fixed read_disk_raw in ReadFATCluster

boot_drive and partition_offset are global pointers now
removed an extra error from mbr disk read
and some general formating and cleanup 😅

include/BIOS/func/ext_read.inc

@@ -97,7 +97,7 @@ read_disk_raw:
 
     %ifdef __STEVIA_MBR
     ERROR MBR_ERROR_DISK_READ_ERR
-    %elifsef __STEVIA_VBR
+    %elifdef __STEVIA_VBR
     ERROR VBR_ERROR_DISK_READ_ERR
     %else
     ERROR STAGE2_MBR_DISK_READ_ERROR

include/fat32/fat32_sys.inc

@@ -37,8 +37,6 @@ InitFATDriver:
 .calc_active_part:
     mov bx, [partition_offset_ptr]
     mov ax, [bx + 0]                     
-    mov bx, ax
-    mov ax, [bx + 0]                       
 
     mov dx, partition_table
     add dx, ax                                                           ; dx points to the partition that was booted from
@@ -66,7 +64,6 @@ InitFATDriver:
     mov dword [fat32_state + FAT32_State_t.first_data_sector_32], eax
 .get_first_root_dir:
     ; TODO
-
     jmp InitFATDriver.endp
 .error:
     ERROR STAGE2_FAT32_INIT_ERROR
@@ -74,7 +71,6 @@ InitFATDriver:
     __CDECL16_EXIT
     ret
 
-; TODO: needs validation
 ; this involves using the low memory buffer for the bios call and moving the file sector by sector to high memory
 ;
 ; SFN is a 8.3 file name, all uppercase, and padded with spaces
@@ -284,15 +280,13 @@ ReadFATCluster:
 .func:
     mov bx, [boot_drive_ptr]
     mov ax, [bx + 0]
-    mov bx, ax
-    movzx ax, byte [bx + 0]                      ; 67h override would probably work but this is the 16bit way to do it
     mov byte [bp - 2], al                        ; save boot drive as a local for easy access
 
     mov dword eax, [bp + 8]
     push dword eax
     call ClusterToLBA    ; uint32_t ClusterToLBA(uint32_t cluster)
     add sp, 0x4         ; eax == LBA
-    
+    mov dword [bp - 6], eax
 
     movzx ax, [bp - 2]
     push ax
@@ -300,8 +294,7 @@ ReadFATCluster:
     mov ax, 0x1
     push ax
 
-    ; load correct fat
-    mov eax, dword [si + FAT32_NextClusterData_t.fat_sector]
+    mov eax, dword [bp + 6]
     push dword eax
 
     mov ax, fat_buffer

src/mbr/mbr.nasm

@@ -138,15 +138,10 @@ main:
         ;                         uint16_t count, uint16_t drive_num)
         call read_disk_raw
         add sp, 0xC
-
-
-        jnc main.goto_vbr
-        ERROR MBR_ERROR_DISK_READ_ERR                     ; error in LBA read
     .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, partition_table_SIZE            ; 72 bytes of data
         push ax
@@ -166,8 +161,13 @@ main:
 ; BIOS Functions
 ;
 ; ###############
+
 %include 'BIOS/func/ext_read.inc'
 
+; ###############
+; End Section
+; ###############
+
 %assign bytes_remaining (440 - ($ - $$))
 %warning MBR has bytes_remaining bytes remaining for code (MAX: 440 bytes)
 times ((512 - 72) - ($ - $$)) nop     ; Fill the rest of sector with nop

src/stage2/stage2.nasm

@@ -23,16 +23,14 @@
 [CPU KATMAI]
 jmp short init
 nop
-; boot drive in dl
-; active partition offset in si
 
 ; ###############
 ;
 ; Headers/Includes/Definitions
 ;
 ; ###############
-%define __STEVIA_STAGE2
 
+%define __STEVIA_STAGE2
 
 %include "cdecl16.inc"
 %include "entry.inc"
@@ -43,6 +41,7 @@ nop
 ; ###############
 ; End Section
 ; ###############
+
 ALIGN 4, db 0x90
 init:
     cli                         ; We do not want to be interrupted
@@ -62,7 +61,6 @@ init:
 
     jmp 0:main
 
-
 ; ###############
 ;
 ; Extra/Shared Functions
@@ -76,6 +74,10 @@ init:
 ; End Section
 ; ###############
 
+;
+; bp - 2 : uint8_t boot_drive
+; bp - 4 : uint16_t part_offset
+;
 main:
     lea ax, [bp - 2]
     mov [boot_drive_ptr], ax
@@ -147,7 +149,6 @@ main:
     add sp, 0x2
     
     ERROR STEVIA_DEBUG_HALT
-
 hcf:
     hlt
     jmp short hcf

src/vbr/vbr.nasm

@@ -37,7 +37,6 @@ times 54 db 0x00
 ; ###############
 %define __STEVIA_VBR
 
-
 %include "cdecl16.inc"
 %include "entry.inc"
 %include "config.inc"
@@ -87,11 +86,8 @@ main:
 .check_FAT_size:                     ; we only support a very specific setup of FAT32
     cmp dword [bsSectorHuge], 0      ; SectorsHuge will not be set if FAT12/16
     ja main.load_stage2
-
     ERROR VBR_ERROR_WRONG_FAT_SIZE
-
-; read sectors 1-63 to stage2 entry point
-.load_stage2:
+.load_stage2:                                          ; read sectors 1-63 to stage2 entry point
     mov ax, (fat32_bpb_SIZE + fat32_ebpb_SIZE)         ; size in byte
     push ax
     mov ax, (phy_bpb_start - 0x3)                      ; start of bpb - 0x3 for the jump short main at the start
@@ -140,10 +136,9 @@ main:
     jmp 0:0x7E00
 
 ; ###############
-;
-; Required BIOS functions
-;
+; Required BIOS function(s)
 ; ###############
+
 %include 'BIOS/func/ext_read.inc'
 
 %assign bytes_remaining (420 - ($ - $$))