From 8d2cde0a3167392bd101a89c4d4f4ead1d1adc1d Mon Sep 17 00:00:00 2001
From: Elaina Claus <elaina.claus@chtm.me>
Date: Wed, 17 Sep 2025 17:02:08 -0400
Subject: [PATCH] added no planned fat32 error codes and added mbr/vbr reading
 error codes

---
 include/BIOS/func/ext_read.nasm |  2 +-
 include/error_codes.inc         | 20 ++++++++++----------
 src/stage2/stage2.nasm          | 22 +++++++++++++---------
 3 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/include/BIOS/func/ext_read.nasm b/include/BIOS/func/ext_read.nasm
index 013e834..2d4b0b1 100644
--- a/include/BIOS/func/ext_read.nasm
+++ b/include/BIOS/func/ext_read.nasm
@@ -94,7 +94,7 @@ read_disk_raw:
     %elifdef __STEVIA_VBR
     ERROR VBR_ERROR_DISK_READ_ERR
     %else
-    ERROR STAGE2_MBR_DISK_READ_ERROR
+    ERROR STAGE2_INT13_DISK_READ_ERR
     %endif
 .endf:
     __CDECL16_PROC_EXIT
diff --git a/include/error_codes.inc b/include/error_codes.inc
index c59a7da..68f4c90 100755
--- a/include/error_codes.inc
+++ b/include/error_codes.inc
@@ -51,16 +51,16 @@
 %define STAGE2_MM_E820_MISC_ERR      'D'
 %define STAGE2_MM_E820_NONSTANDARD   'E'
 %define STAGE2_MM_E820_NO_SMAP       'F'
-%define STAGE2_MBR_DISK_READ_ERROR   'G'
-%define STAGE2_FAT32_INIT_ERROR      'H'
-%define STAGE2_FAT32_NO_FILE         'I'
-%define STAGE2_FAT32_END_OF_CHAIN    'J'
-%define STAGE2_FAT32_NCLUS_CFDIVZ    'K'
-%define STAGE2_FAT32_CLS2LBA_CF      'L'
-%define STAGE2_FAT32_INIT_CF         'M'
-%define STAGE2_ERROR_INFOPRINTER     'N'
-%define STAGE2_ERROR_RESERVED_O      'O'
-%define STAGE2_ERROR_RESERVED_P      'P'
+%define STAGE2_INT13_DISK_READ_ERR   'G'
+%define STAGE2_FAT32_E_FMT           'H'
+%define STAGE2_FAT32_E_RANGE         'I'
+%define STAGE2_FAT32_E_NOSUCH        'J'
+%define STAGE2_FAT32_E_ISDIR         'K'
+%define STAGE2_FAT32_E_TOOLONG       'L'
+%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'
diff --git a/src/stage2/stage2.nasm b/src/stage2/stage2.nasm
index 8168103..deb5af6 100755
--- a/src/stage2/stage2.nasm
+++ b/src/stage2/stage2.nasm
@@ -213,13 +213,13 @@ ReadMbrData:
 .check_sig:
     mov bx, [bp + 6]
     cmp word [bx + 0x1FE], 0xAA55           ; check for bytes at end
-    jne ReadMbrData.error
-    ; TODO: this needs error checking, zero checking, check the sig a bunch of stuff...
+    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:
-    ERROR STEVIA_DEBUG_ERR
+.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)
@@ -239,7 +239,7 @@ ReadVbrData:
     je ReadVbrData.active_found
     add bx, PartEntry_t_size                ; next part entry's attributes
     loop ReadVbrData.find_active_L0
-    jmp ReadVbrData.error
+    jmp ReadVbrData.error_noactive
 .active_found:
     movzx ax, byte [bp + 4]
     push ax                                 ; drive_num (2)
@@ -256,15 +256,19 @@ ReadVbrData:
 .check_sig:
     mov bx, [bp + 6]
     cmp word [bx + 0x1FE], 0xAA55           ; check for bytes at end
-    jne ReadVbrData.error
+    jne ReadVbrData.error_nosign
 .check_FAT_size:
     test word [bx + FAT32_bpb_t.unused2_ZERO_word], 0      ; TotSectors16 will not be set if FAT32
-    jnz ReadVbrData.error
+    jnz ReadVbrData.error_badfatfs
 .endp:
     __CDECL16_PROC_EXIT
     ret
-.error:
-    ERROR STEVIA_DEBUG_ERR
+.error_noactive:
+    ERROR STAGE2_ERROR_BAD_VBR
+.error_nosign:
+    ERROR STAGE2_ERROR_BAD_VBR
+.error_badfatfs:
+    ERROR STAGE2_ERROR_BAD_VBR
 
 ; set ds and es segments back to the base of the loader
 %ifnmacro __TINY_DS_ES