sms: generate TMR SEGA signature in Collapse OS itself

Having the signature generation code in /tools prevents self-hosting
on the SMS.

arch/z80/sms/Makefile

@@ -1,9 +1,8 @@
 # See /doc/hw/z80/sms.txt
-TARGET = os.bin
+TARGET = os.sms
 BASE = ../../..
 STAGE = $(BASE)/cvm/stage
 BLKPACK = $(BASE)/tools/blkpack
-SMSROM = $(BASE)/tools/smsrom
 EMUL = $(BASE)/emul/z80/sms
 
 .PHONY: all
@@ -11,7 +10,6 @@ all: $(TARGET)
 $(TARGET): xcomp.fs $(STAGE) blkfs
 	cat xcomp.fs | $(STAGE) blkfs > $@
 
-$(SMSROM):
 $(BLKPACK):
 	$(MAKE) -C ../tools
 
@@ -21,9 +19,6 @@ blkfs: $(BLKPACK) $(BASE)/blk.fs blk.fs
 $(STAGE):
 	$(MAKE) -C $(BASE)/cvm stage
 
-os.sms: $(TARGET) $(STAGE) $(SMSROM)
-	$(SMSROM) $(TARGET) > $@
-
 $(EMUL):
 	$(MAKE) -C ${@:%/sms=%}
 

arch/z80/sms/xcomp.fs

@@ -16,6 +16,7 @@ SYSVARS 0x74 + CONSTANT PAD_MEM
 : ZFILL, ( u ) 0 DO 0 A, LOOP ;
 262 LOAD  ( xcomp )
 524 LOAD  ( font compiler )
+165 LOAD  ( Sega ROM signer )
 282 LOAD  ( boot.z80.decl )
 270 LOAD  ( xcomp overrides )
 
@@ -37,5 +38,6 @@ CREATE ~FNT CPFNT7x7
 ( Update LATEST )
 PC ORG @ 8 + !
 ," VDP$ GRID$ PAD$ (im1) " EOT,
-ORG @ 0x100 - 256 /MOD 2 PC! 2 PC!
+ORG @ 0x100 - DUP 256 /MOD 2 PC! 2 PC!
-H@ 256 /MOD 2 PC! 2 PC!
+DUP 1 ( 16K ) segasig
+0x4000 + 256 /MOD 2 PC! 2 PC!

arch/z80/sms/xcompkbd.fs

@@ -17,6 +17,7 @@ SYSVARS 0x74 + CONSTANT PS2_MEM
 : ZFILL, ( u ) 0 DO 0 A, LOOP ;
 262 LOAD  ( xcomp )
 524 LOAD  ( font compiler )
+165 LOAD  ( Sega ROM signer )
 282 LOAD  ( boot.z80.decl )
 270 LOAD  ( xcomp overrides )
 
@@ -38,5 +39,6 @@ CREATE ~FNT CPFNT7x7
 ( Update LATEST )
 PC ORG @ 8 + !
 ," VDP$ GRID$ PS2$ (im1) " EOT,
-ORG @ 0x100 - 256 /MOD 2 PC! 2 PC!
+ORG @ 0x100 - DUP 256 /MOD 2 PC! 2 PC!
-H@ 256 /MOD 2 PC! 2 PC!
+DUP 1 ( 16K ) segasig
+0x4000 + 256 /MOD 2 PC! 2 PC!

arch/z80/sms/xcompsdc.fs

@@ -18,6 +18,7 @@ SYSVARS 0x74 + CONSTANT PS2_MEM
 : ZFILL, ( u ) 0 DO 0 A, LOOP ;
 262 LOAD  ( xcomp )
 524 LOAD  ( font compiler )
+165 LOAD  ( Sega ROM signer )
 282 LOAD  ( boot.z80.decl )
 270 LOAD  ( xcomp overrides )
 
@@ -41,5 +42,6 @@ CREATE ~FNT CPFNT7x7
 ( Update LATEST )
 PC ORG @ 8 + !
 ," VDP$ GRID$ PS2$ BLK$ (im1) " EOT,
-ORG @ 0x100 - 256 /MOD 2 PC! 2 PC!
+ORG @ 0x100 - DUP 256 /MOD 2 PC! 2 PC!
-H@ 256 /MOD 2 PC! 2 PC!
+DUP 1 ( 16K ) segasig
+0x4000 + 256 /MOD 2 PC! 2 PC!

arch/z80/sms/xcomptextmode.fs

@@ -18,6 +18,7 @@ SYSVARS 0x74 + CONSTANT PS2_MEM
 : ZFILL, ( u ) 0 DO 0 A, LOOP ;
 262 LOAD  ( xcomp )
 523 LOAD  ( font compiler )
+165 LOAD  ( Sega ROM signer )
 282 LOAD  ( boot.z80.decl )
 270 LOAD  ( xcomp overrides )
 
@@ -40,5 +41,6 @@ CREATE ~FNT CPFNT5x7
 ( Update LATEST )
 PC ORG @ 8 + !
 ," TMS$ GRID$ PS2$ BLK$ ' SDC@ BLK@* ! (im1) " EOT,
-ORG @ 0x100 - 256 /MOD 2 PC! 2 PC!
+ORG @ 0x100 - DUP 256 /MOD 2 PC! 2 PC!
-H@ 256 /MOD 2 PC! 2 PC!
+DUP 1 ( 16K ) segasig
+0x4000 + 256 /MOD 2 PC! 2 PC!

blk.fs

@@ -21,7 +21,7 @@ MASTER INDEX
 005 Z80 assembler             030 8086 assembler
 050 AVR assembler             70-99 unused
 100 Block editor              120 Visual Editor
-160 AVR SPI programmer
+160 AVR SPI programmer        165 Sega ROM signer
 170-259 unused                260 Cross compilation
 280 Z80 boot code             350 Core words
 400 AT28 EEPROM driver        401 Grid subsystem
@@ -957,6 +957,18 @@ VARIABLE aspprevx
 : aspe! ( byte addr --, write to EEPROM )
     256 /MOD ( b lsb msb ) SWAP
     0xc0 ( b msb lsb 0xc0 ) _cmd DROP asprdy ;
+( ----- 165 )
+( Sega ROM signer. See doc/sega.txt )
+: A!+^ ( a c -- a+1 ) OVER A! 1+ ;
+: segasig ( addr size -- )
+    0x2000 OVER LSHIFT ( a sz bytesz )
+    ROT TUCK + 0x10 - ( sz a end )
+    TUCK SWAP 0 ROT> ( sz end sum end a ) DO ( sz end sum )
+        I A@ + LOOP ( sz end sum ) SWAP ( sz sum end )
+    'T' A!+^ 'M' A!+^ 'R' A!+^ 0x20 A!+^ 'S' A!+^ 'E' A!+^
+    'G' A!+^ 'A' A!+^ 0 A!+^ 0 A!+^
+    ( sum's LSB ) OVER A!+^ ( MSB ) SWAP 8 RSHIFT OVER A! 1+
+    ( sz end ) 0 A!+^ 0 A!+^ 0 A!+^ SWAP 0x4a + SWAP A! ;
 ( ----- 260 )
 Cross compilation program
 

doc/hw/z80/sms/intro.txt

@@ -57,7 +57,7 @@ so far. I haven't explored whether this can run on a megadrive).
 
 # Build the ROM
 
-Running "make os.sms" in /arch/z80/sms will produce a "os.sms"
+Running "make" in /arch/z80/sms will produce a "os.sms"
 ROM that can be put as is on a SD card to the everdrive or
 flashed as is on a writable ROM cart. Then, just run the thing!
 

doc/sega.txt

@@ -0,0 +1,40 @@
+# Sega Master System ROM signatures
+
+When loading ROM, the SMS' BIOS checks for a special signature
+at the end of that ROM. If that signature is incorrect, the ROM
+doesn't load.
+
+Collapse OS has a program to generate that signature at B165.
+This document describes what it does.
+
+At boot, the BIOS checks 0x10 bytes before the 0x8000, then
+0x4000, then 0x2000 mark for a signature. This signature has
+the following structure.
+
+0x00-0x07: String constant: "TMR SEGA"
+0x08-0x09: null bytes
+0x0a-0x0b: checksum
+0x0c-0x0e: null bytes
+0x0f     : "size" flag
+
+The checksum is a simple 16-bit sum of all bytes up to the
+beginning of the signature.
+
+The size flag can have 3 values: 0x4a for an 8K ROM, 0x4b for
+16K and 0x4c for 32K. It can have other values for other kinds
+of sizes, but we don't care about them in the context of
+Collapse OS.
+
+## Generating the signature
+
+Before generating the signature, you need to have the contents
+of your ROM somewhere in memory. Then, you load B165 and you
+call "segasig" which has the signature "addr size". "addr" is
+the adress of the beginning of the ROM and "size" is 0, 1 or 2
+depending on whether your ROM is 8K, 16K or 32K.
+
+Calling the word will write the 0x10 bytes signature at the
+end of the ROM.
+
+Note that all I/O use the "Addressed device" words (see
+usage.txt), so I/O indirections will work.

tools/smsrom.c

@@ -1,53 +0,0 @@
-/* ./smsrom fname
-
-Transforms binary at fname into an 8K, 16K or 32K Sega Master System ROM with
-a header fit for an Export SMS. The resulting ROM is spit to stdout.
-
-Whether the ROM is 8, 16 or 32K depends on the size of binary at fname.
-*/
-#include <stdio.h>
-#include <inttypes.h>
-
-int main(int argc, char **argv)
-{
-    if (argc != 2) {
-        fprintf(stderr, "Usage: ./smsrom fname\n");
-        return 1;
-    }
-    FILE *fp = fopen(argv[1], "r");
-    if (!fp) {
-        fprintf(stderr, "Can't open %s.\n", argv[1]);
-        return 1;
-    }
-    fseek(fp, 0, SEEK_END);
-    long fsize = ftell(fp);
-    fseek(fp, 0, SEEK_SET);
-    uint8_t hdsz = 0x4a; // size flag in header. either 4a, 4b or 4c.
-    int romsize = 0x2000;
-    while (romsize-16 < fsize) {
-        romsize *= 2;
-        hdsz++;
-        if (romsize > 0x8000) {
-            fprintf(stderr, "binary too big\n");
-            return 1;
-        }
-    }
-    uint16_t chksum = 0;
-    for (int i=0; i<romsize-16; i++) {
-        int c = getc(fp);
-        if (c == EOF) c = 0;
-        putchar(c);
-        chksum += c;
-    }
-    // and now, the header
-    printf("TMR SEGA");
-    putchar(0);
-    putchar(0);
-    putchar(chksum & 0xff);
-    putchar(chksum >> 8);
-    putchar(0);
-    putchar(0);
-    putchar(0);
-    putchar(hdsz);
-    return 0;
-}