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<a href='https://github.com/akkartik/mu/blob/master/subx/053new_segment.subx'>https://github.com/akkartik/mu/blob/master/subx/053new_segment.subx</a>
<pre id='vimCodeElement'>
<span id="L1" class="LineNr"> 1 </span><span class="subxComment"># Create a new segment (for data) using mmap().</span>
<span id="L2" class="LineNr"> 2 </span>
<span id="L3" class="LineNr"> 3 </span>== code
<span id="L4" class="LineNr"> 4 </span><span class="subxComment"># instruction effective address register displacement immediate</span>
<span id="L5" class="LineNr"> 5 </span><span class="subxS1Comment"># . op subop mod rm32 base index scale r32</span>
<span id="L6" class="LineNr"> 6 </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="L7" class="LineNr"> 7 </span>
<span id="L8" class="LineNr"> 8 </span><span class="subxComment"># main: (manual test if this is the last file loaded)</span>
<span id="L9" class="LineNr"> 9 </span> <span class="subxComment"># EAX = new-segment(0x1000)</span>
<span id="L10" class="LineNr">10 </span> <span class="subxS2Comment"># . . push args</span>
<span id="L11" class="LineNr">11 </span> 68/push 0x1000/imm32
<span id="L12" class="LineNr">12 </span> <span class="subxS2Comment"># . . call</span>
<span id="L13" class="LineNr">13 </span> e8/call new-segment/disp32
<span id="L14" class="LineNr">14 </span> <span class="subxS2Comment"># . . discard args</span>
<span id="L15" class="LineNr">15 </span> 81 0/subop/add 3/mod/direct 4/rm32/ESP <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> 4/imm32 <span class="subxComment"># add to ESP</span>
<span id="L16" class="LineNr">16 </span>
<span id="L17" class="LineNr">17 </span> <span class="subxComment"># write to *EAX to check that we have access to the newly-allocated segment</span>
<span id="L18" class="LineNr">18 </span> c7/copy 0/mod/direct 0/rm32/EAX <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> 0x34/imm32 <span class="subxComment"># copy to *EAX</span>
<span id="L19" class="LineNr">19 </span>
<span id="L20" class="LineNr">20 </span> <span class="subxComment"># syscall(exit, EAX)</span>
<span id="L21" class="LineNr">21 </span> 89/copy 3/mod/direct 3/rm32/EBX <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> 0/r32/EAX <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> <span class="subxComment"># copy EAX to EBX</span>
<span id="L22" class="LineNr">22 </span> b8/copy-to-EAX 1/imm32/exit
<span id="L23" class="LineNr">23 </span> cd/syscall 0x80/imm8
<span id="L24" class="LineNr">24 </span>
<span id="L25" class="LineNr">25 </span><span class="subxFunction">new-segment</span>: <span class="subxComment"># len : int -> address</span>
<span id="L26" class="LineNr">26 </span> <span class="subxS1Comment"># . prolog</span>
<span id="L27" class="LineNr">27 </span> 55/push-EBP
<span id="L28" class="LineNr">28 </span> 89/copy 3/mod/direct 5/rm32/EBP <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> 4/r32/ESP <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> <span class="subxComment"># copy ESP to EBP</span>
<span id="L29" class="LineNr">29 </span> 53/push-EBX
<span id="L30" class="LineNr">30 </span> <span class="subxComment"># copy len to _mmap-new-segment->len</span>
<span id="L31" class="LineNr">31 </span> <span class="subxComment"># TODO: compute _mmap-new-segment+4 before runtime</span>
<span id="L32" class="LineNr">32 </span> 8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none <span class="CommentedCode"> . </span> 0/r32/EAX 8/disp8 <span class="CommentedCode"> . </span> <span class="subxComment"># copy *(EBP+8) to EAX</span>
<span id="L33" class="LineNr">33 </span> bb/copy-to-EBX _mmap-new-segment/imm32
<span id="L34" class="LineNr">34 </span> 89/copy 1/mod/*+disp8 3/rm32/EBX <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> 0/r32/EAX 4/disp8 <span class="CommentedCode"> . </span> <span class="subxComment"># copy EAX to *(EBX+4)</span>
<span id="L35" class="LineNr">35 </span> <span class="subxComment"># mmap(_mmap-new-segment)</span>
<span id="L36" class="LineNr">36 </span> bb/copy-to-EBX _mmap-new-segment/imm32
<span id="L37" class="LineNr">37 </span> b8/copy-to-EAX 0x5a/imm32/mmap
<span id="L38" class="LineNr">38 </span> cd/syscall 0x80/imm8
<span id="L39" class="LineNr">39 </span><span class="Constant">$new-segment:end</span>:
<span id="L40" class="LineNr">40 </span> <span class="subxS1Comment"># . epilog</span>
<span id="L41" class="LineNr">41 </span> 5b/pop-to-EBX
<span id="L42" class="LineNr">42 </span> 89/copy 3/mod/direct 4/rm32/ESP <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> 5/r32/EBP <span class="CommentedCode"> . </span> <span class="CommentedCode"> . </span> <span class="subxComment"># copy EBP to ESP</span>
<span id="L43" class="LineNr">43 </span> 5d/pop-to-EBP
<span id="L44" class="LineNr">44 </span> c3/return
<span id="L45" class="LineNr">45 </span>
<span id="L46" class="LineNr">46 </span>== data
<span id="L47" class="LineNr">47 </span>
<span id="L48" class="LineNr">48 </span><span class="subxComment"># various constants used here were found in the Linux sources (search for file mman-common.h)</span>
<span id="L49" class="LineNr">49 </span><span class="subxMinorFunction">_mmap-new-segment</span>: <span class="subxComment"># type mmap_arg_struct</span>
<span id="L50" class="LineNr">50 </span> <span class="subxComment"># addr</span>
<span id="L51" class="LineNr">51 </span> 00 00 00 00 <span class="subxComment"># null</span>
<span id="L52" class="LineNr">52 </span> <span class="subxComment"># len</span>
<span id="L53" class="LineNr">53 </span> 00 00 00 00 <span class="subxComment"># 0x1000</span>
<span id="L54" class="LineNr">54 </span> <span class="subxComment"># protection flags</span>
<span id="L55" class="LineNr">55 </span> 03 00 00 00 <span class="subxComment"># PROT_READ | PROT_WRITE</span>
<span id="L56" class="LineNr">56 </span> <span class="subxComment"># sharing flags</span>
<span id="L57" class="LineNr">57 </span> 22 00 00 00 <span class="subxComment"># MAP_PRIVATE | MAP_ANONYMOUS</span>
<span id="L58" class="LineNr">58 </span> <span class="subxComment"># fd</span>
<span id="L59" class="LineNr">59 </span> ff ff ff ff <span class="subxComment"># -1 since MAP_ANONYMOUS is specified</span>
<span id="L60" class="LineNr">60 </span> <span class="subxComment"># offset</span>
<span id="L61" class="LineNr">61 </span> 00 00 00 00 <span class="subxComment"># 0 since MAP_ANONYMOUS is specified</span>
<span id="L62" class="LineNr">62 </span>
<span id="L63" class="LineNr">63 </span><span class="subxS2Comment"># . . vim:nowrap:textwidth=0</span>
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