/*����ֻ������������do_execve2,exec.c�������ط���û�иĶ�
* do_execve2��Ҫʵ�����������ط�ʽִ�п�ִ���ļ���ֻ��Ҫ���պ���do_no_page���������ȶ�����ҳ����ҳ���ϴ�������
* ��������my_do_no_page���������ܺ�do_no_page��ȫһ��
* ����дһ����ԭ���ǣ���������ԭ�ȵ�do_no_page�����������Ӵ�ӡ��Ϣ
* �������ʹ��ԭ�ȵ�do_no_page������ÿ��һ�ζ����ӡ��Ϣ
* �������޷��б�do_execve2������û��ʵ���������صĹ���
*/

int do_execve2(unsigned long* eip, long tmp, char* filename,
	char** argv, char** envp)
{
	struct m_inode* inode;
	struct buffer_head* bh;
	struct exec ex;
	unsigned long page[MAX_ARG_PAGES];
	int i, argc, envc;
	int e_uid, e_gid;
	int retval;
	int sh_bang = 0;
	unsigned long p = PAGE_SIZE * MAX_ARG_PAGES - 4;

	if ((0xffff & eip[1]) != 0x000f)
		panic("execve2 called from supervisor mode");

	for (i = 0; i < MAX_ARG_PAGES; i++)	/* clear page-table */
		page[i] = 0;
	if (!(inode = namei(filename)))		/* get executables inode */
		return -ENOENT;
	argc = count(argv);
	envc = count(envp);

restart_interp:
	if (!S_ISREG(inode->i_mode)) {	/* must be regular file */
		retval = -EACCES;
		goto exec_error2;
	}
	i = inode->i_mode;
	e_uid = (i & S_ISUID) ? inode->i_uid : current->euid;
	e_gid = (i & S_ISGID) ? inode->i_gid : current->egid;
	if (current->euid == inode->i_uid)
		i >>= 6;
	else if (current->egid == inode->i_gid)
		i >>= 3;
	if (!(i & 1) &&
		!((inode->i_mode & 0111) && suser())) {
		retval = -ENOEXEC;
		goto exec_error2;
	}
	if (!(bh = bread(inode->i_dev, inode->i_zone[0]))) {
		retval = -EACCES;
		goto exec_error2;
	}
	ex = *((struct exec*)bh->b_data);	/* read exec-header */
	if ((bh->b_data[0] == '#') && (bh->b_data[1] == '!') && (!sh_bang)) {
		/*
		 * This section does the #! interpretation.
		 * Sorta complicated, but hopefully it will work.  -TYT
		 */

		char buf[1023], * cp, * interp, * i_name, * i_arg;
		unsigned long old_fs;

		strncpy(buf, bh->b_data + 2, 1022);
		brelse(bh);
		iput(inode);
		buf[1022] = '\0';
		if (cp = strchr(buf, '\n')) {
			*cp = '\0';
			for (cp = buf; (*cp == ' ') || (*cp == '\t'); cp++);
		}
		if (!cp || *cp == '\0') {
			retval = -ENOEXEC; /* No interpreter name found */
			goto exec_error1;
		}

		interp = i_name = cp;
		i_arg = 0;
		for (; *cp && (*cp != ' ') && (*cp != '\t'); cp++) {
			if (*cp == '/')
				i_name = cp + 1;
		}
		if (*cp) {
			*cp++ = '\0';
			i_arg = cp;
		}
		/*
		 * OK, we've parsed out the interpreter name and
		 * (optional) argument.
		 */
		if (sh_bang++ == 0) {
			p = copy_strings(envc, envp, page, p, 0);
			p = copy_strings(--argc, argv + 1, page, p, 0);
		}
		/*
		 * Splice in (1) the interpreter's name for argv[0]
		 *           (2) (optional) argument to interpreter
		 *           (3) filename of shell script
		 *
		 * This is done in reverse order, because of how the
		 * user environment and arguments are stored.
		 */
		p = copy_strings(1, &filename, page, p, 1);
		argc++;
		if (i_arg) {
			p = copy_strings(1, &i_arg, page, p, 2);
			argc++;
		}
		p = copy_strings(1, &i_name, page, p, 2);
		argc++;
		if (!p) {
			retval = -ENOMEM;
			goto exec_error1;
		}
		/*
		 * OK, now restart the process with the interpreter's inode.
		 */
		old_fs = get_fs();
		set_fs(get_ds());
		if (!(inode = namei(interp))) { /* get executables inode */
			set_fs(old_fs);
			retval = -ENOENT;
			goto exec_error1;
		}
		set_fs(old_fs);
		goto restart_interp;
	}
	brelse(bh);
	if (N_MAGIC(ex) != ZMAGIC || ex.a_trsize || ex.a_drsize ||
		ex.a_text + ex.a_data + ex.a_bss > 0x3000000 ||
		inode->i_size < ex.a_text + ex.a_data + ex.a_syms + N_TXTOFF(ex)) {
		retval = -ENOEXEC;
		goto exec_error2;
	}
	if (N_TXTOFF(ex) != BLOCK_SIZE) {
		printk("%s: N_TXTOFF != BLOCK_SIZE. See a.out.h.", filename);
		retval = -ENOEXEC;
		goto exec_error2;
	}
	if (!sh_bang) {
		p = copy_strings(envc, envp, page, p, 0);
		p = copy_strings(argc, argv, page, p, 0);
		if (!p) {
			retval = -ENOMEM;
			goto exec_error2;
		}
	}
	/* OK, This is the point of no return */
	if (current->executable)
		iput(current->executable);
	current->executable = inode;
	for (i = 0; i < 32; i++)
		current->sigaction[i].sa_handler = NULL;
	for (i = 0; i < NR_OPEN; i++)
		if ((current->close_on_exec >> i) & 1)
			sys_close(i);
	current->close_on_exec = 0;
	free_page_tables(get_base(current->ldt[1]), get_limit(0x0f));
	free_page_tables(get_base(current->ldt[2]), get_limit(0x17));
	if (last_task_used_math == current)
		last_task_used_math = NULL;
	current->used_math = 0;
	p += change_ldt(ex.a_text, page) - MAX_ARG_PAGES * PAGE_SIZE;
	p = (unsigned long)create_tables((char*)p, argc, envc);
	current->brk = ex.a_bss +
		(current->end_data = ex.a_data +
			(current->end_code = ex.a_text));
	current->start_stack = p & 0xfffff000;
	current->euid = e_uid;
	current->egid = e_gid;

	/* �޸IJ��� */
	unsigned long No_Page_Addr;
	unsigned long Addr_End = (current->brk - 1) & 0xfffff000;
	for (No_Page_Addr = 0; No_Page_Addr <= Addr_End; No_Page_Addr += 0x1000)
		my_do_no_page(4, No_Page_Addr + current->start_code);   /* �����ԣ�����������Ϊ4��6�����ԣ�4��ʾ�ɶ���������6��ʾ��д�������� */
	/* �޸IJ��� */
	
	i = ex.a_text + ex.a_data;
	while (i & 0xfff)
		put_fs_byte(0, (char*)(i++));
	eip[0] = ex.a_entry;		/* eip, magic happens :-) */
	eip[3] = p;			/* stack pointer */
	return 0;
exec_error2:
	iput(inode);
exec_error1:
	for (i = 0; i < MAX_ARG_PAGES; i++)
		free_page(page[i]);
	return(retval);
}