# Dump a stack trace when you abort.

== code

abort:  # e: (addr array byte)
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    (set-cursor-position-on-real-screen 0 0)
    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 *(ebp+8) 0xf 0xc)  # 0/real-screen, 0xf/fg=white, 0xc/bg=red
    (dump-call-stack)
    # crash
    {
      eb/jump loop/disp8
    }

# destroys the heap
dump-call-stack:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    # . save registers
    50/push-eax
    51/push-ecx
    52/push-edx
    53/push-ebx
    # var labels/edx: (stream {label-name, address} 0x1000)
    81 5/subop/subtract %esp 0xc000/imm32
    68/push  0xc000/imm32
    68/push  0/imm32/read
    68/push  0/imm32/write
    89/<- %edx 4/r32/esp
    #
    (load-debug-symbols %edx)  # destroys the heap
    # traverse the linked list of ebp pointers: https://wiki.osdev.org/Stack_Trace
    8b/-> *ebp 3/r32/ebx
    {
      # loop termination check
      81 7/subop/compare %ebx 0/imm32
      0f 84/jump-if-= break/disp32
      # loop body
      (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "\n" 0 0xc)
      (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 *(ebx+4) 0xf 0xc)
      # loop update
      8b/-> *ebx 3/r32/ebx
      #
      e9/jump loop/disp32
    }
$dump-call-stack:end:
    # . reclaim locals
    81 0/subop/add %esp 0x100c/imm32
    # . restore registers
    5b/pop-to-ebx
    5a/pop-to-edx
    59/pop-to-ecx
    58/pop-to-eax
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

load-debug-symbols:  # labels/edx: (stream {label-name, address})
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    # . save registers
    50/push-eax
    51/push-ecx
    52/push-edx
    53/push-ebx
    # create space for a stream on the heap, clobbering any existing data
    # var ecx: (addr stream byte)
    b9/copy-to-ecx 0x03000000/imm32
    c7 0/subop/copy *ecx 0/imm32  # write index
    c7 0/subop/copy *(ecx+4) 0/imm32  # read index
    c7 0/subop/copy *(ecx+8) 0x01000000/imm32  # stream capacity = 16MB
    # load 0x100 sectors starting from sector 10080 = 0x2760
    (load-sectors Primary-bus-primary-drive 0x2760 0x100 %ecx)
    b8/copy-to-eax 0x0300000c/imm32
    b9/copy-to-ecx 0/imm32
    {
      3d/compare-eax-and 0x030000ff/imm32
      74/jump-if-= break/disp8
      #
      8a/byte-> *eax 1/r32/CL
      (draw-grapheme-at-cursor 0 %ecx 7 0)
      (move-cursor-rightward-and-downward 0)
      #
      40/increment-eax
      eb/jump loop/disp8
    }
$load-debug-symbols:end:
    # . reclaim locals
    81 0/subop/add %esp 0x100c/imm32
    # . restore registers
    5b/pop-to-ebx
    5a/pop-to-edx
    59/pop-to-ecx
    58/pop-to-eax
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return