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<a href='https://github.com/akkartik/mu/blob/main/boot.subx'>https://github.com/akkartik/mu/blob/main/boot.subx</a>
<pre id='vimCodeElement'>
<span id="L1" class="LineNr"> 1 </span><span class="subxComment"># Code for the first few disk sectors that all programs in this directory need:</span>
<span id="L2" class="LineNr"> 2 </span><span class="subxComment"># - load sectors past the first (using BIOS primitives) since only the first is available by default</span>
<span id="L3" class="LineNr"> 3 </span><span class="subxComment"># - if this fails, print 'D' at top-left of screen and halt</span>
<span id="L4" class="LineNr"> 4 </span><span class="subxComment"># - initialize a minimal graphics mode</span>
<span id="L5" class="LineNr"> 5 </span><span class="subxComment"># - switch to 32-bit mode (giving up access to BIOS primitives)</span>
<span id="L6" class="LineNr"> 6 </span><span class="subxComment"># - set up a handler for keyboard events</span>
<span id="L7" class="LineNr"> 7 </span><span class="subxComment"># - jump to start of program</span>
<span id="L8" class="LineNr"> 8 </span>
<span id="L9" class="LineNr"> 9 </span><span class="subxComment"># Code in this file needs to be more deliberate about the SubX facilities it</span>
<span id="L10" class="LineNr"> 10 </span><span class="subxComment"># uses:</span>
<span id="L11" class="LineNr"> 11 </span><span class="subxComment"># - sigils only support 32-bit general-purpose registers, so don't work with segment registers or 16-bit or 8-bit registers</span>
<span id="L12" class="LineNr"> 12 </span><span class="subxComment"># - metadata like rm32 and r32 can sometimes misleadingly refer to only the bottom 16 bits of the register; pay attention to the register name</span>
<span id="L13" class="LineNr"> 13 </span><span class="subxComment">#</span>
<span id="L14" class="LineNr"> 14 </span><span class="subxComment"># While most of Mu is thoroughly tested, this file is not. I don't yet</span>
<span id="L15" class="LineNr"> 15 </span><span class="subxComment"># understand hardware interfaces well enough to explain to others.</span>
<span id="L16" class="LineNr"> 16 </span>
<span id="L17" class="LineNr"> 17 </span><span class="subxComment"># Memory map of a Mu computer:</span>
<span id="L18" class="LineNr"> 18 </span><span class="subxComment"># code: currently 4 tracks loaded from the primary disk to [0x00007c00, 0x00027400)</span>
<span id="L19" class="LineNr"> 19 </span><span class="subxComment"># stack: grows down from 0x00070000</span>
<span id="L20" class="LineNr"> 20 </span><span class="subxComment"># heap: [0x01000000, 0x02000000)</span>
<span id="L21" class="LineNr"> 21 </span><span class="subxComment"># see 120allocate.subx</span>
<span id="L22" class="LineNr"> 22 </span><span class="subxComment"># Consult <a href="https://wiki.osdev.org/Memory_Map_(x86)">https://wiki.osdev.org/Memory_Map_(x86)</a> before modifying any of this.</span>
<span id="L23" class="LineNr"> 23 </span>
<span id="L24" class="LineNr"> 24 </span>== code
<span id="L25" class="LineNr"> 25 </span>
<span id="L26" class="LineNr"> 26 </span><span class="subxComment">## 16-bit entry point: 0x7c00</span>
<span id="L27" class="LineNr"> 27 </span>
<span id="L28" class="LineNr"> 28 </span><span class="subxComment"># Upon reset, the IBM PC:</span>
<span id="L29" class="LineNr"> 29 </span><span class="subxComment"># - loads the first sector (512 bytes)</span>
<span id="L30" class="LineNr"> 30 </span><span class="subxComment"># from some bootable image (look for the boot-sector-marker further down this file)</span>
<span id="L31" class="LineNr"> 31 </span><span class="subxComment"># to the address range [0x7c00, 0x7e00)</span>
<span id="L32" class="LineNr"> 32 </span><span class="subxComment"># - starts executing code at address 0x7c00</span>
<span id="L33" class="LineNr"> 33 </span>
<span id="L34" class="LineNr"> 34 </span> fa/disable-interrupts
<span id="L35" class="LineNr"> 35 </span>
<span id="L36" class="LineNr"> 36 </span> <span class="subxComment"># initialize segment registers</span>
<span id="L37" class="LineNr"> 37 </span> b8/copy-to-ax 0/imm16
<span id="L38" class="LineNr"> 38 </span> 8e/-&gt;seg 3/mod/direct 0/rm32/ax 3/r32/ds
<span id="L39" class="LineNr"> 39 </span> 8e/-&gt;seg 3/mod/direct 0/rm32/ax 0/r32/es
<span id="L40" class="LineNr"> 40 </span> 8e/-&gt;seg 3/mod/direct 0/rm32/ax 4/r32/fs
<span id="L41" class="LineNr"> 41 </span> 8e/-&gt;seg 3/mod/direct 0/rm32/ax 5/r32/gs
<span id="L42" class="LineNr"> 42 </span>
<span id="L43" class="LineNr"> 43 </span> <span class="subxComment"># initialize stack to 0x00070000</span>
<span id="L44" class="LineNr"> 44 </span> <span class="subxComment"># We don't read or write the stack before we get to 32-bit mode, but BIOS</span>
<span id="L45" class="LineNr"> 45 </span> <span class="subxComment"># calls do. We need to move the stack in case BIOS initializes it to some</span>
<span id="L46" class="LineNr"> 46 </span> <span class="subxComment"># low address that we want to write code into.</span>
<span id="L47" class="LineNr"> 47 </span> b8/copy-to-ax 0x7000/imm16
<span id="L48" class="LineNr"> 48 </span> 8e/-&gt;seg 3/mod/direct 0/rm32/ax 2/r32/ss
<span id="L49" class="LineNr"> 49 </span> bc/copy-to-esp 0/imm16
<span id="L50" class="LineNr"> 50 </span>
<span id="L51" class="LineNr"> 51 </span> <span class="subxComment"># undo the A20 hack: <a href="https://en.wikipedia.org/wiki/A20_line">https://en.wikipedia.org/wiki/A20_line</a></span>
<span id="L52" class="LineNr"> 52 </span> <span class="subxComment"># this is from <a href="https://github.com/mit-pdos/xv6-public/blob/master/bootasm.S">https://github.com/mit-pdos/xv6-public/blob/master/bootasm.S</a></span>
<span id="L53" class="LineNr"> 53 </span> {
<span id="L54" class="LineNr"> 54 </span> e4/read-port-into-al 0x64/imm8
<span id="L55" class="LineNr"> 55 </span> a8/test-bits-in-al 0x02/imm8 <span class="subxComment"># set zf if bit 1 (second-least significant) is not set</span>
<span id="L56" class="LineNr"> 56 </span> 75/jump-if-!zero <span class="Constant">loop</span>/imm8
<span id="L57" class="LineNr"> 57 </span> b0/copy-to-al 0xd1/imm8
<span id="L58" class="LineNr"> 58 </span> e6/write-al-into-port 0x64/imm8
<span id="L59" class="LineNr"> 59 </span> }
<span id="L60" class="LineNr"> 60 </span> {
<span id="L61" class="LineNr"> 61 </span> e4/read-port-into-al 0x64/imm8
<span id="L62" class="LineNr"> 62 </span> a8/test-bits-in-al 0x02/imm8 <span class="subxComment"># set zf if bit 1 (second-least significant) is not set</span>
<span id="L63" class="LineNr"> 63 </span> 75/jump-if-!zero <span class="Constant">loop</span>/imm8
<span id="L64" class="LineNr"> 64 </span> b0/copy-to-al 0xdf/imm8
<span id="L65" class="LineNr"> 65 </span> e6/write-al-into-port 0x64/imm8
<span id="L66" class="LineNr"> 66 </span> }
<span id="L67" class="LineNr"> 67 </span>
<span id="L68" class="LineNr"> 68 </span> <span class="subxComment"># load remaining sectors from first two tracks of disk into addresses [0x7e00, 0x17800)</span>
<span id="L69" class="LineNr"> 69 </span> b4/copy-to-ah 2/imm8/read-drive
<span id="L70" class="LineNr"> 70 </span> <span class="subxComment"># dl comes conveniently initialized at boot time with the index of the device being booted</span>
<span id="L71" class="LineNr"> 71 </span> b5/copy-to-ch 0/imm8/cylinder
<span id="L72" class="LineNr"> 72 </span> b6/copy-to-dh 0/imm8/head
<span id="L73" class="LineNr"> 73 </span> b1/copy-to-cl 2/imm8/sector <span class="subxComment"># 1-based</span>
<span id="L74" class="LineNr"> 74 </span> b0/copy-to-al 0x7d/imm8/num-sectors <span class="subxComment"># 2*63 - 1 = 125</span>
<span id="L75" class="LineNr"> 75 </span> <span class="subxComment"># address to write sectors to = es:bx = 0x7e00, contiguous with boot segment</span>
<span id="L76" class="LineNr"> 76 </span> bb/copy-to-bx 0/imm16
<span id="L77" class="LineNr"> 77 </span> 8e/-&gt;seg 3/mod/direct 3/rm32/bx 0/r32/es
<span id="L78" class="LineNr"> 78 </span> bb/copy-to-bx 0x7e00/imm16
<span id="L79" class="LineNr"> 79 </span> cd/syscall 0x13/imm8/bios-disk-services
<span id="L80" class="LineNr"> 80 </span> 0f 82/jump-if-carry <a href='boot.subx.html#L146'>disk_error</a>/disp16
<span id="L81" class="LineNr"> 81 </span>
<span id="L82" class="LineNr"> 82 </span> <span class="subxComment"># load two more tracks of disk into addresses [0x17800, 0x27400)</span>
<span id="L83" class="LineNr"> 83 </span> b4/copy-to-ah 2/imm8/read-drive
<span id="L84" class="LineNr"> 84 </span> <span class="subxComment"># dl comes conveniently initialized at boot time with the index of the device being booted</span>
<span id="L85" class="LineNr"> 85 </span> b5/copy-to-ch 0/imm8/cylinder
<span id="L86" class="LineNr"> 86 </span> b6/copy-to-dh 2/imm8/head
<span id="L87" class="LineNr"> 87 </span> b1/copy-to-cl 1/imm8/sector <span class="subxComment"># 1-based</span>
<span id="L88" class="LineNr"> 88 </span> b0/copy-to-al 0x7e/imm8/num-sectors <span class="subxComment"># 2*63 = 126</span>
<span id="L89" class="LineNr"> 89 </span> <span class="subxComment"># address to write sectors to = es:bx = 0x17800, contiguous with boot segment</span>
<span id="L90" class="LineNr"> 90 </span> bb/copy-to-bx 0x1780/imm16
<span id="L91" class="LineNr"> 91 </span> 8e/-&gt;seg 3/mod/direct 3/rm32/bx 0/r32/es
<span id="L92" class="LineNr"> 92 </span> bb/copy-to-bx 0/imm16
<span id="L93" class="LineNr"> 93 </span> cd/syscall 0x13/imm8/bios-disk-services
<span id="L94" class="LineNr"> 94 </span> 0f 82/jump-if-carry <a href='boot.subx.html#L146'>disk_error</a>/disp16
<span id="L95" class="LineNr"> 95 </span>
<span id="L96" class="LineNr"> 96 </span> <span class="subxComment"># load two more tracks of disk into addresses [0x27400, 0x37000)</span>
<span id="L97" class="LineNr"> 97 </span> b4/copy-to-ah 2/imm8/read-drive
<span id="L98" class="LineNr"> 98 </span> <span class="subxComment"># dl comes conveniently initialized at boot time with the index of the device being booted</span>
<span id="L99" class="LineNr"> 99 </span> b5/copy-to-ch 0/imm8/cylinder
<span id="L100" class="LineNr"> 100 </span> b6/copy-to-dh 4/imm8/head
<span id="L101" class="LineNr"> 101 </span> b1/copy-to-cl 1/imm8/sector <span class="subxComment"># 1-based</span>
<span id="L102" class="LineNr"> 102 </span> b0/copy-to-al 0x7e/imm8/num-sectors <span class="subxComment"># 2*63 = 126</span>
<span id="L103" class="LineNr"> 103 </span> <span class="subxComment"># address to write sectors to = es:bx = 0x27400, contiguous with boot segment</span>
<span id="L104" class="LineNr"> 104 </span> bb/copy-to-bx 0x2740/imm16
<span id="L105" class="LineNr"> 105 </span> 8e/-&gt;seg 3/mod/direct 3/rm32/bx 0/r32/es
<span id="L106" class="LineNr"> 106 </span> bb/copy-to-bx 0/imm16
<span id="L107" class="LineNr"> 107 </span> cd/syscall 0x13/imm8/bios-disk-services
<span id="L108" class="LineNr"> 108 </span> 0f 82/jump-if-carry <a href='boot.subx.html#L146'>disk_error</a>/disp16
<span id="L109" class="LineNr"> 109 </span>
<span id="L110" class="LineNr"> 110 </span> <span class="subxComment"># reset es</span>
<span id="L111" class="LineNr"> 111 </span> bb/copy-to-bx 0/imm16
<span id="L112" class="LineNr"> 112 </span> 8e/-&gt;seg 3/mod/direct 3/rm32/bx 0/r32/es
<span id="L113" class="LineNr"> 113 </span>
<span id="L114" class="LineNr"> 114 </span> <span class="subxComment"># adjust video mode</span>
<span id="L115" class="LineNr"> 115 </span> b4/copy-to-ah 0x4f/imm8 <span class="subxComment"># VBE commands</span>
<span id="L116" class="LineNr"> 116 </span> b0/copy-to-al 2/imm8 <span class="subxComment"># set video mode</span>
<span id="L117" class="LineNr"> 117 </span> bb/copy-to-bx 0x4105/imm16 <span class="subxComment"># 0x0105 | 0x4000</span>
<span id="L118" class="LineNr"> 118 </span> <span class="subxComment"># 0x0105 = graphics mode 1024x768x256</span>
<span id="L119" class="LineNr"> 119 </span> <span class="subxComment"># (alternative candidate: 0x0101 for 640x480x256)</span>
<span id="L120" class="LineNr"> 120 </span> <span class="subxComment"># 0x4000 bit = configure linear frame buffer in Bochs emulator; hopefully this doesn't hurt anything when running natively</span>
<span id="L121" class="LineNr"> 121 </span> cd/syscall 0x10/imm8/bios-video-services
<span id="L122" class="LineNr"> 122 </span>
<span id="L123" class="LineNr"> 123 </span> <span class="subxComment"># load information for the (hopefully) current video mode</span>
<span id="L124" class="LineNr"> 124 </span> <span class="subxComment"># mostly just for the address to the linear frame buffer</span>
<span id="L125" class="LineNr"> 125 </span> b4/copy-to-ah 0x4f/imm8 <span class="subxComment"># VBE commands</span>
<span id="L126" class="LineNr"> 126 </span> b0/copy-to-al 1/imm8 <span class="subxComment"># get video mode info</span>
<span id="L127" class="LineNr"> 127 </span> b9/copy-to-cx 0x0105/imm16 <span class="subxComment"># mode we requested</span>
<span id="L128" class="LineNr"> 128 </span> bf/copy-to-di <span class="SpecialChar"><a href='boot.subx.html#L513'>Video-mode-info</a></span>/imm16
<span id="L129" class="LineNr"> 129 </span> cd/syscall 0x10/imm8/bios-video-services
<span id="L130" class="LineNr"> 130 </span>
<span id="L131" class="LineNr"> 131 </span> <span class="subxComment">## switch to 32-bit mode</span>
<span id="L132" class="LineNr"> 132 </span> <span class="subxComment"># load global descriptor table</span>
<span id="L133" class="LineNr"> 133 </span> <span class="subxComment"># We can't refer to the label directly because SubX doesn't do the right</span>
<span id="L134" class="LineNr"> 134 </span> <span class="subxComment"># thing for lgdt, so rather than make errors worse in most places we instead</span>
<span id="L135" class="LineNr"> 135 </span> <span class="subxComment"># pin gdt_descriptor below.</span>
<span id="L136" class="LineNr"> 136 </span> 0f 01 2/subop/lgdt 0/mod/indirect 6/rm32/use-disp16 0x7ce0/disp16/gdt_descriptor
<span id="L137" class="LineNr"> 137 </span> <span class="subxComment"># enable paging</span>
<span id="L138" class="LineNr"> 138 </span> 0f 20/&lt;-cr 3/mod/direct 0/rm32/eax 0/r32/cr0
<span id="L139" class="LineNr"> 139 </span> 66 83 1/subop/or 3/mod/direct 0/rm32/eax 1/imm8 <span class="subxComment"># eax &lt;- or 0x1</span>
<span id="L140" class="LineNr"> 140 </span> 0f 22/-&gt;cr 3/mod/direct 0/rm32/eax 0/r32/cr0
<span id="L141" class="LineNr"> 141 </span> <span class="subxComment"># far jump to initialize_32bit_mode that sets cs to offset 8 in the gdt in the process</span>
<span id="L142" class="LineNr"> 142 </span> <span class="subxComment"># We can't refer to the label directly because SubX doesn't have syntax for</span>
<span id="L143" class="LineNr"> 143 </span> <span class="subxComment"># segment selectors. So we instead pin initialize_32bit_mode below.</span>
<span id="L144" class="LineNr"> 144 </span> ea/jump-far-absolute 0x00087d00/disp32 <span class="subxComment"># address 0x7d00 in offset 8 of the gdt</span>
<span id="L145" class="LineNr"> 145 </span>
<span id="L146" class="LineNr"> 146 </span><span class="subxFunction">disk_error</span>:
<span id="L147" class="LineNr"> 147 </span> <span class="subxComment"># print 'D' to top-left of screen to indicate disk error</span>
<span id="L148" class="LineNr"> 148 </span> <span class="subxComment"># *0xb8000 &lt;- 0x0f44</span>
<span id="L149" class="LineNr"> 149 </span> bb/copy-to-bx 0xb800/imm16
<span id="L150" class="LineNr"> 150 </span> 8e/-&gt;seg 3/mod/direct 3/rm32/bx 3/r32/ds
<span id="L151" class="LineNr"> 151 </span> b0/copy-to-al 0x44/imm8/D
<span id="L152" class="LineNr"> 152 </span> b4/copy-to-ah 0x0f/imm8/white-on-black
<span id="L153" class="LineNr"> 153 </span> bb/copy-to-bx 0/imm16
<span id="L154" class="LineNr"> 154 </span> 89/&lt;- 0/mod/indirect 7/rm32/bx 0/r32/ax <span class="subxComment"># *ds:bx &lt;- ax</span>
<span id="L155" class="LineNr"> 155 </span> <span class="subxComment"># loop forever</span>
<span id="L156" class="LineNr"> 156 </span> {
<span id="L157" class="LineNr"> 157 </span> eb/jump <span class="Constant">loop</span>/disp8
<span id="L158" class="LineNr"> 158 </span> }
<span id="L159" class="LineNr"> 159 </span>
<span id="L160" class="LineNr"> 160 </span><span class="subxComment">## GDT: 3 records of 8 bytes each</span>
<span id="L161" class="LineNr"> 161 </span>== data 0x7ce0
<span id="L162" class="LineNr"> 162 </span><span class="subxFunction">gdt_descriptor</span>:
<span id="L163" class="LineNr"> 163 </span> 0x17/imm16 <span class="subxComment"># final index of gdt = size of gdt - 1</span>
<span id="L164" class="LineNr"> 164 </span> <a href='boot.subx.html#L166'>gdt_start</a>/imm32/start
<span id="L165" class="LineNr"> 165 </span>
<span id="L166" class="LineNr"> 166 </span><span class="subxFunction">gdt_start</span>:
<span id="L167" class="LineNr"> 167 </span><span class="subxComment"># offset 0: gdt_null: mandatory null descriptor</span>
<span id="L168" class="LineNr"> 168 </span> 00 00 00 00 00 00 00 00
<span id="L169" class="LineNr"> 169 </span><span class="subxComment"># offset 8: gdt_code</span>
<span id="L170" class="LineNr"> 170 </span> ff ff <span class="subxComment"># limit[0:16]</span>
<span id="L171" class="LineNr"> 171 </span> 00 00 00 <span class="subxComment"># base[0:24]</span>
<span id="L172" class="LineNr"> 172 </span> 9a <span class="subxComment"># 1/present 00/privilege 1/descriptor type = 1001b</span>
<span id="L173" class="LineNr"> 173 </span> <span class="subxComment"># 1/code 0/conforming 1/readable 0/accessed = 1010b</span>
<span id="L174" class="LineNr"> 174 </span> cf <span class="subxComment"># 1/granularity 1/32-bit 0/64-bit-segment 0/AVL = 1100b</span>
<span id="L175" class="LineNr"> 175 </span> <span class="subxComment"># limit[16:20] = 1111b</span>
<span id="L176" class="LineNr"> 176 </span> 00 <span class="subxComment"># base[24:32]</span>
<span id="L177" class="LineNr"> 177 </span><span class="subxComment"># offset 16: gdt_data</span>
<span id="L178" class="LineNr"> 178 </span> ff ff <span class="subxComment"># limit[0:16]</span>
<span id="L179" class="LineNr"> 179 </span> 00 00 00 <span class="subxComment"># base[0:24]</span>
<span id="L180" class="LineNr"> 180 </span> 92 <span class="subxComment"># 1/present 00/privilege 1/descriptor type = 1001b</span>
<span id="L181" class="LineNr"> 181 </span> <span class="subxComment"># 0/data 0/conforming 1/readable 0/accessed = 0010b</span>
<span id="L182" class="LineNr"> 182 </span> cf <span class="subxComment"># same as gdt_code</span>
<span id="L183" class="LineNr"> 183 </span> 00 <span class="subxComment"># base[24:32]</span>
<span id="L184" class="LineNr"> 184 </span><span class="subxComment"># gdt_end:</span>
<span id="L185" class="LineNr"> 185 </span>
<span id="L186" class="LineNr"> 186 </span><span class="subxComment">## 32-bit code from this point</span>
<span id="L187" class="LineNr"> 187 </span>
<span id="L188" class="LineNr"> 188 </span>== code 0x7d00
<span id="L189" class="LineNr"> 189 </span><span class="subxFunction">initialize_32bit_mode</span>:
<span id="L190" class="LineNr"> 190 </span> 66 b8/copy-to-ax 0x10/imm16 <span class="subxComment"># offset 16 from gdt_start</span>
<span id="L191" class="LineNr"> 191 </span> 8e/-&gt;seg 3/mod/direct 0/rm32/ax 3/r32/ds
<span id="L192" class="LineNr"> 192 </span> 8e/-&gt;seg 3/mod/direct 0/rm32/ax 2/r32/ss
<span id="L193" class="LineNr"> 193 </span> 8e/-&gt;seg 3/mod/direct 0/rm32/ax 0/r32/es
<span id="L194" class="LineNr"> 194 </span> 8e/-&gt;seg 3/mod/direct 0/rm32/ax 4/r32/fs
<span id="L195" class="LineNr"> 195 </span> 8e/-&gt;seg 3/mod/direct 0/rm32/ax 5/r32/gs
<span id="L196" class="LineNr"> 196 </span>
<span id="L197" class="LineNr"> 197 </span> bc/copy-to-esp 0x00070000/imm32
<span id="L198" class="LineNr"> 198 </span>
<span id="L199" class="LineNr"> 199 </span> <span class="subxComment">## load interrupt handlers</span>
<span id="L200" class="LineNr"> 200 </span> <span class="subxComment"># We can't refer to the label directly because SubX doesn't do the right</span>
<span id="L201" class="LineNr"> 201 </span> <span class="subxComment"># thing for lidt, so rather than make errors worse in most places we instead</span>
<span id="L202" class="LineNr"> 202 </span> <span class="subxComment"># pin idt_descriptor below.</span>
<span id="L203" class="LineNr"> 203 </span> 0f 01 3/subop/lidt 0/mod/indirect 5/rm32/use-disp32 0x7e00/disp32/idt_descriptor
<span id="L204" class="LineNr"> 204 </span>
<span id="L205" class="LineNr"> 205 </span> <span class="subxComment"># For now, not bothering reprogramming the IRQ to not conflict with software</span>
<span id="L206" class="LineNr"> 206 </span> <span class="subxComment"># exceptions.</span>
<span id="L207" class="LineNr"> 207 </span> <span class="subxComment"># <a href="https://wiki.osdev.org/index.php?title=8259_PIC&amp;oldid=24650#Protected_Mode">https://wiki.osdev.org/index.php?title=8259_PIC&amp;oldid=24650#Protected_Mode</a></span>
<span id="L208" class="LineNr"> 208 </span> <span class="subxComment">#</span>
<span id="L209" class="LineNr"> 209 </span> <span class="subxComment"># Interrupt 1 (keyboard) conflicts with debugger faults. We don't use a</span>
<span id="L210" class="LineNr"> 210 </span> <span class="subxComment"># debugger.</span>
<span id="L211" class="LineNr"> 211 </span> <span class="subxComment"># Reference:</span>
<span id="L212" class="LineNr"> 212 </span> <span class="subxComment"># <a href="https://wiki.osdev.org/Exceptions">https://wiki.osdev.org/Exceptions</a></span>
<span id="L213" class="LineNr"> 213 </span>
<span id="L214" class="LineNr"> 214 </span> <span class="subxComment"># enable keyboard IRQ (1)</span>
<span id="L215" class="LineNr"> 215 </span> b0/copy-to-al 0xfd/imm8 <span class="subxComment"># disable mask for IRQ1</span>
<span id="L216" class="LineNr"> 216 </span> e6/write-al-into-port 0x21/imm8
<span id="L217" class="LineNr"> 217 </span>
<span id="L218" class="LineNr"> 218 </span> fb/enable-interrupts
<span id="L219" class="LineNr"> 219 </span>
<span id="L220" class="LineNr"> 220 </span> (<a href='boot.subx.html#L1277'>initialize-mouse</a>)
<span id="L221" class="LineNr"> 221 </span>
<span id="L222" class="LineNr"> 222 </span> <span class="subxComment">## enable floating point</span>
<span id="L223" class="LineNr"> 223 </span> db/floating-point-coprocessor e3/initialize
<span id="L224" class="LineNr"> 224 </span> <span class="subxComment"># eax &lt;- cr4</span>
<span id="L225" class="LineNr"> 225 </span> 0f 20/&lt;-cr 3/mod/direct 0/rm32/eax 4/r32/cr4
<span id="L226" class="LineNr"> 226 </span> <span class="subxComment"># eax &lt;- or bit 9</span>
<span id="L227" class="LineNr"> 227 </span> 0f ba/bit-test 5/subop/bit-test-and-set 3/mod/direct 0/rm32/eax 9/imm8
<span id="L228" class="LineNr"> 228 </span> <span class="subxComment"># cr4 &lt;- eax</span>
<span id="L229" class="LineNr"> 229 </span> 0f 22/-&gt;cr 3/mod/direct 0/rm32/eax 4/r32/cr4
<span id="L230" class="LineNr"> 230 </span>
<span id="L231" class="LineNr"> 231 </span> e9/jump <span class="SpecialChar">Entry</span>/disp32
<span id="L232" class="LineNr"> 232 </span>
<span id="L233" class="LineNr"> 233 </span>== boot-sector-marker 0x7dfe
<span id="L234" class="LineNr"> 234 </span><span class="subxComment"># final 2 bytes of boot sector</span>
<span id="L235" class="LineNr"> 235 </span>55 aa
<span id="L236" class="LineNr"> 236 </span>
<span id="L237" class="LineNr"> 237 </span><span class="subxComment">## sector 2 onwards loaded by load_disk, not automatically on boot</span>
<span id="L238" class="LineNr"> 238 </span>
<span id="L239" class="LineNr"> 239 </span>== data 0x7e00
<span id="L240" class="LineNr"> 240 </span><span class="subxFunction">idt_descriptor</span>:
<span id="L241" class="LineNr"> 241 </span> ff 03 <span class="subxComment"># final index of idt = size of idt - 1</span>
<span id="L242" class="LineNr"> 242 </span> <a href='boot.subx.html#L246'>idt_start</a>/imm32/start
<span id="L243" class="LineNr"> 243 </span>
<span id="L244" class="Folded"> 244 </span><span class="Folded">+-- 55 lines: # interrupt descriptor table ----------------------------------------------------------------------------------------------------------------------------------------------</span>
<span id="L299" class="LineNr"> 299 </span>
<span id="L300" class="LineNr"> 300 </span>== code
<span id="L301" class="LineNr"> 301 </span>
<span id="L302" class="LineNr"> 302 </span><span class="subxFunction">null-interrupt-handler</span>:
<span id="L303" class="LineNr"> 303 </span> cf/return-from-interrupt
<span id="L304" class="LineNr"> 304 </span>
<span id="L305" class="LineNr"> 305 </span><span class="subxFunction">keyboard-interrupt-handler</span>:
<span id="L306" class="LineNr"> 306 </span> <span class="subxComment"># prologue</span>
<span id="L307" class="LineNr"> 307 </span> fa/disable-interrupts
<span id="L308" class="LineNr"> 308 </span> 60/push-all-registers
<span id="L309" class="LineNr"> 309 </span> <span class="subxComment"># acknowledge interrupt</span>
<span id="L310" class="LineNr"> 310 </span> b0/copy-to-al 0x20/imm8
<span id="L311" class="LineNr"> 311 </span> e6/write-al-into-port 0x20/imm8
<span id="L312" class="LineNr"> 312 </span> 31/xor %eax 0/r32/eax
<span id="L313" class="LineNr"> 313 </span> <span class="subxComment"># check output buffer of 8042 keyboard controller (<a href="https://web.archive.org/web/20040604041507/http://panda.cs.ndsu.nodak.edu/~achapwes/PICmicro/keyboard/atkeyboard.html)">https://web.archive.org/web/20040604041507/http://panda.cs.ndsu.nodak.edu/~achapwes/PICmicro/keyboard/atkeyboard.html)</a></span>
<span id="L314" class="LineNr"> 314 </span> e4/read-port-into-al 0x64/imm8
<span id="L315" class="LineNr"> 315 </span> a8/test-bits-in-al 0x01/imm8 <span class="subxComment"># set zf if bit 0 (least significant) is not set</span>
<span id="L316" class="LineNr"> 316 </span> 74/jump-if-not-set $keyboard-interrupt-handler:epilogue/disp8
<span id="L317" class="LineNr"> 317 </span> <span class="subxH1Comment"># - if keyboard buffer is full, return</span>
<span id="L318" class="LineNr"> 318 </span> <span class="subxComment"># var dest-addr/ecx: (addr byte) = (keyboard-buffer + *keyboard-buffer:write)</span>
<span id="L319" class="LineNr"> 319 </span> 31/xor %ecx 1/r32/ecx
<span id="L320" class="LineNr"> 320 </span> 8a/byte-&gt; *<span class="SpecialChar">Keyboard-buffer</span>:<a href='108write.subx.html#L11'>write</a> 1/r32/cl
<span id="L321" class="LineNr"> 321 </span> 81 0/subop/add %ecx <span class="SpecialChar">Keyboard-buffer</span>:data/imm32
<span id="L322" class="LineNr"> 322 </span> <span class="subxComment"># al = *dest-addr</span>
<span id="L323" class="LineNr"> 323 </span> 8a/byte-&gt; *ecx 0/r32/al
<span id="L324" class="LineNr"> 324 </span> <span class="subxComment"># if (al != 0) return</span>
<span id="L325" class="LineNr"> 325 </span> 3c/compare-al-and 0/imm8
<span id="L326" class="LineNr"> 326 </span> 75/jump-if-!= $keyboard-interrupt-handler:epilogue/disp8
<span id="L327" class="LineNr"> 327 </span> <span class="subxH1Comment"># - read keycode</span>
<span id="L328" class="LineNr"> 328 </span> e4/read-port-into-al 0x60/imm8
<span id="L329" class="LineNr"> 329 </span> <span class="subxH1Comment"># - key released</span>
<span id="L330" class="LineNr"> 330 </span> <span class="subxComment"># if (al == 0xaa) shift = false # left shift is being lifted</span>
<span id="L331" class="LineNr"> 331 </span> {
<span id="L332" class="LineNr"> 332 </span> 3c/compare-al-and 0xaa/imm8
<span id="L333" class="LineNr"> 333 </span> 75/jump-if-!= <span class="Constant">break</span>/disp8
<span id="L334" class="LineNr"> 334 </span> <span class="subxComment"># *shift = 0</span>
<span id="L335" class="LineNr"> 335 </span> c7 0/subop/copy *Keyboard-shift-pressed? 0/imm32
<span id="L336" class="LineNr"> 336 </span> }
<span id="L337" class="LineNr"> 337 </span> <span class="subxComment"># if (al == 0xb6) shift = false # right shift is being lifted</span>
<span id="L338" class="LineNr"> 338 </span> {
<span id="L339" class="LineNr"> 339 </span> 3c/compare-al-and 0xb6/imm8
<span id="L340" class="LineNr"> 340 </span> 75/jump-if-!= <span class="Constant">break</span>/disp8
<span id="L341" class="LineNr"> 341 </span> <span class="subxComment"># *shift = 0</span>
<span id="L342" class="LineNr"> 342 </span> c7 0/subop/copy *Keyboard-shift-pressed? 0/imm32
<span id="L343" class="LineNr"> 343 </span> }
<span id="L344" class="LineNr"> 344 </span> <span class="subxComment"># if (al == 0x9d) ctrl = false # ctrl is being lifted</span>
<span id="L345" class="LineNr"> 345 </span> {
<span id="L346" class="LineNr"> 346 </span> 3c/compare-al-and 0x9d/imm8
<span id="L347" class="LineNr"> 347 </span> 75/jump-if-!= <span class="Constant">break</span>/disp8
<span id="L348" class="LineNr"> 348 </span> <span class="subxComment"># *ctrl = 0</span>
<span id="L349" class="LineNr"> 349 </span> c7 0/subop/copy *Keyboard-ctrl-pressed? 0/imm32
<span id="L350" class="LineNr"> 350 </span> }
<span id="L351" class="LineNr"> 351 </span> <span class="subxComment"># if (al &amp; 0x80) a key is being lifted; return</span>
<span id="L352" class="LineNr"> 352 </span> 50/push-eax
<span id="L353" class="LineNr"> 353 </span> 24/and-al-with 0x80/imm8
<span id="L354" class="LineNr"> 354 </span> 3c/compare-al-and 0/imm8
<span id="L355" class="LineNr"> 355 </span> 58/pop-to-eax
<span id="L356" class="LineNr"> 356 </span> 75/jump-if-!= $keyboard-interrupt-handler:epilogue/disp8
<span id="L357" class="LineNr"> 357 </span> <span class="subxH1Comment"># - key pressed</span>
<span id="L358" class="LineNr"> 358 </span> <span class="subxComment"># if (al == 0x2a) shift = true, return # left shift pressed</span>
<span id="L359" class="LineNr"> 359 </span> {
<span id="L360" class="LineNr"> 360 </span> 3c/compare-al-and 0x2a/imm8
<span id="L361" class="LineNr"> 361 </span> 75/jump-if-!= <span class="Constant">break</span>/disp8
<span id="L362" class="LineNr"> 362 </span> <span class="subxComment"># *shift = 1</span>
<span id="L363" class="LineNr"> 363 </span> c7 0/subop/copy *Keyboard-shift-pressed? 1/imm32
<span id="L364" class="LineNr"> 364 </span> <span class="subxComment"># return</span>
<span id="L365" class="LineNr"> 365 </span> eb/jump $keyboard-interrupt-handler:epilogue/disp8
<span id="L366" class="LineNr"> 366 </span> }
<span id="L367" class="LineNr"> 367 </span> <span class="subxComment"># if (al == 0x36) shift = true, return # right shift pressed</span>
<span id="L368" class="LineNr"> 368 </span> {
<span id="L369" class="LineNr"> 369 </span> 3c/compare-al-and 0x36/imm8
<span id="L370" class="LineNr"> 370 </span> 75/jump-if-!= <span class="Constant">break</span>/disp8
<span id="L371" class="LineNr"> 371 </span> <span class="subxComment"># *shift = 1</span>
<span id="L372" class="LineNr"> 372 </span> c7 0/subop/copy *Keyboard-shift-pressed? 1/imm32
<span id="L373" class="LineNr"> 373 </span> <span class="subxComment"># return</span>
<span id="L374" class="LineNr"> 374 </span> eb/jump $keyboard-interrupt-handler:epilogue/disp8
<span id="L375" class="LineNr"> 375 </span> }
<span id="L376" class="LineNr"> 376 </span> <span class="subxComment"># if (al == 0x1d) ctrl = true, return</span>
<span id="L377" class="LineNr"> 377 </span> {
<span id="L378" class="LineNr"> 378 </span> 3c/compare-al-and 0x1d/imm8
<span id="L379" class="LineNr"> 379 </span> 75/jump-if-!= <span class="Constant">break</span>/disp8
<span id="L380" class="LineNr"> 380 </span> <span class="subxComment"># *ctrl = 1</span>
<span id="L381" class="LineNr"> 381 </span> c7 0/subop/copy *Keyboard-ctrl-pressed? 1/imm32
<span id="L382" class="LineNr"> 382 </span> <span class="subxComment"># return</span>
<span id="L383" class="LineNr"> 383 </span> eb/jump $keyboard-interrupt-handler:epilogue/disp8
<span id="L384" class="LineNr"> 384 </span> }
<span id="L385" class="LineNr"> 385 </span> <span class="subxH1Comment"># - convert key to character</span>
<span id="L386" class="LineNr"> 386 </span> <span class="subxComment"># if (shift) use keyboard shift map</span>
<span id="L387" class="LineNr"> 387 </span> {
<span id="L388" class="LineNr"> 388 </span> 81 7/subop/compare *Keyboard-shift-pressed? 0/imm32
<span id="L389" class="LineNr"> 389 </span> 74/jump-if-= <span class="Constant">break</span>/disp8
<span id="L390" class="LineNr"> 390 </span> <span class="subxComment"># sigils don't currently support labels inside *(eax+label)</span>
<span id="L391" class="LineNr"> 391 </span> 05/add-to-eax <span class="SpecialChar"><a href='boot.subx.html#L471'>Keyboard-shift-map</a></span>/imm32
<span id="L392" class="LineNr"> 392 </span> 8a/byte-&gt; *eax 0/r32/al
<span id="L393" class="LineNr"> 393 </span> eb/jump $keyboard-interrupt-handler:select-map-done/disp8
<span id="L394" class="LineNr"> 394 </span> }
<span id="L395" class="LineNr"> 395 </span> <span class="subxComment"># if (ctrl) al = *(ctrl map + al)</span>
<span id="L396" class="LineNr"> 396 </span> {
<span id="L397" class="LineNr"> 397 </span> 81 7/subop/compare *Keyboard-ctrl-pressed? 0/imm32
<span id="L398" class="LineNr"> 398 </span> 74/jump-if-= <span class="Constant">break</span>/disp8
<span id="L399" class="LineNr"> 399 </span> 05/add-to-eax <span class="SpecialChar"><a href='boot.subx.html#L497'>Keyboard-ctrl-map</a></span>/imm32
<span id="L400" class="LineNr"> 400 </span> 8a/byte-&gt; *eax 0/r32/al
<span id="L401" class="LineNr"> 401 </span> eb/jump $keyboard-interrupt-handler:select-map-done/disp8
<span id="L402" class="LineNr"> 402 </span> }
<span id="L403" class="LineNr"> 403 </span> <span class="subxComment"># otherwise al = *(normal map + al)</span>
<span id="L404" class="LineNr"> 404 </span> 05/add-to-eax <span class="SpecialChar"><a href='boot.subx.html#L443'>Keyboard-normal-map</a></span>/imm32
<span id="L405" class="LineNr"> 405 </span> 8a/byte-&gt; *eax 0/r32/al
<span id="L406" class="LineNr"> 406 </span><span class="Constant">$keyboard-interrupt-handler:select-map-done</span>:
<span id="L407" class="LineNr"> 407 </span> <span class="subxH1Comment"># - if there's no character mapping, return</span>
<span id="L408" class="LineNr"> 408 </span> {
<span id="L409" class="LineNr"> 409 </span> 3c/compare-al-and 0/imm8
<span id="L410" class="LineNr"> 410 </span> 74/jump-if-= <span class="Constant">break</span>/disp8
<span id="L411" class="LineNr"> 411 </span> <span class="subxH1Comment"># - store al in keyboard buffer</span>
<span id="L412" class="LineNr"> 412 </span> 88/&lt;- *ecx 0/r32/al
<span id="L413" class="LineNr"> 413 </span> <span class="subxComment"># increment index</span>
<span id="L414" class="LineNr"> 414 </span> fe/increment-byte *<span class="SpecialChar">Keyboard-buffer</span>:<a href='108write.subx.html#L11'>write</a>
<span id="L415" class="LineNr"> 415 </span> <span class="subxComment"># clear top nibble of index (keyboard buffer is circular)</span>
<span id="L416" class="LineNr"> 416 </span> 80 4/subop/and-byte *<span class="SpecialChar">Keyboard-buffer</span>:<a href='108write.subx.html#L11'>write</a> 0x0f/imm8
<span id="L417" class="LineNr"> 417 </span> }
<span id="L418" class="LineNr"> 418 </span><span class="Constant">$keyboard-interrupt-handler:epilogue</span>:
<span id="L419" class="LineNr"> 419 </span> <span class="subxComment"># epilogue</span>
<span id="L420" class="LineNr"> 420 </span> 61/pop-all-registers
<span id="L421" class="LineNr"> 421 </span> fb/enable-interrupts
<span id="L422" class="LineNr"> 422 </span> cf/return-from-interrupt
<span id="L423" class="LineNr"> 423 </span>
<span id="L424" class="LineNr"> 424 </span>== data
<span id="L425" class="LineNr"> 425 </span>Keyboard-shift-pressed?: <span class="subxComment"># boolean</span>
<span id="L426" class="LineNr"> 426 </span> 0/imm32
<span id="L427" class="LineNr"> 427 </span>
<span id="L428" class="LineNr"> 428 </span>Keyboard-ctrl-pressed?: <span class="subxComment"># boolean</span>
<span id="L429" class="LineNr"> 429 </span> 0/imm32
<span id="L430" class="LineNr"> 430 </span>
<span id="L431" class="LineNr"> 431 </span><span class="subxComment"># var keyboard circular buffer</span>
<span id="L432" class="LineNr"> 432 </span><span class="SpecialChar">Keyboard-buffer</span>:<a href='108write.subx.html#L11'>write</a>: <span class="subxComment"># nibble</span>
<span id="L433" class="LineNr"> 433 </span> 0/imm32
<span id="L434" class="LineNr"> 434 </span><span class="SpecialChar">Keyboard-buffer</span>:read: <span class="subxComment"># nibble</span>
<span id="L435" class="LineNr"> 435 </span> 0/imm32
<span id="L436" class="LineNr"> 436 </span><span class="SpecialChar">Keyboard-buffer</span>:data: <span class="subxComment"># byte[16]</span>
<span id="L437" class="LineNr"> 437 </span> 00 00 00 00
<span id="L438" class="LineNr"> 438 </span> 00 00 00 00
<span id="L439" class="LineNr"> 439 </span> 00 00 00 00
<span id="L440" class="LineNr"> 440 </span> 00 00 00 00
<span id="L441" class="LineNr"> 441 </span>
<span id="L442" class="Folded"> 442 </span><span class="Folded">+-- 70 lines: # Keyboard maps for translating keys to ASCII -----------------------------------------------------------------------------------------------------------------------------</span>
<span id="L512" class="LineNr"> 512 </span>
<span id="L513" class="LineNr"> 513 </span><span class="SpecialChar">Video-mode-info</span>:
<span id="L514" class="Folded"> 514 </span><span class="Folded">+-- 53 lines: # video mode info ---------------------------------------------------------------------------------------------------------------------------------------------------------</span>
<span id="L567" class="LineNr"> 567 </span>
<span id="L568" class="LineNr"> 568 </span><span class="SpecialChar">Font</span>:
<span id="L569" class="Folded"> 569 </span><span class="Folded">+--236 lines: # Bitmaps for some ASCII characters (soon Unicode) ------------------------------------------------------------------------------------------------------------------------</span>
<span id="L805" class="LineNr"> 805 </span>
<span id="L806" class="LineNr"> 806 </span>== code
<span id="L807" class="LineNr"> 807 </span>
<span id="L808" class="LineNr"> 808 </span><span class="subxComment">## Controlling IDE (ATA) hard disks</span>
<span id="L809" class="LineNr"> 809 </span><span class="subxComment"># Uses 28-bit PIO mode.</span>
<span id="L810" class="LineNr"> 810 </span><span class="subxComment"># Inspired by <a href="https://colorforth.github.io/ide.html">https://colorforth.github.io/ide.html</a></span>
<span id="L811" class="LineNr"> 811 </span><span class="subxComment">#</span>
<span id="L812" class="LineNr"> 812 </span><span class="subxComment"># Resources:</span>
<span id="L813" class="LineNr"> 813 </span><span class="subxComment"># <a href="https://wiki.osdev.org/ATA_PIO_Mode">https://wiki.osdev.org/ATA_PIO_Mode</a></span>
<span id="L814" class="LineNr"> 814 </span><span class="subxComment"># <a href="https://forum.osdev.org/viewtopic.php?f=1&amp;p=167798">https://forum.osdev.org/viewtopic.php?f=1&amp;p=167798</a></span>
<span id="L815" class="LineNr"> 815 </span><span class="subxComment"># read-sector, according to <a href="https://www.scs.stanford.edu/11wi-cs140/pintos/specs/ata-3-std.pdf">https://www.scs.stanford.edu/11wi-cs140/pintos/specs/ata-3-std.pdf</a></span>
<span id="L816" class="LineNr"> 816 </span>
<span id="L817" class="LineNr"> 817 </span><span class="subxFunction">load-first-sector-from-primary-bus-secondary-drive</span>: <span class="subxComment"># out: (addr stream byte)</span>
<span id="L818" class="LineNr"> 818 </span> <span class="subxS1Comment"># . prologue</span>
<span id="L819" class="LineNr"> 819 </span> 55/push-ebp
<span id="L820" class="LineNr"> 820 </span> 89/&lt;- %ebp 4/r32/esp
<span id="L821" class="LineNr"> 821 </span> <span class="subxS1Comment"># . save registers</span>
<span id="L822" class="LineNr"> 822 </span> 50/push-eax
<span id="L823" class="LineNr"> 823 </span> 51/push-ecx
<span id="L824" class="LineNr"> 824 </span> 52/push-edx
<span id="L825" class="LineNr"> 825 </span> <span class="subxComment"># check for drive</span>
<span id="L826" class="LineNr"> 826 </span> (<a href='boot.subx.html#L951'>secondary-drive-exists?</a>) <span class="subxComment"># =&gt; eax</span>
<span id="L827" class="LineNr"> 827 </span> 3d/compare-eax-and 0/imm32/false
<span id="L828" class="LineNr"> 828 </span> 0f 84/jump-if-= $load-first-sector-from-primary-bus-secondary-drive:end/disp32
<span id="L829" class="LineNr"> 829 </span> <span class="subxComment"># kick off read</span>
<span id="L830" class="LineNr"> 830 </span> (<a href='boot.subx.html#L1011'>ata-drive-select</a> 0xf0) <span class="subxComment"># primary bus, secondary drive; 4 LSBs contain 4 upper bits of LBA (here 0)</span>
<span id="L831" class="LineNr"> 831 </span> (<a href='boot.subx.html#L1031'>clear-ata-error</a>)
<span id="L832" class="LineNr"> 832 </span> (<a href='boot.subx.html#L1051'>ata-sector-count</a> 1)
<span id="L833" class="LineNr"> 833 </span> (<a href='boot.subx.html#L1071'>ata-lba</a> 0 0 0) <span class="subxComment"># lower 24 bits of LBA, all 0</span>
<span id="L834" class="LineNr"> 834 </span> (<a href='boot.subx.html#L1129'>ata-command</a> 0x20) <span class="subxComment"># read sectors with retries</span>
<span id="L835" class="LineNr"> 835 </span> <span class="subxComment"># poll for results</span>
<span id="L836" class="LineNr"> 836 </span> (<a href='boot.subx.html#L1149'>while-ata-busy</a>)
<span id="L837" class="LineNr"> 837 </span> (<a href='boot.subx.html#L1167'>until-ata-data-available</a>)
<span id="L838" class="LineNr"> 838 </span> <span class="subxComment"># emit results</span>
<span id="L839" class="LineNr"> 839 </span> 31/xor %eax 0/r32/eax
<span id="L840" class="LineNr"> 840 </span> ba/copy-to-edx 0x1f0/imm32
<span id="L841" class="LineNr"> 841 </span> b9/copy-to-ecx 0x200/imm32 <span class="subxComment"># 512 bytes per sector</span>
<span id="L842" class="LineNr"> 842 </span> {
<span id="L843" class="LineNr"> 843 </span> 81 7/subop/compare %ecx 0/imm32
<span id="L844" class="LineNr"> 844 </span> 74/jump-if-= <span class="Constant">break</span>/disp8
<span id="L845" class="LineNr"> 845 </span> 66 ed/read-port-dx-into-ax
<span id="L846" class="LineNr"> 846 </span> <span class="subxComment"># write 2 bytes to stream one at a time</span>
<span id="L847" class="LineNr"> 847 </span> (<a href='115write-byte.subx.html#L12'>append-byte</a> *(ebp+8) %eax)
<span id="L848" class="LineNr"> 848 </span> 49/decrement-ecx
<span id="L849" class="LineNr"> 849 </span> c1/shift 5/subop/right-padding-zeroes %eax 8/imm8
<span id="L850" class="LineNr"> 850 </span> (<a href='115write-byte.subx.html#L12'>append-byte</a> *(ebp+8) %eax)
<span id="L851" class="LineNr"> 851 </span> 49/decrement-ecx
<span id="L852" class="LineNr"> 852 </span> eb/jump <span class="Constant">loop</span>/disp8
<span id="L853" class="LineNr"> 853 </span> }
<span id="L854" class="LineNr"> 854 </span><span class="Constant">$load-first-sector-from-primary-bus-secondary-drive:end</span>:
<span id="L855" class="LineNr"> 855 </span> <span class="subxS1Comment"># . restore registers</span>
<span id="L856" class="LineNr"> 856 </span> 5a/pop-to-edx
<span id="L857" class="LineNr"> 857 </span> 59/pop-to-ecx
<span id="L858" class="LineNr"> 858 </span> 58/pop-to-eax
<span id="L859" class="LineNr"> 859 </span> <span class="subxS1Comment"># . epilogue</span>
<span id="L860" class="LineNr"> 860 </span> 89/&lt;- %esp 5/r32/ebp
<span id="L861" class="LineNr"> 861 </span> 5d/pop-to-ebp
<span id="L862" class="LineNr"> 862 </span> c3/return
<span id="L863" class="LineNr"> 863 </span>
<span id="L864" class="LineNr"> 864 </span><span class="subxFunction">store-first-sector-to-primary-bus-secondary-drive</span>: <span class="subxComment"># in: (addr stream byte)</span>
<span id="L865" class="LineNr"> 865 </span> <span class="subxS1Comment"># . prologue</span>
<span id="L866" class="LineNr"> 866 </span> 55/push-ebp
<span id="L867" class="LineNr"> 867 </span> 89/&lt;- %ebp 4/r32/esp
<span id="L868" class="LineNr"> 868 </span> <span class="subxS1Comment"># . save registers</span>
<span id="L869" class="LineNr"> 869 </span> 50/push-eax
<span id="L870" class="LineNr"> 870 </span> 51/push-ecx
<span id="L871" class="LineNr"> 871 </span> 52/push-edx
<span id="L872" class="LineNr"> 872 </span> 53/push-ebx
<span id="L873" class="LineNr"> 873 </span> <span class="subxComment"># check for drive</span>
<span id="L874" class="LineNr"> 874 </span> (<a href='boot.subx.html#L951'>secondary-drive-exists?</a>) <span class="subxComment"># =&gt; eax</span>
<span id="L875" class="LineNr"> 875 </span> 3d/compare-eax-and 0/imm32/false
<span id="L876" class="LineNr"> 876 </span> 0f 84/jump-if-= $store-first-sector-to-primary-bus-secondary-drive:end/disp32
<span id="L877" class="LineNr"> 877 </span> <span class="subxComment"># kick off write</span>
<span id="L878" class="LineNr"> 878 </span> (<a href='boot.subx.html#L1011'>ata-drive-select</a> 0xf0) <span class="subxComment"># primary bus, secondary drive; 4 LSBs contain 4 upper bits of LBA (here 0)</span>
<span id="L879" class="LineNr"> 879 </span> (<a href='boot.subx.html#L1031'>clear-ata-error</a>)
<span id="L880" class="LineNr"> 880 </span> (<a href='boot.subx.html#L1051'>ata-sector-count</a> 1)
<span id="L881" class="LineNr"> 881 </span> (<a href='boot.subx.html#L1071'>ata-lba</a> 0 0 0) <span class="subxComment"># lower 24 bits of LBA, all 0</span>
<span id="L882" class="LineNr"> 882 </span> (<a href='boot.subx.html#L1129'>ata-command</a> 0x30) <span class="subxComment"># write sectors with retries</span>
<span id="L883" class="LineNr"> 883 </span> <span class="subxComment"># wait</span>
<span id="L884" class="LineNr"> 884 </span> (<a href='boot.subx.html#L1149'>while-ata-busy</a>)
<span id="L885" class="LineNr"> 885 </span> (<a href='boot.subx.html#L1185'>until-ata-ready-for-data</a>)
<span id="L886" class="LineNr"> 886 </span> <span class="subxComment"># send data</span>
<span id="L887" class="LineNr"> 887 </span> ba/copy-to-edx 0x1f0/imm32
<span id="L888" class="LineNr"> 888 </span> b9/copy-to-ecx 0x200/imm32 <span class="subxComment"># 512 bytes per sector</span>
<span id="L889" class="LineNr"> 889 </span> <span class="subxComment"># var first-byte/ebx: byte</span>
<span id="L890" class="LineNr"> 890 </span> <span class="subxComment"># when it's more than 0xff, we're at an even-numbered byte</span>
<span id="L891" class="LineNr"> 891 </span> bb/copy-to-ebx 0xffff/imm32
<span id="L892" class="LineNr"> 892 </span><span class="Constant">$store-first-sector-to-primary-bus-secondary-drive:loop</span>:
<span id="L893" class="LineNr"> 893 </span> {
<span id="L894" class="LineNr"> 894 </span> 81 7/subop/compare %ecx 0/imm32
<span id="L895" class="LineNr"> 895 </span> 74/jump-if-= <span class="Constant">break</span>/disp8
<span id="L896" class="LineNr"> 896 </span> <span class="subxComment"># this loop is slow, but the ATA spec also requires a small delay</span>
<span id="L897" class="LineNr"> 897 </span> (<a href='309stream.subx.html#L6'>stream-empty?</a> *(ebp+8)) <span class="subxComment"># =&gt; eax</span>
<span id="L898" class="LineNr"> 898 </span> 3d/compare-eax-and 0/imm32/false
<span id="L899" class="LineNr"> 899 </span> 75/jump-if-!= <span class="Constant">break</span>/disp8
<span id="L900" class="LineNr"> 900 </span> <span class="subxComment"># read byte from stream</span>
<span id="L901" class="LineNr"> 901 </span> (<a href='112read-byte.subx.html#L13'>read-byte</a> *(ebp+8)) <span class="subxComment"># =&gt; eax</span>
<span id="L902" class="LineNr"> 902 </span> <span class="subxComment"># if we're at an odd-numbered byte, save it to first-byte</span>
<span id="L903" class="LineNr"> 903 </span> 81 7/subop/compare %ebx 0xff/imm32
<span id="L904" class="LineNr"> 904 </span> {
<span id="L905" class="LineNr"> 905 </span> 7e/jump-if-&lt;= <span class="Constant">break</span>/disp8
<span id="L906" class="LineNr"> 906 </span> 89/&lt;- %ebx 0/r32/eax
<span id="L907" class="LineNr"> 907 </span> eb/jump $store-first-sector-to-primary-bus-secondary-drive:<span class="Constant">loop</span>/disp8
<span id="L908" class="LineNr"> 908 </span> }
<span id="L909" class="LineNr"> 909 </span> <span class="subxComment"># otherwise OR it with first-byte and write it out</span>
<span id="L910" class="LineNr"> 910 </span> c1/shift 4/subop/left %eax 8/imm8
<span id="L911" class="LineNr"> 911 </span> 09/or %eax 3/r32/ebx
<span id="L912" class="LineNr"> 912 </span> 66 ef/write-ax-into-port-dx
<span id="L913" class="LineNr"> 913 </span> 49/decrement-ecx
<span id="L914" class="LineNr"> 914 </span> 49/decrement-ecx
<span id="L915" class="LineNr"> 915 </span> <span class="subxComment"># reset first-byte</span>
<span id="L916" class="LineNr"> 916 </span> bb/copy-to-ebx 0xffff/imm32
<span id="L917" class="LineNr"> 917 </span> eb/jump <span class="Constant">loop</span>/disp8
<span id="L918" class="LineNr"> 918 </span> }
<span id="L919" class="LineNr"> 919 </span> <span class="subxComment"># write out first-byte if necessary</span>
<span id="L920" class="LineNr"> 920 </span> 81 7/subop/compare %ebx 0xff/imm32
<span id="L921" class="LineNr"> 921 </span> {
<span id="L922" class="LineNr"> 922 </span> 7f/jump-if-&gt; <span class="Constant">break</span>/disp8
<span id="L923" class="LineNr"> 923 </span> 89/&lt;- %eax 3/r32/ebx
<span id="L924" class="LineNr"> 924 </span> 66 ef/write-ax-into-port-dx
<span id="L925" class="LineNr"> 925 </span> 49/decrement-ecx
<span id="L926" class="LineNr"> 926 </span> 49/decrement-ecx
<span id="L927" class="LineNr"> 927 </span> }
<span id="L928" class="LineNr"> 928 </span> <span class="subxComment"># pad zeroes</span>
<span id="L929" class="LineNr"> 929 </span> 31/xor %eax 0/r32/eax
<span id="L930" class="LineNr"> 930 </span> {
<span id="L931" class="LineNr"> 931 </span> 81 7/subop/compare %ecx 0/imm32
<span id="L932" class="LineNr"> 932 </span> 74/jump-if-= <span class="Constant">break</span>/disp8
<span id="L933" class="LineNr"> 933 </span> 66 ef/write-ax-into-port-dx
<span id="L934" class="LineNr"> 934 </span> 49/decrement-ecx
<span id="L935" class="LineNr"> 935 </span> 49/decrement-ecx
<span id="L936" class="LineNr"> 936 </span> eb/jump <span class="Constant">loop</span>/disp8
<span id="L937" class="LineNr"> 937 </span> }
<span id="L938" class="LineNr"> 938 </span><span class="Constant">$store-first-sector-to-primary-bus-secondary-drive:end</span>:
<span id="L939" class="LineNr"> 939 </span> <span class="subxS1Comment"># . restore registers</span>
<span id="L940" class="LineNr"> 940 </span> 5b/pop-to-ebx
<span id="L941" class="LineNr"> 941 </span> 5a/pop-to-edx
<span id="L942" class="LineNr"> 942 </span> 59/pop-to-ecx
<span id="L943" class="LineNr"> 943 </span> 58/pop-to-eax
<span id="L944" class="LineNr"> 944 </span> <span class="subxS1Comment"># . epilogue</span>
<span id="L945" class="LineNr"> 945 </span> 89/&lt;- %esp 5/r32/ebp
<span id="L946" class="LineNr"> 946 </span> 5d/pop-to-ebp
<span id="L947" class="LineNr"> 947 </span> c3/return
<span id="L948" class="LineNr"> 948 </span>
<span id="L949" class="Folded"> 949 </span><span class="Folded">+--241 lines: # disk helpers ------------------------------------------------------------------------------------------------------------------------------------------------------------</span>
<span id="L1190" class="LineNr">1190 </span>
<span id="L1191" class="LineNr">1191 </span><span class="subxComment">## Controlling a PS/2 mouse</span>
<span id="L1192" class="LineNr">1192 </span><span class="subxComment"># Uses no IRQs, just polling.</span>
<span id="L1193" class="LineNr">1193 </span><span class="subxComment"># Thanks Dave Long: <a href="https://github.com/jtauber/cleese/blob/master/necco/kernel/bochs/py8042.py">https://github.com/jtauber/cleese/blob/master/necco/kernel/bochs/py8042.py</a></span>
<span id="L1194" class="LineNr">1194 </span><span class="subxComment">#</span>
<span id="L1195" class="LineNr">1195 </span><span class="subxComment"># Resources:</span>
<span id="L1196" class="LineNr">1196 </span><span class="subxComment"># <a href="https://wiki.osdev.org/Mouse_Input">https://wiki.osdev.org/Mouse_Input</a></span>
<span id="L1197" class="LineNr">1197 </span>
<span id="L1198" class="LineNr">1198 </span><span class="subxComment"># results x/eax, y/ecx range from -256 to +255</span>
<span id="L1199" class="LineNr">1199 </span><span class="subxComment"># See <a href="https://wiki.osdev.org/index.php?title=Mouse_Input&amp;oldid=25663#Format_of_First_3_Packet_Bytes">https://wiki.osdev.org/index.php?title=Mouse_Input&amp;oldid=25663#Format_of_First_3_Packet_Bytes</a></span>
<span id="L1200" class="LineNr">1200 </span><span class="subxFunction">read-mouse-event</span>: <span class="subxComment"># -&gt; _/eax: int, _/ecx: int</span>
<span id="L1201" class="LineNr">1201 </span> <span class="subxS1Comment"># . prologue</span>
<span id="L1202" class="LineNr">1202 </span> 55/push-ebp
<span id="L1203" class="LineNr">1203 </span> 89/&lt;- %ebp 4/r32/esp
<span id="L1204" class="LineNr">1204 </span> <span class="subxS1Comment"># . save registers</span>
<span id="L1205" class="LineNr">1205 </span> 52/push-edx
<span id="L1206" class="LineNr">1206 </span> 53/push-ebx
<span id="L1207" class="LineNr">1207 </span> <span class="subxComment"># if no event, return 0, 0</span>
<span id="L1208" class="LineNr">1208 </span> b8/copy-to-eax 0/imm32
<span id="L1209" class="LineNr">1209 </span> b9/copy-to-ecx 0/imm32
<span id="L1210" class="LineNr">1210 </span> (<a href='boot.subx.html#L1267'>any-mouse-event?</a>) <span class="subxComment"># =&gt; eax</span>
<span id="L1211" class="LineNr">1211 </span> 3d/compare-eax-and 0/imm32/false
<span id="L1212" class="LineNr">1212 </span> 74/jump-if-= $read-mouse-event:end/disp8
<span id="L1213" class="LineNr">1213 </span> <span class="subxComment"># var f1/edx: byte = inb(0x60)</span>
<span id="L1214" class="LineNr">1214 </span> 31/xor %eax 0/r32/eax
<span id="L1215" class="LineNr">1215 </span> e4/read-port-into-al 0x60/imm8
<span id="L1216" class="LineNr">1216 </span> 89/&lt;- %edx 0/r32/eax
<span id="L1217" class="LineNr">1217 </span> (<a href='boot.subx.html#L1252'>wait-for-mouse-event</a>)
<span id="L1218" class="LineNr">1218 </span> <span class="subxComment"># var dx/ebx: byte = inb(0x60)</span>
<span id="L1219" class="LineNr">1219 </span> 31/xor %eax 0/r32/eax
<span id="L1220" class="LineNr">1220 </span> e4/read-port-into-al 0x60/imm8
<span id="L1221" class="LineNr">1221 </span> 89/&lt;- %ebx 0/r32/eax
<span id="L1222" class="LineNr">1222 </span> (<a href='boot.subx.html#L1252'>wait-for-mouse-event</a>)
<span id="L1223" class="LineNr">1223 </span> <span class="subxComment"># var dy/ecx: byte = inb(0x60)</span>
<span id="L1224" class="LineNr">1224 </span> 31/xor %eax 0/r32/eax
<span id="L1225" class="LineNr">1225 </span> e4/read-port-into-al 0x60/imm8
<span id="L1226" class="LineNr">1226 </span> 89/&lt;- %ecx 0/r32/eax
<span id="L1227" class="LineNr">1227 </span> <span class="subxComment"># eax = dx</span>
<span id="L1228" class="LineNr">1228 </span> 89/&lt;- %eax 3/r32/ebx
<span id="L1229" class="LineNr">1229 </span> <span class="subxComment"># if (f1 &amp; 0x10) dx = -dx</span>
<span id="L1230" class="LineNr">1230 </span> {
<span id="L1231" class="LineNr">1231 </span> f6 0/subop/test-bits %dl 0x10/imm8
<span id="L1232" class="LineNr">1232 </span> 74/jump-if-zero <span class="Constant">break</span>/disp8
<span id="L1233" class="LineNr">1233 </span> 0d/or-eax-with 0xffffff00/imm32
<span id="L1234" class="LineNr">1234 </span> }
<span id="L1235" class="LineNr">1235 </span> <span class="subxComment"># if (f1 &amp; 0x20) dy = -dy</span>
<span id="L1236" class="LineNr">1236 </span> {
<span id="L1237" class="LineNr">1237 </span> f6 0/subop/test-bits %dl 0x20/imm8
<span id="L1238" class="LineNr">1238 </span> 74/jump-if-zero <span class="Constant">break</span>/disp8
<span id="L1239" class="LineNr">1239 </span> 81 1/subop/or %ecx 0xffffff00/imm32
<span id="L1240" class="LineNr">1240 </span> }
<span id="L1241" class="LineNr">1241 </span><span class="Constant">$read-mouse-event:end</span>:
<span id="L1242" class="LineNr">1242 </span> <span class="subxS1Comment"># . restore registers</span>
<span id="L1243" class="LineNr">1243 </span> 5b/pop-to-ebx
<span id="L1244" class="LineNr">1244 </span> 5a/pop-to-edx
<span id="L1245" class="LineNr">1245 </span> <span class="subxS1Comment"># . epilogue</span>
<span id="L1246" class="LineNr">1246 </span> 89/&lt;- %esp 5/r32/ebp
<span id="L1247" class="LineNr">1247 </span> 5d/pop-to-ebp
<span id="L1248" class="LineNr">1248 </span> c3/return
<span id="L1249" class="LineNr">1249 </span>
<span id="L1250" class="Folded">1250 </span><span class="Folded">+--152 lines: # mouse helpers -----------------------------------------------------------------------------------------------------------------------------------------------------------</span>
<span id="L1402" class="LineNr">1402 </span>
<span id="L1403" class="LineNr">1403 </span><span class="subxComment"># vim&#0058;ft=subx</span>
</pre>
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