nivirx/stevia
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tons more work on modularizing the code

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This commit is contained in:
Elaina Claus
2024-10-05 18:55:00 -04:00
parent 5440a1ae61
commit 8f95c8f267
19 changed files with 360 additions and 296 deletions
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179
src/mbr/mbr.nasm
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@@ -23,17 +23,37 @@
[CPU KATMAI]
jmp short init
nop
%include "cdecl16.inc" ; include calling convention macros for cdecl16
%include "entry.inc" ; defines with entry points for various stages & stack
init:
cli ; We do not want to be interrupted
xor ax, ax ; 0 AX
mov ds, ax ; Set segment registers to 0
mov es, ax ; *
mov ss, ax ; Set Stack Segment to 0
mov sp, EARLY_STACK_START
; ###############
;
; Headers/Includes/Definitions
;
; ###############
%define __STEVIA_MBR
%include "cdecl16.inc"
%include "entry.inc"
%include "config.inc"
%include "mem.inc"
%include "error_codes.inc"
%include "partition_table.inc"
; ###############
; End Section
; ###############
ALIGN 4, db 0x90
init:
cli ; We do not want to be interrupted
xor ax, ax ; 0 AX
mov ds, ax ; Set segment registers to 0
mov ss, ax ; Set Stack Segment to 0
mov sp, EARLY_STACK_START ; Setup stack
mov bp, sp ; base ptr = stack ptr
sub sp, 0x20 ; local varible space
mov ch, 0x01 ; 256 WORDs in MBR (512 bytes), 0x0100 in cx
mov si, 0x7C00 ; Current MBR Address (loaded here by BIOS)
@@ -43,16 +63,28 @@ init:
sti
jmp 0:main
nop
%include "config.inc"
%include "memory.inc"
; ###############
;
; Extra/Shared Functions
;
; ###############
%include "kmem_func.inc"
%include "partition_table.inc"
%include "errors.inc"
%include "util/error_func.inc"
; ###############
; End Section
; ###############
;
; bp - 2 : uint8_t boot_drive
; bp - 4 : uint16_t part_offset
;
ALIGN 4, db 0x90
main:
mov [boot_drive], dl ; BIOS passes drive number in DL
mov byte [bp - 2], dl ; BIOS passes drive number in DL
.check_disk:
cmp dl, 0x80
@@ -62,7 +94,7 @@ main:
.check_extentions:
xor ax, ax
mov bx, 0x55AA
mov dl, byte [boot_drive]
mov dl, byte [bp - 2]
int 0x13
jnc main.find_active
ERROR MBR_ERROR_NO_INT32E ; no extended function support
@@ -83,25 +115,30 @@ main:
mov ax, bx
sub ax, DiskSig ; leaves us with the offset relative from start of table
; this gives us an offset from the begining of the partition table
mov word [part_offset], ax ; update part_offset
mov word [bp - 4], ax ; update part_offset
.read_data:
;uint8_t read_disk_raw(size_t count, uint16_t buf_segment, uint16_t buf_offset,
; uint16_t lower_lower_lba, uint16_t upper_lower_lba)
mov eax, dword [bx + PartEntry_t.lba_start]
ror eax, 16
push ax
movzx ax, byte [bp - 2]
push ax ; drive_num
ror eax, 16
push ax
mov ax, 0x1
push ax ; count
mov ax, VBR_ENTRY
push ax
mov dword eax, dword [bx + PartEntry_t.lba_start]
push dword eax ; lba
xor ax, ax
push ax ; segment = 0
push ax ; offset = 0
mov ax, VBR_ENTRY
shr ax, 4
push ax ; segment = 7C0
; uint8_t read_stage2_raw(uint16_t buf_segment, uint16_t buf_offset,
; uint32_t lba,
; uint16_t count, uint16_t drive_num)
call read_disk_raw
add sp, 0xC
call read_vbr_raw
add sp, 0x8
jnc main.goto_vbr
ERROR MBR_ERROR_DISK_READ_ERR ; error in LBA read
@@ -120,86 +157,16 @@ main:
call kmemcpy ; copy partition table to memory
add sp, 0x6
xor ah, ah ; Set Video mode BIOS function
mov al, 0x02 ; 16 color 80x25 Text mode
int 0x10 ; Call video interrupt
mov ah, 0x05 ; Select active display page BIOS function
xor al, al ; page 0
int 0x10 ; call video interrupt
mov si, word [part_offset]
mov dl, byte [boot_drive]
mov si, word [bp - 4]
mov dl, byte [bp - 2]
jmp 0:0x7C00
; Wrapper for AH=0x42 INT13h (Extended Read)
; ###############
;
; BIOS call details
; AH = 42h
; DL = drive number
; DS:SI -> disk address packet
; BIOS Functions
;
; Return:
; CF clear if successful
; AH = 00h
; CF set on error
; AH = error code
; disk address packet's block count field set to number of blocks
; successfully transferred
;
;
; uint8_t read_disk_raw(uint16_t buf_segment, uint16_t buf_offset, uint16_t lower_lower_lba, uint16_t upper_lower_lba)
read_vbr_raw:
__CDECL16_ENTRY
.func:
mov ax, 0x10
push ax ; len = 16 bytes
xor ax, ax
push ax ; val = 0
mov ax, lba_packet
push ax ; dest = lba_packet address
call kmemset
add sp, 0x06
mov byte [lba_packet + LBAPkt_t.size], 0x10
mov word [lba_packet + LBAPkt_t.xfer_size], 0x0001
mov ax, [bp + 10]
shl eax, 16
mov ax, [bp + 8]
mov dword [lba_packet + LBAPkt_t.lower_lba], eax
mov ax, [bp + 6]
mov word [lba_packet + LBAPkt_t.offset], ax
mov ax, [bp + 4]
mov word [lba_packet + LBAPkt_t.segment], ax
mov si, lba_packet
mov ah, 0x42
mov dl, byte [boot_drive]
int 0x13
jnc .endf
ERROR MBR_ERROR_INT13h_EREAD_ERR
.endf:
__CDECL16_EXIT
ret
; #############
;
; Locals
;
; #############
boot_drive:
db 0x00
mbr_reserved1:
db 0x00
; OFFSET from BEGINING of partition table, ie. DiskSig (-6 from PartEntry1)
part_offset:
dw 0x0000
; ###############
%include 'BIOS/func/ext_read.inc'
%assign bytes_remaining (440 - ($ - $$))
%warning MBR has bytes_remaining bytes remaining for code (MAX: 440 bytes)