Restructure kernel to use 1-segment COM convention
This commit is contained in:
parent
71c89387fc
commit
84b754551c
6
Makefile
6
Makefile
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@ -1,5 +1,5 @@
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PROGRAMS = hello.com
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DISTFILES = kernel.bs $(PROGRAMS)
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DISTFILES = @rdos.com $(PROGRAMS)
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ROMS =
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QEMU = qemu-system-i386
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@ -43,7 +43,7 @@ host/%.elf: host/%.c
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%.bs: boot/%.asm
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$(NASM) $(NASM_ARGS) -o $@ $<
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kernel.bs: kernel/*.asm
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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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@ -62,7 +62,7 @@ fat6.bs: boot/fat.asm
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fd%.img: $(DISTFILES) $(SYS)
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mformat -C -i $@ -f $* -c 2 -v "$(LABEL)" ::
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mcopy -i $@ $(DISTFILES) ::
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$(SYS) $@ hello.com
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$(SYS) $@ @rdos.com
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clean:
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rm -f *.com *.bs *.0 *.lst *.img *.bin *.rom
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107
boot/kernel.asm
107
boot/kernel.asm
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@ -1,107 +0,0 @@
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cpu 8086
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org 0x0700
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%include "inc/bpb.asm"
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%include "inc/mbr.asm"
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%include "inc/dpt.asm"
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init: cli
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xor ax, ax
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mov ds, ax
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mov es, ax
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mov ss, ax
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mov sp, ax
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mov si, 0x7C00
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; relocate to 00700
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mov di, text_start
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mov cx, text_length + rodata_length + data_length
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rep movsb
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; clear out bss section
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mov cx, bss_length
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rep stosb
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; jump to copy
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call 0:relinit
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section .rodata
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%define V 0x %+ VERSION
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version: dd V
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section .text
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relinit: ; print banner
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push word [version]
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push word [version+2]
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call printf
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db "RDOS ",2,2, 0x0A, 0x0D, 0
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; initialize the disk i/o
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call dinit
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; init 21h vector
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mov word [0x21*4], int21
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mov word [0x21*4+2], cs
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; set current PSP, directly after us
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mov ax, stack
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mov cl, 4
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shr ax, cl
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mov word [curpsp], ax
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; also the DTA
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mov bx, dta
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call setdta
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; set current drive to boot drive
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mov al, dl
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rol al, 1
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rol al, 1
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or dl, al
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and dl, 3
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call setdd
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mov bx, testfcb
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call fndfst
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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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%include "kernel/drive.asm"
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%include "kernel/printf.asm"
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section .bss
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dta: resb 128
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section .data
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testfcb: db 0
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db "HELLO ", "COM"
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times 30 db 0
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section .text
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text_start equ $$
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text_length equ $-$$
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section .rodata
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rodata_start equ $$
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rodata_length equ $-$$
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section .data
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data_start equ $$
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data_length equ $-$$
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section .bss
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resw 256 ; 512b kern stack
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alignb 16
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stack: ; stack grows into this ^
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; this is also the end marker
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; programs with their psp start here
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bss_start equ $$
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bss_length equ $-$$
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@ -0,0 +1,38 @@
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org 0x100
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jmp init
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%defstr V VERSION
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banner: db "RDOS ", V, 0x0A, 0x0D, 0, 0x1A
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%include "kernel/far.asm"
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%include "inc/bpb.asm"
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%include "kernel/drive.asm"
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section .text
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init: call rstseg
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mov si, banner
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.l01: lodsb
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test al, al
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jz .l02
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mov ah, 0x0e
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xor bx, bx
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int 0x10
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jmp .l01
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.l02:
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call dinit
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mov dl, 0
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call logdrv
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xor ax, ax
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xor dx, dx
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call maprd
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inc word [dskbuf+0x80]
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call dirty
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call flush
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hlt: hlt
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jmp hlt
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16
host/sys.c
16
host/sys.c
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@ -117,14 +117,14 @@ int main(int argc, char** argv) {
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char* putsfunc = ptr;
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// assemble puts function
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ptr = push_imm16(ptr, 0xAC5E);
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ptr = push_imm16(ptr, 0xC084);
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ptr = push_imm16(ptr, 0x0874);
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ptr = push_imm16(ptr, 0x0EB4);
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ptr = push_imm16(ptr, 0xDB31);
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ptr = push_imm16(ptr, 0x10CD);
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ptr = push_imm16(ptr, 0xF3EB);
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ptr = push_imm16(ptr, 0xE6FF);
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//ptr = push_imm16(ptr, 0xAC5E);
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//ptr = push_imm16(ptr, 0xC084);
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//ptr = push_imm16(ptr, 0x0874);
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//ptr = push_imm16(ptr, 0x0EB4);
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//ptr = push_imm16(ptr, 0xDB31);
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//ptr = push_imm16(ptr, 0x10CD);
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//ptr = push_imm16(ptr, 0xF3EB);
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//ptr = push_imm16(ptr, 0xE6FF);
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// assemble entry point to our main code
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push_jmp(bs, ptr);
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@ -1,5 +0,0 @@
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DPTMTT equ 2
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DPTSS equ 3
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DPTSPT equ 4
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DPTSIZE equ 11
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203
kernel/drive.asm
203
kernel/drive.asm
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@ -5,78 +5,68 @@
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; - dirty: inform that dskbuf has been written to
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; access is done by accessing dskbuf directly
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DPTSIZE equ 11
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DPTSPT equ 4
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section .bss
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; drive actually selected for I/O
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dsknum: resb 1
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; bios drive we end up using
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biosnum: resb 1
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dap: resw 2
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.buf: resw 2
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; current sector number
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; absolute, ignores partition
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dskseek: resd 2
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biosnum resb 1
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; bit 0 (1) - dirty flag for dskbuf
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; bit 1 (2) - controller configured
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; bit 2 (4) - EBIOS supported
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dskflag: resb 1
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dskflag resb 1
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; disk buffer for I/O operations
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dskbuf: resb 512
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dskbuf resb 512
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dpt: resb DPTSIZE
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bpb: resb BPBSIZ4
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dpt resb DPTSIZE
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bpb resb BPBSIZ4
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section .data
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; drive actually selected for I/O
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dsknum db 0xFF
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dap db 0x10, 0
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dw 1
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dapbuf dw dskbuf, 0
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dskseek dw 0,0,0,0
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section .text
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; initial setup for disk i/o
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dinit: ; copy previously set DPT to our data area
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push ds
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push cs
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pop es
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lds si, [es:4*0x1E]
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mov di, dpt
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; copy previously set DPT to our data area
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dinit xor ax, ax
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mov es, ax
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les bx, [es:4*0x1E]
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mov dx, dpt
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mov cx, 11
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rep movsb
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; set vector
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mov word [cs:4*0x1E], dpt
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mov word [cs:4*0x1E+2], ds
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; set to invalid drive
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mov byte [cs:dsknum], 0xFF
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pop ds
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call lodfar
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; set interrupt vector
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mov es, cx
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mov word [es:4*0x1E], dpt
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mov word [es:4*0x1E+2], ds
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; set segment addr in DAP
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mov [dapbuf+2], cs
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ret
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; int 13 stub
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int13: ; debug output
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push bx
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push dx
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push cx
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push ax
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call printf
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db "int13 CALL AX=",2," CX=",2," DX=",2," BX=",2,0x0A,0x0D,0
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; do the call
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int 0x13
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jc .err
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ret
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.err: push ax
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call printf
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db "DISK ERR AX=",2,0x0A,0x0D,0
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stc
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; this is meant as a central place to implement
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; stack switching or some other safeguards
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int13 int 0x13
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ret
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; get drive parameters
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; read BIOS int13h/AH=8 values
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; DPT data gets copied over our dpt
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; CHS data gets inserted into our bpb
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getprm: ; skip if EBIOS extension enabled
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test byte [cs:dskflag], 4
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getprm test byte [dskflag], 4
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jnz .ret
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; do the query
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mov ah, 8
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mov dl, [cs:biosnum]
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mov dl, [biosnum]
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call int13
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; bail out if error
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jc .ret
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@ -85,43 +75,31 @@ getprm: ; skip if EBIOS extension enabled
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jz .nochs
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; get and store sector number
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and cx, 0x3F
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mov word [cs:bpb+BPBSPT], cx
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mov word [bpb+BPBSPT], cx
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; get and store number of heads
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xchg dl, dh
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and dx, 0xFF
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inc dx
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mov [cs:bpb+BPBNOS], dx
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mov [bpb+BPBNOS], dx
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; test if DPT ptr is non-zero
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.nochs: mov ax, es
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.nochs mov ax, es
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or ax, di
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test ax, ax
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jz .ret
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; DS:SI = ES:DI
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mov ax, es
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mov ds, ax
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mov si, di
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; ES:DI = dpt
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xor ax, ax
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mov es, ax
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mov di, dpt
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; do the copy
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mov cx, 11
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rep movsb
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.ret: ret
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; copy BIOS dpt table over ours
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mov dx, dpt
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mov bx, di
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call lodfar
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.ret ret
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; log in drive
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; IN dl drive number
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logdrv: ; DS := CS
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push cs
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pop ds
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; dont do anything if drive already selected
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cmp dl, [dsknum]
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logdrv cmp dl, [dsknum]
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je logfdd.ret
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; clear out current contents
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push dx
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push ds
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call flush
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pop ds
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mov ax, 0xFFFF
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mov [dskseek], ax
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mov [dskseek+2], ax
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@ -133,25 +111,20 @@ logdrv: ; DS := CS
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cmp dl, 2
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jnc loghdd
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logfdd: ; save info for bios
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mov [biosnum], dl
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; save info for bios
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logfdd mov [biosnum], dl
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; reset dpt to defaults
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push ds
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call getprm
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pop ds
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; set default geometry (1.44 MB floppy)
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mov word [bpb+BPBNOS], 2
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mov word [bpb+BPBSPT], 18
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; load boot sector
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push ds
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xor ax, ax
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xor dx, dx
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call mapabs
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pop ds
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; copy bios parameter block
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; TODO: guess from first byte of FAT if BPB invalid
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push ds
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pop es
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call rstseg
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mov si, dskbuf+BPBOFF
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mov di, bpb
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mov cx, BPBSIZ4
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@ -163,10 +136,9 @@ logfdd: ; save info for bios
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xor ax, ax
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mov [bpb+BPBHS], ax
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mov [bpb+BPBHS+2], ax
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.ret: ret
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.ret ret
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; assumes that DS == CS
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loghdd: sub dl, 2
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loghdd sub dl, 2
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cmp dl, 4
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jnc logerr
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push dx
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@ -180,16 +152,8 @@ loghdd: sub dl, 2
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jnz .chs
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; enable ebios and assume controller is configured
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or byte [dskflag], (2+4)
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; initialize DAP
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mov word [dap], 0x10
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mov word [dap+2], 1
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mov word [dap+4], dskbuf
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xor ax, ax
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mov word [dap+6], ax
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mov word [dap+12], ax
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mov word [dap+14], ax
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; get chs data (needed or we cant load vbr)
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.chs: call getprm
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.chs call getprm
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; read mbr
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xor ax, ax
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xor dx, dx
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@ -200,20 +164,17 @@ loghdd: sub dl, 2
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mov cl, 4
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sal bx, cl
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; bail out if no partition
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cmp byte [cs:dskbuf+0x1be+bx+4], 0
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cmp byte [dskbuf+0x1be+bx+4], 0
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je logerr
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; load partition offset
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mov ax, [cs:dskbuf+0x1be+bx+8]
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mov dx, [cs:dskbuf+0x1be+bx+8+2]
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mov ax, [dskbuf+0x1be+bx+8]
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mov dx, [dskbuf+0x1be+bx+8+2]
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; save to to stack
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push dx
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push ax
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; load vbr
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call mapabs
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; copy bpb
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mov ax, cs
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mov ds, ax
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mov es, ax
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mov si, dskbuf+BPBOFF
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mov di, bpb
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mov cx, BPBSIZ4
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@ -221,44 +182,44 @@ loghdd: sub dl, 2
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; fix CHS data
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call getprm
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; fix partition offset
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pop ax
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pop dx
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mov [cs:bpb+BPBHS], ax
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mov [cs:bpb+BPBHS+2], dx
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pop word [bpb+BPBHS]
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pop word [bpb+BPBHS+2]
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;pop [bpb+BPBNOS]
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;pop [bpb+BPBSPT]
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ret
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logerr: stc
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logerr stc
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ret
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mapclu: ; counting from begin of cluster area
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mov bx, [cs:bpb+BPBRDE]
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; counting from begin of cluster area
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mapclu mov bx, [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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maprd: ; counting from beginning of dir
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; counting from beginning of dir
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; add fat table sizes
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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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maprd 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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mapfat: ; counting from beginning of FAT
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; counting from beginning of FAT
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; add reserved sector count
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add ax, [cs:bpb+BPBRSC]
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mapfat add ax, [bpb+BPBRSC]
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adc dx, 0
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map: ; count from partition start
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add ax, [cs:bpb+BPBHS]
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add dx, [cs:bpb+BPBHS+2]
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mapabs: ; absolute sector count
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; count from partition start
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map add ax, [bpb+BPBHS]
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add dx, [bpb+BPBHS+2]
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; absolute sector count
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; skip doing a read if sector number matches
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cmp ax, [cs:dskseek]
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mapabs cmp ax, [dskseek]
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jne read
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cmp dx, [cs:dskseek+2]
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cmp dx, [dskseek+2]
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jne read
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ret
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read: push ax
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read push ax
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push dx
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call flush
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pop dx
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@ -271,9 +232,9 @@ read: push ax
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; low level read and write
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; call again to retry, no input registers
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; read or write is configured in cx
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_read: mov ch, 2
|
||||
_read mov ch, 2
|
||||
db 0x3D ; cmp ax, imm16: causes next instr to be skipped
|
||||
_write: mov ch, 3
|
||||
_write mov ch, 3
|
||||
mov cl, 1 ; read len
|
||||
; DS := ES := CS
|
||||
mov ax, cs
|
||||
|
|
@ -287,14 +248,14 @@ _write: mov ch, 3
|
|||
mov si, dap
|
||||
jmp .do
|
||||
; check if we can skip controller reset
|
||||
.l00: test byte [dskflag], 2
|
||||
.l00 test byte [dskflag], 2
|
||||
jnz .l01
|
||||
; do controller reset
|
||||
mov dl, [biosnum]
|
||||
mov ah, 0
|
||||
call int13
|
||||
or byte [dskflag], 2
|
||||
.l01: ; put sectors per cylinder into bx
|
||||
.l01 ; put sectors per cylinder into bx
|
||||
mov ax, [bpb+BPBSPT]
|
||||
mul word [bpb+BPBNOS]
|
||||
mov bx, ax
|
||||
|
|
@ -322,7 +283,7 @@ _write: mov ch, 3
|
|||
xchg cx, dx
|
||||
xchg dh, dl
|
||||
mov bx, dskbuf
|
||||
.do: mov dl, [biosnum]
|
||||
.do mov dl, [biosnum]
|
||||
; ah: subfunction selected via cx previously
|
||||
; al: 1 = reading 1 sector
|
||||
; cx: sector and cylinder number
|
||||
|
|
@ -335,19 +296,19 @@ _write: mov ch, 3
|
|||
and byte [dskflag], 0xFE
|
||||
clc
|
||||
ret
|
||||
.err: ; assume controller is misconfigured
|
||||
.err ; assume controller is misconfigured
|
||||
and byte [dskflag], 0xFD
|
||||
; exit with carry flag set
|
||||
stc
|
||||
ret
|
||||
|
||||
; mark dskbuf as containing unwritten changes
|
||||
dirty: or byte [cs:dskflag], 1 ; dirty
|
||||
dirty or byte [cs:dskflag], 1 ; dirty
|
||||
ret
|
||||
|
||||
; flush buffer if dirty
|
||||
flush: test byte [cs:dskflag], 1
|
||||
flush test byte [cs:dskflag], 1
|
||||
jz .ret
|
||||
; TODO: error handling & retries
|
||||
jmp _write
|
||||
.ret: ret
|
||||
.ret ret
|
||||
|
|
|
|||
|
|
@ -0,0 +1,34 @@
|
|||
; reset segments
|
||||
rstseg mov ax, cs
|
||||
mov ds, ax
|
||||
mov es, ax
|
||||
ret
|
||||
|
||||
; copy to far memory
|
||||
; IN es:bx far memory ptr (preserved)
|
||||
; ds:dx local ptr (preserved)
|
||||
; cx number of bytes to transfer
|
||||
; OUT cx set to zero
|
||||
; si & di trashed
|
||||
stofar mov si, dx
|
||||
mov di, bx
|
||||
rep movsb
|
||||
ret
|
||||
|
||||
; copy from far memory
|
||||
; IN es:bx far memory ptr (preserved)
|
||||
; ds:dx local ptr (preserved)
|
||||
; cx number of bytes to copy
|
||||
; OUT cx set to zero
|
||||
; si & di trashed
|
||||
lodfar call xchgdes
|
||||
mov si, bx
|
||||
mov di, dx
|
||||
rep movsb
|
||||
|
||||
; exchange es and ds
|
||||
xchgdes push ds
|
||||
push es
|
||||
pop ds
|
||||
pop es
|
||||
ret
|
||||
Loading…
Reference in New Issue