Single out PSP management
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@ -3,7 +3,6 @@
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%include "inc/bpb.asm"
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%include "inc/mbr.asm"
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%include "inc/fcb.asm"
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%include "inc/dpt.asm"
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init: cli
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@ -56,10 +55,6 @@ relinit: ; print banner
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sub dl, (0x80-2)
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.k: call setdd
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mov ah, 2
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mov dl, 0x37
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int 0x21
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mov dx, testfcb
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mov ah, 0xF
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int 0x21
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@ -68,6 +63,7 @@ restart:
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hlt: hlt
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jmp hlt
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%include "kernel/psp.asm"
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%include "kernel/syscall.asm"
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%include "kernel/char.asm"
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%include "kernel/fcb.asm"
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@ -1,2 +0,0 @@
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FCBDEN: equ 23 ; directory entry
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FCBSIZ: equ 30
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@ -1,35 +1,27 @@
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; FCB layout
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; 1 byte drive (0=default, 1=A:, 2=B:, ...)
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; 8.3 filename
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; 8.3 filename for rename
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FCBDEN: equ 23 ; WORD directory entry number
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FCBSIZ: equ 30
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section .text
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; set default drive for current process
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; IN dl drive number
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setdd: push ds
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mov ds, [cs:curpsp]
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mov [PSPDD], dl
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pop ds
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ret
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; get default drive for current process
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; OUT al drive number
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getdd: push ds
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mov ds, [cs:curpsp]
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mov al, [PSPDD]
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pop ds
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ret
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; auto-complete drive field in fcb
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; IN ds:dx far ptr FCB
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; OUT si copy of dx
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fixfcb: mov si, dx
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cmp byte [si], 0
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; IN es:bx far ptr FCB
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; OUT si copy of bx
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fixfcb: cmp byte [es:bx], 0
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jne .ret
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call getdd
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inc dl
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mov byte [si], dl
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.ret: mov dx, si
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ret
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mov byte [es:bx], dl
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.ret: ret
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; Load root directory entry
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; IN ax number of directory entry
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; OUT cs:si ptr to directory entry
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lddir: push ax
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mov cl, 4
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shr ax, cl
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@ -43,33 +35,10 @@ lddir: push ax
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add si, dskbuf
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ret
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; find next file
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fnfile: mov ax, [es:bx+FCBDEN]
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inc word [es:bx+FCBDEN]
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; bail out if we are at end of dir
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cmp ax, [bpb+BPBRDE]
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jnc .err
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; load entry and first byte
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push bx
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call lddir
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pop bx
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; next if hidden, dir or vol label
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test byte [si+0x0B], 0xDA
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jnz fnfile
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; bail out if end of dir
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mov al, [si]
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cmp al, 0
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je .err
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; next if deleted entry
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cmp al, 0xE5
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je fnfile
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clc
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ret
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.err: stc
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ret
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; find first matching file
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; IN ES:BX input fcb
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fndfst:
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; Open file using FCB
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; IN DS:DX far ptr to FCB
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open: call fixfcb
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int 3
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open:
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ret
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62
kernel/psp.asm
Normal file
62
kernel/psp.asm
Normal file
@ -0,0 +1,62 @@
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; Program segment prefix headers and constants
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section .bss
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curpsp: resw 1
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absolute 0
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resb 2 ; ret 0 exit
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resb 2 ; next unusable segment
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PSPDD: resb 1 ; BYTE default drive
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; CP/M entry point
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resb 1 ; instruction byte
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resw 1 ; usable length of segment (needs to be here for compata)
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resb 4 ; opcodes to call us
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; saved userdata
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PSPAX: resw 1
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PSPCX: resw 1
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; SS:SP
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PSPSP: resw 1
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PSPSS: resw 1
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; DS:DX
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PSPDX: resw 1
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PSPDS: resw 1
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; ES:BX
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PSPBX: resw 1
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PSPES: resw 1
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PSPDTA: resd 1 ; DWORD ptr to disk transfer area
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section .text
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; set default drive for current process
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; IN dl drive number
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setdd: push es
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mov es, [curpsp]
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mov [es:PSPDD], dl
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pop es
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ret
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; get default drive for current process
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; OUT al drive number
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getdd: push es
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mov es, [curpsp]
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mov al, [es:PSPDD]
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pop es
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ret
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; set DTA ptr
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; IN es:bx far ptr
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setdta: push es
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mov ds, [curpsp]
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mov [PSPDTA], bx
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mov [PSPDTA+2], es
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pop es
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; get DTA ptr
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; OUT es:bx far ptr
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getdta: mov es, [curpsp]
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les bx, [es:PSPDTA]
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ret
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@ -5,11 +5,7 @@
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; - exports a specified set of registers back to userspace
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;
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; The syscall table acts as a "export"-list for kernel near funcs.
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; Code invoked via it can reply on SS being zero.
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section .bss
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curpsp: resw 1
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; Kernel code can expect CS = DS
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section .rodata
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@ -37,31 +33,6 @@ stab: ; syscall table
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section .text
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absolute 0
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resb 2 ; ret 0 exit
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resb 2 ; allocation length
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resb 1
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resb 5 ; CP/M entry point
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; saved userdata
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PSPAX: resw 1
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PSPCX: resw 1
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; SS:SP
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PSPSP: resw 1
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PSPSS: resw 1
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; DS:DX
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PSPDX: resw 1
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PSPDS: resw 1
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; ES:BX
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PSPBX: resw 1
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PSPES: resw 1
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; default drive
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PSPDD: resb 1
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section .text
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; WARNING: BP, SI and DI are not saved
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; If kernel code uses them, they need to be saved to the stack
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int21: push ds
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@ -89,9 +60,12 @@ int21: push ds
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; load sysret and handler ptr
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push word [cs:bx+2]
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push word [cs:bx]
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; restore user data and launch ret chain
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mov bx, [PSPBX]
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mov ds, [PSPDS]
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; DS is always our segment
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push cs
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pop ds
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; ES:BX is syscall argument
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mov bx, [PSPDX]
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mov es, [PSPDS]
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ret
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err: mov ah, 0xFF
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@ -107,6 +81,10 @@ sretw: mov ds, [cs:curpsp]
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mov es, [PSPES]
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jmp sret.l02
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; return carry flag in AL
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sretc: mov ds, [cs:curpsp]
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sbb al, al
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; return AL to user
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sretb: mov ds, [cs:curpsp]
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mov ah, [PSPAX+1]
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