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include <config.h>

#include <arch/x86/page.h>
#include <multiboot.h>

#define STACKSIZE 0x4000          // that is, 16k.

// setting up the Multiboot header - see GRUB docs for details
.section .mboot
.global start
start:
    jmp stage1

.align 4

mboot_header:
    .long MBOOT_MAGIC
    .long MBOOT_FLAGS
    .long MBOOT_CHECKSUM

.text

.extern pagedir
.extern pagetab

#ifdef __CONFIG_CPU_PAE
    .extern pagedir_ptr
#endif

.global stage1
stage1:

   mov   $(stack + STACKSIZE - KERNEL_BASE_ADDR), %esp
   push  %eax
   push  %ebx

    #ifdef __CONFIG_CPU_PAE
        movl $4, %ecx
        movl pagedir_ptr, %esi
        subl $KERNEL_BASE_ADDR, %esi
        .fill_ptr:
            movl $0, (%esi)
            addl $8, %esi
            loop .fill_ptr
    #endif

    movl $PGTAB_MAX, %ecx
    #ifdef __CONFIG_CPU_PAE
        // Map 4 MB!
        shll $1, %ecx
    #endif
    xorl %edx, %edx
    movl $KERNEL_TO_PSYH(pagetab), %esi
    .fill_pagetab:
        movl %edx, (%esi)
        orl $0x3, (%esi)
        addl $PAGE_SIZE, %edx
        addl $PAGE_ENTRY_SIZE, %esi
        loop .fill_pagetab

    movl $PGDIR_MAX, %ecx
    movl $KERNEL_TO_PSYH(pagedir), %esi
    .clear_pgdir:
        movl $0, (%esi)
        addl $PAGE_ENTRY_SIZE, %esi
        loop .clear_pgdir

    movl $KERNEL_TO_PSYH(pagedir), %esi
    movl $KERNEL_TO_PSYH(pagetab), %edi
    #ifdef __CONFIG_CPU_PAE
        movl %edi, (%esi)
        orl $0x3, (%esi)
    #else
        addl $(768 * 4), %esi
        movl %edx, (%esi)
        orl $0x3, (%esi)
    #endif

    #ifdef __CONFIG_CPU_PAE
        movl $KERNEL_TO_PSYH(pagedir_ptr), %esi
        movl $KERNEL_TO_PSYH(pagedir), %edi
        movl %edi, 32(%esi)
        movl %edi, (%esi)
        orl $0x01, 32(%esi)
        orl $0x01, (%esi)

        movl %cr4, %edx
        orl $0x20, %edx
        movl %edx, %cr4

        movl $KERNEL_TO_PSYH(pagedir_ptr), %edx
        movl %edx, %cr3
    #else
        movl $KERNEL_TO_PSYH(pagedir), %edx
        movl %edx, %cr3
    #endif

    movl %cr0, %edx
    orl $0x80000000, %edx
    movl %edx, %cr0

    lea (stage2), %ecx
    jmp *%ecx
stage2:
    addl $KERNEL_BASE_ADDR, %esp
    .extern main
    call main

.bss
// reserve initial kernel stack space
.comm stack, STACKSIZE, 32      // reserve 16k stack on a quadword boundary

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ENTRY(start)
OUTPUT_FORMAT("elf32-i386")
OUTPUT_ARCH("i386")

SECTIONS {
   /* The kernel will live at 3GB + 1MB in the virtual
      address space, which will be mapped to 1MB in the
      physical address space. */
   . = 0xC0100000;
        
   .text : AT(ADDR(.text) - 0xC0000000) {
       arch/x86/start.o(.mboot)
       *(.text)
       *(.rodata*)
   }

   .data ALIGN (0x1000) : AT(ADDR(.data) - 0xC0000000) {
       tty_vga = .; . += 8 * 0x1000;
       *(.data)
   }

   .bss : AT(ADDR(.bss) - 0xC0000000) {
       _sbss = .;
       *(COMMON)
       *(.bss)
       _ebss = .;
   }
   end = . ; _end = . ;
}

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#define MBOOT_MAGIC 0x2BADB002
#define MBOOT_MODULEALIGN ( 1 << 0 ) 
#define MBOOT_MEMINFO     ( 1 << 1 ) 
#define MBOOT_FLAGS       MBOOT_MODULEALIGN | MBOOT_MEMINFO
#define MBOOT_CHECKSUM    -(MBOOT_MAGIC + MBOOT_FLAGS)