cos_gdt.asm

操作系统实验教程核心技术与编程实例书中地例子代码

GDTSEG      SEGMENT PARA USE16              ;全局描述符表
GDT         LABEL BYTE
G_NULL      GDT_DESC <>
REAL_SEG    GDT_DESC <0FFFFH,0,0,92H,0,0>
REAL_SEL    = REAL_SEG - GDT
GDT_INIT_BEGIN LABEL BYTE                   ;setup to start*************
IDT         GDT_DESC <IDTLEN,IDTSEG,0,92H,0,0> ;92H=P ,DPL=0,TYPE=2
IDT_SEL     =  IDT - GDT
TOS_CODE    GDT_DESC <0FFFFH,TOS_CODESEG,0,9AH,0,0> ;9AH=exec/read ,DPL=0
            ;limit must be 0ffffh for returnning to real_mode
TOS_CODE_SEL = TOS_CODE - GDT
TOS_DATA    GDT_DESC <DATA_TOSLEN,DATA_TOS,0,92H,0,0> ;92H=P ,DPL=0,TYPE=2
TOS_DATA_SEL = TOS_DATA - GDT
TOS_STACK   GDT_DESC <TOS_STACKLEN,TOS_STACKSEG,0,92H,0,0>   ;96H=R/W ,DOWN
TOS_STACK_SEL = TOS_STACK - GDT
TOS_TSS     GDT_DESC <TOS_TSSLEN,TOS_TSSSEG,0,089H,0,0> ;89H=386TSS DPL=0
TOS_TSS_SEL  = TOS_TSS - GDT
GDT_ASDATA  GDT_DESC <GDTLEN,GDTSEG,0,92H,0,0>
GDT_ASDATA_SEL = GDT_ASDATA - GDT
TOS_TSSASDATA GDT_DESC <TOS_TSSLEN,TOS_TSSSEG,0,92H,0,0>
TOS_TSSASDATA_SEL  = TOS_TSSASDATA - GDT
USER_PsTSS_mov     GDT_DESC <USER_PsTSSLEN,USER_PsTSSSEG,0,92H,0,0> ;9AH=exec/read ,DPL=0
USER_PsTSS_mov_SEL  = USER_PsTSS_mov - GDT
USER_PsLDT_mov  GDT_DESC <USER_PsLDTLEN,USER_PsLDTSEG,0,92H,0,0>  ;11
USER_PsLDT_mov_SEL = USER_PsLDT_mov - GDT ;+ 04H
DATASEG     GDT_DESC <DATALEN,DATA,0,92H,0,0> ;92H=P ,DPL=0,TYPE=2
DATA_SEL    = DATASEG - GDT
;***************V86
;***************V86
V86_CODE         GDT_DESC <0FFFFH,V86CODESEG,0,0fAH,0,0> 
V86_CODE_SEL     = (V86_CODE - GDT)  
V86_DATA_GDT     GDT_DESC <0FFFFH,V86_DATASEG,0,92H,0,0> 
V86_DATA_GDT_SEL = (V86_DATA_GDT - GDT)  
V86TSS         GDT_DESC <V86TSSLEN,V86TSSSEG,0,89H,0,0> ;89H=386TSS DPL=0
V86TSS_SEL     =V86TSS - GDT 
V86TSS_ASDATA  GDT_DESC <V86TSSLEN,V86TSSSEG,0,92H,0,0> ;89H=386TSS DPL=0
V86TSS_ASDATA_SEL     =V86TSS_ASDATA - GDT 
V86LDTS        GDT_DESC <V86LDTLEN,V86LDTSEG,0,82H,0,0> ;82H=LDT DPL=0
V86LDT_SEL     =V86LDTS - GDT 
;***************V86
;***************V86
GDT_INIT_COUNT  = ($ - GDT_INIT_BEGIN)/(SIZE GDT_DESC) 
; seg_mode -->start
USER_segs_mov     GDT_DESC <0ffffh,0,0C0H,92H,0FH,0> ;9AH=exec/read ,DPL=0
USER_segs_mov_SEL  = USER_segs_mov - GDT
; seg_mode -->end

                ;setup to end *******************************************
V86_VRAM      GDT_DESC <0FFFFH,8000H,0BH,092H,0,0>   ;92H=P ,DPL=0,TYPE=2
V86_VRAM_SEL   =  V86_VRAM - GDT  ;60h
;;;;;;;;file system
V_SFT         GDT_DESC <0FFFFH,0,0FFH,92H,0,0FFH> ;92H=P ,DPL=0,TYPE=2 ,base=FFFF0000H
V_SFT_SEL     = V_SFT - GDT
V_FILE_BUF    GDT_DESC <0FFFFH,0,0FEH,92H,0,0FFH> ;92H=P ,DPL=0,TYPE=2 ,base=FFFE0000H
V_FILE_BUF_SEL = V_FILE_BUF - GDT
;;;;;;;;file system

;;for schedule
V_PCB          GDT_DESC <0ffFFH,0,080H,92H,0fH,0FFH> ;92H=P ,DPL=0,TYPE=2 ,base=FFFF0000H ;LIMIT=1m      
V_PCB_SEL     = V_PCB - GDT               ;LIMIT=4m      21
V_TOS_TSSASDATA     GDT_DESC <TOS_TSSLEN,1000H,40H,092H,0,0C0H> ;89H=386TSS DPL=0
V_TOS_TSSASDATA_SEL  = V_TOS_TSSASDATA - GDT
V_GDT_ASDATA  GDT_DESC <0FFFFH,2000H,40H,92H,0,0C0H>
V_GDT_ASDATA_SEL = V_GDT_ASDATA - GDT

;V_USER_SEGS   GDT_DESC <04FFH,0,40H,92H,10H,0FFH> ;92H=P ,DPL=0,TYPE=2 ,base=FFFF4000H ;LIMIT=4m      
V_USER_SEGS   GDT_DESC <0FFFFH,0,40H,92H,0FH,0FFH> ;92H=P ,DPL=0,TYPE=2 ,base=FFFF4000H ;LIMIT=1m      
V_USER_SEGS_SEL   = V_USER_SEGS - GDT

V_STACK0      GDT_DESC <4095,0,40H,92H,0,0FFH> ;92H=P ,DPL=0,TYPE=2 ,base=FFFD0000H
V_STACK0_SEL = V_STACK0 - GDT
V_USER_PsTSS     GDT_DESC <USER_PsTSSLEN,1000h,40h,089H,0,0FFH> ;9AH=exec/read ,DPL=0
V_USER_PsTSS_SEL  = V_USER_PsTSS - GDT
USER_PsTSS_D     GDT_DESC <USER_PsTSSLEN,1000h,40h,92H,0,0FFH> ;9AH=exec/read ,DPL=0
USER_PsTSS_D_SEL  = USER_PsTSS_D - GDT
V_USER_PsLDTT     GDT_DESC <4095,2000h,40h,82H,0,0FFH> ;82H=LDT
V_USER_PsLDT_SEL = V_USER_PsLDTT - GDT
USER_PsLDTT_ASDATA     GDT_DESC <4095,2000H,40H,92H,0,0FFH> ;82H=LDT
USER_PsLDTT_ASDATA_SEL = USER_PsLDTT_ASDATA - GDT          ;37
;;for schedule

;***********prepare page_memory
G_PDT       GDT_DESC <0FFFH,2000H,21H,92H,0,0>;92H=P ,DPL=0,TYPE=2 ,base=2M+68k
G_PDT_SEL    = G_PDT - GDT
G_PT0       GDT_DESC <0FFFFH,3000H,21H,92H,0,0>;92H=P ,DPL=0,TYPE=2 ,base=2M+72k ;16 PAGES
G_PT0_SEL    = G_PT0 - GDT
G_MOVSEG     GDT_DESC <0FFFFH,0,20H,92H,0FH,0> ;92H=P ,DPL=0,TYPE=2 ,base=2M
G_MOV_SEL    = G_MOVSEG - GDT                  ;LIMIT=1M

;***********next for page_memory
V_DOS_CODE  GDT_DESC <0FFFFH,0,0,9AH,0FH,0> ;9AH=exec/read ,DPL=0
V_DOS_CODE_SEL = V_DOS_CODE - GDT
G_VRAM      GDT_DESC <0FFFFH,0,0,92H,0,0C0H>   ;92H=P ,DPL=0,TYPE=2
G_VRAM_SEL   =  G_VRAM - GDT  
;G_BUF         GDT_DESC <1024,0,40H,92H,80H,0> ;92H=P ,DPL=0,TYPE=2 ,base=4M
G_BUF         GDT_DESC <0FFFFh,0,40H,92H,0FH,0> ;92H=P ,DPL=0,TYPE=2 ,base=4M
G_BUF_SEL     = G_BUF - GDT
V_G_PT0       GDT_DESC <0FFFFH,3000H,41H,92H,0,0C0H>
V_G_PT0_SEL    = V_G_PT0 - GDT
V_TOS_TSS     GDT_DESC <TOS_TSSLEN,1000H,40H,089H,0,0C0H> ;89H=386TSS DPL=0
V_TOS_TSS_SEL  = V_TOS_TSS - GDT                          
V_TOS_CODE    GDT_DESC <0FFFFH,3000H,42H,9AH,0,0C0H> ;9AH=exec/read ,DPL=0
             ;limit must be 0ffffh for returnning to real_mode
V_TOS_CODE_SEL = V_TOS_CODE - GDT                          ;31
V_TOS_STACK   GDT_DESC <01000H,3000H,43H,92H,0,0C0H>   ;96H=R/W ,DOWN 93
V_TOS_STACK_SEL = V_TOS_STACK - GDT
V_TOS_DATA    GDT_DESC <0FFFFH,4000H,43H,92H,0,0C0H> ;92H=P ,DPL=0,TYPE=2
V_TOS_DATA_SEL = V_TOS_DATA - GDT

ps_to_tos_sel  =$

GDTLEN      = $ - GDT
GDTSEGLEN   = $
GDTSEG      ENDS