/*
 *  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/malloc.h>
#include <linux/binfmts.h>
#include <linux/elf.h>
#include <linux/init.h>


#define EM86_INTERP	"/usr/bin/em86"
#define EM86_I_NAME	"em86"

static int do_load_em86(struct linux_binprm *bprm,struct pt_regs *regs)
{
	char *interp, *i_name, *i_arg;
	struct dentry * dentry;
	int retval;
	struct elfhdr	elf_ex;

	/* Make sure this is a Linux/Intel ELF executable... */
	elf_ex = *((struct elfhdr *)bprm->buf);

        if (elf_ex.e_ident[0] != 0x7f ||
            strncmp(&elf_ex.e_ident[1], "ELF",3) != 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->dentry->d_inode->i_op || !bprm->dentry->d_inode->i_op->default_file_ops ||
            !bprm->dentry->d_inode->i_op->default_file_ops->mmap)){
                return -ENOEXEC;
        }

	bprm->sh_bang++;	/* Well, the bang-shell is implicit... */
	dput(bprm->dentry);
	bprm->dentry = 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);
	bprm->p = copy_strings(1, &bprm->filename, bprm->page, bprm->p, 2);
	bprm->argc++;
	if (i_arg) {
		bprm->p = copy_strings(1, &i_arg, bprm->page, bprm->p, 2);
		bprm->argc++;
	}
	bprm->p = copy_strings(1, &i_name, bprm->page, bprm->p, 2);
	bprm->argc++;
	if (!bprm->p) 
		return -E2BIG;
	/*
	 * OK, now restart the process with the interpreter's inode.
	 * Note that we use open_namei() as the name is now in kernel
	 * space, and we don't need to copy it.
	 */
	dentry = open_namei(interp, 0, 0);
	if (IS_ERR(dentry))
		return PTR_ERR(dentry);

	bprm->dentry = dentry;

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

	return search_binary_handler(bprm, regs);
}

static int load_em86(struct linux_binprm *bprm,struct pt_regs *regs)
{
	int retval;
	MOD_INC_USE_COUNT;
	retval = do_load_em86(bprm,regs);
	MOD_DEC_USE_COUNT;
	return retval;
}

struct linux_binfmt em86_format = {
#ifndef MODULE
	NULL, 0, load_em86, NULL, NULL
#else
	NULL, &__this_module, load_em86, NULL, NULL
#endif
};

int __init init_em86_binfmt(void)
{
	return register_binfmt(&em86_format);
}

#ifdef MODULE
int init_module(void)
{
	return init_em86_binfmt();
}

void cleanup_module( void) {
	unregister_binfmt(&em86_format);
}
#endif