esp,GDT等内容目前还在loader中，为了方便控制我们得把他们放到内核比较好。
下面我们：
切换堆栈和GDT
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; ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
; kernel.asm
; ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
; Forrest Yu, 2005
; ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
; ----------------------------------------------------------------------
; 编译连接方法:
; $ rm -f kernel.bin
; $ nasm -f elf -o kernel.o kernel.asm
; $ nasm -f elf -o string.o string.asm
; $ nasm -f elf -o klib.o klib.asm
; $ gcc -c -o start.o start.c
; $ ld -s -Ttext 0x30400 -o kernel.bin kernel.o string.o start.o klib.o
; $ rm -f kernel.o string.o start.o
; $
; ----------------------------------------------------------------------
SELECTOR_KERNEL_CS equ 8
; 导入函数
extern cstart
; 导入全局变量
extern gdt_ptr
[SECTION .bss]
StackSpace resb 2 * 1024
StackTop: ; 栈顶
[section .text] ; 代码在此
global _start ; 导出 _start
_start:
; 此时内存看上去是这样的（更详细的内存情况在 LOADER.ASM 中有说明）：
; ┃ ┃
; ┃ ... ┃
; ┣━━━━━━━━━━━━━━━━━━┫
; ┃■■■■■■Page Tables■■■■■■┃
; ┃■■■■■(大小由LOADER决定)■■■■┃ PageTblBase
; 00101000h ┣━━━━━━━━━━━━━━━━━━┫
; ┃■■■■Page Directory Table■■■■┃ PageDirBase = 1M
; 00100000h ┣━━━━━━━━━━━━━━━━━━┫
; ┃□□□□ Hardware Reserved □□□□┃ B8000h ← gs
; 9FC00h ┣━━━━━━━━━━━━━━━━━━┫
; ┃■■■■■■■LOADER.BIN■■■■■■┃ somewhere in LOADER ← esp
; 90000h ┣━━━━━━━━━━━━━━━━━━┫
; ┃■■■■■■■KERNEL.BIN■■■■■■┃
; 80000h ┣━━━━━━━━━━━━━━━━━━┫
; ┃■■■■■■■■KERNEL■■■■■■■┃ 30400h ← KERNEL 入口 (KernelEntryPointPhyAddr)
; 30000h ┣━━━━━━━━━━━━━━━━━━┫
; ┋ ... ┋
; ┋ ┋
; 0h ┗━━━━━━━━━━━━━━━━━━┛ ← cs, ds, es, fs, ss
;
;
; GDT 以及相应的描述符是这样的：
;
; Descriptors Selectors
; ┏━━━━━━━━━━━━━━━━━━┓
; ┃ Dummy Descriptor ┃
; ┣━━━━━━━━━━━━━━━━━━┫
; ┃ DESC_FLAT_C (0～4G) ┃ 8h = cs
; ┣━━━━━━━━━━━━━━━━━━┫
; ┃ DESC_FLAT_RW (0～4G) ┃ 10h = ds, es, fs, ss
; ┣━━━━━━━━━━━━━━━━━━┫
; ┃ DESC_VIDEO ┃ 1Bh = gs
; ┗━━━━━━━━━━━━━━━━━━┛
;
; 在使用 C 代码的时候一定要保证 ds, es, ss 这几个段寄存器的值是一样的
; 因为编译器有可能编译出使用它们的代码, 而编译器默认它们是一样的. 比如串拷贝操作会用到 ds 和 es.
;
;
; 把 esp 从 LOADER 挪到 KERNEL
mov esp, StackTop ; 堆栈在 bss 段中
sgdt [gdt_ptr] ; cstart() 中将会用到 gdt_ptr
call cstart ; 在此函数中改变了gdt_ptr，让它指向新的GDT
lgdt [gdt_ptr] ; 使用新的GDT
;lidt [idt_ptr]
jmp SELECTOR_KERNEL_CS:csinit
csinit: ; “这个跳转指令强制使用刚刚初始化的结构”——<<OS:D&I 2nd>> P90.
push 0
popfd ; Pop top of stack into EFLAGS
hlt
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gdt_ptr和cstart分别是一个全局变量和全局函数，他们定义在start.c中
|
/*++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
start.c
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Forrest Yu, 2005
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
#include "type.h"
#include "const.h"
#include "protect.h"
PUBLIC void* memcpy(void* pDst, void* pSrc, int iSize);
PUBLIC void disp_str(char * pszInfo);
PUBLIC u8 gdt_ptr[6]; /* 0~15:Limit 16~47:Base */
PUBLIC DESCRIPTOR gdt[GDT_SIZE];
PUBLIC void cstart()
{
disp_str("\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n"
"-----\"cstart\" begins-----\n");
/* 将 LOADER 中的 GDT 复制到新的 GDT 中 */
memcpy(&gdt, /* New GDT */
(void*)(*((u32*)(&gdt_ptr[2]))), /* Base of Old GDT */
*((u16*)(&gdt_ptr[0])) + 1 /* Limit of Old GDT */
);
/* gdt_ptr[6] 共 6 个字节：0~15:Limit 16~47:Base。用作 sgdt/lgdt 的参数。*/
u16* p_gdt_limit = (u16*)(&gdt_ptr[0]);
u32* p_gdt_base = (u32*)(&gdt_ptr[2]);
*p_gdt_limit = GDT_SIZE * sizeof(DESCRIPTOR) - 1;
*p_gdt_base = (u32)&gdt;
}
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函数cstart首先把位于loader中的原GDT全部复制给新的GDT，然后把gdt_ptr中的内容换成新的GDT的基地址和界限。
memcpy在string.asm中
const.h
|
/*++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
const.h
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Forrest Yu, 2005
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
#ifndef _ORANGES_CONST_H_
#define _ORANGES_CONST_H_
/* 函数类型 */
#define PUBLIC /* PUBLIC is the opposite of PRIVATE */
#define PRIVATE static /* PRIVATE x limits the scope of x */
/* GDT 和 IDT 中描述符的个数 */
#define GDT_SIZE 128
#endif /* _ORANGES_CONST_H_ */
|
type.h
|
/*++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
type.h
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Forrest Yu, 2005
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
#ifndef _ORANGES_TYPE_H_
#define _ORANGES_TYPE_H_
typedef unsigned int u32;
typedef unsigned short u16;
typedef unsigned char u8;
#endif /* _ORANGES_TYPE_H_ */
|
protect.h
|
/*++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
protect.h
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Forrest Yu, 2005
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
#ifndef _ORANGES_PROTECT_H_
#define _ORANGES_PROTECT_H_
/* 存储段描述符/系统段描述符 */
typedef struct s_descriptor /* 共 8 个字节 */
{
u16 limit_low; /* Limit */
u16 base_low; /* Base */
u8 base_mid; /* Base */
u8 attr1; /* P(1) DPL(2) DT(1) TYPE(4) */
u8 limit_high_attr2; /* G(1) D(1) 0(1) AVL(1) LimitHigh(4) */
u8 base_high; /* Base */
}DESCRIPTOR;
#endif /* _ORANGES_PROTECT_H_ */
|
好了 编译连接
nasm -f -elf -o kernel.o kernel.asm
nasm -f elf -o string.o string.asm
gcc -c -o start.o start.c
ld -s -Ttext 0x30400 -o kernel.bin kernel.o string.o start.c
好了 可以运行试试了
然后添加显示字符串的代码kliba.asm
|
; ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
; klib.asm
; ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
; Forrest Yu, 2005
; ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[SECTION .data]
disp_pos dd 0
[SECTION .text]
; 导出函数
global disp_str
; ========================================================================
; void disp_str(char * info);
; ========================================================================
disp_str:
push ebp
mov ebp, esp
mov esi, [ebp + 8] ; pszInfo
mov edi, [disp_pos]
mov ah, 0Fh
.1:
lodsb
test al, al
jz .2
cmp al, 0Ah ; 是回车吗?
jnz .3
push eax
mov eax, edi
mov bl, 160
div bl
and eax, 0FFh
inc eax
mov bl, 160
mul bl
mov edi, eax
pop eax
jmp .1
.3:
mov [gs:edi], ax
add edi, 2
jmp .1
.2:
mov [disp_pos], edi
pop ebp
ret
|
在start.c中调用disp_str("\n\n\n\n\n""--------\""cstart\"" begins-----\n");
编译运行：
nasm -f -elf -o kernel.o kernel.asm
nasm -f elf -o string.o string.asm
nasm -f elf -o klib.o klib.asm
gcc -c -o -fno-builtin start.o start.c
ld -s -Ttext 0x30400 -o kernel.bin kernel.o string.o start.o klib.o
整理目录：
---a.img
--bochsrc
--MyOSboot
--MyOSboot.asm
--include
--fat12hdr.inc
--load.inc
--pm.inc
--loader.asm
--include
--const.h
--protect.h
--type.h
--kernel
--kernel.asm
--start.c
--lib
--klib.asm
--string.asm
Makefile:
|
#####################
# Makefile for Tinix #
######################
# Entry point of Tinix
# It must be as same as 'KernelEntryPointPhyAddr' in load.
ENTRYPOINT = 0x30400
# Offset of entry point in kernel file
# It depends on ENTRYPOINT
ENTRYOFFSET = 0x400
# Programs, flags, etc.
ASM = nasm
DASM = ndisasm
CC = gcc
LD = ld
ASMBFLAGS = -I boot/include
ASMKFLAGS = -I include -f elf
CFLAGS = -I include -c -fno-builtin
LDFLAGS = -s -Ttext $(ENTRYPOINT)
DASMFLAGS = -u -o $(ENTRYPOINT) -e $(ENTRYOFFSET)
# This Program
TINIXBOOT = boot/boot.bin boot/loader.bin
TINIXKERNEL = kernel.bin
OBJS = kernel/kernel.o kernel/start.o lib/klib.o lib/string.o
DASMOUTPUT = kernel.bin.asm
# All Phony Targets
.PHONY : everything final image clean realclean disasm all buildimg
# Default starting position
everything : $(TINIXBOOT) $(TINIXKERNEL)
all : realclean everything
final : all clean
image : final buildimg
clean :
rm -f $(OBJS)
realclean :
rm -f $(OBJS) $(TINIXBOOT) $(TINIXKERNEL)
disasm :
$(DASM) $(DASMFLAGS) $(TINIXKERNEL) > $(DASMOUTPUT)
# Write "boot.bin" & "loader.bin" into floppy image "TINIX.IMG"
# We assume that "TINIX.IMG" exists in current folder
buildimg :
mount TINIX.IMG /mnt/floppy -o loop
cp -f boot/loader.bin /mnt/floppy/
cp -f kernel.bin /mnt/floppy
umount /mnt/floppy
boot/boot.bin : boot/boot.asm boot/include/load.inc boot/include/fat12hdr.inc
$(ASM) $(ASMBFLAGS) -o $@ $<
boot/loader.bin : boot/loader.asm boot/include/load.inc boot/include/fat12hdr.inc boot/include/pm.inc
$(ASM) $(ASMBFLAGS) -o $@ $<
$(TINIXKERNEL) : $(OBJS)
$(LD) $(LDFLAGS) -o $(TINIXKERNEL) $(OBJS)
kernel/kernel.o : kernel/kernel.asm
$(ASM) $(ASMKFLAGS) -o $@ $<
kernel/start.o : kernel/start.c ./include/type.h ./include/const.h ./include/protect.h
$(CC) $(CFLAGS) -o $@ $<
lib/klib.o : lib/klib.asm
$(ASM) $(ASMKFLAGS) -o $@ $<
lib/string.o : lib/string.asm
$(ASM) $(ASMKFLAGS) -o $@ $<
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直接 make image 即可运行
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