Add .usb target

src/arch/i386/Makefile

 
 MEDIA			+= exe
 
+# Special target for building Master Boot Record binary
+$(BIN)/mbr.bin : $(BIN)/mbr.o
+	$(OBJCOPY) -O binary $< $@
+
 # Some suffixes (e.g. %.zfd0) are generated directly from other
 # finished files (e.g. %.zdsk), rather than having their own prefix.
 
 %liso:	%lilo util/genliso
 	bash util/genliso $@ $<
 
+# rule to make a USB disk image
+$(BIN)/usbdisk.bin : $(BIN)/usbdisk.o
+	$(OBJCOPY) -O binary $< $@
+
+%usb: $(BIN)/usbdisk.bin %hd
+	cat $^ > $@
+
 # Add NON_AUTO_MEDIA to the media list, so that they show up in the
 # output of "make"
 #

src/arch/i386/prefix/usbdisk.S

+	.text
+	.arch i386
+	.section ".prefix", "awx", @progbits
+	.code16
+	.org 0
+
+#include "mbr.S"
+
+/* Partition table: ZIP-compatible partition 4, 64 heads, 32 sectors/track */
+	.org 446
+	.space 16
+	.space 16
+	.space 16
+	.byte 0x80, 0x01, 0x01, 0x00
+	.byte 0x01, 0x3f, 0x20, 0x01
+	.long 0x00000020
+	.long 0x00000fe0
+
+	.org 510
+	.byte 0x55, 0xaa
+
+/* Skip to start of partition */
+	.org 32 * 512