Remove remnants from earlier kernel attempts
This commit is contained in:
parent
f7d7f48026
commit
0bd59dd252
2
Makefile
2
Makefile
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@ -40,8 +40,6 @@ host/%.elf: host/%.c
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%.bs: boot/%.asm
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$(NASM) $(NASM_ARGS) -o $@ $<
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@rdos.com: kernel/*.asm
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# Special case: variations of FAT vbr
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fat1.bs: boot/fat.asm
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$(NASM) $(NASM_ARGS) -DFAT12 -DCHS -o $@ $<
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@ -1,95 +0,0 @@
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; read/write data from FAT clusters
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; requires defines from fcb.asm
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section .rodata
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; sector sizes for fast lookup
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sstab dw 0x800,0x400,0x200,0x100,0x80
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section .text
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; Map part of cluster into dskbuf
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; IN DX:AX sector number within cluster area
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mapclus mov bx, [cs:bpb+BPBRDE]
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mov cl, 4
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shr bx, cl ; 32 bytes per entry
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add ax, bx
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adc dx, 0
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; counting from beginning of dir
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; add fat table sizes
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maprde xor ch, ch
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mov cl, byte [cs:bpb+BPBFN]
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.loop add ax, [cs:bpb+BPBFS]
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adc dx, 0
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loop .loop
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; counting from beginning of FAT
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; add reserved sector count
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mapfat add ax, [cs:bpb+BPBRSC]
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adc dx, 0
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jmp maprel
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; split AX at a bit boundary
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; basically a DIV 2^CX
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; IN ax divident
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; cx integer log2(divisor)
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; OUT ax quotient
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; dx remainder (lower CX bits)
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split mov dx, 1
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shl dx, cl
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dec dx
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and dx, ax
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shr ax, cl
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ret
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filesec call fcbdrv
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mov bx, dx
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; find sector size scale factor
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mov ax, cs
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mov es, ax
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mov ax, [cs:bpb+BPBSS]
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mov di, sstab
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mov cx, 5
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repne scasw
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; CX is now sector size div 128
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; same format as in DPT
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mov ah, 0
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mov al, [ds:bx+FCBRN]
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call split
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; ax = sector within current cluster
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; dx = record number
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push dx
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mov di, ax
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mov ax, [ds:bx+FCBCLUS]
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sub ax, 2
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mov ch, 0
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mov cl, [cs:bpb+BPBSC]
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mul cx
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add ax, di
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call mapclus
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pop bx
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mov cl, 7
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shl bx, cl
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add bx, dskbuf
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mov dx, bx
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mov ax, cs
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mov ds, ax
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ret
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read mov bp, sp
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call filesec
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call getdta
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mov cx, 0x80
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call stofar
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ret
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write mov bp, sp
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call filesec
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call getdta
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mov cx, 0x80
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call lodfar
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call dirty
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ret
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125
kernel/fat.asm
125
kernel/fat.asm
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@ -1,125 +0,0 @@
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section .bss
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clus resw 1
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section .text
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; Set cluster for next operations
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; IN dx cluster number
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setclus mov [clus], dx
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ret
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; get ptr to single byte in fat table
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; IN dx position byte in fat table
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; OUT bx ptr to byte in dskbuf
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_fat1 push dx
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mov ax, dx
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xor dx, dx
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mov cl, 9
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shr ax, cl
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add ax, [bpb+BPBRSC]
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adc dx, 0
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call map
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pop dx
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mov bx, dx
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and bx, 0x1FF
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add bx, dskbuf
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ret
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; get ptr to word in fat table
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_fat2 push dx
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mov ax, dx
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xor dx, dx
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mov cl, 8
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shr ax, cl
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add ax, [bpb+BPBRSC]
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adc dx, 0
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call map
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pop dx
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mov bl, dl
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mov bh, 0
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add bx, bx
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add bx, dskbuf
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ret
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; read value from fat table
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; index given with setclus
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; OUT bx value
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; carry set if EOF marker
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rdfat mov dx, [clus]
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mov ax, dx
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shr ax, 1
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add dx, ax
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call _fat1
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push word [bx]
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inc dx
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call _fat1
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mov si, bx
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pop bx
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mov bh, [si]
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test word [clus], 1
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jz l001
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mov cl, 4
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shr bx, cl
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l001 and bx, 0xFFF
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cmp bx, 0xFF0
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cmc
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ret
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; set value in FAT table
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; IN dx value
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wrfat and dh, 0x0F
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push dx
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; DX = index * 1.5
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mov dx, [clus]
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mov ax, dx
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shr dx, 1
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add dx, ax
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call _fat1
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pop ax
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test [clus], 1
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jnz l004
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; even, first byte full
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mov [bx], al
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push ax
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call dirty
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; DX = index * 1.5
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mov dx, [clus]
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mov ax, dx
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shr dx, 1
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add dx, ax
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inc dx
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call _fat1
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pop ax
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mov al, [bx]
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and al, 0xF0
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or al, ah
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mov [bx], al
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call dirty
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jmp l005
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; odd, second byte full
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l004: mov ch, [bx]
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; concat existing and our nib
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and ch, 0x0F
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mov cl, 4
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shl ax, cl
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or al, ch
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; write back lower 4 bits
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mov [bx], al
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call dirty
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push ax
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; re-calculate offset
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mov ax, dx
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shr dx, 1
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add dx, ax
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inc dx
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; map second byte
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call _fat1
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pop ax
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; write higher 8 bits
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mov [bx], ah
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call dirty
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l005: ret
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; wrfat from above, FAT16 flavour
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wf16: ret
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@ -1,59 +0,0 @@
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; FCB layout
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struc FCB
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FCBDRV resb 1 ; BYTE drive (0=default, 1=A:, 2=B:, ...)
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FCBFN resb 11 ; 11 BYTES filename
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FCBCLUS resw 1 ; DWORD current cluster
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FCBRN resb 1 ; BYTE record in cluster
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endstruc
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FCBSIZ equ FCB_size
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section .data
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defdrv db 0
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dta dd 0
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section .text
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; auto-complete drive field in fcb
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; also logs in the drive
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; IN ds:dx far ptr FCB
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fcbdrv push ds
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push dx
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mov si, dx
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; if currently zero, ...
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mov dl, [si] ; 1-based
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test dl, dl
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jnz .log
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; replace with current drive
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mov dl, [cs:defdrv] ; 0-based
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inc dl
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mov [si], dl ; 1-based
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.log dec dl
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mov ax, cs
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mov ds, ax
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call logdrv ; 0-based
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pop dx
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pop ds
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; if carry flag set, resume stack at bp
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; this instant-returns some higher level procs
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jnc .ret
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mov sp, bp
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; duplicate carry bit into all 8 AL bits
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; similar to SALC instruction
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.ret sbb al, al
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ret
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; set disk transfer address
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; IN DS:DX dta ptr
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setdta mov [cs:dta], dx
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mov [cs:dta+2], ds
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ret
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; get disk transfer address
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; OUT ES:BX dta ptr
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getdta les bx, [cs:dta]
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ret
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@ -1,8 +0,0 @@
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org 0
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jmp init
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init: mov ax, 0x0e37
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int 0x10
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hlt: hlt
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jmp hlt
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@ -1,66 +0,0 @@
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section .bss
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printr:
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.ax: resw 1
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.cx: resw 1
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.dx: resw 1
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.bx: resw 1
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section .text
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; Stack contents
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; ret-addr arg1 arg2 arg3 ...
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printf: mov [printr.ax], ax
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mov [printr.cx], cx
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mov [printr.dx], dx
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mov [printr.bx], bx
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pop bx
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.loop: mov al, [cs:bx]
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inc bx
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cmp al, 0
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je .end
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cmp al, 2
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je .word
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call pputc
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jmp .loop
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.end: push bx
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mov ax, [printr.ax]
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mov cx, [printr.cx]
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mov dx, [printr.dx]
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mov bx, [printr.bx]
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ret
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.word: pop dx
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call pdx
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jmp printf.loop
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pdx: ; this double-call is essentially a 4 times repeating loop
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call .l1
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.l1: call .l2
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.l2: ; set up cl for bit shifts
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mov cl, 4
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; grab highest nibble from dx
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mov al, dh
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; remove highest nibble from dx
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shl dx, cl
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; shift away second-highest nibble that we accidentally copied
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shr al, cl
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; map 0-9 to ascii codes for '0' to '9'
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add al, 0x30
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; if result is larger than '9', ...
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cmp al, 0x3a
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jl pputc
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; ... add 7 so we continue at 'A'
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add al, 7
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pputc: push bx
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mov ah, 0x0e
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xor bx, bx
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int 0x10
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pop bx
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ret
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@ -1,62 +0,0 @@
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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 ds
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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 ds
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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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@ -1,113 +0,0 @@
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; Load root directory entry into buffer
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; IN ax number of directory entry
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; OUT cs:di ptr to directory entry
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lddir push ax
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push ax
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call rstseg
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pop ax
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mov cl, 4
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shr ax, cl
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xor dx, dx
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; dx:ax = sector number in rootdir
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; add sizes of FAT tables
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xor ch, ch
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mov cl, byte [bpb+BPBFN]
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.loop: add ax, [bpb+BPBFS]
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adc dx, 0
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loop .loop
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; add reserved sector count
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add ax, [bpb+BPBRSC]
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adc dx, 0
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; fetch sector (relative to partition)
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call maprel
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; get di to point to entry
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pop di
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mov cl, 5
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shl di, cl
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and di, 0x1FF
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add di, dskbuf
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ret
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; find first matching file
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; IN DS:DX input fcb
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fndfst mov bp, sp
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call fcbdrv
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; set search state to zero
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les di, [cs:dta]
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xor ax, ax
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mov [es:di+FCBSIZ], ax
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; find next matching file
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; state is kept in DTA
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fndnxt mov bp, sp
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call fcbdrv
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; get next direntry to fetch
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; get number of current entry from DTA
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.loop les di, [cs:dta]
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mov ax, [es:di+FCBSIZ]
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inc word [es:di+FCBSIZ]
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; bail out if we are at end of dir
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cmp ax, [cs:bpb+BPBRDE]
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jnc .err
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; load entry and first byte
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push ds
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push dx
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call lddir
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pop dx
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pop ds
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; next if hidden, dir or vol label
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test byte [cs:di+0x0B], 0xDA
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jnz .loop
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; bail out if end of dir
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mov al, [cs:di]
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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 .loop
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; DS:SI := FCB+1
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; ES:DI := CS:dirent
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mov si, dx
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push si
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inc si
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mov ax, cs
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mov es, ax
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; compare and ; try next if mismatch
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mov cx, 11
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push di
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rep cmpsb
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pop di
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pop si
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jne .loop
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; create FCB in DTA
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call getdta
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xchg bx, di
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; copy over drive byte
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movsb
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; copy filename
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push ds
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push si
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mov ax, cs
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mov ds, ax
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mov si, bx
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mov cx, 11
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rep movsb
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pop si
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pop ds
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; done!
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xor ax, ax
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ret
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.err: stc
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.ret: sbb al, al
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ret
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open call fndfst
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test al, al
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jnz .ret
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; read start cluster
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mov ax, [cs:bx+0x1A]
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mov bx, dx
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mov [ds:bx+FCBCLUS], ax
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; reset record number
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mov byte [ds:bx+FCBRN], 0
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.ret ret
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@ -1,102 +0,0 @@
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; This is the syscall gateway:
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; - backs up the data from user space (kernel funcs trash many regs)
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; - sets up the kernel stack
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; - calls kernel funcs
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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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; Kernel code can expect CS = DS
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section .rodata
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stab: ; syscall table
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; cells: ptr to handler, ptr to sysret
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; 0-7
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dw restart, sret
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dw getc, sretb
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dw putc, sret
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dw err, sret ; reader input
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dw err, sret ; punch outout
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dw err, sret ; list output
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dw conio, sret ; direct console i/o
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dw err, sret
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; 8-f
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dw err, sret
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dw err, sret ; print string
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dw err, sret ; read into buffer
|
||||
dw err, sret ; console status
|
||||
dw err, sret ; return version num
|
||||
dw err, sret ; reset disks
|
||||
dw setdd, sret ; select disk
|
||||
dw open, sretb ; open file
|
||||
.end:
|
||||
|
||||
section .text
|
||||
|
||||
; WARNING: BP, SI and DI are not saved
|
||||
; If kernel code uses them, they need to be saved to the stack
|
||||
int21: push ds
|
||||
; load program PSP and save userdata
|
||||
mov ds, [cs:curpsp]
|
||||
pop word [PSPDS]
|
||||
mov [PSPES], es
|
||||
|
||||
mov [PSPAX], ax
|
||||
mov [PSPCX], cx
|
||||
mov [PSPDX], dx
|
||||
mov [PSPBX], bx
|
||||
|
||||
mov [PSPSS], ss
|
||||
mov [PSPSP], sp
|
||||
|
||||
xor bx, bx
|
||||
mov ss, bx
|
||||
mov sp, stack
|
||||
; get ptr into syscall table
|
||||
mov bl, [PSPAX+1] ; bh is still 0
|
||||
shl bx, 1
|
||||
shl bx, 1
|
||||
add bx, stab
|
||||
; load sysret and handler ptr
|
||||
push word [cs:bx+2]
|
||||
push word [cs:bx]
|
||||
; DS is always our segment
|
||||
push cs
|
||||
pop ds
|
||||
; ES:BX is syscall argument
|
||||
mov bx, [PSPDX]
|
||||
mov es, [PSPDS]
|
||||
ret
|
||||
|
||||
err: mov ah, 0xFF
|
||||
ret
|
||||
|
||||
; sysret handlers
|
||||
; return ES:BX to user
|
||||
sretd: mov ds, [cs:curpsp]
|
||||
jmp sret.l02
|
||||
|
||||
; return BX to user
|
||||
sretw: mov ds, [cs:curpsp]
|
||||
mov es, [PSPES]
|
||||
jmp sret.l02
|
||||
|
||||
; return carry flag in AL
|
||||
sretc: mov ds, [cs:curpsp]
|
||||
sbb al, al
|
||||
|
||||
; return AL to user
|
||||
sretb: mov ds, [cs:curpsp]
|
||||
mov ah, [PSPAX+1]
|
||||
les bx, [PSPBX]
|
||||
jmp sret.l03
|
||||
|
||||
; return without result
|
||||
sret: mov ds, [cs:curpsp]
|
||||
les bx, [PSPBX]
|
||||
.l02: mov ax, [PSPAX]
|
||||
.l03: mov ss, [PSPSS]
|
||||
mov sp, [PSPSP]
|
||||
mov cx, [PSPCX]
|
||||
lds dx, [PSPDX] ; DS last
|
||||
iret
|
||||
Loading…
Reference in New Issue