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a few fixes to complete the move

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Elaina Claus
2025-09-18 14:25:27 -04:00
parent 5f2ca55af7
commit 1e9de446f0
2 changed files with 14 additions and 116 deletions
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23
include/fat32/FAT32_SYS.nasm
View File

@@ -16,7 +16,6 @@
%ifndef __INC_FAT32_SYS %ifndef __INC_FAT32_SYS
%include "partition_table.inc" %include "partition_table.inc"
%include "fat32/bpb_offset_bx.inc"
%include "fat32/fat32_structures.inc" %include "fat32/fat32_structures.inc"
; int read_mbr(int boot_drive, void* dst) ; int read_mbr(int boot_drive, void* dst)
@@ -38,7 +37,7 @@ FAT32_load_mbr:
.check_sig: .check_sig:
mov bx, [bp + 6] mov bx, [bp + 6]
cmp word [bx + 0x1FE], 0xAA55 ; check for bytes at end cmp word [bx + 0x1FE], 0xAA55 ; check for bytes at end
jne ReadMbrData.error_nosign jne .error_nosign
; TODO: this needs more error checking, zero checking, check the sig a bunch of stuff... ; TODO: this needs more error checking, zero checking, check the sig a bunch of stuff...
.endp: .endp:
__CDECL16_PROC_EXIT __CDECL16_PROC_EXIT
@@ -61,21 +60,21 @@ FAT32_load_vbr:
.find_active_L0: .find_active_L0:
mov al, [bx + PartEntry_t.attributes] mov al, [bx + PartEntry_t.attributes]
cmp al, 0x80 ; 0x80 == 1000_0000b cmp al, 0x80 ; 0x80 == 1000_0000b
je ReadVbrData.check_fstype je .check_fstype
add bx, PartEntry_t_size ; next part entry's attributes add bx, PartEntry_t_size ; next part entry's attributes
loop ReadVbrData.find_active_L0 loop .find_active_L0
jmp ReadVbrData.error_noactive jmp .error_noactive
.check_fstype: .check_fstype:
; check for part_type = 0x0C (DOS 7.1+/W95 FAT32 w/ LBA) or 0x1C (Hidden 0x0C) ; check for part_type = 0x0C (DOS 7.1+/W95 FAT32 w/ LBA) or 0x1C (Hidden 0x0C)
__BOCHS_MAGIC_DEBUG __BOCHS_MAGIC_DEBUG
mov al, [bx + PartEntry_t.part_type] mov al, [bx + PartEntry_t.part_type]
cmp al, 0x0C cmp al, 0x0C
je ReadVbrData.active_ok je .active_ok
; *or* ; *or*
cmp al, 0x1C cmp al, 0x1C
je ReadVbrData.active_ok je .active_ok
jmp ReadVbrData.error_badparttype ; error if part_type != 0x1C or 0x0C jmp .error_badparttype ; error if part_type != 0x1C or 0x0C
.active_ok: .active_ok:
movzx ax, byte [bp + 4] movzx ax, byte [bp + 4]
push ax ; drive_num (2) push ax ; drive_num (2)
@@ -92,19 +91,19 @@ FAT32_load_vbr:
.check_sig: .check_sig:
mov bx, [bp + 6] mov bx, [bp + 6]
cmp word [bx + 0x1FE], 0xAA55 ; check for bytes at end cmp word [bx + 0x1FE], 0xAA55 ; check for bytes at end
jne ReadVbrData.error_nosign jne .error_nosign
.check_FAT_sanity: .check_FAT_sanity:
; we only quickly validate that this is *probably* a FAT32 volume ; we only quickly validate that this is *probably* a FAT32 volume
add bx, 11 ; point bx at start of bpb (skip jmp code and ident) add bx, 11 ; point bx at start of bpb (skip jmp code and ident)
cmp word [bx + FAT32_bpb_t.u16_TotalSectors16], 0 ; TotalSectors16 should be 0 (use TotalSectors32 in bpb) cmp word [bx + FAT32_bpb_t.u16_TotalSectors16], 0 ; TotalSectors16 should be 0 (use TotalSectors32 in bpb)
jne ReadVbrData.error_totsectors jne .error_totsectors
cmp word [bx + FAT32_bpb_t.u16_FATSize16], 0 ; FatSize16 will be 0 if FAT32 (use FATSize32 in ebpb) cmp word [bx + FAT32_bpb_t.u16_FATSize16], 0 ; FatSize16 will be 0 if FAT32 (use FATSize32 in ebpb)
jne ReadVbrData.error_fatsz jne .error_fatsz
cmp word [bx + FAT32_bpb_t.u16_RootEntryCount16], 0 ; root dir info is in data clusters on fat32 cmp word [bx + FAT32_bpb_t.u16_RootEntryCount16], 0 ; root dir info is in data clusters on fat32
jne ReadVbrData.error_rootdir jne .error_rootdir
.endp: .endp:
__CDECL16_PROC_EXIT __CDECL16_PROC_EXIT
ret ret

107
src/stage2/stage2.nasm
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@@ -91,7 +91,7 @@ init:
%include "partition_table.inc" %include "partition_table.inc"
%include "fat32/fat32_structures.inc" %include "fat32/fat32_structures.inc"
;%include 'fat32/FAT32_SYS.inc' %include 'fat32/FAT32_SYS.nasm'
; ############### ; ###############
; BIOS functions ; BIOS functions
@@ -135,7 +135,7 @@ main:
push ax ; dst push ax ; dst
movzx ax, byte [u8_BootDrive] movzx ax, byte [u8_BootDrive]
push ax ; boot_drive push ax ; boot_drive
__CDECL16_CALL ReadMbrData, 2 ; fill mbr buffer __CDECL16_CALL FAT32_load_mbr, 2 ; fill/validate mbr buffer
; setup heap space for vbr data ; setup heap space for vbr data
__CDECL16_CALL_ARGS 0x200, 0x10 __CDECL16_CALL_ARGS 0x200, 0x10
@@ -145,7 +145,7 @@ main:
push ax ; dst push ax ; dst
movzx ax, byte [u8_BootDrive] movzx ax, byte [u8_BootDrive]
push ax ; boot_drive push ax ; boot_drive
__CDECL16_CALL ReadVbrData, 2 ; fill vbr buffer __CDECL16_CALL FAT32_load_vbr, 2 ; fill/validate vbr buffer
; enable A20 gate ; enable A20 gate
call EnableA20 call EnableA20
@@ -194,107 +194,6 @@ hcf:
; ;
; ############################## ; ##############################
; int read_mbr(int boot_drive, void* dst)
; destination buffer needs 512 bytes of space
ReadMbrData:
__CDECL16_PROC_ENTRY
.proc:
; read mbr on boot drive to memory (for the partition table)
movzx ax, byte [bp + 4]
push ax ; drive_num (2)
push 0x01 ; count (2)
push dword 0x0 ; lba (4)
push word [bp + 6] ; offset = dst
push __STAGE2_SEGMENT ; this segment
call BIOS_int13h_ext_read
add sp, 0xC
.check_sig:
mov bx, [bp + 6]
cmp word [bx + 0x1FE], 0xAA55 ; check for bytes at end
jne ReadMbrData.error_nosign
; TODO: this needs more error checking, zero checking, check the sig a bunch of stuff...
.endp:
__CDECL16_PROC_EXIT
ret
.error_nosign:
ERROR STAGE2_ERROR_BAD_MBR
; int read_vbr(int boot_drive, void* buf)
; read vbr on boot partition to memory (for fat bpb/ebpb)
ReadVbrData:
__CDECL16_PROC_ENTRY
.proc:
mov bx, SteviaInfo
mov ax, word [bx + SteviaInfoStruct_t.p16_MbrPtr]
add ax, DISK_PARTITION_TABLE_OFFSET
mov bx, ax ; offset to part table
mov cx, 4 ; only checking 4 entries
.find_active_L0:
mov al, [bx + PartEntry_t.attributes]
cmp al, 0x80 ; 0x80 == 1000_0000b
je ReadVbrData.check_fstype
add bx, PartEntry_t_size ; next part entry's attributes
loop ReadVbrData.find_active_L0
jmp ReadVbrData.error_noactive
.check_fstype:
; check for part_type = 0x0C (DOS 7.1+/W95 FAT32 w/ LBA) or 0x1C (Hidden 0x0C)
__BOCHS_MAGIC_DEBUG
mov al, [bx + PartEntry_t.part_type]
cmp al, 0x0C
je ReadVbrData.active_ok
; *or*
cmp al, 0x1C
je ReadVbrData.active_ok
jmp ReadVbrData.error_badparttype ; error if part_type != 0x1C or 0x0C
.active_ok:
movzx ax, byte [bp + 4]
push ax ; drive_num (2)
push 0x01 ; count (2)
mov eax, dword [bx + PartEntry_t.lba_start]
push dword eax ; lba (4)
push word [bp + 6] ; offset = dst
push __STAGE2_SEGMENT ; this segment
call BIOS_int13h_ext_read
add sp, 0xC
; vbr (with fat bpb/ebpb) is at the buffer now
.check_sig:
mov bx, [bp + 6]
cmp word [bx + 0x1FE], 0xAA55 ; check for bytes at end
jne ReadVbrData.error_nosign
.check_FAT_sanity:
; we only quickly validate that this is *probably* a FAT32 volume
add bx, 11 ; point bx at start of bpb (skip jmp code and ident)
cmp word [bx + FAT32_bpb_t.u16_TotalSectors16], 0 ; TotalSectors16 should be 0 (use TotalSectors32 in bpb)
jne ReadVbrData.error_totsectors
cmp word [bx + FAT32_bpb_t.u16_FATSize16], 0 ; FatSize16 will be 0 if FAT32 (use FATSize32 in ebpb)
jne ReadVbrData.error_fatsz
cmp word [bx + FAT32_bpb_t.u16_RootEntryCount16], 0 ; root dir info is in data clusters on fat32
jne ReadVbrData.error_rootdir
.endp:
__CDECL16_PROC_EXIT
ret
.error_noactive:
ERROR STAGE2_VBR_E_ACTIVE
.error_nosign:
ERROR STAGE2_VBR_E_SIGN
.error_totsectors:
ERROR STAGE2_VBR_E_TOT
.error_fatsz:
ERROR STAGE2_VBR_E_FATSZ
.error_rootdir:
ERROR STAGE2_VBR_E_DIRENT
.error_badparttype:
ERROR STAGE2_VBR_E_PARTTYPE
; set ds and es segments back to the base of the loader ; set ds and es segments back to the base of the loader
%ifnmacro __TINY_DS_ES %ifnmacro __TINY_DS_ES
%macro __TINY_DS_ES 0 %macro __TINY_DS_ES 0