nivirx/stevia
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base: nivirx:aa0efe5ff83a3fb1c9f0026b60df08dda9877c95
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nivirx:trunk nivirx:fat_v2 nivirx:fat32_sys_rewrite
nivirx:v0.0.1
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compare: nivirx:3c654b1be0f125ebe4ca0c8ee54fbbc66b3cf327
Branches Tags
nivirx:fat_v2 nivirx:trunk nivirx:fat32_sys_rewrite
nivirx:v0.0.1

3 Commits
aa0efe5ff8 ... 3c654b1be0

Author SHA1 Message Date
Elaina Claus
3c654b1be0 more rtfm'ing with encoding, 25 bytes of free code space in vbr now 2025-09-09 18:37:39 -04:00
Elaina Claus
0d90b3efd6 I rtfm'ed and saw there was a push m/16 encoding 
mbr now has 93 bytes free for more code
 2025-09-09 18:25:24 -04:00
Elaina Claus
b08605f295 remove dep on fat32_structures 2025-09-09 17:47:17 -04:00
2 changed files with 30 additions and 51 deletions
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35
src/mbr/mbr.nasm
View File

@@ -33,7 +33,6 @@ nop
%include "config.inc"
%include "error_codes.inc"
%include "partition_table.inc"
%include "fat32/fat32_structures.inc"
%undef __STEVIA_DEV_DEBUG
@@ -58,7 +57,7 @@ init:
cld
rep stosb ; zero bss section
sub sp, 0x20 ; local varible space (32 bytes)
sub sp, 0x10 ; local varible space (32 bytes)
push bp ; setup top of stack frame
xor cx, cx
@@ -121,19 +120,14 @@ main:
mov word [bp - 4], ax ; update part_offset
.read_data:
movzx ax, byte [bp - 2]
push ax ; drive_num
mov ax, 0x1
push ax ; count
push ax ; drive_num (2)
push 0x01 ; count (2)
mov dword eax, dword [bx + PartEntry_t.lba_start]
push dword eax ; lba
push dword eax ; lba (4)
mov ax, VBR_ENTRY
push ax ; offset = 0x7c00
xor ax, ax
push ax ; segment = 0
push word VBR_ENTRY ; offset = 0x7c00 (2)
push 0x00 ; segment = 0 (2)
; uint8_t read_stage2_raw(uint16_t buf_segment, uint16_t buf_offset,
; uint32_t lba,
@@ -143,14 +137,11 @@ main:
.goto_vbr:
cmp word [VBR_ENTRY + 0x1FE], 0xAA55
je main.sig_ok
ERROR MBR_ERROR_NO_VBR_SIG ; no signature present
.sig_ok:
mov ax, PartTable_t_size
push ax
mov ax, DiskSig ; start of partition table
push ax
mov ax, partition_table
push ax
ERROR MBR_ERROR_NO_VBR_SIG ; no signature present
.sig_ok:
push PartTable_t_size ; len
push DiskSig ; src -> start of partition table
push partition_table ; dst -> addr in bss
call kmemcpy ; copy partition table to bss
add sp, 0x6
@@ -196,7 +187,7 @@ align 16, resb 1
lba_packet resb LBAPkt_t_size
align 512, resb 1
stack_bottom resb 512 ; 512 byte stack early on
stack_bottom resb 512 - 16 ; 512 byte stack early on
stack_top:
mbr_redzone resb 32
mbr_redzone resb 16
end_bss:

46
src/vbr/vbr.nasm
View File

@@ -72,7 +72,7 @@ init:
cld
rep stosb
sub sp, 0x20 ; local varible space (32 bytes)
sub sp, 0x10 ; local varible space (32 bytes)
push bp
sti ; all done with inital setup and relocation, reenable interupts
@@ -100,23 +100,17 @@ main:
mov word [bp - 4], si ; part_offset
mov word [bp - 6], bx ; partition_table
.load_fs_data:
mov ax, PartTable_t_size ; count=
push ax
mov ax, [bp - 6] ; src= ptr partition_table
push ax
mov ax, partition_table ; dst=
push ax
call kmemcpy ; copy partition table data
.load_fs_data:
push PartTable_t_size ; count=
push word [bp - 6] ; src= ptr partition_table
push partition_table ; dst=
call kmemcpy ; copy partition table data to bss
add sp, 0x6
mov ax, (FAT32_bpb_t_size + FAT32_ebpb_t_size) ; size in byte, should be 90 bytes
push ax
mov ax, __ENTRY
push ax
mov ax, fat32_bpb ;
push ax
call kmemcpy ; copy bpb & ebpb to memory
push (FAT32_bpb_t_size + FAT32_ebpb_t_size) ; size in byte, should be 90 bytes
push __ENTRY ; src
push fat32_bpb ; dst
call kmemcpy ; copy bpb & ebpb to bss
add sp, 0x6
.check_FAT_size: ; we only support a very specific setup of FAT32
@@ -129,17 +123,13 @@ main:
movzx ax, byte [bp - 2]
push ax ; drive_num
mov ax, STAGE2_SECTOR_COUNT
push ax ; count
push STAGE2_SECTOR_COUNT ; count
mov dword eax, 0x1
push dword eax ; lba
mov ax, STAGE2_ENTRY
push ax ; offset
xor ax, ax
push ax ; segment = 0
push STAGE2_ENTRY ; offset
push 0x00 ; segment = 0
; uint8_t read_stage2_raw(uint16_t buf_segment, uint16_t buf_offset,
; uint32_t lba,
@@ -166,6 +156,7 @@ times (510 - ($ - $$)) nop ; Fill the rest of sector with nop
BootSig:
dw 0xAA55 ; Add boot signature at the end of bootloader
; !!! END VBR !!!
section .bss follows=.text
begin_bss:
@@ -177,14 +168,11 @@ align 16, resb 1
fat32_bpb resb FAT32_bpb_t_size
fat32_ebpb resb FAT32_ebpb_t_size
align 16, resb 1
fat32_nc_data resb 16
align 16, resb 1
lba_packet resb LBAPkt_t_size
align 512, resb 1
stack_bottom resb 512 ; 512b stack early on
stack_bottom resb (512 - 16) ; 512b stack early on
stack_top:
vbr_redzone resb 32
vbr_redzone resb 16
end_bss: