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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
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<title>Mu - apps/ex5.subx</title>
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a { color:inherit; }
* { font-size:12pt; font-size: 1em; }
.subxComment { color: #005faf; }
.subxS2Comment { color: #8a8a8a; }
.LineNr { }
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<a href='https://github.com/akkartik/mu/blob/master/apps/ex5.subx'>https://github.com/akkartik/mu/blob/master/apps/ex5.subx</a>
<pre id='vimCodeElement'>
<span id="L1" class="LineNr"> 1 </span><span class="subxComment"># Read a character from stdin, save it to a local on the stack, write it to stdout.</span>
<span id="L2" class="LineNr"> 2 </span><span class="subxComment">#</span>
<span id="L3" class="LineNr"> 3 </span><span class="subxComment"># To run:</span>
<span id="L4" class="LineNr"> 4 </span><span class="subxComment">#   $ ./bootstrap translate init.linux apps/ex5.subx -o apps/ex5</span>
<span id="L5" class="LineNr"> 5 </span><span class="subxComment">#   $ ./bootstrap run apps/ex5</span>
<span id="L6" class="LineNr"> 6 </span>
<span id="L7" class="LineNr"> 7 </span>== code
<span id="L8" class="LineNr"> 8 </span><span class="subxComment">#   instruction                     effective address                                                   register    displacement    immediate</span>
<span id="L9" class="LineNr"> 9 </span><span class="subxS1Comment"># . op          subop               mod             rm32          base        index         scale       r32</span>
<span id="L10" class="LineNr">10 </span><span class="subxS1Comment"># . 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes</span>
<span id="L11" class="LineNr">11 </span>
<span id="L12" class="LineNr">12 </span><span class="SpecialChar">Entry</span>:
<span id="L13" class="LineNr">13 </span>
<span id="L14" class="LineNr">14 </span>    <span class="subxComment"># allocate x on the stack</span>
<span id="L15" class="LineNr">15 </span>    81          5/subop/subtract    3/mod/direct    4/rm32/esp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>         <span class="Normal"> . </span>         <span class="Normal"> . </span>              4/imm32           <span class="subxComment"># subtract from esp</span>
<span id="L16" class="LineNr">16 </span>
<span id="L17" class="LineNr">17 </span>    <span class="subxComment"># read(stdin, x, 1)</span>
<span id="L18" class="LineNr">18 </span>    <span class="subxS1Comment"># . fd = 0 (stdin)</span>
<span id="L19" class="LineNr">19 </span>    bb/copy-to-ebx  0/imm32
<span id="L20" class="LineNr">20 </span>    <span class="subxS1Comment"># . data = x (location to write result to)</span>
<span id="L21" class="LineNr">21 </span>    8d/copy-address                 1/mod/*+disp8   4/rm32/sib    4/base/esp  4/index/none              1/r32/ecx   4/disp8        <span class="Normal"> . </span>                <span class="subxComment"># copy esp+4 to ecx</span>
<span id="L22" class="LineNr">22 </span>    <span class="subxS1Comment"># . size = 1 character</span>
<span id="L23" class="LineNr">23 </span>    ba/copy-to-edx  1/imm32
<span id="L24" class="LineNr">24 </span>    <span class="subxS1Comment"># . syscall</span>
<span id="L25" class="LineNr">25 </span>    e8/call  syscall_read/disp32
<span id="L26" class="LineNr">26 </span>
<span id="L27" class="LineNr">27 </span>    <span class="subxComment"># syscall(write, stdout, x, 1)</span>
<span id="L28" class="LineNr">28 </span>    <span class="subxS1Comment"># . fd = 1 (stdout)</span>
<span id="L29" class="LineNr">29 </span>    bb/copy-to-ebx  1/imm32
<span id="L30" class="LineNr">30 </span>    <span class="subxS1Comment"># . data = x (location to read from)</span>
<span id="L31" class="LineNr">31 </span>    8d/copy-address                 1/mod/*+disp8   4/rm32/sib    4/base/esp  4/index/none              1/r32/ecx   4/disp8        <span class="Normal"> . </span>                <span class="subxComment"># copy esp+4 to ecx</span>
<span id="L32" class="LineNr">32 </span>    <span class="subxS1Comment"># . size = 1 character</span>
<span id="L33" class="LineNr">33 </span>    ba/copy-to-edx  1/imm32
<span id="L34" class="LineNr">34 </span>    <span class="subxS1Comment"># . syscall</span>
<span id="L35" class="LineNr">35 </span>    b8/copy-to-eax  4/imm32/write
<span id="L36" class="LineNr">36 </span>    cd/syscall  0x80/imm8
<span id="L37" class="LineNr">37 </span>
<span id="L38" class="LineNr">38 </span>    <span class="subxComment"># exit(ebx)</span>
<span id="L39" class="LineNr">39 </span>    e8/call  syscall_exit/disp32
<span id="L40" class="LineNr">40 </span>
<span id="L41" class="LineNr">41 </span><span class="subxS2Comment"># . . vim&#0058;nowrap:textwidth=0</span>
</pre>
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