Added partition table to OS image, automatically format the first partition using FAT12

.travis.yml

@@ -19,6 +19,7 @@ addons:
       - wmctrl
       # example-os build dependencies:
       - nasm
+      - mtools
 
 matrix:
   include:

example-os/Makefile

@@ -1,6 +1,12 @@
 os_filename = os.bat
 tests = test/qemu-system-i386 test/qemu-system-arm test/virtualbox test/bochs test/gui-sh test/dosbox
 
+os_image_size_kb = 1440
+os_sectors_before_partition = 720
+# CHS parameters for 1.44 MB floppy disk
+os_floppy_chs_h = 2
+os_floppy_chs_s = 9
+
 .PHONY: all
 # all: os.arm.disasm
 all: $(os_filename) os.ndisasm.disasm os.reasm.asm os.reasm os.file .gitignore Makefile
@@ -12,6 +18,12 @@ all: $(os_filename) os.ndisasm.disasm os.reasm.asm os.reasm os.file .gitignore M
 $(os_filename): os.asm ../deploy-screenshots Makefile
 	rm -f $@
 	nasm -o $@ $<
+	mformat -v "Example OS" \
+	 -T $$(($(os_image_size_kb)*1024/512-$(os_sectors_before_partition))) \
+	 -h $(os_floppy_chs_h) \
+	 -s $(os_floppy_chs_s) \
+	 -i "$@@@$$(($(os_sectors_before_partition)*512))"
+#	mcopy … "$@@@$$(($(os_sectors_before_partition)*512))"
 	chmod a+x-w $@
 
 os.file: $(os_filename) Makefile

example-os/os.asm

@@ -5,23 +5,24 @@ db `#!/usr/bin/env sh\n`
 db `: <<'EOF'\n`
 db `GOTO msdos\n`
 
+;;; The #!… above is interpreted as … jnz short 0x7c78 in x86 assembly.
 times 0x7c78-0x7c00-($-$$) db 0
-        
-;; Switch to 320x200x256 VGA mode
+
+;;; Switch to 320x200x256 VGA mode
 mov ax, 0x0013
 int 10h
 
-;; Framebuffer address is 0xa000, store it into the fs register (the segment base, in multiples of 16)
+;;; Framebuffer address is 0xa000, store it into the fs register (the segment base, in multiples of 16)
 push 0xa000
 pop fs
 
-;; Set pixel value (0, then increase at each step below)
+;;; Set pixel value (0, then increase at each step below)
 xor bl, bl
 
-;; set register di to 0
+;;; set register di to 0
 xor di,di
 
-;; Store pixels, display something flashy.
+;;; Store pixels, display something flashy.
 loop:
 	mov byte [fs:di], bl
 	inc bl
@@ -38,33 +39,46 @@ endline:
 	je end
 	jmp loop
 
-;; Infinite loop
+;;; Infinite loop
 end:
 	jmp end
 
-;; Fill the remaining bytes with 0 and end with 55 AA
-times 512-2-($-$$) db 0
-db 0x55
-db 0xaa
+;;; Fill the remaining bytes with 0 and write a partition table
+times 0x1b8-($-$$) db 0
+db "ExOSxx"        ;; 0x1b8 unique disk ID (4 bytes, can be any value)
+;;; Partition table entries follow this format:
+;;; 1 byte  Bootable flag (0x00 = no, 0x80 = yes)
+;;; 3 bytes Start Head Sector Cylinder (8 bits + 6 bits + 10 bits)
+;;; 1 byte  Partition type (0x01 = FAT12)
+;;; 3 bytes End Head Sector Cylinder (8 bits + 6 bits + 10 bits)
+;;; 4 bytes LBA offset
+;;; 4 bytes LBA length
+db 0x80, 0x00, 0x00, 0x00,  0x01, 0x00, 0x00, 0x00,  0x03, 0x00, 0x00, 0x00,  0x3d, 0x0b, 0x00, 0x00 ;; 0x1be p1
+db 0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00 ;; 0x1ce p2
+db 0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00 ;; 0x1de p3
+db 0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00 ;; 0x1ee p4
+db 0x55, 0xaa  ;; 0x1fe End the bootsector with 55 AA, which is the MBR signature.
 
-;; end of the bootsector, close the sh here-document skipped via : <<'EOF'
+;;; This is the end of the first 512 bytes (the bootsector).
+
+;;; After the bootsector, close the sh here-document skipped via : <<'EOF'
 db `\n`
 db `EOF\n`
 db `echo Hello world by the OS, from sh!\n`
 db `while sleep 10; do :; done\n`
 db `exit\n`
-;; for good measure: go into an infinite loop if the exit did not happen.
+;;; for good measure: go into an infinite loop if the exit did not happen.
 db `while :; do sleep 1; done\n`
 
-;; end of the SH section, everything until this point is skipped by MS-DOS batch due to the GOTO'
+;;; end of the SH section, everything until this point is skipped by MS-DOS batch due to the GOTO'
 db `:msdos\n`
 db `@cls\n`
 db `@echo Hello world by the OS, from MS-DOS!\n`
 db `command.com\n`
 db `exit\n`
-;; for good measure: go into an infinite loop if the exit did not happen.
+;;; for good measure: go into an infinite loop if the exit did not happen.
 db `:loop\n`
 db `GOTO loop\n`
 
-;; Fill up to 1.44M with 0
+;;; Fill up to 1.44M with 0
 times (1440*1024)-($-$$) db 0