binfmt_em86.c

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/*
 *  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,struct pt_regs *regs)
{
    char *interp, *i_name, *i_arg;
    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 || !bprm->file->f_op->mmap)) {
            return -ENOEXEC;
    }

    bprm->recursion_depth++; /* Well, the bang-shell is implicit... */
    allow_write_access(bprm->file);
    fput(bprm->file);
    bprm->file = NULL;

    /* 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_strings_kernel(1, &bprm->filename, bprm);
    if (retval < 0) return retval; 
    bprm->argc++;
    if (i_arg) {
        retval = copy_strings_kernel(1, &i_arg, bprm);
        if (retval < 0) return retval; 
        bprm->argc++;
    }
    retval = copy_strings_kernel(1, &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->file = file;

    retval = prepare_binprm(bprm);
    if (retval < 0)
        return retval;

    return search_binary_handler(bprm, regs);
}

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");