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<span id="L1" class="LineNr"> 1 </span><span class="SalientComment">## example showing file syscalls</span>
<span id="L2" class="LineNr"> 2 </span><span class="Comment"># Create a file, open it for writing, write a character to it, close it, open</span>
<span id="L3" class="LineNr"> 3 </span><span class="Comment"># it for reading, read a character from it, close it, delete it, and return</span>
<span id="L4" class="LineNr"> 4 </span><span class="Comment"># the character read.</span>
<span id="L5" class="LineNr"> 5 </span><span class="Comment">#</span>
<span id="L6" class="LineNr"> 6 </span><span class="Comment"># To run:</span>
<span id="L7" class="LineNr"> 7 </span><span class="Comment"># $ subx translate ex8.subx ex8</span>
<span id="L8" class="LineNr"> 8 </span><span class="Comment"># $ subx run ex8</span>
<span id="L9" class="LineNr"> 9 </span><span class="Comment"># Expected result:</span>
<span id="L10" class="LineNr">10 </span><span class="Comment"># $ echo $?</span>
<span id="L11" class="LineNr">11 </span><span class="Comment"># 97</span>
<span id="L12" class="LineNr">12 </span>
<span id="L13" class="LineNr">13 </span>== 0x08048074 <span class="Comment"># code segment, after leaving room for ELF header and segment headers</span>
<span id="L14" class="LineNr">14 </span><span class="Comment"># instruction effective address operand displacement immediate</span>
<span id="L15" class="LineNr">15 </span><span class="Comment"># op subop mod rm32 base index scale r32</span>
<span id="L16" class="LineNr">16 </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="L17" class="LineNr">17 </span>
<span id="L18" class="LineNr">18 </span> <span class="SalientComment">## creat(filename)</span>
<span id="L19" class="LineNr">19 </span> bb/copy <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="Delimiter"> . </span> 0x08049131/imm32/fname <span class="Comment"># copy to EBX</span>
<span id="L20" class="LineNr">20 </span> b9/copy <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="Delimiter"> . </span> 0x180/imm32/fixed-perms <span class="Comment"># copy 0 to ECX</span>
<span id="L21" class="LineNr">21 </span> b8/copy <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="Delimiter"> . </span> 8/imm32/creat <span class="Comment"># copy 8 to EAX</span>
<span id="L22" class="LineNr">22 </span> cd/syscall <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="Delimiter"> . </span> 0x80/imm8 <span class="Comment"># int 80h</span>
<span id="L23" class="LineNr">23 </span>
<span id="L24" class="LineNr">24 </span> <span class="SalientComment">## fd = open(filename, O_WRONLY, 0)</span>
<span id="L25" class="LineNr">25 </span> bb/copy <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="Delimiter"> . </span> 0x08049131/imm32/fname <span class="Comment"># copy to EBX</span>
<span id="L26" class="LineNr">26 </span> b9/copy <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="Delimiter"> . </span> 1/imm32/wronly <span class="Comment"># copy 1 to ECX</span>
<span id="L27" class="LineNr">27 </span> ba/copy <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="Delimiter"> . </span> 0x180/imm32/fixed-perms <span class="Comment"># copy 0 to EDX</span>
<span id="L28" class="LineNr">28 </span> b8/copy <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="Delimiter"> . </span> 5/imm32/open <span class="Comment"># copy 5 to EAX</span>
<span id="L29" class="LineNr">29 </span> cd/syscall <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="Delimiter"> . </span> 0x80/imm8 <span class="Comment"># int 80h</span>
<span id="L30" class="LineNr">30 </span> <span class="Comment"># save fd</span>
<span id="L31" class="LineNr">31 </span> bb/copy <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="Delimiter"> . </span> 0x08049125/imm32/fd <span class="Comment"># copy to EBX</span>
<span id="L32" class="LineNr">32 </span> 89/copy 0/mod/indirect 3/rm32/EBX 0/r32/EAX <span class="Comment"># copy EAX to *EBX</span>
<span id="L33" class="LineNr">33 </span>
<span id="L34" class="LineNr">34 </span> <span class="SalientComment">## write(fd, "a", 1)</span>
<span id="L35" class="LineNr">35 </span> <span class="Comment"># load fd</span>
<span id="L36" class="LineNr">36 </span> bb/copy <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="Delimiter"> . </span> 0x08049125/imm32/fd <span class="Comment"># copy to EBX</span>
<span id="L37" class="LineNr">37 </span> 8b/copy 0/mod/indirect 3/rm32/EBX 3/r32/EBX <span class="Comment"># copy *EBX to EBX</span>
<span id="L38" class="LineNr">38 </span> <span class="Comment">#</span>
<span id="L39" class="LineNr">39 </span> b9/copy <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="Delimiter"> . </span> 0x08049129/imm32/a <span class="Comment"># copy to ECX</span>
<span id="L40" class="LineNr">40 </span> ba/copy <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="Delimiter"> . </span> 1/imm32/size <span class="Comment"># copy 1 to EDX</span>
<span id="L41" class="LineNr">41 </span> b8/copy <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="Delimiter"> . </span> 4/imm32/write <span class="Comment"># copy 4 to EAX</span>
<span id="L42" class="LineNr">42 </span> cd/syscall <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="Delimiter"> . </span> 0x80/imm8 <span class="Comment"># int 80h</span>
<span id="L43" class="LineNr">43 </span>
<span id="L44" class="LineNr">44 </span> <span class="SalientComment">## close(fd)</span>
<span id="L45" class="LineNr">45 </span> <span class="Comment"># load fd</span>
<span id="L46" class="LineNr">46 </span> bb/copy <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="Delimiter"> . </span> 0x08049125/imm32/fd <span class="Comment"># copy to EBX</span>
<span id="L47" class="LineNr">47 </span> 8b/copy 0/mod/indirect 3/rm32/EBX 3/r32/EBX <span class="Comment"># copy *EBX to EBX</span>
<span id="L48" class="LineNr">48 </span> <span class="Comment">#</span>
<span id="L49" class="LineNr">49 </span> b8/copy <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="Delimiter"> . </span> 6/imm32/close <span class="Comment"># copy 6 to EAX</span>
<span id="L50" class="LineNr">50 </span> cd/syscall <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="Delimiter"> . </span> 0x80/imm8 <span class="Comment"># int 80h</span>
<span id="L51" class="LineNr">51 </span>
<span id="L52" class="LineNr">52 </span> <span class="SalientComment">## fd = open(filename, O_RDONLY, 0)</span>
<span id="L53" class="LineNr">53 </span> bb/copy <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="Delimiter"> . </span> 0x08049131/imm32/fname <span class="Comment"># copy to EBX</span>
<span id="L54" class="LineNr">54 </span> b9/copy <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="Delimiter"> . </span> 0/imm32/rdonly <span class="Comment"># copy 0 to ECX</span>
<span id="L55" class="LineNr">55 </span> ba/copy <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="Delimiter"> . </span> 0x180/imm32/fixed-perms <span class="Comment"># copy 0 to EDX</span>
<span id="L56" class="LineNr">56 </span> b8/copy <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="Delimiter"> . </span> 5/imm32/open <span class="Comment"># copy 5 to EAX</span>
<span id="L57" class="LineNr">57 </span> cd/syscall <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="Delimiter"> . </span> 0x80/imm8 <span class="Comment"># int 80h</span>
<span id="L58" class="LineNr">58 </span> <span class="Comment"># save fd</span>
<span id="L59" class="LineNr">59 </span> bb/copy <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="Delimiter"> . </span> 0x08049125/imm32/fd <span class="Comment"># copy to EBX</span>
<span id="L60" class="LineNr">60 </span> 89/copy 0/mod/indirect 3/rm32/EBX 0/r32/EAX <span class="Comment"># copy EAX to *EBX</span>
<span id="L61" class="LineNr">61 </span>
<span id="L62" class="LineNr">62 </span> <span class="SalientComment">## read(fd, b, 1)</span>
<span id="L63" class="LineNr">63 </span> <span class="Comment"># load fd</span>
<span id="L64" class="LineNr">64 </span> bb/copy <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="Delimiter"> . </span> 0x08049125/imm32/fd <span class="Comment"># copy to EBX</span>
<span id="L65" class="LineNr">65 </span> 8b/copy 0/mod/indirect 3/rm32/EBX 3/r32/EBX <span class="Comment"># copy *EBX to EBX</span>
<span id="L66" class="LineNr">66 </span> <span class="Comment">#</span>
<span id="L67" class="LineNr">67 </span> b9/copy <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="Delimiter"> . </span> 0x0804912d/imm32/b <span class="Comment"># copy to ECX</span>
<span id="L68" class="LineNr">68 </span> ba/copy <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="Delimiter"> . </span> 1/imm32/size <span class="Comment"># copy 1 to EDX</span>
<span id="L69" class="LineNr">69 </span> b8/copy <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="Delimiter"> . </span> 3/imm32/read <span class="Comment"># copy 3 to EAX</span>
<span id="L70" class="LineNr">70 </span> cd/syscall <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="Delimiter"> . </span> 0x80/imm8 <span class="Comment"># int 80h</span>
<span id="L71" class="LineNr">71 </span>
<span id="L72" class="LineNr">72 </span> <span class="SalientComment">## close(fd)</span>
<span id="L73" class="LineNr">73 </span> <span class="Comment"># load fd</span>
<span id="L74" class="LineNr">74 </span> bb/copy <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="Delimiter"> . </span> 0x08049125/imm32/fd <span class="Comment"># copy to EBX</span>
<span id="L75" class="LineNr">75 </span> 8b/copy 0/mod/indirect 3/rm32/EBX 3/r32/EBX <span class="Comment"># copy *EBX to EBX</span>
<span id="L76" class="LineNr">76 </span> <span class="Comment">#</span>
<span id="L77" class="LineNr">77 </span> b8/copy <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="Delimiter"> . </span> 6/imm32/close <span class="Comment"># copy 8 to EAX</span>
<span id="L78" class="LineNr">78 </span> cd/syscall <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="Delimiter"> . </span> 0x80/imm8 <span class="Comment"># int 80h</span>
<span id="L79" class="LineNr">79 </span>
<span id="L80" class="LineNr">80 </span> <span class="SalientComment">## unlink(filename)</span>
<span id="L81" class="LineNr">81 </span> bb/copy <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="Delimiter"> . </span> 0x08049131/imm32/fname <span class="Comment"># copy to EBX</span>
<span id="L82" class="LineNr">82 </span> b8/copy <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="Delimiter"> . </span> 0xa/imm32/unlink <span class="Comment"># copy 8 to EAX</span>
<span id="L83" class="LineNr">83 </span> cd/syscall <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="Delimiter"> . </span> 0x80/imm8 <span class="Comment"># int 80h</span>
<span id="L84" class="LineNr">84 </span>
<span id="L85" class="LineNr">85 </span> <span class="SalientComment">## exit(b)</span>
<span id="L86" class="LineNr">86 </span> <span class="Comment"># load b</span>
<span id="L87" class="LineNr">87 </span> bb/copy <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="Delimiter"> . </span> 0x0804912d/imm32/b <span class="Comment"># copy to EBX</span>
<span id="L88" class="LineNr">88 </span> 8b/copy 0/mod/indirect 3/rm32/EBX 3/r32/EBX <span class="Comment"># copy *EBX to EBX</span>
<span id="L89" class="LineNr">89 </span> <span class="Comment">#</span>
<span id="L90" class="LineNr">90 </span> b8/copy <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="Delimiter"> . </span> 1/imm32/exit <span class="Comment"># copy 1 to EAX</span>
<span id="L91" class="LineNr">91 </span> cd/syscall <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="Delimiter"> . </span> 0x80/imm8 <span class="Comment"># int 80h</span>
<span id="L92" class="LineNr">92 </span>
<span id="L93" class="LineNr">93 </span>== 0x08049125 <span class="Comment"># data segment</span>
<span id="L94" class="LineNr">94 </span>00 00 00 00 <span class="Comment"># fd</span>
<span id="L95" class="LineNr">95 </span>61 00 00 00 <span class="Comment"># a: string to write to file: 'a'</span>
<span id="L96" class="LineNr">96 </span>00 00 00 00 <span class="Comment"># b: space for string read from file</span>
<span id="L97" class="LineNr">97 </span>2e 66 6f 6f 00 00 00 00 <span class="Comment"># filename: '.foo'</span>
<span id="L98" class="LineNr">98 </span>
<span id="L99" class="LineNr">99 </span><span class="Comment"># vim:ft=subx:nowrap:tw&</span>
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