001 /* Copyright (C) 1999 Free Software Foundation, Inc.
002
003 This program is free software; you can redistribute it and/or
004 modify it under the terms of the GNU General Public License
005 as published by the Free Software Foundation; either version 2
006 of the License, or (at your option) any later version.
007
008 This program is distributed in the hope that it will be useful,
009 but WITHOUT ANY WARRANTY; without even the implied warranty of
010 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
011 GNU General Public License for more details.
012
013 You should have received a copy of the GNU General Public License
014 along with this program; if not, write to the Free Software
015 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
016 USA.
017 */
018
019
020 /* The operating system is booted by Grub, so we almost have nothing
021 to do to boot it. We only have to conform to the Multiboot
022 standard, as defined by the Grub documentation */
023
024 #define ASM 1
025 /* The multiboot.h header contains a lot of multiboot standard
026 definitions */
027 #include "multiboot.h"
028
029 /* The multiboot header itself. It must come first. */
030 .section ".multiboot"
031 /* Multiboot header must be aligned on a 4-byte boundary */
032 .align 4
033 multiboot_header:
034 /* magic= */ .long MULTIBOOT_HEADER_MAGIC
035 /* flags= */ .long MULTIBOOT_HEADER_FLAGS
036 /* checksum= */ .long -(MULTIBOOT_HEADER_MAGIC \
037 +MULTIBOOT_HEADER_FLAGS)
038 /* header_addr= */ .long multiboot_header
039 /* load_addr= */ .long __b_kernel
040 /* load_end_addr=*/ .long __e_load
041 /* bss_end_addr= */ .long __e_kernel
042 /* entry_addr= */ .long multiboot_entry
043
044 /* Here is the beginning of the code of our operating system */
045 .text
046
047 .globl start, _start
048 start:
049 _start:
050 multiboot_entry:
051 /* Set up a stack */
052 movl $(stack + MULTIBOOT_STACK_SIZE), %ebp
053 movl %ebp, %esp
054
055 /* Set EFLAGS to 0 */
056 pushl $0
057 /* pop stack into the EFLAGS register */
058 popf
059
060 /* Push the magic and the address on the stack, so that they
061 will be the parameters of the cmain function */
062 pushl %ebx
063 pushl %eax
064
065 /* Call the cmain function (os.c) */
066 call EXT_C(sos_main)
067
068 /* Should never get there */
069 loop:
070 hlt
071 jmp loop
072
073 /* Here is the stack */
074 .comm stack, MULTIBOOT_STACK_SIZE