/* boot.S - bootstrap the kernel */
/* Copyright (C) 1999, 2001, 2010  Free Software Foundation, Inc.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#define ASM_FILE        1
#include <multiboot.h>

/* C symbol format. HAVE_ASM_USCORE is defined by configure. */
#ifdef HAVE_ASM_USCORE
# define EXT_C(sym)                     _ ## sym
#else
# define EXT_C(sym)                     sym
#endif

/* The size of our stack (16KB). */
#define STACK_SIZE                      0x4000

/* The flags for the Multiboot header. */
#ifdef __ELF__
# define AOUT_KLUDGE 0
#else
# define AOUT_KLUDGE MULTIBOOT_AOUT_KLUDGE
#endif
#define MULTIBOOT_HEADER_FLAGS                  MULTIBOOT_PAGE_ALIGN | MULTIBOOT_MEMORY_INFO | MULTIBOOT_VIDEO_MODE | AOUT_KLUDGE
        
        .text

        .globl  start, _start
start:
_start:
        jmp     multiboot_entry

        /* Align 32 bits boundary. */
        .align  4
        
        /* Multiboot header. */
multiboot_header:
        /* magic */
        .long   MULTIBOOT_HEADER_MAGIC
        /* flags */
        .long   MULTIBOOT_HEADER_FLAGS
        /* checksum */
        .long   -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
#ifndef __ELF__
        /* header_addr */
        .long   multiboot_header
        /* load_addr */
        .long   _start
        /* load_end_addr */
        .long   _edata
        /* bss_end_addr */
        .long   _end
        /* entry_addr */
        .long   multiboot_entry
#else /* ! __ELF__ */
        .long   0
        .long   0
        .long   0
        .long   0
        .long   0       
#endif /* __ELF__ */
        .long 0
        .long 1024
        .long 768
        .long 32

multiboot_entry:
        /* Initialize the stack pointer. */
        movl    $(stack + STACK_SIZE), %esp

        /* Reset EFLAGS. */
        pushl   $0
        popf

        /* Push the pointer to the Multiboot information structure. */
        pushl   %ebx
        /* Push the magic value. */
        pushl   %eax

        /* Now enter the C main function... */
        call    EXT_C(cmain)

        /* Halt. */
        pushl   $halt_message
        call    EXT_C(printf)
        
loop:   hlt
        jmp     loop

halt_message:
        .asciz  "Halted."

        /* Our stack area. */
        .comm   stack, STACK_SIZE