From fc3032deb729855c0dc59f096b6e2f6aac0cb32a Mon Sep 17 00:00:00 2001
From: "E. C. Masloch" <pushbx@ulukai.org>
Date: Wed, 7 Feb 2024 00:39:37 +0100
Subject: [PATCH] oemboot: use magic offsets macro
---
boot/magic.mac | 4 ++--
boot/makefile | 4 ++--
boot/oemboot.asm | 15 +++++++++++++--
3 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/boot/magic.mac b/boot/magic.mac
index 8580f48..c97aa01 100644
--- a/boot/magic.mac
+++ b/boot/magic.mac
@@ -44,7 +44,7 @@ _appenddigitstrdef %1, (%2 >> (0 * 4)) & 0Fh
%endif
%endmacro
- %macro magicoffset 2-3.nolist
+ %macro magicoffset 2-4.nolist ,0
%if ISFAT1216DUAL
%ifdef ISFAT12
%define SYSOFFSET %2
@@ -62,7 +62,7 @@ _appenddigitstrdef %1, (%2 >> (0 * 4)) & 0Fh
%error Not in dual mode
%endif
%endif
-%assign NEWOFFSET $ - Entry
+%assign NEWOFFSET $ + %4 - Entry
%if NEWOFFSET != SYSOFFSET
_autohexitsstrdef NEWOFFSETHEX, NEWOFFSET
%strcat _NEWOFFSETHEX _NEWOFFSETHEX,'h'
diff --git a/boot/makefile b/boot/makefile
index 6bd7f68..9be6f78 100644
--- a/boot/makefile
+++ b/boot/makefile
@@ -19,10 +19,10 @@ fat32chs.bin: boot32.asm magic.mac
fat32lba.bin: boot32lb.asm magic.mac
$(NASM) $(NASMBOOTFLAGS) boot32lb.asm -l$*.lst -ofat32lba.bin
-oemfat12.bin: oemboot.asm
+oemfat12.bin: oemboot.asm magic.mac
$(NASM) -dISFAT12 $(NASMBOOTFLAGS) oemboot.asm -l$*.lst -ooemfat12.bin
-oemfat16.bin: oemboot.asm
+oemfat16.bin: oemboot.asm magic.mac
$(NASM) -dISFAT16 $(NASMBOOTFLAGS) oemboot.asm -l$*.lst -ooemfat16.bin
clobber: clean
diff --git a/boot/oemboot.asm b/boot/oemboot.asm
index 66eb805..5b1de2e 100644
--- a/boot/oemboot.asm
+++ b/boot/oemboot.asm
@@ -116,6 +116,11 @@
; |IVT | Interrupt Vector Table
; +--------+ 0000:0000
+ ; NOTE: sys must be updated if magic offsets change
+%assign ISFAT1216DUAL 1
+ %include "magic.mac"
+
+
CPU 8086 ; enable assembler warnings to limit instruction set
;%define ISFAT12 1 ; only 1 of these should be set,
@@ -227,15 +232,17 @@ Entry: jmp short real_start
; The filesystem ID is used by lDOS's instsect (by ecm)
; by default to validate that the filesystem matches.
%ifdef ISFAT12
- db "FAT12" ; filesystem id
+ %define FATFS "FAT12"
%ifdef ISFAT16
%error Must select one FS
%endif
%elifdef ISFAT16
- db "FAT16"
+ %define FATFS "FAT16"
%else
+ %define FATFS "unknown"
%error Must select one FS
%endif
+ db FATFS ; filesystem id
times 3Eh - ($ - $$) db 32
;-----------------------------------------------------------------------
@@ -282,6 +289,7 @@ real_start:
; in DL, however we work around this in SYS.COM by NOP'ing out the use of DL
; (formerly we checked for [drive]==0xff; update sys.c if code moves)
;
+ magicoffset "set unit", 4Fh, 4Fh
mov [drive], dl ; rely on BIOS drive number in DL
@@ -470,6 +478,7 @@ cluster_next: lodsw ; AX = next cluster to read
%else
jmp LOADSEG:0000 ; yes, pass control to kernel
%endif
+ magicoffset "load jump ofs", 11Ah, 118h, -4
; failed to boot
@@ -655,6 +664,8 @@ read_skip:
ret
times 0x01f1-$+$$ db 0
+
+ magicoffset "kernel name", 1F1h, 1F1h
%ifdef MSCOMPAT
filename db "IO SYS"
%else