From 1ba82ac77f3f611d73fc781f3da17e21dfa3bfda Mon Sep 17 00:00:00 2001
From: josh <josh@5b3e749e-e535-0410-8002-a9bb6afbdfca>
Date: Thu, 25 Jun 2009 15:02:46 +0000
Subject: [PATCH] added svn:ignore to a few directories; kernel linked to
 virtual address 0xE000_0000 and running there in segmented mode

git-svn-id: svn://anubis/hos/trunk@15 5b3e749e-e535-0410-8002-a9bb6afbdfca
---
 kernel/boot.asm | 106 +++++++++++++++++++++++++++++++++++++++++-------
 kernel/link.ld  |   3 +-
 2 files changed, 93 insertions(+), 16 deletions(-)

diff --git a/kernel/boot.asm b/kernel/boot.asm
index 833570a..eaa644a 100644
--- a/kernel/boot.asm
+++ b/kernel/boot.asm
@@ -1,25 +1,101 @@
 
-%define MULTIBOOT_HEADER_MAGIC 0x1BADB002
-%define MULTIBOOT_HEADER_FLAGS 0x3
+; boot.asm
+; Author: Josh Holtrop
+; Date: 2009-06-25
+; Adapted from HOS 0.16 source
 
+%define MULTIBOOT_HEADER_MAGIC      0x1BADB002
+%define MULTIBOOT_HEADER_FLAGS      0x00010003
+
+%define VIRTUAL_OFFSET              0xE0000000          ; kernel virtual addr
+
+%define TEMPORARY_STACK_PHYSICAL    0x01000000-4        ; top of first 16MB
+%define TEMPORARY_STACK_VIRTUAL     TEMPORARY_STACK_PHYSICAL + VIRTUAL_OFFSET
+
+; Get these symbols from the linker
+extern _end, _bss
+
+;**************************************************************************
+;* Begin execution from the bootloader here                               *
+;**************************************************************************
 [global start]
 start:
-	jmp	multiboot_entry
-	align 4
+    jmp multiboot_entry                 ; jump over the multiboot header block
 
+
+;**************************************************************************
+;* Multiboot header data block                                            *
+;**************************************************************************
+    align 4
 multiboot_header:
-	; magic
-	dd	MULTIBOOT_HEADER_MAGIC
-	; flags
-	dd	MULTIBOOT_HEADER_FLAGS
-	; checksum
-	dd	-(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
+    dd  MULTIBOOT_HEADER_MAGIC                              ; magic
+    dd  MULTIBOOT_HEADER_FLAGS                              ; flags
+    dd  -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)  ; checksum
 
+    dd  multiboot_header - VIRTUAL_OFFSET                   ; header_addr
+    dd  start - VIRTUAL_OFFSET                              ; load_addr
+    dd  _bss - VIRTUAL_OFFSET                               ; load_end_addr
+    dd  _end - VIRTUAL_OFFSET                               ; bss_end_addr
+    dd  multiboot_entry - VIRTUAL_OFFSET                    ; entry_addr
+
+
+;**************************************************************************
+;* Resume execution                                                       *
+;**************************************************************************
 multiboot_entry:
-	mov ax, 0x0700 + 'J'
-	mov [0xB8000+160*10+2*2], ax
+    lgdt    [gdtr_tmp32-VIRTUAL_OFFSET]    ; load temporary GDTR
+    jmp KERNEL_CODE_32_TMP_SEG:segmented_start
 
-looplbl:
-	hlt
-	jmp looplbl
+;**************************************************************************
+;* At this point address 0xE000_0000 is mapped to physical address 0x0    *
+;**************************************************************************
+segmented_start:
+    mov cx, KERNEL_DATA_32_TMP_SEG
+    mov ss, cx
+    mov ds, cx
+    mov es, cx
+    mov gs, cx
+    mov fs, cx
+    mov esp, TEMPORARY_STACK_VIRTUAL-4  ; set up temporary stack space
 
+    mov ax, 0x0700 + 'J'
+    mov [VIRTUAL_OFFSET+0xB8000+160*8+4*2], ax
+
+idle_loop:
+    hlt
+    jmp idle_loop
+
+
+;-------------------------------------------------------
+[section .rodata]
+gdtr_tmp32:
+    dw  gdt_end_tmp32-gdt_tmp32-1
+    dd  gdt_tmp32-VIRTUAL_OFFSET
+
+gdt_tmp32:            ; 0 = null descriptor
+    dd  0
+    dd  0
+
+    ; a base of 0x2000_0000, when added to 0xE000_0000 will produce
+    ; 0x0000_0000 physical before paging in effect
+KERNEL_CODE_32_TMP_SEG equ $-gdt_tmp32  ; 8
+    db  0xff        ;limit  7:0
+    db  0xff        ;limit  15:8
+    db  0x00        ;base   7:0
+    db  0x00        ;base   15:8
+    db  0x00        ;base   23:16
+    db  0x9a        ;access
+    db  0xcf        ;flags / limit 19:16
+    db  0x20        ;base   31:24
+
+KERNEL_DATA_32_TMP_SEG equ $-gdt_tmp32  ; 16
+    db  0xff        ;limit  7:0
+    db  0xff        ;limit  15:8
+    db  0x00        ;base   7:0
+    db  0x00        ;base   15:8
+    db  0x00        ;base   23:16
+    db  0x92        ;access
+    db  0xcf        ;flags / limit 19:16
+    db  0x20        ;base   31:24
+
+gdt_end_tmp32:
diff --git a/kernel/link.ld b/kernel/link.ld
index 8550ce2..52f7ddc 100644
--- a/kernel/link.ld
+++ b/kernel/link.ld
@@ -1,7 +1,8 @@
+OUTPUT_FORMAT(binary)
 ENTRY(start)
 SECTIONS
 {
-  .text  0x00100000 : {
+  .text  0xE0100000 : {
     code = .; _code = .; __code = .;
     *(.text)
   }