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authorKartik Agaram <vc@akkartik.com>2021-03-23 17:31:08 -0700
committerKartik Agaram <vc@akkartik.com>2021-03-23 17:31:08 -0700
commit3350c34a74844e21ea69077e01efff3bae64bdcd (patch)
treefa06ba58542297d1cff6b78958d4547a40a25d21 /html/linux/ex12.subx.html
parent62a244211024a8367332541c571621883c05bcce (diff)
downloadmu-3350c34a74844e21ea69077e01efff3bae64bdcd.tar.gz
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+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
+<html>
+<head>
+<meta http-equiv="content-type" content="text/html; charset=UTF-8">
+<title>Mu - linux/ex12.subx</title>
+<meta name="Generator" content="Vim/8.1">
+<meta name="plugin-version" content="vim8.1_v1">
+<meta name="syntax" content="none">
+<meta name="settings" content="number_lines,use_css,no_foldcolumn,expand_tabs,line_ids,prevent_copy=">
+<meta name="colorscheme" content="minimal-light">
+<style type="text/css">
+<!--
+pre { font-family: monospace; color: #000000; background-color: #c6c6c6; }
+body { font-size:12pt; font-family: monospace; color: #000000; background-color: #c6c6c6; }
+a { color:inherit; }
+* { font-size:12pt; font-size: 1em; }
+.subxComment { color: #005faf; }
+.subxS1Comment { color: #0000af; }
+.subxS2Comment { color: #8a8a8a; }
+.LineNr { }
+.SpecialChar { color: #d70000; }
+.Normal { color: #000000; background-color: #c6c6c6; padding-bottom: 1px; }
+-->
+</style>
+
+<script type='text/javascript'>
+<!--
+
+/* function to open any folds containing a jumped-to line before jumping to it */
+function JumpToLine()
+{
+  var lineNum;
+  lineNum = window.location.hash;
+  lineNum = lineNum.substr(1); /* strip off '#' */
+
+  if (lineNum.indexOf('L') == -1) {
+    lineNum = 'L'+lineNum;
+  }
+  var lineElem = document.getElementById(lineNum);
+  /* Always jump to new location even if the line was hidden inside a fold, or
+   * we corrected the raw number to a line ID.
+   */
+  if (lineElem) {
+    lineElem.scrollIntoView(true);
+  }
+  return true;
+}
+if ('onhashchange' in window) {
+  window.onhashchange = JumpToLine;
+}
+
+-->
+</script>
+</head>
+<body onload='JumpToLine();'>
+<a href='https://github.com/akkartik/mu/blob/main/linux/ex12.subx'>https://github.com/akkartik/mu/blob/main/linux/ex12.subx</a>
+<pre id='vimCodeElement'>
+<span id="L1" class="LineNr"> 1 </span><span class="subxComment"># Example showing mmap syscall.</span>
+<span id="L2" class="LineNr"> 2 </span><span class="subxComment"># Create a new segment using mmap, save the address, write to it.</span>
+<span id="L3" class="LineNr"> 3 </span><span class="subxComment">#</span>
+<span id="L4" class="LineNr"> 4 </span><span class="subxComment"># To run:</span>
+<span id="L5" class="LineNr"> 5 </span><span class="subxComment">#   $ bootstrap/bootstrap translate apps/ex12.subx -o apps/ex12</span>
+<span id="L6" class="LineNr"> 6 </span><span class="subxComment">#   $ bootstrap/bootstrap run ex12</span>
+<span id="L7" class="LineNr"> 7 </span><span class="subxComment"># You shouldn't get a segmentation fault.</span>
+<span id="L8" class="LineNr"> 8 </span>
+<span id="L9" class="LineNr"> 9 </span>== code
+<span id="L10" class="LineNr">10 </span><span class="subxComment">#   instruction                     effective address                                                   register    displacement    immediate</span>
+<span id="L11" class="LineNr">11 </span><span class="subxS1Comment"># . op          subop               mod             rm32          base        index         scale       r32</span>
+<span id="L12" class="LineNr">12 </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="L13" class="LineNr">13 </span>
+<span id="L14" class="LineNr">14 </span><span class="SpecialChar">Entry</span>:
+<span id="L15" class="LineNr">15 </span>    <span class="subxComment"># mmap(Mmap-new-segment-&gt;len)</span>
+<span id="L16" class="LineNr">16 </span>    bb/copy-to-ebx  <span class="SpecialChar"><a href='ex12.subx.html#L29'>Mmap-new-segment</a></span>/imm32
+<span id="L17" class="LineNr">17 </span>    e8/call  <a href='000init.subx.html#L71'>syscall_mmap</a>/disp32
+<span id="L18" class="LineNr">18 </span>
+<span id="L19" class="LineNr">19 </span>    <span class="subxComment"># write to *eax to check that we have access to the newly-allocated segment</span>
+<span id="L20" class="LineNr">20 </span>    c7          0/subop/copy        0/mod/direct    0/rm32/eax   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>         <span class="Normal"> . </span>         <span class="Normal"> . </span>              0x34/imm32        <span class="subxComment"># copy to *eax</span>
+<span id="L21" class="LineNr">21 </span>
+<span id="L22" class="LineNr">22 </span>    <span class="subxComment"># exit(eax)</span>
+<span id="L23" class="LineNr">23 </span>    89/copy                         3/mod/direct    3/rm32/ebx   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          0/r32/eax  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># copy eax to ebx</span>
+<span id="L24" class="LineNr">24 </span>    e8/call  <a href='000init.subx.html#L18'>syscall_exit</a>/disp32
+<span id="L25" class="LineNr">25 </span>
+<span id="L26" class="LineNr">26 </span>== data
+<span id="L27" class="LineNr">27 </span>
+<span id="L28" class="LineNr">28 </span><span class="subxComment"># various constants used here were found in the Linux sources (search for file mman-common.h)</span>
+<span id="L29" class="LineNr">29 </span><span class="SpecialChar">Mmap-new-segment</span>:  <span class="subxComment"># type mmap_arg_struct</span>
+<span id="L30" class="LineNr">30 </span>    <span class="subxComment"># addr</span>
+<span id="L31" class="LineNr">31 </span>    0/imm32
+<span id="L32" class="LineNr">32 </span>    <span class="subxComment"># len</span>
+<span id="L33" class="LineNr">33 </span>    0x100/imm32
+<span id="L34" class="LineNr">34 </span>    <span class="subxComment"># protection flags</span>
+<span id="L35" class="LineNr">35 </span>    3/imm32  <span class="subxComment"># PROT_READ | PROT_WRITE</span>
+<span id="L36" class="LineNr">36 </span>    <span class="subxComment"># sharing flags</span>
+<span id="L37" class="LineNr">37 </span>    0x22/imm32  <span class="subxComment"># MAP_PRIVATE | MAP_ANONYMOUS</span>
+<span id="L38" class="LineNr">38 </span>    <span class="subxComment"># fd</span>
+<span id="L39" class="LineNr">39 </span>    -1/imm32  <span class="subxComment"># since MAP_ANONYMOUS is specified</span>
+<span id="L40" class="LineNr">40 </span>    <span class="subxComment"># offset</span>
+<span id="L41" class="LineNr">41 </span>    0/imm32  <span class="subxComment"># since MAP_ANONYMOUS is specified</span>
+<span id="L42" class="LineNr">42 </span>
+<span id="L43" class="LineNr">43 </span><span class="subxS2Comment"># . . vim&#0058;nowrap:textwidth=0</span>
+</pre>
+</body>
+</html>
+<!-- vim: set foldmethod=manual : -->

 

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