
> - return 0;
> -}
> -
> -static void __exit exit_em86_binfmt(void)
> -{
> - unregister_binfmt(&em86_format);
> -}
> -
> -core_initcall(init_em86_binfmt);
> -module_exit(exit_em86_binfmt);
> -MODULE_LICENSE("GPL");
> --
> 2.30.2
>
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