nivirx/stevia
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1KiB stack stage2 gets doesn't need extra information from the mbr/vbr now.

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Elaina Claus
2025-09-12 23:13:57 -04:00
parent a8b24c7b01
commit 40fa4062ce
2 changed files with 7 additions and 44 deletions
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13
src/mbr/mbr.nasm
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@@ -140,15 +140,7 @@ main:
je main.sig_ok
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
mov si, word [bp - 4] ; partition_offset address
mov dl, byte [bp - 2] ; pass drive # from BIOS to VBR in dl
mov bx, partition_table ; partition_table address
jmp word 0x0000:VBR_ENTRY
; ###############
@@ -181,14 +173,11 @@ BootSig:
section .bss follows=.text
begin_bss:
align 16, resb 1
partition_table resb PartTable_t_size
align 16, resb 1
lba_packet resb LBAPkt_t_size
align 512, resb 1
stack_bottom resb 512 - 16 ; 512 byte stack early on
stack_bottom resb 1024 - 16 ; 512 byte stack early on
stack_top:
mbr_redzone resb 16
end_bss:

32
src/vbr/vbr.nasm
View File

@@ -21,6 +21,7 @@
%define __STEVIA_VBR
section .text
__ENTRY:
phy_bpb_start:
jmp short (init - $$)
nop
@@ -92,24 +93,8 @@ init:
ALIGN 4, db 0x90
main:
mov byte [bp - 2], dl ; boot_drive
mov word [bp - 4], si ; part_offset (i.e offset into partition table our boot partition is
mov word [bp - 6], bx ; partition_table
.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
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
mov bx, fat32_bpb
mov bx, phy_bpb_start
test word [bx + FAT32_bpb_t.unused2_ZERO_word], 0 ; TotSectors16 will not be set if FAT32
jz main.load_stage2
ERROR VBR_ERROR_WRONG_FAT_SIZE
@@ -132,11 +117,7 @@ main:
call read_disk_raw
add sp, 0xC
.enter_stage2:
; TODO: review what we pass to stage2, do we need to do this?
mov dl, byte [bp - 2] ; byte boot_drive
mov ax, word [bp - 4] ; word part_offset
mov si, partition_table ; ptr partition_table
mov di, fat32_bpb ; ptr fat32_bpb
jmp word 0x0000:STAGE2_ENTRY
; ###############
@@ -157,18 +138,11 @@ BootSig:
section .bss follows=.text
begin_bss:
align 16, resb 1
partition_table resb PartTable_t_size
align 16, resb 1
fat32_bpb resb FAT32_bpb_t_size
fat32_ebpb resb FAT32_ebpb_t_size
align 16, resb 1
lba_packet resb LBAPkt_t_size
align 512, resb 1
stack_bottom resb (512 - 16) ; 512b stack early on
stack_bottom resb (1024 - 16) ; 512b stack early on
stack_top:
vbr_redzone resb 16
end_bss: