binfmt_em86.c

// 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");