diff options
| -rw-r--r-- | baremetal/boot.hex | 18 | ||||
| -rw-r--r-- | baremetal/ex3.hex | 57 |
2 files changed, 68 insertions, 7 deletions
diff --git a/baremetal/boot.hex b/baremetal/boot.hex index 6090eef3..cae8b456 100644 --- a/baremetal/boot.hex +++ b/baremetal/boot.hex @@ -240,7 +240,7 @@ e9 fb ff # loop forever # . var index/ecx: byte 8a # copy m8 at r32 to r8 0d # 00/mod/indirect 001/r8/cl 101/rm32/use-disp32 - cf 7d 00 00 # disp32 [label] + ce 7d 00 00 # disp32 [label] # . al = *(keyboard buffer + index) 8a # copy m8 at r32 to r8 81 # 10/mod/*+disp32 000/r8/al 001/rm32/ecx @@ -263,12 +263,12 @@ e9 fb ff # loop forever # increment index fe # increment byte 05 # 00/mod/indirect 000/subop/increment 101/rm32/use-disp32 - cf 7d 00 00 # disp32 [label] + ce 7d 00 00 # disp32 [label] # clear top nibble of index (keyboard buffer is circular) 80 # and byte 25 # 00/mod/indirect 100/subop/and 101/rm32/use-disp32 - cf 7d 00 00 # disp32 [label] - f0 # imm8 + ce 7d 00 00 # disp32 [label] + 0f # imm8 # 14d: # epilogue 61 # pop all registers @@ -284,12 +284,16 @@ e9 fb ff # loop forever 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 -00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 +00 00 00 00 00 00 00 00 00 00 00 00 00 00 +# 1ce: +# var keyboard circular buffer +# write index: nibble +00 # 1cf: -# var keyboard circular buffer index: nibble +# read index: nibble 00 -# var keyboard circular buffer: byte[16] +# circular buffer: byte[16] 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 # padding diff --git a/baremetal/ex3.hex b/baremetal/ex3.hex new file mode 100644 index 00000000..79fe8cf8 --- /dev/null +++ b/baremetal/ex3.hex @@ -0,0 +1,57 @@ +# Draw pixels in response to keyboard events. +# +# To run, first prepare a realistically sized disk image: +# dd if=/dev/zero of=disk.img count=20160 # 512-byte sectors, so 10MB +# Load the program on the disk image: +# cat baremetal/boot.hex baremetal/ex3.hex |./bootstrap run apps/hex > a.bin +# dd if=a.bin of=disk.img conv=notrunc +# To run: +# qemu-system-i386 disk.img +# Or: +# bochs -f apps/boot.bochsrc # boot.bochsrc loads disk.img + +# main: (address 0x8800) + +# eax <- LFB +8b # copy *rm32 to r32 + 05 # 00/mod/indirect 000/r32/eax 101/rm32/use-disp32 + 28 7f 00 00 # disp32 [label] + +# var read index/ecx: byte = 0 +31 c9 # ecx <- xor ecx; 11/direct 001/r32/ecx 001/rm32/ecx + +# $loop: + # CL = *read index + 8a # copy m8 at r32 to r8 + 0d # 00/mod/indirect 001/r8/cl 101/rm32/use-disp32 + cf 7d 00 00 # disp32 [label] + # CL = *(keyboard buffer + ecx) + 8a # copy m8 at r32 to r8 + 89 # 10/mod/*+disp32 001/r8/cl 001/rm32/ecx + d0 7d 00 00 # disp32 [label] + # if (CL == 0) loop (spin loop) + 80 + f9 # 11/mod/direct 111/subop/compare 001/rm8/CL + 00 # imm8 + 74 ef # loop -17 [label] +# offset 0x19: + # otherwise increment read index + fe # increment byte + 05 # 00/mod/indirect 000/subop/increment 101/rm32/use-disp32 + cf 7d 00 00 # disp32 [label] + # clear top nibble of index (keyboard buffer is circular) + 80 # and byte + 25 # 00/mod/indirect 100/subop/and 101/rm32/use-disp32 + cf 7d 00 00 # disp32 [label] + 0f # imm8 + # print a pixel in fluorescent green + c6 # copy imm8 to m8 at rm32 + 00 # 00/mod/indirect 000/subop 000/rm32/eax + 31 # imm32 + 40 # increment eax + eb dc # loop -36 [label] + +# $break: +e9 fb ff ff ff # hang indefinitely + +# vim:ft=subx |