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removed bpb_offset_bx dep

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reworked init: process
512 byte stack...should be more than enough for the vbr
This commit is contained in:
Elaina Claus
2024-10-15 12:57:54 -04:00
parent 2b9d0d9946
commit 8e2ca06406
1 changed files with 20 additions and 19 deletions
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33
src/vbr/vbr.nasm
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@@ -50,7 +50,6 @@ times 54 db 0x00
%include "error_codes.inc" %include "error_codes.inc"
%include "partition_table.inc" %include "partition_table.inc"
%include "fat32/fat32_structures.inc" %include "fat32/fat32_structures.inc"
%include "fat32/bpb_offset_bx.inc"
; ;
; dl = boot_drive ; dl = boot_drive
; si = part_offset ; si = part_offset
@@ -61,6 +60,12 @@ init:
xor ax, ax xor ax, ax
mov ds, ax ; Set segment registers to 0x0000 mov ds, ax ; Set segment registers to 0x0000
mov es, ax mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax ; Set Stack Segment to 0
mov sp, end_bss ; Setup stack
mov bp, sp ; base ptr = stack ptr
; zero bss section ; zero bss section
mov cx, (end_bss - begin_bss) ; count = bss length mov cx, (end_bss - begin_bss) ; count = bss length
@@ -70,13 +75,9 @@ init:
cld cld
rep stosb rep stosb
xor ax, ax sub sp, 0x20 ; local varible space
mov ss, ax ; Set Stack Segment to 0 push bp
mov sp, stack_top ; Setup stack
mov bp, sp ; base ptr = stack ptr
sub sp, 0x10 ; local varible space
mov cx, bx ; mov partition_table locaiton to cx
sti ; all done with inital setup and relocation, reenable interupts sti ; all done with inital setup and relocation, reenable interupts
jmp 0:main ; fix up cs:ip just in case and jump to relocated code jmp 0:main ; fix up cs:ip just in case and jump to relocated code
@@ -100,18 +101,19 @@ ALIGN 4, db 0x90
main: main:
mov byte [bp - 2], dl ; boot_drive mov byte [bp - 2], dl ; boot_drive
mov word [bp - 4], si ; part_offset mov word [bp - 4], si ; part_offset
mov word [bp - 6], cx ; partition_table mov word [bp - 6], bx ; partition_table
.load_fs_data: .load_fs_data:
mov ax, PartTable_t_size mov ax, PartTable_t_size ; count=
push ax push ax
mov ax, [bp - 6] ; ptr partition_table mov ax, [bp - 6] ; src= ptr partition_table
mov ax, partition_table push ax
mov ax, partition_table ; dst=
push ax push ax
call kmemcpy ; copy partition table data call kmemcpy ; copy partition table data
add sp, 0x6 add sp, 0x6
mov ax, (FAT32_bpb_t_size + FAT32_ebpb_t_size) ; size in byte mov ax, (FAT32_bpb_t_size + FAT32_ebpb_t_size) ; size in byte, should be 90 bytes
push ax push ax
mov ax, __ENTRY mov ax, __ENTRY
push ax push ax
@@ -120,9 +122,9 @@ main:
call kmemcpy ; copy bpb & ebpb to memory call kmemcpy ; copy bpb & ebpb to memory
add sp, 0x6 add sp, 0x6
mov bx, fat32_bpb ; bx now points to aligned memory structure
.check_FAT_size: ; we only support a very specific setup of FAT32 .check_FAT_size: ; we only support a very specific setup of FAT32
cmp dword [bsSectorHuge], 0 ; SectorsHuge will not be set if FAT12/16 mov bx, fat32_bpb
cmp dword [bx + FAT32_bpb_t.sector_count_32], 0 ; SectorsHuge will not be set if FAT12/16
ja main.load_stage2 ja main.load_stage2
ERROR VBR_ERROR_WRONG_FAT_SIZE ERROR VBR_ERROR_WRONG_FAT_SIZE
.load_stage2: .load_stage2:
@@ -185,8 +187,7 @@ align 16, resb 1
lba_packet resb LBAPkt_t_size lba_packet resb LBAPkt_t_size
align 512, resb 1 align 512, resb 1
stack_bottom resb 1024 ; 1Kib stack early on stack_bottom resb 512 ; 512b stack early on
stack_top: stack_top:
vbr_redzone resb 32 vbr_redzone resb 32
end_bss: end_bss: