explicitly pass data disk to main

1 files changed, 296 insertions, 99 deletions

diff --git a/boot.subx b/boot.subx
index bc49b49d..8a4a5595 100644
--- a/boot.subx
+++ b/boot.subx
@@ -814,7 +814,42 @@ Font:
 #   https://forum.osdev.org/viewtopic.php?f=1&p=167798
 #   read-sector, according to https://www.scs.stanford.edu/11wi-cs140/pintos/specs/ata-3-std.pdf
 
-load-first-sector-from-primary-bus-secondary-drive:  # out: (addr stream byte)
+== data
+
+# We'll be gaining access just to the secondary drive on the primary bus for
+# now. It will have the designated 'data' disk so we don't mess with the code
+# disk.
+#
+# The type definition for this variable is in safe Mu (rather than unsafe
+# SubX) code.
+# All ports are 8-bit except data-port, which is 16-bit.
+Primary-bus-secondary-drive:
+  # command-port: int (write)
+  0x1f7/imm32
+  # status-port: int (read)
+  0x1f7/imm32
+  # alternative-status-port: int (read)
+  0x3f6/imm32
+  # error-port: int (read)
+  0x1f1/imm32
+  # drive-and-head-port: int
+  0x1f6/imm32
+  # sector-count-port: int
+  0x1f2/imm32
+  # lba-low-port: int
+  0x1f3/imm32
+  # lba-mid-port: int
+  0x1f4/imm32
+  # lba-high-port: int
+  0x1f5/imm32
+  # data-port: int
+  0x1f0/imm32
+  # drive-code: byte                # only drive-specific field
+  0xf0/imm32  # LBA mode also enabled
+
+== code
+
+load-sector:  # disk: (addr disk), lba: int, out: (addr stream byte)
   # . prologue
   55/push-ebp
   89/<- %ebp 4/r32/esp
@@ -823,35 +858,46 @@ load-first-sector-from-primary-bus-secondary-drive:  # out: (addr stream byte)
   51/push-ecx
   52/push-edx
   # check for drive
-  (secondary-drive-exists?)  # => eax
+  (drive-exists? *(ebp+8))  # => eax
   3d/compare-eax-and 0/imm32/false
-  0f 84/jump-if-= $load-first-sector-from-primary-bus-secondary-drive:end/disp32
+  0f 84/jump-if-= $load-sector:end/disp32
   # kick off read
-  (ata-drive-select 0xf0)  # primary bus, secondary drive; 4 LSBs contain 4 upper bits of LBA (here 0)
-  (clear-ata-error)
-  (ata-sector-count 1)
-  (ata-lba 0 0 0)  # lower 24 bits of LBA, all 0
-  (ata-command 0x20)  # read sectors with retries
+  (ata-drive-select *(ebp+8) *(ebp+0xc))
+  (clear-ata-error *(ebp+8))
+  (ata-sector-count *(ebp+8) 1)
+  (ata-lba *(ebp+8) *(ebp+0xc))
+  (ata-command *(ebp+8) 0x20)  # read sectors with retries
   # poll for results
-  (while-ata-busy)
-  (until-ata-data-available)
+  (while-ata-busy *(ebp+8))
+  (until-ata-data-available *(ebp+8))
+  # var data-port/edx = disk->data-port
+  8b/-> *(ebp+8) 0/r32/eax
+  8b/-> *(eax+0x24) 2/r32/edx
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "A: " 7 0)
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %edx 7 0)
+    (move-cursor-to-left-margin-of-next-line 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
   # emit results
   31/xor %eax 0/r32/eax
-  ba/copy-to-edx 0x1f0/imm32
   b9/copy-to-ecx 0x200/imm32  # 512 bytes per sector
   {
     81 7/subop/compare %ecx 0/imm32
     74/jump-if-= break/disp8
     66 ed/read-port-dx-into-ax
     # write 2 bytes to stream one at a time
-    (append-byte *(ebp+8) %eax)
+    (append-byte *(ebp+0x10) %eax)
     49/decrement-ecx
     c1/shift 5/subop/right-padding-zeroes %eax 8/imm8
-    (append-byte *(ebp+8) %eax)
+    (append-byte *(ebp+0x10) %eax)
     49/decrement-ecx
     eb/jump loop/disp8
   }
-$load-first-sector-from-primary-bus-secondary-drive:end:
+$load-sector:end:
   # . restore registers
   5a/pop-to-edx
   59/pop-to-ecx
@@ -861,7 +907,7 @@ $load-first-sector-from-primary-bus-secondary-drive:end:
   5d/pop-to-ebp
   c3/return
 
-store-first-sector-to-primary-bus-secondary-drive:  # in: (addr stream byte)
+store-sector:  # disk: (addr disk), lba: int, in: (addr stream byte)
   # . prologue
   55/push-ebp
   89/<- %ebp 4/r32/esp
@@ -871,40 +917,42 @@ store-first-sector-to-primary-bus-secondary-drive:  # in: (addr stream byte)
   52/push-edx
   53/push-ebx
   # check for drive
-  (secondary-drive-exists?)  # => eax
+  (drive-exists? *(ebp+8))  # => eax
   3d/compare-eax-and 0/imm32/false
-  0f 84/jump-if-= $store-first-sector-to-primary-bus-secondary-drive:end/disp32
+  0f 84/jump-if-= $store-sector:end/disp32
   # kick off write
-  (ata-drive-select 0xf0)  # primary bus, secondary drive; 4 LSBs contain 4 upper bits of LBA (here 0)
-  (clear-ata-error)
-  (ata-sector-count 1)
-  (ata-lba 0 0 0)  # lower 24 bits of LBA, all 0
-  (ata-command 0x30)  # write sectors with retries
+  (ata-drive-select *(ebp+8) *(ebp+0xc))
+  (clear-ata-error *(ebp+8))
+  (ata-sector-count *(ebp+8) 1)
+  (ata-lba *(ebp+8) *(ebp+0xc))
+  (ata-command *(ebp+8) 0x30)  # write sectors with retries
   # wait
-  (while-ata-busy)
-  (until-ata-ready-for-data)
+  (while-ata-busy *(ebp+8))
+  (until-ata-ready-for-data *(ebp+8))
+  # var data-port/edx = disk->data-port
+  8b/-> *(ebp+8) 0/r32/eax
+  8b/-> *(eax+0x24) 2/r32/edx
   # send data
-  ba/copy-to-edx 0x1f0/imm32
   b9/copy-to-ecx 0x200/imm32  # 512 bytes per sector
-  # var first-byte/ebx: byte
-  # when it's more than 0xff, we're at an even-numbered byte
+  # . var first-byte/ebx: byte
+  # . when it's more than 0xff, we're at an even-numbered byte
   bb/copy-to-ebx 0xffff/imm32
-$store-first-sector-to-primary-bus-secondary-drive:loop:
+$store-sector:loop:
   {
     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+8))  # => eax
+    (stream-empty? *(ebp+0x10))  # => eax
     3d/compare-eax-and 0/imm32/false
     75/jump-if-!= break/disp8
     # read byte from stream
-    (read-byte *(ebp+8))  # => eax
+    (read-byte *(ebp+0x10))  # => 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-first-sector-to-primary-bus-secondary-drive:loop/disp8
+      eb/jump $store-sector:loop/disp8
     }
     # otherwise OR it with first-byte and write it out
     c1/shift 4/subop/left %eax 8/imm8
@@ -935,7 +983,7 @@ $store-first-sector-to-primary-bus-secondary-drive:loop:
     49/decrement-ecx
     eb/jump loop/disp8
   }
-$store-first-sector-to-primary-bus-secondary-drive:end:
+$store-sector:end:
   # . restore registers
   5b/pop-to-ebx
   5a/pop-to-edx
@@ -948,7 +996,7 @@ $store-first-sector-to-primary-bus-secondary-drive:end:
 
 # disk helpers {{{
 
-secondary-drive-exists?:  # -> _/eax: boolean
+drive-exists?:  # disk: (addr disk) -> _/eax: boolean
   # . prologue
   55/push-ebp
   89/<- %ebp 4/r32/esp
@@ -958,37 +1006,69 @@ secondary-drive-exists?:  # -> _/eax: boolean
   {
     31/xor %eax 0/r32/eax
     ba/copy-to-edx 0x1f7/imm32
+    {
+      50/push-eax
+      51/push-ecx
+      (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "B: " 7 0)
+      (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %edx 7 0)
+      (move-cursor-to-left-margin-of-next-line 0)
+      59/pop-to-ecx
+      58/pop-to-eax
+    }
     ec/read-port-dx-into-al
     3d/compare-eax-and 0xff/imm32
     # if eax is 0xff, primary bus has no drives
     b8/copy-to-eax 0/imm32/false
-    74/jump-if-= $secondary-drive-exists?:end/disp8
+    74/jump-if-= $drive-exists?:end/disp8
   }
   # identify
-  (ata-drive-select 0xf0)  # primary bus, secondary drive
-  (ata-sector-count 0)
-  (ata-lba 0 0 0)
-  (ata-command 0xec)  # identify
-  # read status register
+  (ata-drive-select *(ebp+8) 0)
+  (ata-sector-count *(ebp+8) 0)
+  (ata-lba *(ebp+8) 0)
+  (ata-command *(ebp+8) 0xec)  # identify
+  # var status-port/edx = disk->status-port
+  8b/-> *(ebp+8) 0/r32/eax
+  8b/-> *(eax+4) 2/r32/edx  # 4 = status-port offset
+  # read status port
   # TODO: might need to spin here for 400ns: https://wiki.osdev.org/index.php?title=ATA_PIO_Mode&oldid=25664#400ns_delays
   31/xor %eax 0/r32/eax
-  ba/copy-to-edx 0x1f7/imm32
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "C: " 7 0)
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %edx 7 0)
+    (move-cursor-to-left-margin-of-next-line 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
   ec/read-port-dx-into-al
-  # if eax is 0, secondary drive does not exist
+  # if eax is 0, drive does not exist
   3d/compare-eax-and 0/imm32
   {
     74/jump-if-= break/disp8
     b8/copy-to-eax 1/imm32/true
-    eb/jump $secondary-drive-exists?:complete-identify/disp8
+    eb/jump $drive-exists?:complete-identify/disp8
   }
   # TODO: might need to perform remaining steps at https://wiki.osdev.org/index.php?title=ATA_PIO_Mode&oldid=25664#IDENTIFY_command
   b8/copy-to-eax 0/imm32/false
-$secondary-drive-exists?:complete-identify:
+$drive-exists?:complete-identify:
   50/push-eax
+  # var data-port/edx = disk->data-port
+  8b/-> *(ebp+8) 0/r32/eax
+  8b/-> *(eax+0x24) 2/r32/edx  # 0x24 = data-port offset
   # clear FIFO from the drive
-  ba/copy-to-edx 0x1f0/imm32
   b9/copy-to-ecx 0x200/imm32
   {
+      50/push-eax
+      51/push-ecx
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "D: " 7 0)
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %edx 7 0)
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 " " 7 0)
+    (move-cursor-to-left-margin-of-next-line 0)
+      59/pop-to-ecx
+      58/pop-to-eax
+  }
+  {
     81 7/subop/compare %ecx 0/imm32
     74/jump-if-= break/disp8
     # read 4 bytes
@@ -1000,7 +1080,7 @@ $secondary-drive-exists?:complete-identify:
     eb/jump loop/disp8
   }
   58/pop-to-eax
-$secondary-drive-exists?:end:
+$drive-exists?:end:
   # . restore registers
   5a/pop-to-edx
   # . epilogue
@@ -1008,19 +1088,45 @@ $secondary-drive-exists?:end:
   5d/pop-to-ebp
   c3/return
 
-ata-drive-select:  # n: byte
+ata-drive-select:  # disk: (addr disk), lba: int
   # . prologue
   55/push-ebp
   89/<- %ebp 4/r32/esp
   # . save registers
   50/push-eax
   52/push-edx
-  #
-  8b/-> *(ebp+8) 0/r32/eax
-  ba/copy-to-edx 0x1f6/imm32
+  56/push-esi
+  # esi = disk
+  8b/-> *(ebp+8) 6/r32/esi
+  # var drive-head/edx: byte = lba >> 24
+  8b/-> *(ebp+0xc) 2/r32/edx
+  c1/shift 5/subop/right-padding-zeroes %edx 0x18/imm8
+  # var drive-code/eax: byte = disk->drive-code | drive-head
+  8b/-> *(esi+0x28) 0/r32/eax  # 0x28 = drive-code offset
+  09/or= %eax 2/r32/edx
+  # var drive-and-head-port/edx: int
+  8b/-> *(esi+0x10) 2/r32/edx  # 0x10 = drive-and-head-port offset
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "E: " 7 0)
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %edx 7 0)
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 " " 7 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %eax 7 0)
+    (move-cursor-to-left-margin-of-next-line 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
   ee/write-al-into-port-dx
 $ata-drive-select:end:
   # . restore registers
+  5e/pop-to-esi
   5a/pop-to-edx
   58/pop-to-eax
   # . epilogue
@@ -1028,16 +1134,35 @@ $ata-drive-select:end:
   5d/pop-to-ebp
   c3/return
 
-clear-ata-error:
+clear-ata-error:  # disk: (addr disk)
   # . prologue
   55/push-ebp
   89/<- %ebp 4/r32/esp
   # . save registers
   50/push-eax
   52/push-edx
+  # var error-port/edx = disk->error-port
+  8b/-> *(ebp+8) 0/r32/eax
+  8b/-> *(eax+0xc) 2/r32/edx  # 0xc = error-port offset
   #
   b8/copy-to-eax 0/imm32
-  ba/copy-to-edx 0x1f1/imm32
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "F: " 7 0)
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %edx 7 0)
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 " " 7 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %eax 7 0)
+    (move-cursor-to-left-margin-of-next-line 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
   ee/write-al-into-port-dx
 $ata-error:end:
   # . restore registers
@@ -1048,16 +1173,35 @@ $ata-error:end:
   5d/pop-to-ebp
   c3/return
 
-ata-sector-count:  # n: byte
+ata-sector-count:  # disk: (addr disk), n: byte
   # . prologue
   55/push-ebp
   89/<- %ebp 4/r32/esp
   # . save registers
   50/push-eax
   52/push-edx
-  #
+  # var sector-count-port/edx = disk->sector-count-port
   8b/-> *(ebp+8) 0/r32/eax
-  ba/copy-to-edx 0x1f2/imm32
+  8b/-> *(eax+0x14) 2/r32/edx  # 0x14 = sector-count-port offset
+  #
+  8b/-> *(ebp+0xc) 0/r32/eax
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "G: " 7 0)
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %edx 7 0)
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 " " 7 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %eax 7 0)
+    (move-cursor-to-left-margin-of-next-line 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
   ee/write-al-into-port-dx
 $ata-sector-count:end:
   # . restore registers
@@ -1068,24 +1212,68 @@ $ata-sector-count:end:
   5d/pop-to-ebp
   c3/return
 
-ata-lba:  # lo: byte, mid: byte, hi: byte
+ata-lba:  # disk: (addr disk), lba: int
   # . prologue
   55/push-ebp
   89/<- %ebp 4/r32/esp
   # . save registers
   50/push-eax
   52/push-edx
-  # lo
+  # var port/edx = disk->port
   8b/-> *(ebp+8) 0/r32/eax
-  ba/copy-to-edx 0x1f3/imm32
+  8b/-> *(eax+0x18) 2/r32/edx  # 0x18 = lba-low-port offset
+  # eax = lba
+  8b/-> *(ebp+0xc) 0/r32/eax
+  # lo
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "H: " 7 0)
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %edx 7 0)
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 " " 7 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %eax 7 0)
+    (move-cursor-to-left-margin-of-next-line 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
   ee/write-al-into-port-dx
   # mid
-  8b/-> *(ebp+0xc) 0/r32/eax
-  ba/copy-to-edx 0x1f4/imm32
+  42/increment-dx  # lba-mid-port
+  c1/shift 5/subop/right-padding-zeroes %eax 8/imm8
+  {
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "I: " 7 0)
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %edx 7 0)
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 " " 7 0)
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %eax 7 0)
+    (move-cursor-to-left-margin-of-next-line 0)
+  }
   ee/write-al-into-port-dx
   # hi
-  8b/-> *(ebp+0x10) 0/r32/eax
-  ba/copy-to-edx 0x1f5/imm32
+  42/increment-dx  # lba-high-port
+  c1/shift 5/subop/right-padding-zeroes %eax 8/imm8
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "J: " 7 0)
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %edx 7 0)
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 " " 7 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %eax 7 0)
+    (move-cursor-to-left-margin-of-next-line 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
   ee/write-al-into-port-dx
 $ata-lba:end:
   # . restore registers
@@ -1096,46 +1284,35 @@ $ata-lba:end:
   5d/pop-to-ebp
   c3/return
 
-# sector: [1, 63]
-# cylinder: [0, 1023]
-ata-cyl-sector:  # sector: byte, cyl-lo: byte, cyl-hi: byte
+ata-command:  # disk: (addr disk), cmd: byte
   # . prologue
   55/push-ebp
   89/<- %ebp 4/r32/esp
   # . save registers
   50/push-eax
   52/push-edx
-  # sector
+  # var command-port/edx = disk->command-port
   8b/-> *(ebp+8) 0/r32/eax
-  ba/copy-to-edx 0x1f3/imm32
-  ee/write-al-into-port-dx
-  # cyl-lo
-  8b/-> *(ebp+0xc) 0/r32/eax
-  ba/copy-to-edx 0x1f4/imm32
-  ee/write-al-into-port-dx
-  # cyl-hi
-  8b/-> *(ebp+0x10) 0/r32/eax
-  ba/copy-to-edx 0x1f5/imm32
-  ee/write-al-into-port-dx
-$ata-lba:end:
-  # . restore registers
-  5a/pop-to-edx
-  58/pop-to-eax
-  # . epilogue
-  89/<- %esp 5/r32/ebp
-  5d/pop-to-ebp
-  c3/return
-
-ata-command:  # cmd: byte
-  # . prologue
-  55/push-ebp
-  89/<- %ebp 4/r32/esp
-  # . save registers
-  50/push-eax
-  52/push-edx
+  8b/-> *(eax+0) 2/r32/edx  # 0 = command-port offset
   #
-  8b/-> *(ebp+8) 0/r32/eax
-  ba/copy-to-edx 0x1f7/imm32
+  8b/-> *(ebp+0xc) 0/r32/eax
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "K: " 7 0)
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %edx 7 0)
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 " " 7 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %eax 7 0)
+    (move-cursor-to-left-margin-of-next-line 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
   ee/write-al-into-port-dx
 $ata-command:end:
   # . restore registers
@@ -1146,12 +1323,22 @@ $ata-command:end:
   5d/pop-to-ebp
   c3/return
 
-while-ata-busy:
+while-ata-busy:  # disk: (addr disk)
   # . save registers
   50/push-eax
   52/push-edx
-  #
-  ba/copy-to-edx 0x1f7/imm32
+  # var status-port/edx = disk->status-port
+  8b/-> *(ebp+8) 0/r32/eax
+  8b/-> *(eax+4) 2/r32/edx  # 4 = status-port offset
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "L: " 7 0)
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %edx 7 0)
+    (move-cursor-to-left-margin-of-next-line 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
   {
     ec/read-port-dx-into-al
     a8/test-bits-in-al 0x80/imm8/bsy  # set zf if bit 7 (most significant) is not set
@@ -1164,12 +1351,22 @@ $while-ata-busy:end:
   # . epilogue
   c3/return
 
-until-ata-data-available:
+until-ata-data-available:  # disk: (addr disk)
   # . save registers
   50/push-eax
   52/push-edx
-  #
-  ba/copy-to-edx 0x1f7/imm32
+  # var status-port/edx = disk->status-port
+  8b/-> *(ebp+8) 0/r32/eax
+  8b/-> *(eax+4) 2/r32/edx  # 4 = status-port offset
+  {
+    50/push-eax
+    51/push-ecx
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "M: " 7 0)
+    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %edx 7 0)
+    (move-cursor-to-left-margin-of-next-line 0)
+    59/pop-to-ecx
+    58/pop-to-eax
+  }
   {
     ec/read-port-dx-into-al
     a8/test-bits-in-al 8/imm8/drq  # set zf if bit 3 is not set