diff options
| author | Kartik Agaram <vc@akkartik.com> | 2018-11-27 12:04:53 -0800 |
|---|---|---|
| committer | Kartik Agaram <vc@akkartik.com> | 2018-11-27 12:04:53 -0800 |
| commit | 2131b055f5ce1292e5f115fe66b25b8e5c6c5883 (patch) | |
| tree | 65adcf8ddf2d18a37a3a92ac0deffb78dff08c3c | |
| parent | 71d7081a7ccf0af6e5887856ada32b468bcca30f (diff) | |
| download | mu-2131b055f5ce1292e5f115fe66b25b8e5c6c5883.tar.gz | |
4787
| -rw-r--r-- | html/subx/057stop.subx.html | 361 | ||||
| -rw-r--r-- | subx/057stop.subx | 13 |
2 files changed, 194 insertions, 180 deletions
diff --git a/html/subx/057stop.subx.html b/html/subx/057stop.subx.html index c926ace5..2649724e 100644 --- a/html/subx/057stop.subx.html +++ b/html/subx/057stop.subx.html @@ -75,190 +75,197 @@ if ('onhashchange' in window) { <span id="L16" class="LineNr"> 16 </span><span class="Comment"># input target with an output status parameter into a type called 'exit-descriptor'.</span> <span id="L17" class="LineNr"> 17 </span><span class="Comment">#</span> <span id="L18" class="LineNr"> 18 </span><span class="Comment"># So the exit-descriptor looks like this:</span> -<span id="L19" class="LineNr"> 19 </span><span class="Comment"># target : address # input return address for 'stop' to unwind to</span> -<span id="L20" class="LineNr"> 20 </span><span class="Comment"># value : int # output exit status stop was called with</span> +<span id="L19" class="LineNr"> 19 </span><span class="Comment"># target : address # return address for 'stop' to unwind to</span> +<span id="L20" class="LineNr"> 20 </span><span class="Comment"># value : int # exit status stop was called with</span> <span id="L21" class="LineNr"> 21 </span><span class="Comment">#</span> <span id="L22" class="LineNr"> 22 </span><span class="Comment"># 'stop' thus takes two parameters: an exit-descriptor and the exit status.</span> <span id="L23" class="LineNr"> 23 </span><span class="Comment">#</span> -<span id="L24" class="LineNr"> 24 </span><span class="Comment"># We won't bother cleaning up any other processor state besides the stack,</span> +<span id="L24" class="LineNr"> 24 </span><span class="Comment"># 'stop' won't bother cleaning up any other processor state besides the stack,</span> <span id="L25" class="LineNr"> 25 </span><span class="Comment"># such as registers. Only ESP will have a well-defined value after 'stop'</span> <span id="L26" class="LineNr"> 26 </span><span class="Comment"># returns. (This is a poor man's setjmp/longjmp, if you know what that is.)</span> -<span id="L27" class="LineNr"> 27 </span> -<span id="L28" class="LineNr"> 28 </span>== code -<span id="L29" class="LineNr"> 29 </span><span class="Comment"># instruction effective address operand displacement immediate</span> -<span id="L30" class="LineNr"> 30 </span><span class="Comment"># op subop mod rm32 base index scale r32</span> -<span id="L31" class="LineNr"> 31 </span><span class="Comment"># 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="L32" class="LineNr"> 32 </span> -<span id="L33" class="LineNr"> 33 </span><span class="Comment"># main:</span> -<span id="L34" class="LineNr"> 34 </span> e8/call run-tests/disp32 <span class="Comment"># 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'.</span> -<span id="L35" class="LineNr"> 35 </span><span class="CommentedCode">#? e8/call test-stop-skips-returns-on-exit/disp32</span> -<span id="L36" class="LineNr"> 36 </span> <span class="Comment"># syscall(exit, Num-test-failures)</span> -<span id="L37" class="LineNr"> 37 </span> 8b/copy 0/mod/indirect 5/rm32/.disp32 <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 3/r32/EBX <span class="Special">Num-test-failures</span>/disp32 <span class="Comment"># copy *Num-test-failures to EBX</span> -<span id="L38" class="LineNr"> 38 </span> b8/copy-to-EAX 1/imm32 -<span id="L39" class="LineNr"> 39 </span> cd/syscall 0x80/imm8 -<span id="L40" class="LineNr"> 40 </span> -<span id="L41" class="LineNr"> 41 </span><span class="Comment"># Configure an exit-descriptor for a call pushing 'nbytes' bytes of args to</span> -<span id="L42" class="LineNr"> 42 </span><span class="Comment"># the stack.</span> -<span id="L43" class="LineNr"> 43 </span><span class="Comment"># Ugly that we need to know the size of args, but so it goes.</span> -<span id="L44" class="LineNr"> 44 </span>tailor-exit-descriptor: <span class="Comment"># ed : (address exit-descriptor), nbytes : int -> <void></span> -<span id="L45" class="LineNr"> 45 </span> <span class="Comment"># 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="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/r32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy ESP to EBP</span> -<span id="L48" class="LineNr"> 48 </span> <span class="Comment"># 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="Comment"># EAX = nbytes</span> -<span id="L52" class="LineNr"> 52 </span> 8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none <span class="Delimiter"> . </span> 0/r32/EAX 0xc/disp8 <span class="Delimiter"> . </span> <span class="Comment"># copy *(EBP+12) to EAX</span> -<span id="L53" class="LineNr"> 53 </span> <span class="Comment"># 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="Comment"># The return address for a call in the caller's body will be at:</span> -<span id="L55" class="LineNr"> 55 </span> <span class="Comment"># 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="Comment"># X-12 if the caller takes 8 bytes of args</span> -<span id="L57" class="LineNr"> 57 </span> <span class="Comment"># ..and so on</span> -<span id="L58" class="LineNr"> 58 </span> <span class="Comment"># That's the value we need to return: X-nbytes-4</span> -<span id="L59" class="LineNr"> 59 </span> <span class="Comment">#</span> -<span id="L60" class="LineNr"> 60 </span> <span class="Comment"># However, we also need to account for the perturbance to ESP caused by the</span> -<span id="L61" class="LineNr"> 61 </span> <span class="Comment"># call to tailor-exit-descriptor. It pushes 8 bytes of args followed by 4</span> -<span id="L62" class="LineNr"> 62 </span> <span class="Comment"># bytes for the return address and 4 bytes to push EBP above.</span> -<span id="L63" class="LineNr"> 63 </span> <span class="Comment"># So EBP at this point is X-16.</span> -<span id="L64" class="LineNr"> 64 </span> <span class="Comment">#</span> -<span id="L65" class="LineNr"> 65 </span> <span class="Comment"># So the return address for the next call in the caller is:</span> -<span id="L66" class="LineNr"> 66 </span> <span class="Comment"># EBP+8 if the caller takes 4 bytes of args</span> -<span id="L67" class="LineNr"> 67 </span> <span class="Comment"># EBP+4 if the caller takes 8 bytes of args</span> -<span id="L68" class="LineNr"> 68 </span> <span class="Comment"># EBP if the caller takes 12 bytes of args</span> -<span id="L69" class="LineNr"> 69 </span> <span class="Comment"># EBP-4 if the caller takes 16 bytes of args</span> -<span id="L70" class="LineNr"> 70 </span> <span class="Comment"># ..and so on</span> -<span id="L71" class="LineNr"> 71 </span> <span class="Comment"># That's EBP+12-nbytes.</span> -<span id="L72" class="LineNr"> 72 </span> <span class="Comment"># 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="Comment"># 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="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># 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="Delimiter"> . </span> 0/r32/EAX 0xc/disp8 <span class="Delimiter"> . </span> <span class="Comment"># copy EBP+EAX+12 to EAX</span> -<span id="L78" class="LineNr"> 78 </span> <span class="Comment"># copy EAX to ed->target</span> -<span id="L79" class="LineNr"> 79 </span> 8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none <span class="Delimiter"> . </span> 1/r32/ECX 8/disp8 <span class="Delimiter"> . </span> <span class="Comment"># copy *(EBP+8) to ECX</span> -<span id="L80" class="LineNr"> 80 </span> 89/copy 0/mod/indirect 1/rm32/ECX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 0/r32/EAX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy EAX to *ECX</span> -<span id="L81" class="LineNr"> 81 </span> <span class="Comment"># initialize ed->value</span> -<span id="L82" class="LineNr"> 82 </span> c7/copy 1/mod/*+disp8 1/rm32/ECX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/disp8 0/imm32 <span class="Comment"># copy to *(ECX+4)</span> -<span id="L83" class="LineNr"> 83 </span> <span class="Comment"># restore registers</span> -<span id="L84" class="LineNr"> 84 </span> 59/pop-to-ECX -<span id="L85" class="LineNr"> 85 </span> 58/pop-to-EAX -<span id="L86" class="LineNr"> 86 </span> <span class="Comment"># epilog</span> -<span id="L87" class="LineNr"> 87 </span> 89/copy 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 5/r32/EBP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy EBP to ESP</span> -<span id="L88" class="LineNr"> 88 </span> 5d/pop-to-EBP -<span id="L89" class="LineNr"> 89 </span> c3/return -<span id="L90" class="LineNr"> 90 </span> -<span id="L91" class="LineNr"> 91 </span>stop: <span class="Comment"># ed : (address exit-descriptor), value : int</span> -<span id="L92" class="LineNr"> 92 </span> <span class="Comment"># no prolog; one way or another, we're going to clobber registers</span> -<span id="L93" class="LineNr"> 93 </span> <span class="Comment"># EAX = ed</span> -<span id="L94" class="LineNr"> 94 </span> 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none <span class="Delimiter"> . </span> 0/r32/EAX 4/disp8 <span class="Delimiter"> . </span> <span class="Comment"># copy *(ESP+4) to EAX</span> -<span id="L95" class="LineNr"> 95 </span> <span class="Comment"># exit(value) if ed->target == 0</span> -<span id="L96" class="LineNr"> 96 </span> 81 7/subop/compare 0/mod/indirect 0/rm32/EAX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 0/imm32 <span class="Comment"># compare *EAX</span> -<span id="L97" class="LineNr"> 97 </span> 75/jump-if-not-equal $stop:fake/disp8 -<span id="L98" class="LineNr"> 98 </span> <span class="Comment"># syscall(exit, value)</span> -<span id="L99" class="LineNr"> 99 </span> 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none <span class="Delimiter"> . </span> 3/r32/EBX 8/disp8 <span class="Delimiter"> . </span> <span class="Comment"># copy *(ESP+8) to EBX</span> -<span id="L100" class="LineNr">100 </span> b8/copy-to-EAX 1/imm32 -<span id="L101" class="LineNr">101 </span> cd/syscall 0x80/imm8 -<span id="L102" class="LineNr">102 </span>$stop:fake: -<span id="L103" class="LineNr">103 </span> <span class="Comment"># ed->value = value+1</span> -<span id="L104" class="LineNr">104 </span> 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none <span class="Delimiter"> . </span> 1/r32/ECX 8/disp8 <span class="Delimiter"> . </span> <span class="Comment"># copy *(ESP+8) to ECX</span> -<span id="L105" class="LineNr">105 </span> 41/inc-ECX -<span id="L106" class="LineNr">106 </span> 89/copy 1/mod/*+disp8 0/rm32/EAX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 1/r32/ECX 4/disp8 <span class="Delimiter"> . </span> <span class="Comment"># copy ECX to *(EAX+4)</span> -<span id="L107" class="LineNr">107 </span> <span class="Comment"># non-local jump to ed->target</span> -<span id="L108" class="LineNr">108 </span> 8b/copy 0/mod/indirect 0/rm32/EAX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/r32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy *EAX to ESP</span> -<span id="L109" class="LineNr">109 </span> c3/return <span class="Comment"># doesn't return to caller</span> -<span id="L110" class="LineNr">110 </span> -<span id="L111" class="LineNr">111 </span>test-stop-skips-returns-on-exit: -<span id="L112" class="LineNr">112 </span> <span class="Comment"># This looks like the standard prolog, but is here for different reasons.</span> -<span id="L113" class="LineNr">113 </span> <span class="Comment"># A function calling 'stop' can't rely on EBP persisting past the call.</span> -<span id="L114" class="LineNr">114 </span> <span class="Comment">#</span> -<span id="L115" class="LineNr">115 </span> <span class="Comment"># Use EBP here as a stable base to refer to locals and arguments from in the</span> -<span id="L116" class="LineNr">116 </span> <span class="Comment"># presence of push/pop/call instructions.</span> -<span id="L117" class="LineNr">117 </span> <span class="Comment"># *Don't* use EBP as a way to restore ESP.</span> -<span id="L118" class="LineNr">118 </span> 55/push-EBP -<span id="L119" class="LineNr">119 </span> 89/copy 3/mod/direct 5/rm32/EBP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/r32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy ESP to EBP</span> -<span id="L120" class="LineNr">120 </span> <span class="Comment"># Make room for an exit descriptor on the stack. That's almost always the</span> -<span id="L121" class="LineNr">121 </span> <span class="Comment"># right place for it, available only as long as it's legal to use. Once this</span> -<span id="L122" class="LineNr">122 </span> <span class="Comment"># containing function returns we'll need a new exit descriptor.</span> -<span id="L123" class="LineNr">123 </span> <span class="Comment"># var ed/EAX : (address exit-descriptor)</span> -<span id="L124" class="LineNr">124 </span> 81 5/subop/subtract 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 8/imm32 <span class="Comment"># subtract from ESP</span> -<span id="L125" class="LineNr">125 </span> 8d/copy-address 0/mod/indirect 4/rm32/sib 4/base/ESP 4/index/none <span class="Delimiter"> . </span> 0/r32/EAX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy ESP to EAX</span> -<span id="L126" class="LineNr">126 </span> <span class="Comment"># Size the exit-descriptor precisely for the next call below, to _test-stop-1.</span> -<span id="L127" class="LineNr">127 </span> <span class="Comment"># tailor-exit-descriptor(ed, 4)</span> -<span id="L128" class="LineNr">128 </span> <span class="Comment"># push args</span> -<span id="L129" class="LineNr">129 </span> 68/push 4/imm32/nbytes-of-args-for-_test-stop-1 -<span id="L130" class="LineNr">130 </span> 50/push-EAX -<span id="L131" class="LineNr">131 </span> <span class="Comment"># call</span> -<span id="L132" class="LineNr">132 </span> e8/call tailor-exit-descriptor/disp32 -<span id="L133" class="LineNr">133 </span> <span class="Comment"># discard args</span> -<span id="L134" class="LineNr">134 </span> 81 0/subop/add 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 8/imm32 <span class="Comment"># add to ESP</span> -<span id="L135" class="LineNr">135 </span> <span class="Comment"># call _test-stop-1(ed)</span> -<span id="L136" class="LineNr">136 </span> <span class="Comment"># push args</span> +<span id="L27" class="LineNr"> 27 </span><span class="Comment">#</span> +<span id="L28" class="LineNr"> 28 </span><span class="Comment"># Before you an call any function that may call 'stop', you need to pass in an</span> +<span id="L29" class="LineNr"> 29 </span><span class="Comment"># exit-descriptor to it. To create an exit-descriptor use 'tailor-exit-descriptor'</span> +<span id="L30" class="LineNr"> 30 </span><span class="Comment"># below. It's not the most pleasant abstraction in the world.</span> +<span id="L31" class="LineNr"> 31 </span><span class="Comment">#</span> +<span id="L32" class="LineNr"> 32 </span><span class="Comment"># An exit-descriptor's target is its input, computed during 'tailor-exit-descriptor'.</span> +<span id="L33" class="LineNr"> 33 </span><span class="Comment"># 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="Comment"># instruction effective address operand displacement immediate</span> +<span id="L37" class="LineNr"> 37 </span><span class="Comment"># op subop mod rm32 base index scale r32</span> +<span id="L38" class="LineNr"> 38 </span><span class="Comment"># 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="Comment"># main:</span> +<span id="L41" class="LineNr"> 41 </span> e8/call run-tests/disp32 <span class="Comment"># 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'.</span> +<span id="L42" class="LineNr"> 42 </span><span class="CommentedCode">#? e8/call test-stop-skips-returns-on-exit/disp32</span> +<span id="L43" class="LineNr"> 43 </span> <span class="Comment"># syscall(exit, Num-test-failures)</span> +<span id="L44" class="LineNr"> 44 </span> 8b/copy 0/mod/indirect 5/rm32/.disp32 <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 3/r32/EBX <span class="Special">Num-test-failures</span>/disp32 <span class="Comment"># copy *Num-test-failures to EBX</span> +<span id="L45" class="LineNr"> 45 </span> b8/copy-to-EAX 1/imm32 +<span id="L46" class="LineNr"> 46 </span> cd/syscall 0x80/imm8 +<span id="L47" class="LineNr"> 47 </span> +<span id="L48" class="LineNr"> 48 </span><span class="Comment"># Configure an exit-descriptor for a call pushing 'nbytes' bytes of args to</span> +<span id="L49" class="LineNr"> 49 </span><span class="Comment"># the stack.</span> +<span id="L50" class="LineNr"> 50 </span><span class="Comment"># Ugly that we need to know the size of args, but so it goes.</span> +<span id="L51" class="LineNr"> 51 </span>tailor-exit-descriptor: <span class="Comment"># ed : (address exit-descriptor), nbytes : int -> <void></span> +<span id="L52" class="LineNr"> 52 </span> <span class="Comment"># prolog</span> +<span id="L53" class="LineNr"> 53 </span> 55/push-EBP +<span id="L54" class="LineNr"> 54 </span> 89/copy 3/mod/direct 5/rm32/EBP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/r32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy ESP to EBP</span> +<span id="L55" class="LineNr"> 55 </span> <span class="Comment"># save registers</span> +<span id="L56" class="LineNr"> 56 </span> 50/push-EAX +<span id="L57" class="LineNr"> 57 </span> 51/push-ECX +<span id="L58" class="LineNr"> 58 </span> <span class="Comment"># EAX = nbytes</span> +<span id="L59" class="LineNr"> 59 </span> 8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none <span class="Delimiter"> . </span> 0/r32/EAX 0xc/disp8 <span class="Delimiter"> . </span> <span class="Comment"># copy *(EBP+12) to EAX</span> +<span id="L60" class="LineNr"> 60 </span> <span class="Comment"># Let X be the value of ESP in the caller, before the call to tailor-exit-descriptor.</span> +<span id="L61" class="LineNr"> 61 </span> <span class="Comment"># The return address for a call in the caller's body will be at:</span> +<span id="L62" class="LineNr"> 62 </span> <span class="Comment"># X-8 if the caller takes 4 bytes of args for the exit-descriptor (add 4 bytes for the return address)</span> +<span id="L63" class="LineNr"> 63 </span> <span class="Comment"># X-12 if the caller takes 8 bytes of args</span> +<span id="L64" class="LineNr"> 64 </span> <span class="Comment"># ..and so on</span> +<span id="L65" class="LineNr"> 65 </span> <span class="Comment"># That's the value we need to return: X-nbytes-4</span> +<span id="L66" class="LineNr"> 66 </span> <span class="Comment">#</span> +<span id="L67" class="LineNr"> 67 </span> <span class="Comment"># However, we also need to account for the perturbance to ESP caused by the</span> +<span id="L68" class="LineNr"> 68 </span> <span class="Comment"># call to tailor-exit-descriptor. It pushes 8 bytes of args followed by 4</span> +<span id="L69" class="LineNr"> 69 </span> <span class="Comment"># bytes for the return address and 4 bytes to push EBP above.</span> +<span id="L70" class="LineNr"> 70 </span> <span class="Comment"># So EBP at this point is X-16.</span> +<span id="L71" class="LineNr"> 71 </span> <span class="Comment">#</span> +<span id="L72" class="LineNr"> 72 </span> <span class="Comment"># So the return address for the next call in the caller is:</span> +<span id="L73" class="LineNr"> 73 </span> <span class="Comment"># EBP+8 if the caller takes 4 bytes of args</span> +<span id="L74" class="LineNr"> 74 </span> <span class="Comment"># EBP+4 if the caller takes 8 bytes of args</span> +<span id="L75" class="LineNr"> 75 </span> <span class="Comment"># EBP if the caller takes 12 bytes of args</span> +<span id="L76" class="LineNr"> 76 </span> <span class="Comment"># EBP-4 if the caller takes 16 bytes of args</span> +<span id="L77" class="LineNr"> 77 </span> <span class="Comment"># ..and so on</span> +<span id="L78" class="LineNr"> 78 </span> <span class="Comment"># That's EBP+12-nbytes.</span> +<span id="L79" class="LineNr"> 79 </span> <span class="Comment"># option 1: 6 + 3 bytes</span> +<span id="L80" class="LineNr"> 80 </span><span class="CommentedCode">#? 2d/subtract 3/mod/direct 0/rm32/EAX . . . . . 8/imm32 # subtract from EAX</span> +<span id="L81" class="LineNr"> 81 </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="L82" class="LineNr"> 82 </span> <span class="Comment"># option 2: 2 + 4 bytes</span> +<span id="L83" class="LineNr"> 83 </span> f7 3/subop/negate 3/mod/direct 0/rm32/EAX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># negate EAX</span> +<span id="L84" class="LineNr"> 84 </span> 8d/copy-address 1/mod/*+disp8 4/rm32/sib 5/base/EBP 0/index/EAX <span class="Delimiter"> . </span> 0/r32/EAX 0xc/disp8 <span class="Delimiter"> . </span> <span class="Comment"># copy EBP+EAX+12 to EAX</span> +<span id="L85" class="LineNr"> 85 </span> <span class="Comment"># copy EAX to ed->target</span> +<span id="L86" class="LineNr"> 86 </span> 8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none <span class="Delimiter"> . </span> 1/r32/ECX 8/disp8 <span class="Delimiter"> . </span> <span class="Comment"># copy *(EBP+8) to ECX</span> +<span id="L87" class="LineNr"> 87 </span> 89/copy 0/mod/indirect 1/rm32/ECX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 0/r32/EAX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy EAX to *ECX</span> +<span id="L88" class="LineNr"> 88 </span> <span class="Comment"># initialize ed->value</span> +<span id="L89" class="LineNr"> 89 </span> c7/copy 1/mod/*+disp8 1/rm32/ECX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/disp8 0/imm32 <span class="Comment"># copy to *(ECX+4)</span> +<span id="L90" class="LineNr"> 90 </span> <span class="Comment"># restore registers</span> +<span id="L91" class="LineNr"> 91 </span> 59/pop-to-ECX +<span id="L92" class="LineNr"> 92 </span> 58/pop-to-EAX +<span id="L93" class="LineNr"> 93 </span> <span class="Comment"># epilog</span> +<span id="L94" class="LineNr"> 94 </span> 89/copy 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 5/r32/EBP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy EBP to ESP</span> +<span id="L95" class="LineNr"> 95 </span> 5d/pop-to-EBP +<span id="L96" class="LineNr"> 96 </span> c3/return +<span id="L97" class="LineNr"> 97 </span> +<span id="L98" class="LineNr"> 98 </span>stop: <span class="Comment"># ed : (address exit-descriptor), value : int</span> +<span id="L99" class="LineNr"> 99 </span> <span class="Comment"># no prolog; one way or another, we're going to clobber registers</span> +<span id="L100" class="LineNr">100 </span> <span class="Comment"># EAX = ed</span> +<span id="L101" class="LineNr">101 </span> 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none <span class="Delimiter"> . </span> 0/r32/EAX 4/disp8 <span class="Delimiter"> . </span> <span class="Comment"># copy *(ESP+4) to EAX</span> +<span id="L102" class="LineNr">102 </span> <span class="Comment"># exit(value) if ed->target == 0</span> +<span id="L103" class="LineNr">103 </span> 81 7/subop/compare 0/mod/indirect 0/rm32/EAX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 0/imm32 <span class="Comment"># compare *EAX</span> +<span id="L104" class="LineNr">104 </span> 75/jump-if-not-equal $stop:fake/disp8 +<span id="L105" class="LineNr">105 </span> <span class="Comment"># syscall(exit, value)</span> +<span id="L106" class="LineNr">106 </span> 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none <span class="Delimiter"> . </span> 3/r32/EBX 8/disp8 <span class="Delimiter"> . </span> <span class="Comment"># copy *(ESP+8) to EBX</span> +<span id="L107" class="LineNr">107 </span> b8/copy-to-EAX 1/imm32 +<span id="L108" class="LineNr">108 </span> cd/syscall 0x80/imm8 +<span id="L109" class="LineNr">109 </span>$stop:fake: +<span id="L110" class="LineNr">110 </span> <span class="Comment"># ed->value = value+1</span> +<span id="L111" class="LineNr">111 </span> 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none <span class="Delimiter"> . </span> 1/r32/ECX 8/disp8 <span class="Delimiter"> . </span> <span class="Comment"># copy *(ESP+8) to ECX</span> +<span id="L112" class="LineNr">112 </span> 41/inc-ECX +<span id="L113" class="LineNr">113 </span> 89/copy 1/mod/*+disp8 0/rm32/EAX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 1/r32/ECX 4/disp8 <span class="Delimiter"> . </span> <span class="Comment"># copy ECX to *(EAX+4)</span> +<span id="L114" class="LineNr">114 </span> <span class="Comment"># non-local jump to ed->target</span> +<span id="L115" class="LineNr">115 </span> 8b/copy 0/mod/indirect 0/rm32/EAX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/r32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy *EAX to ESP</span> +<span id="L116" class="LineNr">116 </span> c3/return <span class="Comment"># doesn't return to caller</span> +<span id="L117" class="LineNr">117 </span> +<span id="L118" class="LineNr">118 </span>test-stop-skips-returns-on-exit: +<span id="L119" class="LineNr">119 </span> <span class="Comment"># This looks like the standard prolog, but is here for different reasons.</span> +<span id="L120" class="LineNr">120 </span> <span class="Comment"># A function calling 'stop' can't rely on EBP persisting past the call.</span> +<span id="L121" class="LineNr">121 </span> <span class="Comment">#</span> +<span id="L122" class="LineNr">122 </span> <span class="Comment"># Use EBP here as a stable base to refer to locals and arguments from in the</span> +<span id="L123" class="LineNr">123 </span> <span class="Comment"># presence of push/pop/call instructions.</span> +<span id="L124" class="LineNr">124 </span> <span class="Comment"># *Don't* use EBP as a way to restore ESP.</span> +<span id="L125" class="LineNr">125 </span> 55/push-EBP +<span id="L126" class="LineNr">126 </span> 89/copy 3/mod/direct 5/rm32/EBP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/r32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy ESP to EBP</span> +<span id="L127" class="LineNr">127 </span> <span class="Comment"># Make room for an exit descriptor on the stack. That's almost always the</span> +<span id="L128" class="LineNr">128 </span> <span class="Comment"># right place for it, available only as long as it's legal to use. Once this</span> +<span id="L129" class="LineNr">129 </span> <span class="Comment"># containing function returns we'll need a new exit descriptor.</span> +<span id="L130" class="LineNr">130 </span> <span class="Comment"># var ed/EAX : (address exit-descriptor)</span> +<span id="L131" class="LineNr">131 </span> 81 5/subop/subtract 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 8/imm32 <span class="Comment"># subtract from ESP</span> +<span id="L132" class="LineNr">132 </span> 8d/copy-address 0/mod/indirect 4/rm32/sib 4/base/ESP 4/index/none <span class="Delimiter"> . </span> 0/r32/EAX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy ESP to EAX</span> +<span id="L133" class="LineNr">133 </span> <span class="Comment"># Size the exit-descriptor precisely for the next call below, to _test-stop-1.</span> +<span id="L134" class="LineNr">134 </span> <span class="Comment"># tailor-exit-descriptor(ed, 4)</span> +<span id="L135" class="LineNr">135 </span> <span class="Comment"># push args</span> +<span id="L136" class="LineNr">136 </span> 68/push 4/imm32/nbytes-of-args-for-_test-stop-1 <span id="L137" class="LineNr">137 </span> 50/push-EAX <span id="L138" class="LineNr">138 </span> <span class="Comment"># call</span> -<span id="L139" class="LineNr">139 </span> e8/call _test-stop-1/disp32 -<span id="L140" class="LineNr">140 </span> <span class="SalientComment">## registers except ESP may be clobbered at this point</span> -<span id="L141" class="LineNr">141 </span> <span class="Comment"># restore args</span> -<span id="L142" class="LineNr">142 </span> 58/pop-to-EAX -<span id="L143" class="LineNr">143 </span> <span class="Comment"># check that _test-stop-1 tried to call exit(1)</span> -<span id="L144" class="LineNr">144 </span> <span class="Comment"># check-ints-equal(ed->value, 2, msg) # i.e. stop was called with value 1</span> -<span id="L145" class="LineNr">145 </span> <span class="Comment"># push args</span> -<span id="L146" class="LineNr">146 </span> 68/push <span class="Constant">"F - test-stop-skips-returns-on-exit"</span>/imm32 -<span id="L147" class="LineNr">147 </span> 68/push 2/imm32 -<span id="L148" class="LineNr">148 </span> <span class="Comment"># push ed->value</span> -<span id="L149" class="LineNr">149 </span> ff 6/subop/push 1/mod/*+disp8 0/rm32/EAX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/disp8 <span class="Delimiter"> . </span> <span class="Comment"># push *(EAX+4)</span> -<span id="L150" class="LineNr">150 </span> <span class="Comment"># call</span> -<span id="L151" class="LineNr">151 </span> e8/call check-ints-equal/disp32 -<span id="L152" class="LineNr">152 </span> <span class="Comment"># discard args</span> -<span id="L153" class="LineNr">153 </span> 81 0/subop/add 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 0xc/imm32 <span class="Comment"># add to ESP</span> -<span id="L154" class="LineNr">154 </span> <span class="Comment"># epilog</span> -<span id="L155" class="LineNr">155 </span> 5d/pop-to-EBP -<span id="L156" class="LineNr">156 </span> <span class="Comment"># don't restore ESP from EBP; manually reclaim locals</span> -<span id="L157" class="LineNr">157 </span> 81 0/subop/add 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 8/imm32 <span class="Comment"># add to ESP</span> -<span id="L158" class="LineNr">158 </span> c3/return -<span id="L159" class="LineNr">159 </span> -<span id="L160" class="LineNr">160 </span>_test-stop-1: <span class="Comment"># ed : (address exit-descriptor)</span> -<span id="L161" class="LineNr">161 </span> <span class="Comment"># prolog</span> -<span id="L162" class="LineNr">162 </span> 55/push-EBP -<span id="L163" class="LineNr">163 </span> 89/copy 3/mod/direct 5/rm32/EBP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/r32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy ESP to EBP</span> -<span id="L164" class="LineNr">164 </span> <span class="Comment"># _test-stop-2(ed)</span> -<span id="L165" class="LineNr">165 </span> <span class="Comment"># push args</span> -<span id="L166" class="LineNr">166 </span> ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 8/disp8 <span class="Delimiter"> . </span> <span class="Comment"># push *(EBP+8)</span> -<span id="L167" class="LineNr">167 </span> <span class="Comment"># call</span> -<span id="L168" class="LineNr">168 </span> e8/call _test-stop-2/disp32 -<span id="L169" class="LineNr">169 </span> <span class="SalientComment">## should never get past this point</span> -<span id="L170" class="LineNr">170 </span> <span class="Comment"># discard args</span> -<span id="L171" class="LineNr">171 </span> 81 0/subop/add 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/imm32 <span class="Comment"># add to ESP</span> -<span id="L172" class="LineNr">172 </span> <span class="Comment"># signal test failed: check-ints-equal(1, 0, msg)</span> -<span id="L173" class="LineNr">173 </span> <span class="Comment"># push args</span> -<span id="L174" class="LineNr">174 </span> 68/push <span class="Constant">"F - test-stop-skips-returns-on-exit"</span>/imm32 -<span id="L175" class="LineNr">175 </span> 68/push 0/imm32 -<span id="L176" class="LineNr">176 </span> 68/push 1/imm32 -<span id="L177" class="LineNr">177 </span> <span class="Comment"># call</span> -<span id="L178" class="LineNr">178 </span> e8/call check-ints-equal/disp32 -<span id="L179" class="LineNr">179 </span> <span class="Comment"># discard args</span> -<span id="L180" class="LineNr">180 </span> 81 0/subop/add 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 0xc/imm32 <span class="Comment"># add to ESP</span> -<span id="L181" class="LineNr">181 </span> <span class="Comment"># epilog</span> -<span id="L182" class="LineNr">182 </span> 89/copy 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 5/r32/EBP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy EBP to ESP</span> -<span id="L183" class="LineNr">183 </span> 5d/pop-to-EBP -<span id="L184" class="LineNr">184 </span> c3/return -<span id="L185" class="LineNr">185 </span> -<span id="L186" class="LineNr">186 </span>_test-stop-2: <span class="Comment"># ed : (address exit-descriptor)</span> -<span id="L187" class="LineNr">187 </span> <span class="Comment"># prolog</span> -<span id="L188" class="LineNr">188 </span> 55/push-EBP -<span id="L189" class="LineNr">189 </span> 89/copy 3/mod/direct 5/rm32/EBP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/r32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy ESP to EBP</span> -<span id="L190" class="LineNr">190 </span> <span class="Comment"># call stop(ed, 1)</span> -<span id="L191" class="LineNr">191 </span> <span class="Comment"># push args</span> -<span id="L192" class="LineNr">192 </span> 68/push 1/imm32 -<span id="L193" class="LineNr">193 </span> ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 8/disp8 <span class="Delimiter"> . </span> <span class="Comment"># push *(EBP+8)</span> -<span id="L194" class="LineNr">194 </span> <span class="Comment"># call</span> -<span id="L195" class="LineNr">195 </span> e8/call stop/disp32 -<span id="L196" class="LineNr">196 </span> <span class="SalientComment">## should never get past this point</span> -<span id="L197" class="LineNr">197 </span> <span class="Comment"># epilog</span> -<span id="L198" class="LineNr">198 </span> 89/copy 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 5/r32/EBP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy EBP to ESP</span> -<span id="L199" class="LineNr">199 </span> 5d/pop-to-EBP -<span id="L200" class="LineNr">200 </span> c3/return -<span id="L201" class="LineNr">201 </span> -<span id="L202" class="LineNr">202 </span><span class="Comment"># vim:nowrap:textwidth=0</span> +<span id="L139" class="LineNr">139 </span> e8/call tailor-exit-descriptor/disp32 +<span id="L140" class="LineNr">140 </span> <span class="Comment"># discard args</span> +<span id="L141" class="LineNr">141 </span> 81 0/subop/add 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 8/imm32 <span class="Comment"># add to ESP</span> +<span id="L142" class="LineNr">142 </span> <span class="Comment"># call _test-stop-1(ed)</span> +<span id="L143" class="LineNr">143 </span> <span class="Comment"># push args</span> +<span id="L144" class="LineNr">144 </span> 50/push-EAX +<span id="L145" class="LineNr">145 </span> <span class="Comment"># call</span> +<span id="L146" class="LineNr">146 </span> e8/call _test-stop-1/disp32 +<span id="L147" class="LineNr">147 </span> <span class="SalientComment">## registers except ESP may be clobbered at this point</span> +<span id="L148" class="LineNr">148 </span> <span class="Comment"># restore args</span> +<span id="L149" class="LineNr">149 </span> 58/pop-to-EAX +<span id="L150" class="LineNr">150 </span> <span class="Comment"># check that _test-stop-1 tried to call exit(1)</span> +<span id="L151" class="LineNr">151 </span> <span class="Comment"># check-ints-equal(ed->value, 2, msg) # i.e. stop was called with value 1</span> +<span id="L152" class="LineNr">152 </span> <span class="Comment"># push args</span> +<span id="L153" class="LineNr">153 </span> 68/push <span class="Constant">"F - test-stop-skips-returns-on-exit"</span>/imm32 +<span id="L154" class="LineNr">154 </span> 68/push 2/imm32 +<span id="L155" class="LineNr">155 </span> <span class="Comment"># push ed->value</span> +<span id="L156" class="LineNr">156 </span> ff 6/subop/push 1/mod/*+disp8 0/rm32/EAX <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/disp8 <span class="Delimiter"> . </span> <span class="Comment"># push *(EAX+4)</span> +<span id="L157" class="LineNr">157 </span> <span class="Comment"># call</span> +<span id="L158" class="LineNr">158 </span> e8/call check-ints-equal/disp32 +<span id="L159" class="LineNr">159 </span> <span class="Comment"># discard args</span> +<span id="L160" class="LineNr">160 </span> 81 0/subop/add 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 0xc/imm32 <span class="Comment"># add to ESP</span> +<span id="L161" class="LineNr">161 </span> <span class="Comment"># epilog</span> +<span id="L162" class="LineNr">162 </span> 5d/pop-to-EBP +<span id="L163" class="LineNr">163 </span> <span class="Comment"># don't restore ESP from EBP; manually reclaim locals</span> +<span id="L164" class="LineNr">164 </span> 81 0/subop/add 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 8/imm32 <span class="Comment"># add to ESP</span> +<span id="L165" class="LineNr">165 </span> c3/return +<span id="L166" class="LineNr">166 </span> +<span id="L167" class="LineNr">167 </span>_test-stop-1: <span class="Comment"># ed : (address exit-descriptor)</span> +<span id="L168" class="LineNr">168 </span> <span class="Comment"># prolog</span> +<span id="L169" class="LineNr">169 </span> 55/push-EBP +<span id="L170" class="LineNr">170 </span> 89/copy 3/mod/direct 5/rm32/EBP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/r32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy ESP to EBP</span> +<span id="L171" class="LineNr">171 </span> <span class="Comment"># _test-stop-2(ed)</span> +<span id="L172" class="LineNr">172 </span> <span class="Comment"># push args</span> +<span id="L173" class="LineNr">173 </span> ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 8/disp8 <span class="Delimiter"> . </span> <span class="Comment"># push *(EBP+8)</span> +<span id="L174" class="LineNr">174 </span> <span class="Comment"># call</span> +<span id="L175" class="LineNr">175 </span> e8/call _test-stop-2/disp32 +<span id="L176" class="LineNr">176 </span> <span class="SalientComment">## should never get past this point</span> +<span id="L177" class="LineNr">177 </span> <span class="Comment"># discard args</span> +<span id="L178" class="LineNr">178 </span> 81 0/subop/add 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/imm32 <span class="Comment"># add to ESP</span> +<span id="L179" class="LineNr">179 </span> <span class="Comment"># signal test failed: check-ints-equal(1, 0, msg)</span> +<span id="L180" class="LineNr">180 </span> <span class="Comment"># push args</span> +<span id="L181" class="LineNr">181 </span> 68/push <span class="Constant">"F - test-stop-skips-returns-on-exit"</span>/imm32 +<span id="L182" class="LineNr">182 </span> 68/push 0/imm32 +<span id="L183" class="LineNr">183 </span> 68/push 1/imm32 +<span id="L184" class="LineNr">184 </span> <span class="Comment"># call</span> +<span id="L185" class="LineNr">185 </span> e8/call check-ints-equal/disp32 +<span id="L186" class="LineNr">186 </span> <span class="Comment"># discard args</span> +<span id="L187" class="LineNr">187 </span> 81 0/subop/add 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 0xc/imm32 <span class="Comment"># add to ESP</span> +<span id="L188" class="LineNr">188 </span> <span class="Comment"># epilog</span> +<span id="L189" class="LineNr">189 </span> 89/copy 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 5/r32/EBP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy EBP to ESP</span> +<span id="L190" class="LineNr">190 </span> 5d/pop-to-EBP +<span id="L191" class="LineNr">191 </span> c3/return +<span id="L192" class="LineNr">192 </span> +<span id="L193" class="LineNr">193 </span>_test-stop-2: <span class="Comment"># ed : (address exit-descriptor)</span> +<span id="L194" class="LineNr">194 </span> <span class="Comment"># prolog</span> +<span id="L195" class="LineNr">195 </span> 55/push-EBP +<span id="L196" class="LineNr">196 </span> 89/copy 3/mod/direct 5/rm32/EBP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 4/r32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy ESP to EBP</span> +<span id="L197" class="LineNr">197 </span> <span class="Comment"># call stop(ed, 1)</span> +<span id="L198" class="LineNr">198 </span> <span class="Comment"># push args</span> +<span id="L199" class="LineNr">199 </span> 68/push 1/imm32 +<span id="L200" class="LineNr">200 </span> ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 8/disp8 <span class="Delimiter"> . </span> <span class="Comment"># push *(EBP+8)</span> +<span id="L201" class="LineNr">201 </span> <span class="Comment"># call</span> +<span id="L202" class="LineNr">202 </span> e8/call stop/disp32 +<span id="L203" class="LineNr">203 </span> <span class="SalientComment">## should never get past this point</span> +<span id="L204" class="LineNr">204 </span> <span class="Comment"># epilog</span> +<span id="L205" class="LineNr">205 </span> 89/copy 3/mod/direct 4/rm32/ESP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> 5/r32/EBP <span class="Delimiter"> . </span> <span class="Delimiter"> . </span> <span class="Comment"># copy EBP to ESP</span> +<span id="L206" class="LineNr">206 </span> 5d/pop-to-EBP +<span id="L207" class="LineNr">207 </span> c3/return +<span id="L208" class="LineNr">208 </span> +<span id="L209" class="LineNr">209 </span><span class="Comment"># vim:nowrap:textwidth=0</span> </pre> </body> </html> diff --git a/subx/057stop.subx b/subx/057stop.subx index 8de167f0..9bdf69c3 100644 --- a/subx/057stop.subx +++ b/subx/057stop.subx @@ -16,14 +16,21 @@ # input target with an output status parameter into a type called 'exit-descriptor'. # # So the exit-descriptor looks like this: -# target : address # input return address for 'stop' to unwind to -# value : int # output exit status stop was called with +# target : address # return address for 'stop' to unwind to +# value : int # exit status stop was called with # # 'stop' thus takes two parameters: an exit-descriptor and the exit status. # -# We won't bother cleaning up any other processor state besides the stack, +# 'stop' won't bother cleaning up any other processor state besides the stack, # such as registers. Only ESP will have a well-defined value after 'stop' # returns. (This is a poor man's setjmp/longjmp, if you know what that is.) +# +# Before you an call any function that may call 'stop', you need to pass in an +# exit-descriptor to it. To create an exit-descriptor use 'tailor-exit-descriptor' +# below. It's not the most pleasant abstraction in the world. +# +# An exit-descriptor's target is its input, computed during 'tailor-exit-descriptor'. +# Its value is its output, computed during stop and available to the test. == code # instruction effective address operand displacement immediate |