diff options
| -rw-r--r-- | boot.subx | 107 |
1 files changed, 55 insertions, 52 deletions
diff --git a/boot.subx b/boot.subx index 78d553cc..c19ab02a 100644 --- a/boot.subx +++ b/boot.subx @@ -987,62 +987,65 @@ store-sectors: # disk: (addr disk), lba: int, n: int, in: (addr stream byte) (ata-sector-count *(ebp+8) *(ebp+0x10)) (ata-lba *(ebp+8) *(ebp+0xc)) (ata-command *(ebp+8) 0x30) # write sectors with retries - # wait - (while-ata-busy *(ebp+8)) - (until-ata-ready-for-data *(ebp+8)) - # var data-port/edx = disk->data-port - 8b/-> *(ebp+8) 0/r32/eax - 8b/-> *(eax+0x24) 2/r32/edx - # send data - b9/copy-to-ecx 0x200/imm32 # 512 bytes per sector - # . var first-byte/ebx: byte - # . when it's more than 0xff, we're at an even-numbered byte - bb/copy-to-ebx 0xffff/imm32 -$store-sectors:loop: + # for each sector { - 81 7/subop/compare %ecx 0/imm32 - 74/jump-if-= break/disp8 - # this loop is slow, but the ATA spec also requires a small delay - (stream-empty? *(ebp+0x14)) # => eax - 3d/compare-eax-and 0/imm32/false - 75/jump-if-!= break/disp8 - # read byte from stream - (read-byte *(ebp+0x14)) # => eax - # if we're at an odd-numbered byte, save it to first-byte + # wait + (while-ata-busy *(ebp+8)) + (until-ata-ready-for-data *(ebp+8)) + # var data-port/edx = disk->data-port + 8b/-> *(ebp+8) 0/r32/eax + 8b/-> *(eax+0x24) 2/r32/edx + # send data + b9/copy-to-ecx 0x200/imm32 # 512 bytes per sector + # . var first-byte/ebx: byte + # . when it's more than 0xff, we're at an even-numbered byte + bb/copy-to-ebx 0xffff/imm32 +$store-sectors:store-sector: + { + 81 7/subop/compare %ecx 0/imm32 + 74/jump-if-= break/disp8 + # this loop is slow, but the ATA spec also requires a small delay + (stream-empty? *(ebp+0x14)) # => eax + 3d/compare-eax-and 0/imm32/false + 75/jump-if-!= break/disp8 + # read byte from stream + (read-byte *(ebp+0x14)) # => eax + # if we're at an odd-numbered byte, save it to first-byte + 81 7/subop/compare %ebx 0xff/imm32 + { + 7e/jump-if-<= break/disp8 + 89/<- %ebx 0/r32/eax + eb/jump $store-sectors:store-sector/disp8 + } + # otherwise OR it with first-byte and write it out + c1/shift 4/subop/left %eax 8/imm8 + 09/or %eax 3/r32/ebx + 66 ef/write-ax-into-port-dx + 49/decrement-ecx + 49/decrement-ecx + # reset first-byte + bb/copy-to-ebx 0xffff/imm32 + eb/jump loop/disp8 + } + # write out final first-byte if necessary 81 7/subop/compare %ebx 0xff/imm32 { - 7e/jump-if-<= break/disp8 - 89/<- %ebx 0/r32/eax - eb/jump $store-sectors:loop/disp8 + 7f/jump-if-> break/disp8 + 89/<- %eax 3/r32/ebx + 66 ef/write-ax-into-port-dx + 49/decrement-ecx + 49/decrement-ecx + } + # pad zeroes + 31/xor %eax 0/r32/eax + { + 81 7/subop/compare %ecx 0/imm32 + 74/jump-if-= break/disp8 + 66 ef/write-ax-into-port-dx + 49/decrement-ecx + 49/decrement-ecx + eb/jump loop/disp8 } - # otherwise OR it with first-byte and write it out - c1/shift 4/subop/left %eax 8/imm8 - 09/or %eax 3/r32/ebx - 66 ef/write-ax-into-port-dx - 49/decrement-ecx - 49/decrement-ecx - # reset first-byte - bb/copy-to-ebx 0xffff/imm32 - eb/jump loop/disp8 - } - # write out first-byte if necessary - 81 7/subop/compare %ebx 0xff/imm32 - { - 7f/jump-if-> break/disp8 - 89/<- %eax 3/r32/ebx - 66 ef/write-ax-into-port-dx - 49/decrement-ecx - 49/decrement-ecx - } - # pad zeroes - 31/xor %eax 0/r32/eax - { - 81 7/subop/compare %ecx 0/imm32 - 74/jump-if-= break/disp8 - 66 ef/write-ax-into-port-dx - 49/decrement-ecx - 49/decrement-ecx - eb/jump loop/disp8 } $store-sectors:end: # . restore registers |