more error codes and checks in vbr

.gitignore

@@ -10,4 +10,5 @@ stevia-log
 *.map
 compose-dev.yaml
 eth_null-tx.log
-eth_null-txdump.txt
+eth_null-txdump.txt
+*.log

Makefile

@@ -38,9 +38,6 @@ QEMU_ARGS := \
     -device e1000,netdev=n0,mac=52:54:00:12:34:56 \
     -netdev user,id=n0 \
     -device piix3-usb-uhci \
-    -device usb-ohci,id=ohci0 \
-    -device usb-ehci,id=ehci0 \
-    -device pcspk \
     -parallel null \
     -serial null -serial none -serial none -serial none \
     -chardev file,id=dbg,path=bochs-e9.log,append=on \

include/error_codes.inc

@@ -15,8 +15,7 @@
 
 %ifndef __INC_ERROR_CODES
 
-; Errors
-; 12 Errors, 5 in use
+; MBR Error codes
 %define MBR_ERROR_DISK_T_ERR         'a'
 %define MBR_ERROR_NO_INT32E          'b'
 %define MBR_ERROR_NO_NO_BOOT_PART    'c'
@@ -30,7 +29,7 @@
 %define MBR_ERROR_RESERVED_k         'k'
 %define MBR_ERROR_INT13h_EREAD_ERR   'l'
 
-; 12 Error
+; VBR Error codes
 %define VBR_ERROR_WRONG_FAT_SIZE     'm'
 %define VBR_ERROR_NO_SIGNATURE       'n'
 %define VBR_ERROR_DISK_READ_ERR      'o'
@@ -44,7 +43,7 @@
 %define VBR_ERROR_RESERVED_w         'w'
 %define VBR_ERROR_RESERVED_x         'x'
 
-; 22 errors, 8 in use
+; Stage2 Error codes
 %define STAGE2_A20_FAILED            'A'
 %define STAGE2_SIGNATURE_MISSING     'B'
 %define STAGE2_MM_E820_NO_SUPPORT    'C'
@@ -60,19 +59,19 @@
 %define STAGE2_FAT32_E_UNSUPPORTED   'M'
 %define STAGE2_FAT32_E_UNIMPLEMENTED 'N'
 %define STAGE2_ERROR_BAD_MBR         'O'
-%define STAGE2_ERROR_BAD_VBR         'P'
-%define STAGE2_ERROR_RESERVED_Q      'Q'
-%define STAGE2_ERROR_RESERVED_R      'R'
-%define STAGE2_ERROR_RESERVED_S      'S'
-%define STAGE2_ERROR_RESERVED_T      'T'
-%define STAGE2_ERROR_RESERVED_U      'U'
-%define STAGE2_ERROR_RESERVED_V      'V'
+%define STAGE2_VBR_E_ACTIVE          'P'
+%define STAGE2_VBR_E_SIGN            'Q'
+%define STAGE2_VBR_E_TOT             'R'
+%define STAGE2_VBR_E_FATSZ           'S'
+%define STAGE2_VBR_E_DIRENT          'T'
+%define STAGE2_VBR_E_PARTTYPE        'U'
+%define STAGE2_RESERVED_E_V          'V'
 
-; for development only, specific errors should be above.
-%define STEVIA_DEBUG_OK      'W'
-%define STEVIA_DEBUG_ERR      'X'
-%define STEVIA_DEBUG_UNIMPLEMENTED      'Y'
-%define STEVIA_DEBUG_HALT      'Z'
+; Debug error codes
+%define STEVIA_DEBUG_OK              'W'
+%define STEVIA_DEBUG_ERR             'X'
+%define STEVIA_DEBUG_UNIMPLEMENTED   'Y'
+%define STEVIA_DEBUG_HALT            'Z'
 
 %endif
 %define __INC_ERROR_CODES

include/fat32/fat32_structures.inc

@@ -65,11 +65,11 @@ struc FAT32_bpb_t
     .u16_RootEntryCount16    resw 1      ; Root dir entry count field, 0 on fat32
     .u16_TotalSectors16      resw 1      ; total number of sectors size, 0 on fat32
     .u8_MediaDesc            resb 1
-    .u16_FatSize16           resw 1      ; FAT size 16, 0 on fat32
+    .u16_FATSize16           resw 1      ; FAT size 16, 0 on fat32
     .u16_SectorsPerTrack     resw 1
     .u16_HeadCount           resw 1
     .u32_HiddenSectors       resd 1
-    .u32_TotalSectors        resd 1
+    .u32_TotalSectors32      resd 1
 endstruc
 
 ; EBPB Information (FAT32)
@@ -89,7 +89,7 @@ endstruc
 ;   8 	System identifier string. Always "FAT32   ". The spec says never to trust the contents of this string for any use.
 
 struc FAT32_ebpb_t
-    .u32_FATSz             resd 1      ; size of *each* fat in sectors, total = FATSz * (# of FATs)
+    .u32_FATSize32         resd 1      ; size of *each* fat in sectors, total = FATSz * (# of FATs)
     .u16_ExtFlags          resw 1
     .u16_FSVersion         resw 1
     .u32_RootDirCluster    resd 1

src/stage2/stage2.nasm

@@ -230,17 +230,27 @@ ReadVbrData:
     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
-    mov si, PartEntry_t.attributes
+
 .find_active_L0:
-    mov al, byte [bx + si]
-    test al, 0x80                           ; 0x80 == 1000_0000b
-    je ReadVbrData.active_found
+    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
-.active_found:
+.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)
@@ -257,18 +267,33 @@ ReadVbrData:
     mov bx, [bp + 6]
     cmp word [bx + 0x1FE], 0xAA55           ; check for bytes at end
     jne ReadVbrData.error_nosign
-.check_FAT_size:
-    test word [bx + FAT32_bpb_t.u16_TotalSectors16], 0      ; TotSectors16 will not be set if FAT32
-    jnz ReadVbrData.error_badfatfs
+.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_ERROR_BAD_VBR
+    ERROR STAGE2_VBR_E_ACTIVE
 .error_nosign:
-    ERROR STAGE2_ERROR_BAD_VBR
-.error_badfatfs:
-    ERROR STAGE2_ERROR_BAD_VBR
+    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
 %ifnmacro __TINY_DS_ES