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十分感谢mik的帮助。问题找到了。
LDT为系统段，我把它设为数据段，结果不行了。
Intel手册中没说，我以为两个都行的都行的。
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我的VM乱报错 ，以后我可不相信它了。 结果让我绕了好大弯子，什么ss段出错，什么ds段不对。
我吐血。发了我好多精力啊。
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PS:看了intel的sample，我才明白什么才叫assembler。那叫什么乱七八糟的代码。是人看的么？？又是cp，又是builer分配的。我手上没有masm，也没有dos，分析目标代码都不行。
附上：intel的代码
- 10.4.5 First Task
- The initialization procedure can run awhile in protected mode without
- initializing the task register; however, before the first task switch, the
- following conditions must prevail:
- ● There must be a valid task state segment (TSS) for the new task. The
- stack pointers in the TSS for privilege levels numerically less than or
- equal to the initial CPL must point to valid stack segments.
- ● The task register must point to an area in which to save the current
- task state. After the first task switch, the information dumped in this
- area is not needed, and the area can be used for other purposes.
- 10.5 Initialization Example
- $TITLE ('Initial Task')
- NAME INIT
- init_stack SEGMENT RW
- DW 20 DUP(?)
- tos LABEL WORD
- init_stack ENDS
- init_data SEGMENT RW PUBLIC
- DW 20 DUP(?)
- init_data ENDS
- init_code SEGMENT ER PUBLIC
- ASSUME DS:init_data
- nop
- nop
- nop
- init_start:
- ; set up stack
- mov ax, init_stack
- mov ss, ax
- mov esp, offset tos
- mov a1,1
- blink:
- xor a1,1
- out 0e4h,a1
- mov cx,3FFFh
- here:
- dec cx
- jnz here
- jmp SHORT blink
- INTEL 80386 PROGRAMMER'S REFERENCE MANUAL 1986
- Page 179 of 421
- hlt
- init_code ends
- END init_start, SS:init_stack, DS:init_data
- $TITLE('Protected Mode Transition -- 386 initialization')
- NAME RESET
- ;*****************************************************************
- ; Upon reset the 386 starts executing at address 0FFFFFFF0H. The
- ; upper 12 address bits remain high until a FAR call or jump is
- ; executed.
- ;
- ; Assume the following:
- ;
- ;
- ; - a short jump at address 0FFFFFFF0H (placed there by the
- ; system builder) causes execution to begin at START in segment
- ; RESET_CODE.
- ;
- ;
- ; - segment RESET_CODE is based at physical address 0FFFF0000H,
- ; i.e. at the start of the last 64K in the 4G address space.
- ; Note that this is the base of the CS register at reset. If
- ; you locate ROMcode above this address, you will need to
- ; figure out an adjustment factor to address things within this
- ; segment.
- ;
- ;*****************************************************************
- $EJECT ;
- ; Define addresses to locate GDT and IDT in RAM.
- ; These addresses are also used in the BLD386 file that defines
- ; the GDT and IDT. If you change these addresses, make sure you
- ; change the base addresses specified in the build file.
- GDTbase EQU 00001000H ; physical address for GDT base
- IDTbase EQU 00000400H ; physical address for IDT base
- PUBLIC GDT_EPROM
- PUBLIC IDT_EPROM
- PUBLIC START
- DUMMY segment rw ; ONLY for ASM386 main module stack init
- DW 0
- DUMMY ends
- ;*****************************************************************
- ;
- ; Note: RESET CODE must be USEl6 because the 386 initally executes
- ; in real mode.
- ;
- RESET_CODE segment er PUBLIC USE16
- ASSUME DS:nothing, ES:nothing
- INTEL 80386 PROGRAMMER'S REFERENCE MANUAL 1986
- Page 180 of 421
- ;
- ; 386 Descriptor template
- DESC STRUC
- lim_0_15 DW 0 ; limit bits (0..15)
- bas_0_15 DW 0 ; base bits (0..15)
- bas_16_23 DB 0 ; base bits (16..23)
- access DB 0 ; access byte
- gran DB 0 ; granularity byte
- bas_24_31 DB 0 ; base bits (24..31)
- DESC ENDS
- ; The following is the layout of the real GDT created by BLD386.
- ; It is located in EPROM and will be copied to RAM.
- ;
- ; GDT[O] ... NULL
- ; GDT[1] ... Alias for RAM GDT
- ; GDT[2] ... Alias for RAM IDT
- ; GDT[2] ... initial task TSS
- ; GDT[3] ... initial task TSS alias
- ; GDT[4] ... initial task LDT
- ; GDT[5] ... initial task LDT alias
- ;
- ; define entries in GDT and IDT.
- GDT_ENTRIES EQU 8
- IDT_ENTRIES EQU 32
- ; define some constants to index into the real GDT
- GDT_ALIAS EQU 1*SIZE DESC
- IDT_ALIAS EQU 2*SIZE DESC
- INIT_TSS EQU 3*SIZE DESC
- INIT_TSS_A EQU 4*SIZE DESC
- INIT_LDT EQU 5*SIZE DESC
- INIT_LDT_A EQU 6*SIZE DESC
- ;
- ; location of alias in INIT_LDT
- INIT_LDT_ALIAS EQU 1*SIZE DESC
- ;
- ; access rights byte for DATA and TSS descriptors
- DS_ACCESS EQU 010010010B
- TSS_ACCESS EQU 010001001B
- ;
- ; This temporary GDT will be used to set up the real GDT in RAM.
- Temp_GDT LABEL BYTE ; tag for begin of scratch GDT
- NULL_DES DESC <> ; NULL descriptor
- INTEL 80386 PROGRAMMER'S REFERENCE MANUAL 1986
- Page 181 of 421
- ; 32-Gigabyte data segment based at 0
- FLAT_DES DESC <0FFFFH,0,0,92h,0CFh,0>
- GDT_eprom DP ? ; Builder places GDT address and limit
- ; in this 6 byte area.
- IDT_eprom DP ? ; Builder places IDT address and limit
- ; in this 6 byte area.
- ;
- ; Prepare operand for loadings GDTR and LDTR.
- TGDT_pword LABEL PWORD ; for temp GDT
- DW end_Temp_GDT_Temp_GDT -1
- DD 0
- GDT_pword LABEL PWORD ; for GDT in RAM
- DW GDT_ENTRIES * SIZE DESC -1
- DD GDTbase
- IDT_pword LABEL PWORD ; for IDT in RAM
- DW IDT_ENTRIES * SIZE DESC -1
- DD IDTbase
- end_Temp_GDT LABEL BYTE
- ;
- ; Define equates for addressing convenience.
- GDT_DES_FLAT EQU DS:GDT_ALIAS +GDTbase
- IDT_DES_FLAT EQU DS:IDT_ALIAS +GDTbase
- INIT_TSS_A_OFFSET EQU DS:INIT_TSS_A
- INIT_TSS_OFFSET EQU DS:INIT_TSS
- INIT_LDT_A_OFFSET EQU DS:INIT_LDT_A
- INIT_LDT_OFFSET EQU DS:INIT_LDT
- ; define pointer for first task switch
- ENTRY POINTER LABEL DWORD
- DW 0, INIT_TSS
- ;******************************************************************
- ;
- ; Jump from reset vector to here.
- START:
- CLI ;disable interrupts
- CLD ;clear direction flag
- LIDT NULL_des ;force shutdown on errors
- INTEL 80386 PROGRAMMER'S REFERENCE MANUAL 1986
- Page 182 of 421
- ;
- ; move scratch GDT to RAM at physical 0
- XOR DI,DI
- MOV ES,DI ;point ES:DI to physical location 0
- MOV SI,OFFSET Temp_GDT
- MOV CX,end_Temp_GDT-Temp_GDT ;set byte count
- INC CX
- ;
- ; move table
- REP MOVS BYTE PTR ES:[DI],BYTE PTR CS:[SI]
- LGDT tGDT_pword ;load GDTR for Temp. GDT
- ;(located at 0)
- ; switch to protected mode
- MOV EAX,CR0 ;get current CRO
- MOV EAX,1 ;set PE bit
- MOV CRO,EAX ;begin protected mode
- ;
- ; clear prefetch queue
- JMP SHORT flush
- flush:
- ; set DS,ES,SS to address flat linear space (0 ... 4GB)
- MOV BX,FLAT_DES-Temp_GDT
- MOV US,BX
- MOV ES,BX
- MOV SS,BX
- ;
- ; initialize stack pointer to some (arbitrary) RAM location
- MOV ESP, OFFSET end_Temp_GDT
- ;
- ; copy eprom GDT to RAM
- MOV ESI,DWORD PTR GDT_eprom +2 ; get base of eprom GDT
- ; (put here by builder).
- MOV EDI,GDTbase ; point ES:EDI to GDT base in RAM.
- MOV CX,WORD PTR gdt_eprom +0 ; limit of eprom GDT
- INC CX
- SHR CX,1 ; easier to move words
- CLD
- REP MOVS WORD PTR ES:[EDI],WORD PTR DS:[ESI]
- ;
- ; copy eprom IDT to RAM
- ;
- INTEL 80386 PROGRAMMER'S REFERENCE MANUAL 1986
- Page 183 of 421
- MOV ESI,DWORD PTR IDT_eprom +2 ; get base of eprom IDT
- ; (put here by builder)
- MOV EDI,IDTbase ; point ES:EDI to IDT base in RAM.
- MOV CX,WORD PTR idt_eprom +0 ; limit of eprom IDT
- INC CX
- SHR CX,1
- CLD
- REP MOVS WORD PTR ES:[EDI],WORD PTR DS:[ESI]
- ; switch to RAM GDT and IDT
- ;
- LIDT IDT_pword
- LGDT GDT_pword
- ;
- MOV BX,GDT_ALIAS ; point DS to GDT alias
- MOV DS,BX
- ;
- ; copy eprom TSS to RAM
- ;
- MOV BX,INIT_TSS_A ; INIT TSS A descriptor base
- ; has RAM location of INIT TSS.
- MOV ES,BX ; ES points to TSS in RAM
- MOV BX,INIT_TSS ; get inital task selector
- LAR DX,BX ; save access byte
- MOV [BX].access,DS_ACCESS ; set access as data segment
- MOV FS,BX ; FS points to eprom TSS
- XOR si,si ; FS:si points to eprom TSS
- XOR di,di ; ES:di points to RAM TSS
- MOV CX,[BX].lim_0_15 ; get count to move
- INC CX
- ;
- ; move INIT_TSS to RAM.
- REP MOVS BYTE PTR ES:[di],BYTE PTR FS:[si]
- MOV [BX].access,DH ; restore access byte
- ;
- ; change base of INIT TSS descriptor to point to RAM.
- MOV AX,INIT_TSS_A_OFFSET.bas_0_15
- MOV INIT_TSS_OFFSET.bas_0_15,AX
- MOV AL,INIT_TSS_A_OFFSET.bas_16_23
- MOV INIT_TSS_OFFSET.bas_16_23,AL
- MOV AL,INIT_TSS_A_OFFSET.bas_24_31
- MOV INIT_TSS_OFFSET.bas_24_31,AL
- ;
- ; change INIT TSS A to form a save area for TSS on first task
- INTEL 80386 PROGRAMMER'S REFERENCE MANUAL 1986
- Page 184 of 421
- ; switch. Use RAM at location 0.
- MOV BX,INIT_TSS_A
- MOV WORD PTR [BX].bas_0_15,0
- MOV [BX].bas_16_23,0
- MOV [BX].bas_24_31,0
- MOV [BX].access,TSS_ACCESS
- MOV [BX].gran,O
- LTR BX ; defines save area for TSS
- ;
- ; copy eprom LDT to RAM
- MOV BX,INIT_LDT_A ; INIT_LDT_A descriptor has
- ; base address in RAM for INIT_LDT.
- MOV ES,BX ; ES points LDT location in RAM.
- MOV AH,[BX].bas_24_31
- MOV AL,[BX].bas_16_23
- SHL EAX,16
- MOV AX,[BX].bas_0_15 ; save INIT_LDT base (ram) in EAX
- MOV BX,INIT_LDT ; get inital LDT selector
- LAR DX,BX ; save access rights
- MOV [BX].access,DS_ACCESS ; set access as data segment
- MOV FS,BX ; FS points to eprom LDT
- XOR si,si ; FS:SI points to eprom LDT
- XOR di,di ; ES:DI points to RAM LDT
- MOV CX,[BX].lim_0_15 ; get count to move
- INC CX
- ;
- ; move initial LDT to RAM
- REP MOVS BYTE PTR ES:[di],BYTE PTR FS:[si]
- MOV [BX].access,DH ; restore access rights in
- ; INIT_LDT descriptor
- ;
- ; change base of alias (of INIT_LDT) to point to location in RAM.
- MOV ES:[INIT_LDT_ALIAS].bas_0_15,AX
- SHR EAX,16
- MOV ES:[INIT_LDT_ALIAS].bas_16_23,AL
- MOV ES:[INIT_LDT_ALIAS].bas_24_31,AH
- ;
- ; now set the base value in INIT_LDT descriptor
- MOV AX,INIT_LDT_A_OFFSET.bas_0_15
- MOV INIT_LDT_OFFSET.bas_0_15,AX
- MOV AL,INIT_LDT_A_OFFSET.bas_16_23
- MOV INIT_LDT_OFFSET.bas_16_23,AL
- MOV AL,INIT_LDT_A_OFFSET.bas_24_31
- INTEL 80386 PROGRAMMER'S REFERENCE MANUAL 1986
- Page 185 of 421
- MOV INIT_LDT_OFFSET.bas_24_31,AL
- ;
- ; Now GDT, IDT, initial TSS and initial LDT are all set up.
- ;
- ; Start the first task!
- '
- JMP ENTRY_POINTER
- RESET_CODE ends
- END START, SS:DUMMY,DS:DUMMY
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楼主: folklore
发表于 2007-08-31 00:44
