From 07e50313c7035daf9c969f559fd626310ca6dd71 Mon Sep 17 00:00:00 2001
From: Virgil Dupras <hsoft@hardcoded.net>
Date: Sat, 13 Jun 2020 15:35:16 -0400
Subject: [PATCH] pcat: separate MBR code and OS code

MBR code now strictly loads OS code into memory and jumps into it.

Now, I've got to consolidate my assembler code, modrm logic is
messed up.
---
 blk/753               |  1 +
 blk/811               | 11 +++--------
 blk/812               | 10 ++++++++++
 recipes/pcat/Makefile | 14 ++++++++++++--
 recipes/pcat/mbr.fs   |  4 ++++
 recipes/pcat/xcomp.fs |  2 +-
 6 files changed, 31 insertions(+), 11 deletions(-)
 create mode 100644 blk/812
 create mode 100644 recipes/pcat/mbr.fs

diff --git a/blk/753 b/blk/753
index 8c16863..425fda8 100644
--- a/blk/753
+++ b/blk/753
@@ -4,6 +4,7 @@
 : INT, 0xcd A, A, ;
 ( no argument, flow ops are special )
 : JMP8, 0xeb A, ; : JMP16, 0xe9 A, ; : JZ, 0x74 A, ;
+: JMPr, 0xff A, 7 AND 0xe0 OR A, ;
 : LODSB, 0xac A, ; : CLI, 0xfa A, ; : HLT, 0xf4 A, ;
 : STI, 0xfb A, ;
 : ORrr, 0x08 A, MODRMrr A, ;
diff --git a/blk/811 b/blk/811
index 8f55a6d..a2d4b97 100644
--- a/blk/811
+++ b/blk/811
@@ -2,14 +2,9 @@ H@ ORG ! 0x7c00 BIN( ! ( BIOS loads boot bin at 0x7c00 )
 JMP8, L1 FWR8 ( start )
 ORG @ 0x25 + HERE ! ( bypass BPB )
 L1 FSET ( start )
-CLI, CLD, AX AX XORxx, DS AX MOVsx, ES AX MOVsx, STI,
+CLI, CLD, AX AX XORxx, DS AX MOVsx, ES AX MOVsx,
+SS AX MOVsx, SP 0xffff MOVrI, STI,
 AH 2 MOVri, DX 0 MOVrI, CH 0 MOVri, CL 2 MOVri, AL 1 MOVri,
 BX 0x8000 MOVrI, 0x13 INT, ( read 2nd sector of boot floppy )
-SI 0x8000 MOVrI, AH 0x0e MOVri, ( print char )
-L1 BSET ( loop ) LODSB, AL AL ORrr, ( end of str? )
-JZ, L2 FWR8 ( next ) 0x10 INT, ( print char )
-JMP8, L1 ( loop ) BWR
-L2 FSET ( next ) AH 0 MOVri, 0x16 INT, ( read kbd )
-AH 0x0e MOVri, 0x10 INT, ( spit read char ) HLT, ( done )
+BX JMPr,
 ORG @ 0x1fe + HERE ! 0x55 A, 0xaa A,
-," Hello from 2nd sector of boot floppy!" 0 A,
diff --git a/blk/812 b/blk/812
new file mode 100644
index 0000000..87dac03
--- /dev/null
+++ b/blk/812
@@ -0,0 +1,10 @@
+H@ ORG ! 0x8000 BIN( !
+JMP8, L1 FWR8 ( start )
+L2 ( msg ) BSET ," Hello World!" 0 A,
+L1 FSET ( start )
+SI L2 @ ( msg ) MOVrI, AH 0x0e MOVri, ( print char )
+L1 BSET ( loop ) LODSB, AL AL ORrr, ( end of str? )
+JZ, L2 FWR8 ( next ) 0x10 INT, ( print char )
+JMP8, L1 ( loop ) BWR
+L2 FSET ( next ) AH 0 MOVri, 0x16 INT, ( read kbd )
+AH 0x0e MOVri, 0x10 INT, ( spit read char ) HLT, ( done )
diff --git a/recipes/pcat/Makefile b/recipes/pcat/Makefile
index 07e34e3..6c6394c 100644
--- a/recipes/pcat/Makefile
+++ b/recipes/pcat/Makefile
@@ -1,16 +1,26 @@
-TARGET = boot.bin
+TARGET = disk.bin
 BASEDIR = ../..
 EDIR = $(BASEDIR)/emul
 STAGE = $(EDIR)/stage
 
 .PHONY: all
 all: $(TARGET) 
-$(TARGET): xcomp.fs $(STAGE)
+mbr.bin: mbr.fs $(STAGE)
+	cat mbr.fs | $(STAGE) > $@
+
+os.bin: xcomp.fs $(STAGE)
 	cat xcomp.fs | $(STAGE) > $@
 
+disk.bin: mbr.bin os.bin
+	cat mbr.bin os.bin > $@
+
 $(STAGE):
 	$(MAKE) -C $(EDIR) stage
 
 .PHONY: emul
 emul: $(TARGET)
 	qemu-system-i386 -fda $(TARGET)
+
+.PHONY: clean
+clean:
+	rm *.bin
diff --git a/recipes/pcat/mbr.fs b/recipes/pcat/mbr.fs
new file mode 100644
index 0000000..1b856d1
--- /dev/null
+++ b/recipes/pcat/mbr.fs
@@ -0,0 +1,4 @@
+750 LOAD
+811 LOAD
+ORG @ 256 /MOD 2 PC! 2 PC!
+H@ 256 /MOD 2 PC! 2 PC!
diff --git a/recipes/pcat/xcomp.fs b/recipes/pcat/xcomp.fs
index 1b856d1..dc2fb4e 100644
--- a/recipes/pcat/xcomp.fs
+++ b/recipes/pcat/xcomp.fs
@@ -1,4 +1,4 @@
 750 LOAD
-811 LOAD
+812 LOAD
 ORG @ 256 /MOD 2 PC! 2 PC!
 H@ 256 /MOD 2 PC! 2 PC!