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* 6631Kartik Agaram2020-07-101-0/+137
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<a href='https://github.com/akkartik/mu/blob/master/059stop.subx'>https://github.com/akkartik/mu/blob/master/059stop.subx</a>
<pre id='vimCodeElement'>
<span id="L1" class="LineNr">  1 </span><span class="subxComment"># stop: dependency-injected wrapper around the exit() syscall</span>
<span id="L2" class="LineNr">  2 </span><span class="subxComment">#</span>
<span id="L3" class="LineNr">  3 </span><span class="subxComment"># We'd like to be able to write tests for functions that call exit(), and to</span>
<span id="L4" class="LineNr">  4 </span><span class="subxComment"># make assertions about whether they exit() or not in a given situation. To</span>
<span id="L5" class="LineNr">  5 </span><span class="subxComment"># achieve this we'll call exit() via a smarter wrapper called 'stop'.</span>
<span id="L6" class="LineNr">  6 </span><span class="subxComment">#</span>
<span id="L7" class="LineNr">  7 </span><span class="subxComment"># In the context of a test, calling a function X that calls 'stop' (directly</span>
<span id="L8" class="LineNr">  8 </span><span class="subxComment"># or through further intervening calls) will unwind the stack until X returns,</span>
<span id="L9" class="LineNr">  9 </span><span class="subxComment"># so that we can say check any further assertions after the execution of X. To</span>
<span id="L10" class="LineNr"> 10 </span><span class="subxComment"># achieve this end, we'll pass the return address of X as a 'target' argument</span>
<span id="L11" class="LineNr"> 11 </span><span class="subxComment"># into X, plumbing it through to 'stop'. When 'stop' gets a non-null target it</span>
<span id="L12" class="LineNr"> 12 </span><span class="subxComment"># unwinds the stack until the target. If it gets a null target it calls</span>
<span id="L13" class="LineNr"> 13 </span><span class="subxComment"># exit().</span>
<span id="L14" class="LineNr"> 14 </span><span class="subxComment">#</span>
<span id="L15" class="LineNr"> 15 </span><span class="subxComment"># We'd also like to get the exit status out of 'stop', so we'll combine the</span>
<span id="L16" class="LineNr"> 16 </span><span class="subxComment"># input target with an output status parameter into a type called 'exit-descriptor'.</span>
<span id="L17" class="LineNr"> 17 </span><span class="subxComment">#</span>
<span id="L18" class="LineNr"> 18 </span><span class="subxComment"># So the exit-descriptor looks like this:</span>
<span id="L19" class="LineNr"> 19 </span><span class="subxComment">#   target : address  # return address for 'stop' to unwind to</span>
<span id="L20" class="LineNr"> 20 </span><span class="subxComment">#   value : int  # exit status stop was called with</span>
<span id="L21" class="LineNr"> 21 </span><span class="subxComment">#</span>
<span id="L22" class="LineNr"> 22 </span><span class="subxComment"># 'stop' thus takes two parameters: an exit-descriptor and the exit status.</span>
<span id="L23" class="LineNr"> 23 </span><span class="subxComment">#</span>
<span id="L24" class="LineNr"> 24 </span><span class="subxComment"># 'stop' won't bother cleaning up any other processor state besides the stack,</span>
<span id="L25" class="LineNr"> 25 </span><span class="subxComment"># such as registers. Only esp will have a well-defined value after 'stop'</span>
<span id="L26" class="LineNr"> 26 </span><span class="subxComment"># returns. (This is a poor man's setjmp/longjmp, if you know what that is.)</span>
<span id="L27" class="LineNr"> 27 </span><span class="subxComment">#</span>
<span id="L28" class="LineNr"> 28 </span><span class="subxComment"># Before you can call any function that may call 'stop', you need to pass in an</span>
<span id="L29" class="LineNr"> 29 </span><span class="subxComment"># exit-descriptor to it. To create an exit-descriptor use 'tailor-exit-descriptor'</span>
<span id="L30" class="LineNr"> 30 </span><span class="subxComment"># below. It's not the most pleasant abstraction in the world.</span>
<span id="L31" class="LineNr"> 31 </span><span class="subxComment">#</span>
<span id="L32" class="LineNr"> 32 </span><span class="subxComment"># An exit-descriptor's target is its input, computed during 'tailor-exit-descriptor'.</span>
<span id="L33" class="LineNr"> 33 </span><span class="subxComment"># Its value is its output, computed during stop and available to the test.</span>
<span id="L34" class="LineNr"> 34 </span>
<span id="L35" class="LineNr"> 35 </span>== code
<span id="L36" class="LineNr"> 36 </span><span class="subxComment">#   instruction                     effective address                                                   register    displacement    immediate</span>
<span id="L37" class="LineNr"> 37 </span><span class="subxS1Comment"># . op          subop               mod             rm32          base        index         scale       r32</span>
<span id="L38" class="LineNr"> 38 </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="L39" class="LineNr"> 39 </span>
<span id="L40" class="LineNr"> 40 </span><span class="subxComment"># Configure an exit-descriptor for a call pushing 'nbytes' bytes of args to</span>
<span id="L41" class="LineNr"> 41 </span><span class="subxComment"># the stack.</span>
<span id="L42" class="LineNr"> 42 </span><span class="subxComment"># Ugly that we need to know the size of args. Don't allocate variables between</span>
<span id="L43" class="LineNr"> 43 </span><span class="subxComment"># tailor-exit-descriptor and the call it's for.</span>
<span id="L44" class="LineNr"> 44 </span><span class="subxFunction">tailor-exit-descriptor</span>:  <span class="subxComment"># ed : (address exit-descriptor), nbytes : int -&gt; &lt;void&gt;</span>
<span id="L45" class="LineNr"> 45 </span>    <span class="subxS1Comment"># . prolog</span>
<span id="L46" class="LineNr"> 46 </span>    55/push-ebp
<span id="L47" class="LineNr"> 47 </span>    89/copy                         3/mod/direct    5/rm32/ebp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          4/r32/esp  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># copy esp to ebp</span>
<span id="L48" class="LineNr"> 48 </span>    <span class="subxS1Comment"># . save registers</span>
<span id="L49" class="LineNr"> 49 </span>    50/push-eax
<span id="L50" class="LineNr"> 50 </span>    51/push-ecx
<span id="L51" class="LineNr"> 51 </span>    <span class="subxComment"># eax = nbytes</span>
<span id="L52" class="LineNr"> 52 </span>    8b/copy                         1/mod/*+disp8   5/rm32/ebp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          0/r32/eax   0xc/disp8      <span class="Normal"> . </span>                <span class="subxComment"># copy *(ebp+12) to eax</span>
<span id="L53" class="LineNr"> 53 </span>    <span class="subxComment"># Let X be the value of esp in the caller, before the call to tailor-exit-descriptor.</span>
<span id="L54" class="LineNr"> 54 </span>    <span class="subxComment"># The return address for a call in the caller's body will be at:</span>
<span id="L55" class="LineNr"> 55 </span>    <span class="subxComment">#   X-8 if the caller takes 4 bytes of args for the exit-descriptor (add 4 bytes for the return address)</span>
<span id="L56" class="LineNr"> 56 </span>    <span class="subxComment">#   X-12 if the caller takes 8 bytes of args</span>
<span id="L57" class="LineNr"> 57 </span>    <span class="subxComment">#   ..and so on</span>
<span id="L58" class="LineNr"> 58 </span>    <span class="subxComment"># That's the value we need to return: X-nbytes-4</span>
<span id="L59" class="LineNr"> 59 </span>    <span class="subxComment">#</span>
<span id="L60" class="LineNr"> 60 </span>    <span class="subxComment"># However, we also need to account for the perturbance to esp caused by the</span>
<span id="L61" class="LineNr"> 61 </span>    <span class="subxComment"># call to tailor-exit-descriptor. It pushes 8 bytes of args followed by 4</span>
<span id="L62" class="LineNr"> 62 </span>    <span class="subxComment"># bytes for the return address and 4 bytes to push ebp above.</span>
<span id="L63" class="LineNr"> 63 </span>    <span class="subxComment"># So ebp at this point is X-16.</span>
<span id="L64" class="LineNr"> 64 </span>    <span class="subxComment">#</span>
<span id="L65" class="LineNr"> 65 </span>    <span class="subxComment"># So the return address for the next call in the caller is:</span>
<span id="L66" class="LineNr"> 66 </span>    <span class="subxComment">#   ebp+8 if the caller takes 4 bytes of args</span>
<span id="L67" class="LineNr"> 67 </span>    <span class="subxComment">#   ebp+4 if the caller takes 8 bytes of args</span>
<span id="L68" class="LineNr"> 68 </span>    <span class="subxComment">#   ebp if the caller takes 12 bytes of args</span>
<span id="L69" class="LineNr"> 69 </span>    <span class="subxComment">#   ebp-4 if the caller takes 16 bytes of args</span>
<span id="L70" class="LineNr"> 70 </span>    <span class="subxComment">#   ..and so on</span>
<span id="L71" class="LineNr"> 71 </span>    <span class="subxComment"># That's ebp+12-nbytes.</span>
<span id="L72" class="LineNr"> 72 </span>    <span class="subxComment"># option 1: 6 + 3 bytes</span>
<span id="L73" class="LineNr"> 73 </span><span class="CommentedCode">#?     2d/subtract                     3/mod/direct    0/rm32/eax    .           .             .           .           .               8/imm32           # subtract from eax</span>
<span id="L74" class="LineNr"> 74 </span><span class="CommentedCode">#?     8d/copy-address                 0/mod/indirect  4/rm32/sib    5/base/ebp  0/index/eax   .           0/r32/eax   .               .                 # copy ebp+eax to eax</span>
<span id="L75" class="LineNr"> 75 </span>    <span class="subxComment"># option 2: 2 + 4 bytes</span>
<span id="L76" class="LineNr"> 76 </span>    f7          3/subop/negate      3/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>             <span class="Normal"> . </span>                <span class="subxComment"># negate eax</span>
<span id="L77" class="LineNr"> 77 </span>    8d/copy-address                 1/mod/*+disp8   4/rm32/sib    5/base/ebp  0/index/eax  <span class="Normal"> . </span>          0/r32/eax   0xc/disp8        <span class="Normal"> . </span>              <span class="subxComment"># copy ebp+eax+12 to eax</span>
<span id="L78" class="LineNr"> 78 </span>    <span class="subxComment"># copy eax to ed-&gt;target</span>
<span id="L79" class="LineNr"> 79 </span>    8b/copy                         1/mod/*+disp8   5/rm32/ebp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          1/r32/ecx   8/disp8        <span class="Normal"> . </span>                <span class="subxComment"># copy *(ebp+8) to ecx</span>
<span id="L80" class="LineNr"> 80 </span>    89/copy                         0/mod/indirect  1/rm32/ecx   <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 *ecx</span>
<span id="L81" class="LineNr"> 81 </span>    <span class="subxComment"># initialize ed-&gt;value</span>
<span id="L82" class="LineNr"> 82 </span>    c7          0/subop/copy        1/mod/*+disp8   1/rm32/ecx   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>         <span class="Normal"> . </span>          4/disp8         0/imm32           <span class="subxComment"># copy to *(ecx+4)</span>
<span id="L83" class="LineNr"> 83 </span><span class="Constant">$tailor-exit-descriptor:end</span>:
<span id="L84" class="LineNr"> 84 </span>    <span class="subxS1Comment"># . restore registers</span>
<span id="L85" class="LineNr"> 85 </span>    59/pop-to-ecx
<span id="L86" class="LineNr"> 86 </span>    58/pop-to-eax
<span id="L87" class="LineNr"> 87 </span>    <span class="subxS1Comment"># . epilog</span>
<span id="L88" class="LineNr"> 88 </span>    89/copy                         3/mod/direct    4/rm32/esp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          5/r32/ebp  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># copy ebp to esp</span>
<span id="L89" class="LineNr"> 89 </span>    5d/pop-to-ebp
<span id="L90" class="LineNr"> 90 </span>    c3/return
<span id="L91" class="LineNr"> 91 </span>
<span id="L92" class="LineNr"> 92 </span><span class="subxFunction">stop</span>:  <span class="subxComment"># ed : (address exit-descriptor), value : int</span>
<span id="L93" class="LineNr"> 93 </span>    <span class="subxComment"># no prolog; one way or another, we're going to clobber registers</span>
<span id="L94" class="LineNr"> 94 </span>    <span class="subxComment"># eax = ed</span>
<span id="L95" class="LineNr"> 95 </span>    8b/copy                         1/mod/*+disp8   4/rm32/sib    4/base/esp  4/index/none <span class="Normal"> . </span>          0/r32/eax   4/disp8        <span class="Normal"> . </span>                <span class="subxComment"># copy *(esp+4) to eax</span>
<span id="L96" class="LineNr"> 96 </span>    <span class="subxComment"># if (ed-&gt;target == 0) really exit</span>
<span id="L97" class="LineNr"> 97 </span>    81          7/subop/compare     0/mod/indirect  0/rm32/eax   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>         <span class="Normal"> . </span>         <span class="Normal"> . </span>              0/imm32           <span class="subxComment"># compare *eax</span>
<span id="L98" class="LineNr"> 98 </span>    75/jump-if-not-equal  $stop:fake/disp8
<span id="L99" class="LineNr"> 99 </span>    <span class="subxS1Comment"># . syscall(exit, value)</span>
<span id="L100" class="LineNr">100 </span>    8b/copy                         1/mod/*+disp8   4/rm32/sib    4/base/esp  4/index/none <span class="Normal"> . </span>          3/r32/ebx   8/disp8        <span class="Normal"> . </span>                <span class="subxComment"># copy *(esp+8) to ebx</span>
<span id="L101" class="LineNr">101 </span>    b8/copy-to-eax  1/imm32/exit
<span id="L102" class="LineNr">102 </span>    cd/syscall  0x80/imm8
<span id="L103" class="LineNr">103 </span><span class="Constant">$stop:fake</span>:
<span id="L104" class="LineNr">104 </span>    <span class="subxComment"># otherwise:</span>
<span id="L105" class="LineNr">105 </span>    <span class="subxComment"># ed-&gt;value = value+1</span>
<span id="L106" class="LineNr">106 </span>    8b/copy                         1/mod/*+disp8   4/rm32/sib    4/base/esp  4/index/none <span class="Normal"> . </span>          1/r32/ecx   8/disp8        <span class="Normal"> . </span>                <span class="subxComment"># copy *(esp+8) to ecx</span>
<span id="L107" class="LineNr">107 </span>    41/increment-ecx
<span id="L108" class="LineNr">108 </span>    89/copy                         1/mod/*+disp8   0/rm32/eax   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          1/r32/ecx   4/disp8        <span class="Normal"> . </span>                <span class="subxComment"># copy ecx to *(eax+4)</span>
<span id="L109" class="LineNr">109 </span>    <span class="subxComment"># perform a non-local jump to ed-&gt;target</span>
<span id="L110" class="LineNr">110 </span>    8b/copy                         0/mod/indirect  0/rm32/eax   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          4/r32/esp  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># copy *eax to esp</span>
<span id="L111" class="LineNr">111 </span><span class="Constant">$stop:end</span>:
<span id="L112" class="LineNr">112 </span>    c3/return  <span class="subxComment"># doesn't return to caller</span>
<span id="L113" class="LineNr">113 </span>
<span id="L114" class="LineNr">114 </span><span class="subxTest">test-stop-skips-returns-on-exit</span>:
<span id="L115" class="LineNr">115 </span>    <span class="subxComment"># This looks like the standard prolog, but is here for different reasons.</span>
<span id="L116" class="LineNr">116 </span>    <span class="subxComment"># A function calling 'stop' can't rely on ebp persisting past the call.</span>
<span id="L117" class="LineNr">117 </span>    <span class="subxComment">#</span>
<span id="L118" class="LineNr">118 </span>    <span class="subxComment"># Use ebp here as a stable base to refer to locals and arguments from in the</span>
<span id="L119" class="LineNr">119 </span>    <span class="subxComment"># presence of push/pop/call instructions.</span>
<span id="L120" class="LineNr">120 </span>    <span class="subxComment"># *Don't* use ebp as a way to restore esp.</span>
<span id="L121" class="LineNr">121 </span>    55/push-ebp
<span id="L122" class="LineNr">122 </span>    89/copy                         3/mod/direct    5/rm32/ebp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          4/r32/esp  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># copy esp to ebp</span>
<span id="L123" class="LineNr">123 </span>    <span class="subxComment"># Make room for an exit descriptor on the stack. That's almost always the</span>
<span id="L124" class="LineNr">124 </span>    <span class="subxComment"># right place for it, available only as long as it's legal to use. Once this</span>
<span id="L125" class="LineNr">125 </span>    <span class="subxComment"># containing function returns we'll need a new exit descriptor.</span>
<span id="L126" class="LineNr">126 </span>    <span class="subxComment"># var ed/eax : (address exit-descriptor)</span>
<span id="L127" class="LineNr">127 </span>    68/push  0/imm32
<span id="L128" class="LineNr">128 </span>    68/push  0/imm32
<span id="L129" class="LineNr">129 </span>    89/copy                         3/mod/direct    0/rm32/eax   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          4/r32/esp  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># copy esp to eax</span>
<span id="L130" class="LineNr">130 </span>    <span class="subxComment"># Size the exit-descriptor precisely for the next call below, to _test-stop-1.</span>
<span id="L131" class="LineNr">131 </span>    <span class="subxComment"># tailor-exit-descriptor(ed, 4)</span>
<span id="L132" class="LineNr">132 </span>    <span class="subxS2Comment"># . . push args</span>
<span id="L133" class="LineNr">133 </span>    68/push  4/imm32/nbytes-of-args-for-_test-stop-1
<span id="L134" class="LineNr">134 </span>    50/push-eax
<span id="L135" class="LineNr">135 </span>    <span class="subxS2Comment"># . . call</span>
<span id="L136" class="LineNr">136 </span>    e8/call  <a href='059stop.subx.html#L44'>tailor-exit-descriptor</a>/disp32
<span id="L137" class="LineNr">137 </span>    <span class="subxS2Comment"># . . discard args</span>
<span id="L138" class="LineNr">138 </span>    81          0/subop/add         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>              8/imm32           <span class="subxComment"># add to esp</span>
<span id="L139" class="LineNr">139 </span>    <span class="subxS1Comment"># . _test-stop-1(ed)</span>
<span id="L140" class="LineNr">140 </span>    <span class="subxS2Comment"># . . push args</span>
<span id="L141" class="LineNr">141 </span>    50/push-eax
<span id="L142" class="LineNr">142 </span>    <span class="subxS2Comment"># . . call</span>
<span id="L143" class="LineNr">143 </span>    e8/call  <a href='059stop.subx.html#L164'>_test-stop-1</a>/disp32
<span id="L144" class="LineNr">144 </span>    <span class="subxComment"># registers except esp may be clobbered at this point</span>
<span id="L145" class="LineNr">145 </span>    <span class="subxComment"># restore args</span>
<span id="L146" class="LineNr">146 </span>    58/pop-to-eax
<span id="L147" class="LineNr">147 </span>    <span class="subxComment"># check that _test-stop-1 tried to call exit(1)</span>
<span id="L148" class="LineNr">148 </span>    <span class="subxS1Comment"># . check-ints-equal(ed-&gt;value, 2, msg)  # i.e. stop was called with value 1</span>
<span id="L149" class="LineNr">149 </span>    <span class="subxS2Comment"># . . push args</span>
<span id="L150" class="LineNr">150 </span>    68/push  <span class="Constant">&quot;F - test-stop-skips-returns-on-exit&quot;</span>/imm32
<span id="L151" class="LineNr">151 </span>    68/push  2/imm32
<span id="L152" class="LineNr">152 </span>    <span class="subxS2Comment"># . . push ed-&gt;value</span>
<span id="L153" class="LineNr">153 </span>    ff          6/subop/push        1/mod/*+disp8   0/rm32/eax   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>         <span class="Normal"> . </span>          4/disp8        <span class="Normal"> . </span>                <span class="subxComment"># push *(eax+4)</span>
<span id="L154" class="LineNr">154 </span>    <span class="subxS2Comment"># . . call</span>
<span id="L155" class="LineNr">155 </span>    e8/call  <a href='051test.subx.html#L24'>check-ints-equal</a>/disp32
<span id="L156" class="LineNr">156 </span>    <span class="subxS2Comment"># . . discard args</span>
<span id="L157" class="LineNr">157 </span>    81          0/subop/add         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>              0xc/imm32         <span class="subxComment"># add to esp</span>
<span id="L158" class="LineNr">158 </span>    <span class="subxS1Comment"># . epilog</span>
<span id="L159" class="LineNr">159 </span>    <span class="subxComment"># don't restore esp from ebp; manually reclaim locals</span>
<span id="L160" class="LineNr">160 </span>    81          0/subop/add         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>              8/imm32           <span class="subxComment"># add to esp</span>
<span id="L161" class="LineNr">161 </span>    5d/pop-to-ebp
<span id="L162" class="LineNr">162 </span>    c3/return
<span id="L163" class="LineNr">163 </span>
<span id="L164" class="LineNr">164 </span><span class="subxMinorFunction">_test-stop-1</span>:  <span class="subxComment"># ed : (address exit-descriptor)</span>
<span id="L165" class="LineNr">165 </span>    <span class="subxS1Comment"># . prolog</span>
<span id="L166" class="LineNr">166 </span>    55/push-ebp
<span id="L167" class="LineNr">167 </span>    89/copy                         3/mod/direct    5/rm32/ebp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          4/r32/esp  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># copy esp to ebp</span>
<span id="L168" class="LineNr">168 </span>    <span class="subxComment"># _test-stop-2(ed)</span>
<span id="L169" class="LineNr">169 </span>    <span class="subxS2Comment"># . . push args</span>
<span id="L170" class="LineNr">170 </span>    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>         <span class="Normal"> . </span>          8/disp8        <span class="Normal"> . </span>                <span class="subxComment"># push *(ebp+8)</span>
<span id="L171" class="LineNr">171 </span>    <span class="subxS2Comment"># . . call</span>
<span id="L172" class="LineNr">172 </span>    e8/call  <a href='059stop.subx.html#L191'>_test-stop-2</a>/disp32
<span id="L173" class="LineNr">173 </span>    <span class="subxComment"># should never get past this point</span>
<span id="L174" class="LineNr">174 </span><span class="Constant">$_test-stop-1:dead-end</span>:
<span id="L175" class="LineNr">175 </span>    <span class="subxS2Comment"># . . discard args</span>
<span id="L176" class="LineNr">176 </span>    81          0/subop/add         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"># add to esp</span>
<span id="L177" class="LineNr">177 </span>    <span class="subxComment"># signal test failed: check-ints-equal(1, 0, msg)</span>
<span id="L178" class="LineNr">178 </span>    <span class="subxS2Comment"># . . push args</span>
<span id="L179" class="LineNr">179 </span>    68/push  <span class="Constant">&quot;F - test-stop-skips-returns-on-exit&quot;</span>/imm32
<span id="L180" class="LineNr">180 </span>    68/push  0/imm32
<span id="L181" class="LineNr">181 </span>    68/push  1/imm32
<span id="L182" class="LineNr">182 </span>    <span class="subxS2Comment"># . . call</span>
<span id="L183" class="LineNr">183 </span>    e8/call  <a href='051test.subx.html#L24'>check-ints-equal</a>/disp32
<span id="L184" class="LineNr">184 </span>    <span class="subxS2Comment"># . . discard args</span>
<span id="L185" class="LineNr">185 </span>    81          0/subop/add         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>              0xc/imm32         <span class="subxComment"># add to esp</span>
<span id="L186" class="LineNr">186 </span>    <span class="subxS1Comment"># . epilog</span>
<span id="L187" class="LineNr">187 </span>    89/copy                         3/mod/direct    4/rm32/esp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          5/r32/ebp  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># copy ebp to esp</span>
<span id="L188" class="LineNr">188 </span>    5d/pop-to-ebp
<span id="L189" class="LineNr">189 </span>    c3/return
<span id="L190" class="LineNr">190 </span>
<span id="L191" class="LineNr">191 </span><span class="subxMinorFunction">_test-stop-2</span>:  <span class="subxComment"># ed : (address exit-descriptor)</span>
<span id="L192" class="LineNr">192 </span>    <span class="subxS1Comment"># . prolog</span>
<span id="L193" class="LineNr">193 </span>    55/push-ebp
<span id="L194" class="LineNr">194 </span>    89/copy                         3/mod/direct    5/rm32/ebp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          4/r32/esp  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># copy esp to ebp</span>
<span id="L195" class="LineNr">195 </span>    <span class="subxS1Comment"># . stop(ed, 1)</span>
<span id="L196" class="LineNr">196 </span>    <span class="subxS2Comment"># . . push args</span>
<span id="L197" class="LineNr">197 </span>    68/push  1/imm32
<span id="L198" class="LineNr">198 </span>    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>         <span class="Normal"> . </span>          8/disp8        <span class="Normal"> . </span>                <span class="subxComment"># push *(ebp+8)</span>
<span id="L199" class="LineNr">199 </span>    <span class="subxS2Comment"># . . call</span>
<span id="L200" class="LineNr">200 </span>    e8/call  <a href='059stop.subx.html#L92'>stop</a>/disp32
<span id="L201" class="LineNr">201 </span>    <span class="subxComment"># should never get past this point</span>
<span id="L202" class="LineNr">202 </span><span class="Constant">$_test-stop-2:dead-end</span>:
<span id="L203" class="LineNr">203 </span>    <span class="subxS1Comment"># . epilog</span>
<span id="L204" class="LineNr">204 </span>    89/copy                         3/mod/direct    4/rm32/esp   <span class="Normal"> . </span>         <span class="Normal"> . </span>           <span class="Normal"> . </span>          5/r32/ebp  <span class="Normal"> . </span>             <span class="Normal"> . </span>                <span class="subxComment"># copy ebp to esp</span>
<span id="L205" class="LineNr">205 </span>    5d/pop-to-ebp
<span id="L206" class="LineNr">206 </span>    c3/return
<span id="L207" class="LineNr">207 </span>
<span id="L208" class="LineNr">208 </span><span class="subxS2Comment"># . . vim&#0058;nowrap:textwidth=0</span>
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