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<a href='https://github.com/akkartik/mu/blob/main/linux/apps/ex7.subx'>https://github.com/akkartik/mu/blob/main/linux/apps/ex7.subx</a>
<pre id='vimCodeElement'>
<span id="L1" class="LineNr"> 1 </span><span class="subxComment"># Example showing file syscalls.</span>
<span id="L2" class="LineNr"> 2 </span><span class="subxComment">#</span>
<span id="L3" class="LineNr"> 3 </span><span class="subxComment"># Create a file, open it for writing, write a character to it, close it, open</span>
<span id="L4" class="LineNr"> 4 </span><span class="subxComment"># it for reading, read a character from it, close it, delete it, and return</span>
<span id="L5" class="LineNr"> 5 </span><span class="subxComment"># the character read.</span>
<span id="L6" class="LineNr"> 6 </span><span class="subxComment">#</span>
<span id="L7" class="LineNr"> 7 </span><span class="subxComment"># To run:</span>
<span id="L8" class="LineNr"> 8 </span><span class="subxComment"># $ bootstrap/bootstrap translate apps/ex7.subx -o ex7</span>
<span id="L9" class="LineNr"> 9 </span><span class="subxComment"># $ bootstrap/bootstrap run ex7</span>
<span id="L10" class="LineNr">10 </span><span class="subxComment"># Expected result:</span>
<span id="L11" class="LineNr">11 </span><span class="subxComment"># $ echo $?</span>
<span id="L12" class="LineNr">12 </span><span class="subxComment"># 97</span>
<span id="L13" class="LineNr">13 </span>
<span id="L14" class="LineNr">14 </span>== code
<span id="L15" class="LineNr">15 </span><span class="subxComment"># instruction effective address register displacement immediate</span>
<span id="L16" class="LineNr">16 </span><span class="subxS1Comment"># . op subop mod rm32 base index scale r32</span>
<span id="L17" class="LineNr">17 </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="L18" class="LineNr">18 </span>
<span id="L19" class="LineNr">19 </span><span class="SpecialChar">Entry</span>:
<span id="L20" class="LineNr">20 </span> <span class="subxComment"># creat(Filename)</span>
<span id="L21" class="LineNr">21 </span> bb/copy-to-ebx <span class="SpecialChar"><a href='ex7.subx.html#L94'>Filename</a></span>/imm32
<span id="L22" class="LineNr">22 </span> b9/copy-to-ecx 0x180/imm32/fixed-perms
<span id="L23" class="LineNr">23 </span> e8/call <a href='../000init.subx.html#L53'>syscall_creat</a>/disp32
<span id="L24" class="LineNr">24 </span>
<span id="L25" class="LineNr">25 </span> <span class="subxComment"># stream = open(Filename, O_WRONLY, 0) # we can't use 'fd' because it looks like a hex byte</span>
<span id="L26" class="LineNr">26 </span> bb/copy-to-ebx <span class="SpecialChar"><a href='ex7.subx.html#L94'>Filename</a></span>/imm32
<span id="L27" class="LineNr">27 </span> b9/copy-to-ecx 1/imm32/wronly
<span id="L28" class="LineNr">28 </span> ba/copy-to-edx 0x180/imm32/fixed-perms
<span id="L29" class="LineNr">29 </span> e8/call <a href='../000init.subx.html#L35'>syscall_open</a>/disp32
<span id="L30" class="LineNr">30 </span> <span class="subxComment"># save stream</span>
<span id="L31" class="LineNr">31 </span> bb/copy-to-ebx <span class="SpecialChar"><a href='ex7.subx.html#L88'>Stream</a></span>/imm32
<span id="L32" class="LineNr">32 </span> 89/copy 0/mod/indirect 3/rm32/ebx <span class="Normal"> . </span> <span class="Normal"> . </span> <span class="Normal"> . </span> 0/r32/eax <span class="Normal"> . </span> <span class="Normal"> . </span> <span class="subxComment"># copy eax to *ebx</span>
<span id="L33" class="LineNr">33 </span>
<span id="L34" class="LineNr">34 </span> <span class="subxComment"># write(Stream, "a", 1)</span>
<span id="L35" class="LineNr">35 </span> <span class="subxS1Comment"># . load stream</span>
<span id="L36" class="LineNr">36 </span> bb/copy-to-ebx <span class="SpecialChar"><a href='ex7.subx.html#L88'>Stream</a></span>/imm32
<span id="L37" class="LineNr">37 </span> 8b/copy 0/mod/indirect 3/rm32/ebx <span class="Normal"> . </span> <span class="Normal"> . </span> <span class="Normal"> . </span> 3/r32/ebx <span class="Normal"> . </span> <span class="Normal"> . </span> <span class="subxComment"># copy *ebx to ebx</span>
<span id="L38" class="LineNr">38 </span> <span class="subxS1Comment"># .</span>
<span id="L39" class="LineNr">39 </span> b9/copy-to-ecx <span class="SpecialChar"><a href='ex7.subx.html#L90'>A</a></span>/imm32
<span id="L40" class="LineNr">40 </span> ba/copy-to-edx 1/imm32/size
<span id="L41" class="LineNr">41 </span> e8/call <a href='../000init.subx.html#L29'>syscall_write</a>/disp32
<span id="L42" class="LineNr">42 </span>
<span id="L43" class="LineNr">43 </span> <span class="subxComment"># close(Stream)</span>
<span id="L44" class="LineNr">44 </span> <span class="subxS1Comment"># . load stream</span>
<span id="L45" class="LineNr">45 </span> bb/copy-to-ebx <span class="SpecialChar"><a href='ex7.subx.html#L88'>Stream</a></span>/imm32
<span id="L46" class="LineNr">46 </span> 8b/copy 0/mod/indirect 3/rm32/ebx <span class="Normal"> . </span> <span class="Normal"> . </span> <span class="Normal"> . </span> 3/r32/ebx <span class="Normal"> . </span> <span class="Normal"> . </span> <span class="subxComment"># copy *ebx to ebx</span>
<span id="L47" class="LineNr">47 </span> <span class="subxS1Comment"># .</span>
<span id="L48" class="LineNr">48 </span> e8/call <a href='../000init.subx.html#L41'>syscall_close</a>/disp32
<span id="L49" class="LineNr">49 </span>
<span id="L50" class="LineNr">50 </span> <span class="subxComment"># stream = open(Filename, O_RDONLY, 0)</span>
<span id="L51" class="LineNr">51 </span> bb/copy-to-ebx <span class="SpecialChar"><a href='ex7.subx.html#L94'>Filename</a></span>/imm32
<span id="L52" class="LineNr">52 </span> b9/copy-to-ecx 0/imm32/rdonly
<span id="L53" class="LineNr">53 </span> ba/copy-to-edx 0x180/imm32/fixed-perms
<span id="L54" class="LineNr">54 </span> e8/call <a href='../000init.subx.html#L35'>syscall_open</a>/disp32
<span id="L55" class="LineNr">55 </span> <span class="subxS1Comment"># . save Stream</span>
<span id="L56" class="LineNr">56 </span> bb/copy-to-ebx <span class="SpecialChar"><a href='ex7.subx.html#L88'>Stream</a></span>/imm32
<span id="L57" class="LineNr">57 </span> 89/copy 0/mod/indirect 3/rm32/ebx <span class="Normal"> . </span> <span class="Normal"> . </span> <span class="Normal"> . </span> 0/r32/eax <span class="Normal"> . </span> <span class="Normal"> . </span> <span class="subxComment"># copy eax to *ebx</span>
<span id="L58" class="LineNr">58 </span>
<span id="L59" class="LineNr">59 </span> <span class="subxComment"># read(Stream, B, 1)</span>
<span id="L60" class="LineNr">60 </span> <span class="subxS1Comment"># . load stream</span>
<span id="L61" class="LineNr">61 </span> bb/copy-to-ebx <span class="SpecialChar"><a href='ex7.subx.html#L88'>Stream</a></span>/imm32
<span id="L62" class="LineNr">62 </span> 8b/copy 0/mod/indirect 3/rm32/ebx <span class="Normal"> . </span> <span class="Normal"> . </span> <span class="Normal"> . </span> 3/r32/ebx <span class="Normal"> . </span> <span class="Normal"> . </span> <span class="subxComment"># copy *ebx to ebx</span>
<span id="L63" class="LineNr">63 </span> <span class="subxS1Comment"># .</span>
<span id="L64" class="LineNr">64 </span> b9/copy-to-ecx <span class="SpecialChar"><a href='ex7.subx.html#L92'>B</a></span>/imm32
<span id="L65" class="LineNr">65 </span> ba/copy-to-edx 1/imm32/size
<span id="L66" class="LineNr">66 </span> e8/call <a href='../000init.subx.html#L23'>syscall_read</a>/disp32
<span id="L67" class="LineNr">67 </span>
<span id="L68" class="LineNr">68 </span> <span class="subxComment"># close(Stream)</span>
<span id="L69" class="LineNr">69 </span> <span class="subxS1Comment"># . load stream</span>
<span id="L70" class="LineNr">70 </span> bb/copy-to-ebx <span class="SpecialChar"><a href='ex7.subx.html#L88'>Stream</a></span>/imm32
<span id="L71" class="LineNr">71 </span> 8b/copy 0/mod/indirect 3/rm32/ebx <span class="Normal"> . </span> <span class="Normal"> . </span> <span class="Normal"> . </span> 3/r32/ebx <span class="Normal"> . </span> <span class="Normal"> . </span> <span class="subxComment"># copy *ebx to ebx</span>
<span id="L72" class="LineNr">72 </span> <span class="subxComment">#</span>
<span id="L73" class="LineNr">73 </span> e8/call <a href='../000init.subx.html#L41'>syscall_close</a>/disp32
<span id="L74" class="LineNr">74 </span>
<span id="L75" class="LineNr">75 </span> <span class="subxComment"># unlink(filename)</span>
<span id="L76" class="LineNr">76 </span> bb/copy-to-ebx <span class="SpecialChar"><a href='ex7.subx.html#L94'>Filename</a></span>/imm32
<span id="L77" class="LineNr">77 </span> e8/call <a href='../000init.subx.html#L59'>syscall_unlink</a>/disp32
<span id="L78" class="LineNr">78 </span>
<span id="L79" class="LineNr">79 </span> <span class="subxComment"># exit(b)</span>
<span id="L80" class="LineNr">80 </span> <span class="subxS1Comment"># . load b</span>
<span id="L81" class="LineNr">81 </span> bb/copy-to-ebx <span class="SpecialChar"><a href='ex7.subx.html#L92'>B</a></span>/imm32
<span id="L82" class="LineNr">82 </span> 8b/copy 0/mod/indirect 3/rm32/ebx <span class="Normal"> . </span> <span class="Normal"> . </span> <span class="Normal"> . </span> 3/r32/ebx <span class="Normal"> . </span> <span class="Normal"> . </span> <span class="subxComment"># copy *ebx to ebx</span>
<span id="L83" class="LineNr">83 </span> <span class="subxComment">#</span>
<span id="L84" class="LineNr">84 </span> e8/call <a href='../000init.subx.html#L18'>syscall_exit</a>/disp32
<span id="L85" class="LineNr">85 </span>
<span id="L86" class="LineNr">86 </span>== data
<span id="L87" class="LineNr">87 </span>
<span id="L88" class="LineNr">88 </span><span class="SpecialChar">Stream</span>:
<span id="L89" class="LineNr">89 </span> 0/imm32
<span id="L90" class="LineNr">90 </span><span class="SpecialChar">A</span>:
<span id="L91" class="LineNr">91 </span> 61/imm32/A
<span id="L92" class="LineNr">92 </span><span class="SpecialChar">B</span>:
<span id="L93" class="LineNr">93 </span> 0/imm32
<span id="L94" class="LineNr">94 </span><span class="SpecialChar">Filename</span>:
<span id="L95" class="LineNr">95 </span> 2e 66 6f 6f 00 00 00 00
<span id="L96" class="LineNr">96 </span><span class="subxComment"># . f o o null</span>
<span id="L97" class="LineNr">97 </span>
<span id="L98" class="LineNr">98 </span><span class="subxS2Comment"># . . vim:nowrap:textwidth=0</span>
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