baremetal/ex2.subx


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# Test out the video mode by filling in the screen with pixels.
#
# To build a disk image:
#   ./translate_subx_baremetal baremetal/ex2.subx    # emits disk.img
# To run:
#   qemu-system-i386 disk.img
# Or:
#   bochs -f baremetal/boot.bochsrc  # boot.bochsrc loads disk.img

# main:  (address 0x8800)

== code

# ecx <- start of video memory
8b/-> 0/mod/indirect 5/rm32/use-disp32 0x7f28/disp32/video-memory  1/r32/ecx

# eax <- final pixel of video memory
8d/copy-address *(ecx + 0x0bffff) 0/r32/eax  # 0xbffff = 1024*768 - 1

# for each pixel in video memory
{
  39/compare %eax 1/r32/ecx
  7c/jump-if-< break/disp8
  # write its column number to it
  88/byte<- *eax 0/r32/AL
  48/decrement-eax
  eb/jump loop/disp8
}

# hang indefinitely
{
  eb/jump loop/disp8
}

# vim:ft=subx