entry.s

从网上下载的一个自己编写的简单的操作系统源代码,对底层了解很有好处的

;/*
; *  ExpOS
; *            
; *
; *
; *   Copyright 2002 
; *                hyl
; */



SEG_NOT_VECTOR     	EQU	11	; segment not present
STACK_FAULT_VECTOR 	EQU	12	; stack exception
PROTECTION_VECTOR  	EQU	13	; general protection
PAGE_FAULT_VECTOR   	EQU	14
COPROC_ERR_VECTOR   	EQU	16	; coprocessor error

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;GATE     STRUC      ;门结构类型定义
;    OFFSETL  DW      0  ;32位偏移的低16位
;    SELECTOR DW      0  ;选择子
;    Reserve  DB      0  
;    GTYPE    DB      0  ;类型
;    OFFSETH  DW      0  ;32位偏移的高16位
;    GATE     ENDS
;
[bits 32]

section .data

global _idt,__lidt, _nop_handler

_idt: times 256*2 dd 0  ; idt is uninitialized
; idt 操作函数在arch.c 中

align 2
   dw 0
idt_descr:              ;装载idt 的伪描述符
	dw  256*8-1	; idt contains 256 entries
	dd _idt

section .text
__lidt:
      lidt	[idt_descr]		; reload idt with kernel idt
      ret


;;;;;;;;;;;;
;空中断处理

extern _live
_nop_handler:
       push edx
       push eax
       ;push ds

       
       call _live   ;_kbdledoff
       mov al, 0x20; //clear 8259 int       
       out 0x20,al

       ;pop ds
       pop eax
       pop edx
       iret



;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; 描述符分类
; Gate Descripters: 
;      Task Gate  不使用
;      Call Gate  不使用
;      Interrupt Gate (IG) 发生后自动清除IF.
;      Trap Gate  发生后不清除中断使能位(IF).  (Minix 的Gate 都是IG )
;//doc at tail

; 来自cup之外的叫中断(Interrupt): 
;           *可屏蔽中断(IRQs) 
;           *不可屏蔽中断(NMI) 
;      可屏蔽中断(IRQs) 可以由cli/sti 指令控制.
;      两者都可以被cpu外的硬件所屏蔽. 
; 来自cup内部的叫异常(Exceptions): 
;    **CUP 侦测到的异常: 
;        *故障(Fault): 在当前指令执行前发生. 如除0, 非法操作码,page fault. 
;        *陷阱(Trap): 在执行当前指令后发生. 程序指令int 产生的异常都是陷阱. 
;        *Abort: 异常位置不可确定.如 double fault, coprocessor segment overrun. 
;    **程序主动产生的异常 :
;        INT instruction 
;        INT3 instruction 
;        INTO instruction 
;        BOUND instruction 
;*************************************
;Intel 保留的32 个中断/异常: 
;|Number | interrupt/exception| err code |    notes 
;+-----+----------------------+---+------+-------------------------------------
;|  0  | F  divide  error     | N |could be overflow as well as zero denominator 
;+-----+----------------------+---+--------------------------------------------
;|  1  | F/T debug exception  | N |  
;+-----+----------------------+-------------------------------------------------
;|  2  | I  NMI               | N |
;+-----+----------------------+-------------------------------------------------
;|  3  | T INT3 instruction   | N |debugger breakpoint 
;+-----+----------------------+-------------------------------------------------
;|  4  | T INTO instruction   | N |detected overflow  
;+-----+----------------------+-------------------------------------------------
;|  5  | F BOUND instruction  | N |detected overrange  
;+-----+----------------------+-------------------------------------------------
;|  6  |  invalid instruction | N |
;+-----+  opcode              +   |------------------------------------------------
;|     | F                    |   | 
;+-----+----------------------+-------------------------------------------------
;|  7  | F no coprocessor     | N |ESC, WAIT instructions 
;+-----+----------------------+-------------------------------------------------
;|  8  | A double fault       | Y | possible for 386+ in real mode 
;|     |                      |(0)| if INT vector exceeds IDT limit 
;+-----+----------------------+---+---------------------------------------------
;|  9  |  coprocessor segment | N |not in real mode
;|     | F overrun            |   |
;+-----+----------------------+---+---------------------------------------------
;|  10 | F invalid task state | Y | not in real mode
;|     |   segment (TSS)      |   |
;+-----+----------------------+-------------------------------------------------
;|  11 |F segment not present | Y | not in real mode 
;+-----+----------------------+-------------------------------------------------
;|  12 | F stack fault        | Y | possible in real mode if stack access 
;|     |                      |   | straddles offset 0 or FFFFh 
;+-----+----------------------+-------------------------------------------------
;|  13 | F general protection |   |possible in real mode if non-stack memory access straddles
;|     |    fault (GPF)       | Y |0 or FFFFh, or if instruction is longer than 15 bytes,
;|     |                      |   |or if a 32-bit address greater than FFFFh is used 
;+-----+----------------------+-------------------------------------------------
;|  14 | F page fault         | Y |not in real mode 
;+-----+----------------------+-------------------------------------------------
;|  15 |   (reserved)         | N 
;+-----+----------------------+-------------------------------------------------
;|  16 | F coprocessor error  | N | ESC, WAIT instructions 
;+-----+----------------------+-------------------------------------------------
;|  17 | F alignment check    | Y(0) | not in real mode; 486+ only 
;+-----+----------------------+-------------------------------------------------
;|  18 | A machine check      | N | Pentium+ only 
;+-----+----------------------+-------------------------------------------------
;| 19  |F SIMD float point err | N | SSE and SSE2 floating-point instructions
;+-----+----------------------+-------------------------------------------------
;|20-31|  (reserved)          |
;+-----+----------------------+------------------------------------------------
;*****************************************
; interrupt/exception 发生后CPU 的动作
; 1. 如果伴随 pmode 特权级切换, CPU 从当前的TSS 中加载 SS (E)SP . 
; 2. 如果伴随 pmode 特权级切换, 原来的 SS 和 (E)SP 入新堆栈. 
; 3. CS, (E)IP, (E)FLAGS 入新栈. 一些异常可能还把一个错误码入新栈. 
; 4. 如果通过一个中断门,CPU 清 IF .  
; 5. CPU 做一个 far jump; 从门中加载 CS and (E)IP . 
;
; 中断/异常发生后可能形成10 种栈布局. 3 个16-bit 保护模式; 2个virtual 8086 模式.
; 还有一个16 bit 实模式. 对我们比较有意义的4个32位保护模式下的栈格式是: 
;+--------------------------------+----------------------------------+
;|          无特权级切换          |           伴随特权级切换         |
;+----------------+---------------+-----------------+----------------+
;|  <- 32 bits -> | <- 32 bits -> |  <- 32 bits ->  |<- 32 bits ->   |
;|    ... ...     |   ... ...     |    ... ...      |   ...  ...     |
;|    ... ...     |   ... ...     |    ... ...      |   ... user SS  |
;|    ... ...     |   ... ...     |    ... user SS  |    user ESP    |
;|    ... ...     |   EFLAGS      |    user ESP     |    EFLAGS      |
;|    EFLAGS      |   ... CS      |     EFLAGS      |    ... CS      |
;|    ... CS      |    EIP        |    ... CS       |     EIP        |
;|      EIP       |  error code   |      EIP        |   error code   |
;+----------------+---------------+-----------------+----------------+
;|    无错误码    |   有错误码    |     无错误码    |   有错误码     |
;+----------------+---------------+-----------------+----------------+
;*===========================================================================*
;*				exception handlers			     *
;*===========================================================================*
_divide_error:
	push	dword	0  ;Divide error vector
	jmp	exception

_single_step_exception:
	push	dword	1  ;Debug (single step )
	jmp	exception

_nmi:
	push	dword	2  ;NMI 
	jmp	exception

_breakpoint_exception:
	push	dword	3  ;Breakpoint vector
	jmp	exception

_overflow:
	push	dword	4  ;into ,overflow exception vector
	jmp	exception

_bounds_check:
	push	dword	5  ;Detected bounds error
	jmp	exception

_inval_opcode:
	push	dword	6  ;Invalid opcode vector 
	jmp	exception

_copr_not_available:
	push	dword	7  ;Coprocessor not avalible
	jmp	exception

_double_fault:
	push	dword	8  ;Double Fault vector 
	jmp	errexception

_copr_seg_overrun:
	push	dword	9   ;Coprocessor segment overrun 
	jmp	exception

_inval_tss:
	push	dword	10   ;Invalid tss vector
	jmp	errexception

_segment_not_present:
	push	dword	11   ; segment not present vector
	jmp	errexception

_stack_exception:
	push	dword	12   ; Stack exception
	jmp	errexception

_general_protection:
	push	dword	13   ;General protection vector
	jmp	errexception

_page_fault:
	push	dword	14   ;Page falt 
	jmp	errexception

_res15_:
        push    dword   15   ;Reserve vectro 15
        jmp     exception
        
_copr_error:
	push	dword	16   ;Coprocessor error
	jmp	exception

_align_check:
        push    dword   17   ; | Y(0) | not in real mode; 486+ only 
        jmp     errexception 

_machine_check:
        push    dword   18   ;machine check    Pentium+ only 
        jmp     exception
        
_simd_fpoint_err:
        push    dword   19   ; SIMD float point err , SSE and SSE2 floating-point instructions
        jmp     exception

;;;;;;;;;;;;;;;;;;;;;;;;;;;;        
	align	16
exception:
 	;mov	dword [ss:trap_errno], 0
 	;pop	dword [ss:ex_number]
	jmp	exception1

	align	16
errexception:
	;pop	dword [ss:ex_number]
	;pop	dword [ss:trap_errno]
exception1:
	push	eax
	mov	eax, dword [esp+4]
 	;mov	dword [ss:old_eip], eax
	mov	eax, dword [esp+8]
	;mov	dword [ss:old_cs], eax
	mov	eax, dword [esp+12]
 	;mov	dword [ss:old_eflags], eax
	pop	eax
	;save
	;push	dword [old_eflags]
	;push	dword [old_cs]
	;push	dword [old_eip]
	;push	dword [trap_errno]
	;push	dword [ex_number]
	;call	_exception

	add	esp, 5*4
	;load
	ret




;/*
; *  硬件中断处理
; *  
; *
; */
section .data
global __irq_table   ; void vector(int vct_num)
__irq_table dd 0
            times 32 dd 0


section .text
%macro int_handle 1
        cld
        push	ds		; save ds
        push	es		; save es
        ;push	fs		; save fs
        ;push	gs		; save gs
        pusha			; save "general" registers
      
      
	;mov	dx, ss		; ss is kernel data segment
	;mov	ds, dx		; load rest of kernel segments
	;mov	es, dx		; kernel does not use fs, gs

        push dword %1              ; vct_num
        call [__irq_table + 4*%1] ; 
        add esp,4
       
       
        popa			; save "general" registers
        ;pop	gs		; save gs
        ;pop	fs		; save fs
	pop	es		; save es
	pop	ds		; save ds
        iret
%endmacro


;/*
; * 用宏产生中断处理函数, 这是第一级中断处理
; * 这些处理函数的地址填入IDT 0x20----0x2F  
; * 
; */
%macro Int_Handler 1-*   ;多参数宏, 产生IDT Interrupt Handler 
    %rep %0  ; 0 号参数是参数个数

       ;本文件访问就可以了
       align 16
       __hw_int_h%1:
                 int_handle %1;

    %rotate 1 ; 1 号参数变成下一个参数
    %endrep 
%endmacro

;==========
Int_Handler 00,01,02,03,04,05,06,07,08,09,10,11,12,13,14,15  ;idt 中irq的中断门


%macro handler_array_def 1-*   ;多参数宏, 把
    %rep %0  ; 0 号参数是参数个数
               dd __hw_int_h%1;
    %rotate 1 ; 1 号参数变成下一个参数
    %endrep 
%endmacro

;=======================
global __all_int_handler
__all_int_handler:
  handler_array_def 00,01,02,03,04,05,06,07,08,09,10,11,12,13,14,15