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naming changes to ReadMbr/Vbr

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This commit is contained in:
Elaina Claus
2025-09-13 14:56:26 -04:00
parent 7f1b4fa632
commit 935cbd1089
1 changed files with 12 additions and 15 deletions
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27
src/stage2/stage2.nasm
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@@ -139,7 +139,7 @@ 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 read_mbr, 2 ; fill mbr buffer __CDECL16_CALL ReadMbrData, 2 ; fill mbr buffer
__CDECL16_CALL_ARGS 0x200, 0x10 __CDECL16_CALL_ARGS 0x200, 0x10
__CDECL16_CALL arena_alloc, 2 __CDECL16_CALL arena_alloc, 2
@@ -148,7 +148,7 @@ 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 read_vbr, 2 ; fill vbr buffer __CDECL16_CALL ReadVbrData, 2 ; fill vbr buffer
; enable A20 gate ; enable A20 gate
call EnableA20 call EnableA20
@@ -199,7 +199,7 @@ hcf:
; int read_mbr(int boot_drive, void* dst) ; int read_mbr(int boot_drive, void* dst)
; destination buffer needs 512 bytes of space ; destination buffer needs 512 bytes of space
read_mbr: ReadMbrData:
__CDECL16_PROC_ENTRY __CDECL16_PROC_ENTRY
.proc: .proc:
; read mbr on boot drive to memory (for the partition table) ; read mbr on boot drive to memory (for the partition table)
@@ -213,11 +213,10 @@ read_mbr:
push __STAGE2_SEGMENT ; this segment push __STAGE2_SEGMENT ; this segment
call read_disk_raw call read_disk_raw
add sp, 0xC add sp, 0xC
.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 read_mbr.error jne ReadMbrData.error
; TODO: this needs error checking, zero checking, check the sig a bunch of stuff... ; TODO: this needs error checking, zero checking, check the sig a bunch of stuff...
.update_globals: .update_globals:
mov ax, [bp + 6] mov ax, [bp + 6]
@@ -230,22 +229,20 @@ read_mbr:
ERROR STEVIA_DEBUG_ERR ERROR STEVIA_DEBUG_ERR
; int read_vbr(int boot_drive, void* buf) ; int read_vbr(int boot_drive, void* buf)
read_vbr: ; read vbr on boot partition to memory (for fat bpb/ebpb)
ReadVbrData:
__CDECL16_PROC_ENTRY __CDECL16_PROC_ENTRY
.proc: .proc:
__BOCHS_MAGIC_DEBUG mov bx, word [part_table_ptr] ; calculate offset; base pointer @ partition table
; read vbr on boot partition to memory (for fat bpb/ebpb)
.calc_part_offset:
mov bx, word [part_table_ptr] ; base pointer @ partition table
mov cx, 4 ; only checking 4 entries mov cx, 4 ; only checking 4 entries
mov si, PartEntry_t.attributes mov si, PartEntry_t.attributes
.find_active_L0: .find_active_L0:
mov al, byte [bx + si] mov al, byte [bx + si]
test al, 0x80 ; 0x80 == 1000_0000b test al, 0x80 ; 0x80 == 1000_0000b
je read_vbr.active_found je ReadVbrData.active_found
add si, 0x10 ; add 16 bytes to offset (next part entry's attributes) add si, 0x10 ; add 16 bytes to offset (next part entry's attributes)
loop read_vbr.find_active_L0 loop ReadVbrData.find_active_L0
jmp read_vbr.error jmp ReadVbrData.error
.active_found: .active_found:
add bx, si ; update base to active part add bx, si ; update base to active part
@@ -264,10 +261,10 @@ read_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 read_mbr.error jne ReadVbrData.error
.check_FAT_size: .check_FAT_size:
test word [bx + FAT32_bpb_t.unused2_ZERO_word], 0 ; TotSectors16 will not be set if FAT32 test word [bx + FAT32_bpb_t.unused2_ZERO_word], 0 ; TotSectors16 will not be set if FAT32
jnz read_vbr.error jnz ReadVbrData.error
.update_globals: .update_globals:
mov word [fat32_bpb_ptr], bx mov word [fat32_bpb_ptr], bx
add bx, FAT32_bpb_t_size ; offset to ebpb add bx, FAT32_bpb_t_size ; offset to ebpb