duskos

commit ee0beaf1bbed9779c107ea59d4ca605400dd4e56
parent f29541dacb9cc2aec81fd403a66d11c6b835dd1a
Author: Virgil Dupras <hsoft@hardcoded.net>
Date:   Thu, 21 Jul 2022 15:20:02 -0400

pc: separate bootloader and payload

Diffstat:
M
buildpc.fs
 | 
4
+++-
M
fs/asm/i386.fs
 | 
2
+-
A
fs/xcomp/pc/boot.fs
 | 
6
++++++
M
fs/xcomp/pc/mbr.fs
 | 
11
++++++-----

4 files changed, 16 insertions(+), 7 deletions(-)
diff --git a/buildpc.fs b/buildpc.fs
@@ -1,4 +1,6 @@
 : spit ( a u -- ) >r begin c@+ stderr next ;
+f<< /asm/i386.fs
 f<< /xcomp/pc/mbr.fs
+f<< /xcomp/pc/boot.fs
 
-ORG $200 spit bye
+ORG $400 spit bye
diff --git a/fs/asm/i386.fs b/fs/asm/i386.fs
@@ -130,7 +130,7 @@ AL _ al   BL _ bl   CL _ cl   DL _ dl   AH _ ah   BH _ bh   CH _ ch   DH _ dh
 
 \ Inherent
 : op ( opcode -- ) doer c, does> ( a -- ) c@ c, asm$ ;
-$c3 op ret,
+$c3 op ret,        $fa op cli,         $fc op cld,
 
 \ Jumps and relative addresses
 \ i386 jumps and calls in their immediate modes are relative. We keep it that
diff --git a/fs/xcomp/pc/boot.fs b/fs/xcomp/pc/boot.fs
@@ -0,0 +1,6 @@
+\ This part is called when the bootloader has finished loading the kernel as
+\ well as the Forth boot code following it in memory. We're still in real mode,
+\ SS is uninitialized. This code lives at $8000
+ax $0e59 i) mov,
+$10 int,
+0 jmp, \ infinite loop
diff --git a/fs/xcomp/pc/mbr.fs b/fs/xcomp/pc/mbr.fs
@@ -1,11 +1,12 @@
 \ x86 bootloader
-?f<< /asm/i386.fs
 
+\ Bootsector is loaded at address $7c00
 1 to realmode
 create ORG here $200 0 fill
 $26 jmp, \ bypass BPB
 $23 allot
-ax $0e58 i) mov,
-$10 int,
-0 jmp, \ infinite loop
-$55 ORG $1fe + c!+ $aa swap c!
+cli, cld,
+\ read sector 2 from boot floppy in memory at address $8000
+ax $0201 i) mov, bx $8000 i) mov, cx $0002 i) mov, dx $0000 i) mov,  $13 int,
+ax $8000 i) mov, ax jmp,
+ORG $1fe + to here $55 c, $aa c,