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<pre id='vimCodeElement'>
<span id="L1" class="LineNr">  1 </span><span class="Comment">//: The bedrock level 1 of abstraction is now done, and we're going to start</span>
<span id="L2" class="LineNr">  2 </span><span class="Comment">//: building levels above it that make programming in x86 machine code a</span>
<span id="L3" class="LineNr">  3 </span><span class="Comment">//: little more ergonomic.</span>
<span id="L4" class="LineNr">  4 </span><span class="Comment">//:</span>
<span id="L5" class="LineNr">  5 </span><span class="Comment">//: All levels will be &quot;pass through by default&quot;. Whatever they don't</span>
<span id="L6" class="LineNr">  6 </span><span class="Comment">//: understand they will silently pass through to lower levels.</span>
<span id="L7" class="LineNr">  7 </span><span class="Comment">//:</span>
<span id="L8" class="LineNr">  8 </span><span class="Comment">//: Since raw hex bytes of machine code are always possible to inject, SubX is</span>
<span id="L9" class="LineNr">  9 </span><span class="Comment">//: not a language, and we aren't building a compiler. This is something</span>
<span id="L10" class="LineNr"> 10 </span><span class="Comment">//: deliberately leakier. Levels are more for improving auditing, checks and</span>
<span id="L11" class="LineNr"> 11 </span><span class="Comment">//: error messages rather than for hiding low-level details.</span>
<span id="L12" class="LineNr"> 12 </span>
<span id="L13" class="LineNr"> 13 </span><span class="Comment">//: Translator workflow: read 'source' file. Run a series of transforms on it,</span>
<span id="L14" class="LineNr"> 14 </span><span class="Comment">//: each passing through what it doesn't understand. The final program should</span>
<span id="L15" class="LineNr"> 15 </span><span class="Comment">//: be just machine code, suitable to write to an ELF binary.</span>
<span id="L16" class="LineNr"> 16 </span><span class="Comment">//:</span>
<span id="L17" class="LineNr"> 17 </span><span class="Comment">//: Higher levels usually transform code on the basis of metadata.</span>
<span id="L18" class="LineNr"> 18 </span>
<span id="L19" class="LineNr"> 19 </span><span class="Delimiter">:(before &quot;End Main&quot;)</span>
<span id="L20" class="LineNr"> 20 </span><span class="Normal">if</span> <span class="Delimiter">(</span>is_equal<span class="Delimiter">(</span>argv[<span class="Constant">1</span>]<span class="Delimiter">,</span> <span class="Constant">&quot;translate&quot;</span><span class="Delimiter">))</span> <span class="Delimiter">{</span>
<span id="L21" class="LineNr"> 21 </span>  START_TRACING_UNTIL_END_OF_SCOPE<span class="Delimiter">;</span>
<span id="L22" class="LineNr"> 22 </span>  reset<span class="Delimiter">();</span>
<span id="L23" class="LineNr"> 23 </span>  <span class="Comment">// Begin subx translate</span>
<span id="L24" class="LineNr"> 24 </span>  program p<span class="Delimiter">;</span>
<span id="L25" class="LineNr"> 25 </span>  string output_filename<span class="Delimiter">;</span>
<span id="L26" class="LineNr"> 26 </span>  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Comment">/*</span><span class="Comment">skip 'subx translate'</span><span class="Comment">*/</span><span class="Constant">2</span><span class="Delimiter">;</span>  i &lt; argc<span class="Delimiter">;</span>  ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L27" class="LineNr"> 27 </span>    <span class="Normal">if</span> <span class="Delimiter">(</span>is_equal<span class="Delimiter">(</span>argv[i]<span class="Delimiter">,</span> <span class="Constant">&quot;-o&quot;</span><span class="Delimiter">))</span> <span class="Delimiter">{</span>
<span id="L28" class="LineNr"> 28 </span>      ++i<span class="Delimiter">;</span>
<span id="L29" class="LineNr"> 29 </span>      <span class="Normal">if</span> <span class="Delimiter">(</span>i &gt;= argc<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L30" class="LineNr"> 30 </span>        print_translate_usage<span class="Delimiter">();</span>
<span id="L31" class="LineNr"> 31 </span>        cerr &lt;&lt; <span class="Constant">&quot;'-o' must be followed by a filename to write results to</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span><span class="Delimiter">;</span>
<span id="L32" class="LineNr"> 32 </span>        exit<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">);</span>
<span id="L33" class="LineNr"> 33 </span>      <span class="Delimiter">}</span>
<span id="L34" class="LineNr"> 34 </span>      output_filename = argv[i]<span class="Delimiter">;</span>
<span id="L35" class="LineNr"> 35 </span>    <span class="Delimiter">}</span>
<span id="L36" class="LineNr"> 36 </span>    <span class="Normal">else</span> <span class="Delimiter">{</span>
<span id="L37" class="LineNr"> 37 </span>      ifstream fin<span class="Delimiter">(</span>argv[i]<span class="Delimiter">);</span>
<span id="L38" class="LineNr"> 38 </span>      <span class="Normal">if</span> <span class="Delimiter">(</span>!fin<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L39" class="LineNr"> 39 </span>        cerr &lt;&lt; <span class="Constant">&quot;could not open &quot;</span> &lt;&lt; argv[i] &lt;&lt; <span class="cSpecial">'\n'</span><span class="Delimiter">;</span>
<span id="L40" class="LineNr"> 40 </span>        <span class="Identifier">return</span> <span class="Constant">1</span><span class="Delimiter">;</span>
<span id="L41" class="LineNr"> 41 </span>      <span class="Delimiter">}</span>
<span id="L42" class="LineNr"> 42 </span>      parse<span class="Delimiter">(</span>fin<span class="Delimiter">,</span> p<span class="Delimiter">);</span>
<span id="L43" class="LineNr"> 43 </span>      <span class="Normal">if</span> <span class="Delimiter">(</span>trace_contains_errors<span class="Delimiter">())</span> <span class="Identifier">return</span> <span class="Constant">1</span><span class="Delimiter">;</span>
<span id="L44" class="LineNr"> 44 </span>    <span class="Delimiter">}</span>
<span id="L45" class="LineNr"> 45 </span>  <span class="Delimiter">}</span>
<span id="L46" class="LineNr"> 46 </span>  <span class="Normal">if</span> <span class="Delimiter">(</span>p<span class="Delimiter">.</span>segments<span class="Delimiter">.</span>empty<span class="Delimiter">())</span> <span class="Delimiter">{</span>
<span id="L47" class="LineNr"> 47 </span>    print_translate_usage<span class="Delimiter">();</span>
<span id="L48" class="LineNr"> 48 </span>    cerr &lt;&lt; <span class="Constant">&quot;nothing to do; must provide at least one file to read</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span><span class="Delimiter">;</span>
<span id="L49" class="LineNr"> 49 </span>    exit<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">);</span>
<span id="L50" class="LineNr"> 50 </span>  <span class="Delimiter">}</span>
<span id="L51" class="LineNr"> 51 </span>  <span class="Normal">if</span> <span class="Delimiter">(</span>output_filename<span class="Delimiter">.</span>empty<span class="Delimiter">())</span> <span class="Delimiter">{</span>
<span id="L52" class="LineNr"> 52 </span>    print_translate_usage<span class="Delimiter">();</span>
<span id="L53" class="LineNr"> 53 </span>    cerr &lt;&lt; <span class="Constant">&quot;must provide a filename to write to using '-o'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span><span class="Delimiter">;</span>
<span id="L54" class="LineNr"> 54 </span>    exit<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">);</span>
<span id="L55" class="LineNr"> 55 </span>  <span class="Delimiter">}</span>
<span id="L56" class="LineNr"> 56 </span>  transform<span class="Delimiter">(</span>p<span class="Delimiter">);</span>
<span id="L57" class="LineNr"> 57 </span>  <span class="Normal">if</span> <span class="Delimiter">(</span>trace_contains_errors<span class="Delimiter">())</span> <span class="Identifier">return</span> <span class="Constant">1</span><span class="Delimiter">;</span>
<span id="L58" class="LineNr"> 58 </span>  save_elf<span class="Delimiter">(</span>p<span class="Delimiter">,</span> output_filename<span class="Delimiter">);</span>
<span id="L59" class="LineNr"> 59 </span>  <span class="Normal">if</span> <span class="Delimiter">(</span>trace_contains_errors<span class="Delimiter">())</span> <span class="Delimiter">{</span>
<span id="L60" class="LineNr"> 60 </span>    unlink<span class="Delimiter">(</span>output_filename<span class="Delimiter">.</span>c_str<span class="Delimiter">());</span>
<span id="L61" class="LineNr"> 61 </span>    <span class="Identifier">return</span> <span class="Constant">1</span><span class="Delimiter">;</span>
<span id="L62" class="LineNr"> 62 </span>  <span class="Delimiter">}</span>
<span id="L63" class="LineNr"> 63 </span>  <span class="Comment">// End subx translate</span>
<span id="L64" class="LineNr"> 64 </span>  <span class="Identifier">return</span> <span class="Constant">0</span><span class="Delimiter">;</span>
<span id="L65" class="LineNr"> 65 </span><span class="Delimiter">}</span>
<span id="L66" class="LineNr"> 66 </span>
<span id="L67" class="LineNr"> 67 </span><span class="Delimiter">:(code)</span>
<span id="L68" class="LineNr"> 68 </span><span class="Normal">void</span> print_translate_usage<span class="Delimiter">()</span> <span class="Delimiter">{</span>
<span id="L69" class="LineNr"> 69 </span>  cerr &lt;&lt; <span class="Constant">&quot;Usage: subx translate file1 file2 ... -o output</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span><span class="Delimiter">;</span>
<span id="L70" class="LineNr"> 70 </span><span class="Delimiter">}</span>
<span id="L71" class="LineNr"> 71 </span>
<span id="L72" class="LineNr"> 72 </span><span class="Comment">// write out a program to a bare-bones ELF file</span>
<span id="L73" class="LineNr"> 73 </span><span class="Normal">void</span> save_elf<span class="Delimiter">(</span><span class="Normal">const</span> program&amp; p<span class="Delimiter">,</span> <span class="Normal">const</span> string&amp; filename<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L74" class="LineNr"> 74 </span>  ofstream out<span class="Delimiter">(</span>filename<span class="Delimiter">.</span>c_str<span class="Delimiter">(),</span> ios::binary<span class="Delimiter">);</span>
<span id="L75" class="LineNr"> 75 </span>  write_elf_header<span class="Delimiter">(</span>out<span class="Delimiter">,</span> p<span class="Delimiter">);</span>
<span id="L76" class="LineNr"> 76 </span>  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">size_t</span> i = <span class="Constant">0</span><span class="Delimiter">;</span>  i &lt; p<span class="Delimiter">.</span>segments<span class="Delimiter">.</span>size<span class="Delimiter">();</span>  ++i<span class="Delimiter">)</span>
<span id="L77" class="LineNr"> 77 </span>    write_segment<span class="Delimiter">(</span>p<span class="Delimiter">.</span>segments<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">),</span> out<span class="Delimiter">);</span>
<span id="L78" class="LineNr"> 78 </span>  out<span class="Delimiter">.</span>close<span class="Delimiter">();</span>
<span id="L79" class="LineNr"> 79 </span><span class="Delimiter">}</span>
<span id="L80" class="LineNr"> 80 </span>
<span id="L81" class="LineNr"> 81 </span><span class="Normal">void</span> write_elf_header<span class="Delimiter">(</span>ostream&amp; out<span class="Delimiter">,</span> <span class="Normal">const</span> program&amp; p<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L82" class="LineNr"> 82 </span>  <span class="Normal">char</span> c = <span class="cSpecial">'\0'</span><span class="Delimiter">;</span>
<span id="L83" class="LineNr"> 83 </span><span class="Comment">#define O(X)  c = (X); out.write(&amp;c, sizeof(c))</span>
<span id="L84" class="LineNr"> 84 </span><span class="Comment">// host is required to be little-endian</span>
<span id="L85" class="LineNr"> 85 </span><span class="Comment">#define emit(X)  out.write(reinterpret_cast&lt;const char*&gt;(&amp;X), sizeof(X))</span>
<span id="L86" class="LineNr"> 86 </span>  <span class="SalientComment">//// ehdr</span>
<span id="L87" class="LineNr"> 87 </span>  <span class="Comment">// e_ident</span>
<span id="L88" class="LineNr"> 88 </span>  O<span class="Delimiter">(</span><span class="Constant">0x7f</span><span class="Delimiter">);</span> O<span class="Delimiter">(</span><span class="Comment">/*</span><span class="Comment">E</span><span class="Comment">*/</span><span class="Constant">0x45</span><span class="Delimiter">);</span> O<span class="Delimiter">(</span><span class="Comment">/*</span><span class="Comment">L</span><span class="Comment">*/</span><span class="Constant">0x4c</span><span class="Delimiter">);</span> O<span class="Delimiter">(</span><span class="Comment">/*</span><span class="Comment">F</span><span class="Comment">*/</span><span class="Constant">0x46</span><span class="Delimiter">);</span>
<span id="L89" class="LineNr"> 89 </span>    O<span class="Delimiter">(</span><span class="Constant">0x1</span><span class="Delimiter">);</span>  <span class="Comment">// 32-bit format</span>
<span id="L90" class="LineNr"> 90 </span>    O<span class="Delimiter">(</span><span class="Constant">0x1</span><span class="Delimiter">);</span>  <span class="Comment">// little-endian</span>
<span id="L91" class="LineNr"> 91 </span>    O<span class="Delimiter">(</span><span class="Constant">0x1</span><span class="Delimiter">);</span> O<span class="Delimiter">(</span><span class="Constant">0x0</span><span class="Delimiter">);</span>
<span id="L92" class="LineNr"> 92 </span>  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">size_t</span> i = <span class="Constant">0</span><span class="Delimiter">;</span>  i &lt; <span class="Constant">8</span><span class="Delimiter">;</span>  ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span> O<span class="Delimiter">(</span><span class="Constant">0x0</span><span class="Delimiter">);</span> <span class="Delimiter">}</span>
<span id="L93" class="LineNr"> 93 </span>  <span class="Comment">// e_type</span>
<span id="L94" class="LineNr"> 94 </span>  O<span class="Delimiter">(</span><span class="Constant">0x02</span><span class="Delimiter">);</span> O<span class="Delimiter">(</span><span class="Constant">0x00</span><span class="Delimiter">);</span>
<span id="L95" class="LineNr"> 95 </span>  <span class="Comment">// e_machine</span>
<span id="L96" class="LineNr"> 96 </span>  O<span class="Delimiter">(</span><span class="Constant">0x03</span><span class="Delimiter">);</span> O<span class="Delimiter">(</span><span class="Constant">0x00</span><span class="Delimiter">);</span>
<span id="L97" class="LineNr"> 97 </span>  <span class="Comment">// e_version</span>
<span id="L98" class="LineNr"> 98 </span>  O<span class="Delimiter">(</span><span class="Constant">0x01</span><span class="Delimiter">);</span> O<span class="Delimiter">(</span><span class="Constant">0x00</span><span class="Delimiter">);</span> O<span class="Delimiter">(</span><span class="Constant">0x00</span><span class="Delimiter">);</span> O<span class="Delimiter">(</span><span class="Constant">0x00</span><span class="Delimiter">);</span>
<span id="L99" class="LineNr"> 99 </span>  <span class="Comment">// e_entry</span>
<span id="L100" class="LineNr">100 </span>  <span class="Normal">int</span> e_entry = p<span class="Delimiter">.</span>segments<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>start<span class="Delimiter">;</span>  <span class="Comment">// convention</span>
<span id="L101" class="LineNr">101 </span>  emit<span class="Delimiter">(</span>e_entry<span class="Delimiter">);</span>
<span id="L102" class="LineNr">102 </span>  <span class="Comment">// e_phoff -- immediately after ELF header</span>
<span id="L103" class="LineNr">103 </span>  <span class="Normal">int</span> e_phoff = <span class="Constant">0x34</span><span class="Delimiter">;</span>
<span id="L104" class="LineNr">104 </span>  emit<span class="Delimiter">(</span>e_phoff<span class="Delimiter">);</span>
<span id="L105" class="LineNr">105 </span>  <span class="Comment">// e_shoff; unused</span>
<span id="L106" class="LineNr">106 </span>  <span class="Normal">int</span> dummy32 = <span class="Constant">0</span><span class="Delimiter">;</span>
<span id="L107" class="LineNr">107 </span>  emit<span class="Delimiter">(</span>dummy32<span class="Delimiter">);</span>
<span id="L108" class="LineNr">108 </span>  <span class="Comment">// e_flags; unused</span>
<span id="L109" class="LineNr">109 </span>  emit<span class="Delimiter">(</span>dummy32<span class="Delimiter">);</span>
<span id="L110" class="LineNr">110 </span>  <span class="Comment">// e_ehsize</span>
<span id="L111" class="LineNr">111 </span>  <span class="Normal">uint16_t</span> e_ehsize = <span class="Constant">0x34</span><span class="Delimiter">;</span>
<span id="L112" class="LineNr">112 </span>  emit<span class="Delimiter">(</span>e_ehsize<span class="Delimiter">);</span>
<span id="L113" class="LineNr">113 </span>  <span class="Comment">// e_phentsize</span>
<span id="L114" class="LineNr">114 </span>  <span class="Normal">uint16_t</span> e_phentsize = <span class="Constant">0x20</span><span class="Delimiter">;</span>
<span id="L115" class="LineNr">115 </span>  emit<span class="Delimiter">(</span>e_phentsize<span class="Delimiter">);</span>
<span id="L116" class="LineNr">116 </span>  <span class="Comment">// e_phnum</span>
<span id="L117" class="LineNr">117 </span>  <span class="Normal">uint16_t</span> e_phnum = SIZE<span class="Delimiter">(</span>p<span class="Delimiter">.</span>segments<span class="Delimiter">);</span>
<span id="L118" class="LineNr">118 </span>  emit<span class="Delimiter">(</span>e_phnum<span class="Delimiter">);</span>
<span id="L119" class="LineNr">119 </span>  <span class="Comment">// e_shentsize</span>
<span id="L120" class="LineNr">120 </span>  <span class="Normal">uint16_t</span> dummy16 = <span class="Constant">0x0</span><span class="Delimiter">;</span>
<span id="L121" class="LineNr">121 </span>  emit<span class="Delimiter">(</span>dummy16<span class="Delimiter">);</span>
<span id="L122" class="LineNr">122 </span>  <span class="Comment">// e_shnum</span>
<span id="L123" class="LineNr">123 </span>  emit<span class="Delimiter">(</span>dummy16<span class="Delimiter">);</span>
<span id="L124" class="LineNr">124 </span>  <span class="Comment">// e_shstrndx</span>
<span id="L125" class="LineNr">125 </span>  emit<span class="Delimiter">(</span>dummy16<span class="Delimiter">);</span>
<span id="L126" class="LineNr">126 </span>
<span id="L127" class="LineNr">127 </span>  <span class="Normal">uint32_t</span> p_offset = <span class="Comment">/*</span><span class="Comment">size of ehdr</span><span class="Comment">*/</span><span class="Constant">0x34</span> + SIZE<span class="Delimiter">(</span>p<span class="Delimiter">.</span>segments<span class="Delimiter">)</span>*<span class="Constant">0x20</span><span class="Comment">/*</span><span class="Comment">size of each phdr</span><span class="Comment">*/</span><span class="Delimiter">;</span>
<span id="L128" class="LineNr">128 </span>  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Constant">0</span><span class="Delimiter">;</span>  i &lt; SIZE<span class="Delimiter">(</span>p<span class="Delimiter">.</span>segments<span class="Delimiter">);</span>  ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L129" class="LineNr">129 </span>    <span class="SalientComment">//// phdr</span>
<span id="L130" class="LineNr">130 </span>    <span class="Comment">// p_type</span>
<span id="L131" class="LineNr">131 </span>    <span class="Normal">uint32_t</span> p_type = <span class="Constant">0x1</span><span class="Delimiter">;</span>
<span id="L132" class="LineNr">132 </span>    emit<span class="Delimiter">(</span>p_type<span class="Delimiter">);</span>
<span id="L133" class="LineNr">133 </span>    <span class="Comment">// p_offset</span>
<span id="L134" class="LineNr">134 </span>    emit<span class="Delimiter">(</span>p_offset<span class="Delimiter">);</span>
<span id="L135" class="LineNr">135 </span>    <span class="Comment">// p_vaddr</span>
<span id="L136" class="LineNr">136 </span>    <span class="Normal">uint32_t</span> p_start = p<span class="Delimiter">.</span>segments<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>start<span class="Delimiter">;</span>
<span id="L137" class="LineNr">137 </span>    emit<span class="Delimiter">(</span>p_start<span class="Delimiter">);</span>
<span id="L138" class="LineNr">138 </span>    <span class="Comment">// p_paddr</span>
<span id="L139" class="LineNr">139 </span>    emit<span class="Delimiter">(</span>p_start<span class="Delimiter">);</span>
<span id="L140" class="LineNr">140 </span>    <span class="Comment">// p_filesz</span>
<span id="L141" class="LineNr">141 </span>    <span class="Normal">uint32_t</span> size = num_words<span class="Delimiter">(</span>p<span class="Delimiter">.</span>segments<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">));</span>
<span id="L142" class="LineNr">142 </span>    assert<span class="Delimiter">(</span>p_offset + size &lt; INITIAL_SEGMENT_SIZE<span class="Delimiter">);</span>
<span id="L143" class="LineNr">143 </span>    emit<span class="Delimiter">(</span>size<span class="Delimiter">);</span>
<span id="L144" class="LineNr">144 </span>    <span class="Comment">// p_memsz</span>
<span id="L145" class="LineNr">145 </span>    emit<span class="Delimiter">(</span>size<span class="Delimiter">);</span>
<span id="L146" class="LineNr">146 </span>    <span class="Comment">// p_flags</span>
<span id="L147" class="LineNr">147 </span>    <span class="Normal">uint32_t</span> p_flags = <span class="Delimiter">(</span>i == <span class="Constant">0</span><span class="Delimiter">)</span> ? <span class="Comment">/*</span><span class="Comment">r-x</span><span class="Comment">*/</span><span class="Constant">0x5</span> : <span class="Comment">/*</span><span class="Comment">rw-</span><span class="Comment">*/</span><span class="Constant">0x6</span><span class="Delimiter">;</span>  <span class="Comment">// convention: only first segment is code</span>
<span id="L148" class="LineNr">148 </span>    emit<span class="Delimiter">(</span>p_flags<span class="Delimiter">);</span>
<span id="L149" class="LineNr">149 </span>
<span id="L150" class="LineNr">150 </span>    <span class="Comment">// p_align</span>
<span id="L151" class="LineNr">151 </span>    <span class="Comment">// &quot;As the system creates or augments a process image, it logically copies</span>
<span id="L152" class="LineNr">152 </span>    <span class="Comment">// a file's segment to a virtual memory segment.  When—and if— the system</span>
<span id="L153" class="LineNr">153 </span>    <span class="Comment">// physically reads the file depends on the program's execution behavior,</span>
<span id="L154" class="LineNr">154 </span>    <span class="Comment">// system load, and so on.  A process does not require a physical page</span>
<span id="L155" class="LineNr">155 </span>    <span class="Comment">// unless it references the logical page during execution, and processes</span>
<span id="L156" class="LineNr">156 </span>    <span class="Comment">// commonly leave many pages unreferenced. Therefore delaying physical</span>
<span id="L157" class="LineNr">157 </span>    <span class="Comment">// reads frequently obviates them, improving system performance. To obtain</span>
<span id="L158" class="LineNr">158 </span>    <span class="Comment">// this efficiency in practice, executable and shared object files must</span>
<span id="L159" class="LineNr">159 </span>    <span class="Comment">// have segment images whose file offsets and virtual addresses are</span>
<span id="L160" class="LineNr">160 </span>    <span class="Comment">// congruent, modulo the page size.&quot; -- <a href="http://refspecs.linuxbase.org/elf/elf.pdf">http://refspecs.linuxbase.org/elf/elf.pdf</a> (page 95)</span>
<span id="L161" class="LineNr">161 </span>    <span class="Normal">uint32_t</span> p_align = <span class="Constant">0x1000</span><span class="Delimiter">;</span>  <span class="Comment">// default page size on linux</span>
<span id="L162" class="LineNr">162 </span>    emit<span class="Delimiter">(</span>p_align<span class="Delimiter">);</span>
<span id="L163" class="LineNr">163 </span>    <span class="Normal">if</span> <span class="Delimiter">(</span>p_offset % p_align != p_start % p_align<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L164" class="LineNr">164 </span>      raise &lt;&lt; <span class="Constant">&quot;segment starting at 0x&quot;</span> &lt;&lt; HEXWORD &lt;&lt; p_start &lt;&lt; <span class="Constant">&quot; is improperly aligned; alignment for p_offset &quot;</span> &lt;&lt; p_offset &lt;&lt; <span class="Constant">&quot; should be &quot;</span> &lt;&lt; <span class="Delimiter">(</span>p_offset % p_align<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot; but is &quot;</span> &lt;&lt; <span class="Delimiter">(</span>p_start % p_align<span class="Delimiter">)</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
<span id="L165" class="LineNr">165 </span>      <span class="Identifier">return</span><span class="Delimiter">;</span>
<span id="L166" class="LineNr">166 </span>    <span class="Delimiter">}</span>
<span id="L167" class="LineNr">167 </span>
<span id="L168" class="LineNr">168 </span>    <span class="Comment">// prepare for next segment</span>
<span id="L169" class="LineNr">169 </span>    p_offset += size<span class="Delimiter">;</span>
<span id="L170" class="LineNr">170 </span>  <span class="Delimiter">}</span>
<span id="L171" class="LineNr">171 </span><span class="Comment">#undef O</span>
<span id="L172" class="LineNr">172 </span><span class="Comment">#undef emit</span>
<span id="L173" class="LineNr">173 </span><span class="Delimiter">}</span>
<span id="L174" class="LineNr">174 </span>
<span id="L175" class="LineNr">175 </span><span class="Normal">void</span> write_segment<span class="Delimiter">(</span><span class="Normal">const</span> segment&amp; s<span class="Delimiter">,</span> ostream&amp; out<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L176" class="LineNr">176 </span>  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Constant">0</span><span class="Delimiter">;</span>  i &lt; SIZE<span class="Delimiter">(</span>s<span class="Delimiter">.</span>lines<span class="Delimiter">);</span>  ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L177" class="LineNr">177 </span>    <span class="Normal">const</span> vector&lt;word&gt;&amp; w = s<span class="Delimiter">.</span>lines<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>words<span class="Delimiter">;</span>
<span id="L178" class="LineNr">178 </span>    <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> j = <span class="Constant">0</span><span class="Delimiter">;</span>  j &lt; SIZE<span class="Delimiter">(</span>w<span class="Delimiter">);</span>  ++j<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L179" class="LineNr">179 </span>      <span class="Normal">uint8_t</span> x = hex_byte<span class="Delimiter">(</span>w<span class="Delimiter">.</span>at<span class="Delimiter">(</span>j<span class="Delimiter">).</span>data<span class="Delimiter">);</span>  <span class="Comment">// we're done with metadata by this point</span>
<span id="L180" class="LineNr">180 </span>      out<span class="Delimiter">.</span>write<span class="Delimiter">(</span><span class="Normal">reinterpret_cast</span>&lt;<span class="Normal">const</span> <span class="Normal">char</span>*&gt;<span class="Delimiter">(</span>&amp;x<span class="Delimiter">),</span> <span class="Comment">/*</span><span class="Comment">sizeof(byte)</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">);</span>
<span id="L181" class="LineNr">181 </span>    <span class="Delimiter">}</span>
<span id="L182" class="LineNr">182 </span>  <span class="Delimiter">}</span>
<span id="L183" class="LineNr">183 </span><span class="Delimiter">}</span>
<span id="L184" class="LineNr">184 </span>
<span id="L185" class="LineNr">185 </span><span class="Normal">uint32_t</span> num_words<span class="Delimiter">(</span><span class="Normal">const</span> segment&amp; s<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L186" class="LineNr">186 </span>  <span class="Normal">uint32_t</span> sum = <span class="Constant">0</span><span class="Delimiter">;</span>
<span id="L187" class="LineNr">187 </span>  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Constant">0</span><span class="Delimiter">;</span>  i &lt; SIZE<span class="Delimiter">(</span>s<span class="Delimiter">.</span>lines<span class="Delimiter">);</span>  ++i<span class="Delimiter">)</span>
<span id="L188" class="LineNr">188 </span>    sum += SIZE<span class="Delimiter">(</span>s<span class="Delimiter">.</span>lines<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>words<span class="Delimiter">);</span>
<span id="L189" class="LineNr">189 </span>  <span class="Identifier">return</span> sum<span class="Delimiter">;</span>
<span id="L190" class="LineNr">190 </span><span class="Delimiter">}</span>
<span id="L191" class="LineNr">191 </span>
<span id="L192" class="LineNr">192 </span><span class="Delimiter">:(before &quot;End Includes&quot;)</span>
<span id="L193" class="LineNr">193 </span><span class="Normal">using</span> std::ios<span class="Delimiter">;</span>
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