From: Alan Cox <alan@linux.intel.com>
Date: Sat, 5 Jan 2019 22:41:51 +0000 (+0000)
Subject: filo: rework some code so we can use it nicely as a boot block loader
X-Git-Url: https://git.ndcode.org/public/gitweb.cgi?a=commitdiff_plain;h=adbe92cded14156e534d90846ec697a9e6863c44;p=FUZIX.git

filo: rework some code so we can use it nicely as a boot block loader
---

diff --git a/Kernel/filo/README b/Kernel/filo/README
index 6a5a128c..1bb4679f 100644
--- a/Kernel/filo/README
+++ b/Kernel/filo/README
@@ -2,3 +2,14 @@ FILO
 
 Initial draft of a loader that is designed to be a portable Z80 loading tool
 that can load Fuzix images out of a Fuzix file system.
+
+Commands
+
+*xxx		anything beginning * is handed to the platform specific code
+		so may be relevant or not.
+
+[A-P]:		capital required - select drive to load from
+		(will also allow A0-P3 once we do partitions)
+
+any other string is taken as a filename to search for in / of the current
+volume and boot as a kernel image.
diff --git a/Kernel/filo/filo.s b/Kernel/filo/filo.s
index a4c1a93b..1b61871d 100644
--- a/Kernel/filo/filo.s
+++ b/Kernel/filo/filo.s
@@ -88,21 +88,6 @@ filo:
 	.ascii 'Fuzix Intermediate Loader v0.01.\n'
 	.asciz '(C)2019 Alan Cox\n\n'
 
-	.area _DATA
-
-loadname:
-	.ds 31
-ibuf:
-	.ds 64
-dbuf:
-	.ds 512
-partbase_l:
-	.dw 0
-partbase_h:
-	.dw 0
-
-	.area _CODE
-
 partitions:
 	; No partitions found (hack for now)
 	ld hl,#0
@@ -363,7 +348,7 @@ reader_loop:
 bread:
 	ld a,d
 	or e
-	jr nz, bread_disk
+	jp nz, bread_disk
 	ld d,h
 	ld e,l
 	ld bc,#511
@@ -394,4 +379,16 @@ cmploop:
 	djnz cmploop
 	ret			; Z 
 
+	.area _DATA
+
+loadname:
+	.ds 31
+ibuf:
+	.ds 64
+dbuf:
+	.ds 512
+partbase_l:
+	.dw 0
+partbase_h:
+	.dw 0
 
diff --git a/Kernel/platform-sc114/loader.s b/Kernel/platform-sc114/loader.s
index d6002ccd..8709a3a9 100644
--- a/Kernel/platform-sc114/loader.s
+++ b/Kernel/platform-sc114/loader.s
@@ -4,19 +4,50 @@
 ;
 ;	Currently this and the glue driver code is well under 2 disk blocks.
 ;	Adding partitions should still fit 2 blocks nicely.
+;
+;	Our SCM command 'BOOT' loads the MBR of the media and then runs it
+;	if appropriate. We are loaded at 0xF000 and hold all of CODE
+;
+;
+;	Section ordering
 ;
 	.area _CODE
+	.area _STACK
+	.area _CODE2
+	.area _DATA
 
 ;
+;	_CODE and _STACK goes in the boot sector.
+;	_CODE2 and _DATA are split across them or beyond (as data is
+;	uninitialized
+;
+	.area _CODE
+
+;
+;	So we can check set up
+;
+	.globl start
+	.globl stack
+;
 ;	Magic for the loader
 ;
 	.byte 'Z'
 	.byte 80
 
 ;
-;	Loader core
+;	We have 446 bytes of space in the boot sector before the
+;	partitions that is loaded (and the partition table), but we
+;	need to load the second sector holding the core of FILO
 ;
-	.include '../filo/filo.s'
+
+start:
+	ld sp, #stack
+	ld bc, #0xF200		; Straight after us
+	ld hl, #0x0001		; Sector 1
+	ld de, #0x0000
+	call bread_raw
+	jp boot_begin		; Run FILO
+
 ;
 ; ****************************************************************************
 ;
@@ -104,6 +135,14 @@ nocarry_lba:
 	xor a
 	ret
 ;
+;	Private helper
+;
+bread_raw:
+	push hl
+	ld h,b
+	ld l,c
+	jr nocarry_lba
+;
 ;	Timeout might be a good idea
 ;
 ide_ready:
@@ -254,3 +293,15 @@ delay10ms:
 	ld c,#0x0a
 	ld de,#0x10
 	jr mcall
+
+	.area _STACK
+
+	.ds 16
+stack:
+
+	.area _CODE2
+
+;
+;	Loader core loaded from sector 1
+;
+	.include '../filo/filo.s'