ZealOS/docs/Demo/Asm/AsmHelloWorld.ZC.html
2021-12-30 22:21:33 -05:00

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<a name="l1"></a><span class=cF2>/*Asm labels can only be defined once</span><span class=cF0>
<a name="l2"></a></span><span class=cF2>in a task. &lt;F5&gt; will spawn a new task</span><span class=cF0>
<a name="l3"></a></span><span class=cF2>each time, so you don't get redefine</span><span class=cF0>
<a name="l4"></a></span><span class=cF2>error, like when repeatedly #including</span><span class=cF0>
<a name="l5"></a></span><span class=cF2>it from the cmd line.</span><span class=cF0>
<a name="l6"></a>
<a name="l7"></a></span><span class=cF2>These are many useful kernel</span><span class=cF0>
<a name="l8"></a></span><span class=cF2>routines </span><a href="https://zeal-operating-system.github.io/ZealOS/Kernel/StrA.ZC.html#l56"><span class=cF4>::/Kernel/StrA.ZC</span></a><span class=cF0>
<a name="l9"></a></span><span class=cF2>intended to be called from</span><span class=cF0>
<a name="l10"></a></span><span class=cF2>asm. Generally, they</span><span class=cF0>
<a name="l11"></a></span><span class=cF2>preserve registers.</span><span class=cF0>
<a name="l12"></a>
<a name="l13"></a></span><span class=cF2>You can call any routine you</span><span class=cF0>
<a name="l14"></a></span><span class=cF2>like, C or asm, if you import it.</span><span class=cF0>
<a name="l15"></a></span><span class=cF2>Be aware that C routines do not</span><span class=cF0>
<a name="l16"></a></span><span class=cF2>preserve RAX, RBX, RCX, RDX, R8, or R9.</span><span class=cF0>
<a name="l17"></a></span><span class=cF2>When calling from the shell or</span><span class=cF0>
<a name="l18"></a></span><span class=cF2>from C, preserve all other registers.</span><span class=cF0>
<a name="l19"></a>
<a name="l20"></a></span><span class=cF2>*/</span><span class=cF0>
<a name="l21"></a>
<a name="l22"></a></span><span class=cF1>asm</span><span class=cF0> {
<a name="l23"></a></span><span class=cF2>//Opcodes are slightly different to make writing the x86_64 assembler easier.</span><span class=cF0>
<a name="l24"></a></span><span class=cF2>//See </span><a href="https://zeal-operating-system.github.io/ZealOS/Compiler/OpCodes.DD.html#l1"><span class=cF4>::/Compiler/OpCodes.DD</span></a><span class=cF2>.</span><span class=cF0>
<a name="l25"></a>
<a name="l26"></a>MY_WORLD_MESSAGE:
<a name="l27"></a></span><span class=cF2>//Define U8 does not put terminating zeros</span><span class=cF0>
<a name="l28"></a></span><span class=cF2>//on strings.</span><span class=cF0>
<a name="l29"></a> </span><span class=cF1>DU8</span><span class=cF0> </span><span class=cF6>&quot;World\n&quot;</span><span class=cF0>, </span><span class=cFE>0</span><span class=cF0>;
<a name="l30"></a>
<a name="l31"></a></span><span class=cF2>//The convention is to put an underscore</span><span class=cF0>
<a name="l32"></a></span><span class=cF2>//on C callable asm routines.</span><span class=cF0>
<a name="l33"></a>_HELLO_WORLD::
<a name="l34"></a> </span><span class=cF1>PUSH</span><span class=cF0> </span><span class=cFC>RSI</span><span class=cF0> </span><span class=cF2>//See </span><a href="https://zeal-operating-system.github.io/ZealOS/Kernel/KernelA.HH.html#l1939"><span class=cF4>REGG_LOCAL_VARS</span></a><span class=cF2> &amp; </span><a href="https://zeal-operating-system.github.io/ZealOS/Kernel/KernelA.HH.html#l1940"><span class=cF4>REGG_LOCAL_NON_PTR_VARS</span></a><span class=cF0>
<a name="l35"></a> </span><span class=cF1>MOV</span><span class=cF0> </span><span class=cFC>RCX</span><span class=cF0>, </span><span class=cFE>10</span><span class=cF0>
<a name="l36"></a>@@05: </span><span class=cF1>MOV</span><span class=cF0> </span><span class=cFC>RAX</span><span class=cF0>, </span><span class=cFC>RCX</span><span class=cF0>
<a name="l37"></a> </span><span class=cF1>CALL</span><span class=cF0> </span><span class=cFD>PUT_HEX_U8</span><span class=cF0>
<a name="l38"></a> </span><span class=cF1>MOV</span><span class=cF0> </span><span class=cFC>RAX</span><span class=cF0>, </span><span class=cF3>CH_SPACE</span><span class=cF0>
<a name="l39"></a> </span><span class=cF1>CALL</span><span class=cF0> </span><span class=cFD>PUT_CHARS</span><span class=cF0>
<a name="l40"></a> </span><span class=cF1>MOV</span><span class=cF0> </span><span class=cFC>RAX</span><span class=cF0>, </span><span class=cF6>'Hello '</span><span class=cF0> </span><span class=cF2>//Supports multi-byte char consts</span><span class=cF0>
<a name="l41"></a> </span><span class=cF1>CALL</span><span class=cF0> </span><span class=cFD>PUT_CHARS</span><span class=cF0>
<a name="l42"></a></span><span class=cF2>//We broke it in two pieces to show different ways.</span><span class=cF0>
<a name="l43"></a> </span><span class=cF1>MOV</span><span class=cF0> </span><span class=cFC>RSI</span><span class=cF0>, MY_WORLD_MESSAGE
<a name="l44"></a> </span><span class=cF1>CALL</span><span class=cF0> </span><span class=cFD>PUT_STR</span><span class=cF0>
<a name="l45"></a> </span><span class=cF1>LOOP</span><span class=cF0> @@05
<a name="l46"></a> </span><span class=cF1>POP</span><span class=cF0> </span><span class=cFC>RSI</span><span class=cF0>
<a name="l47"></a> </span><span class=cF1>RET</span><span class=cF0>
<a name="l48"></a>};
<a name="l49"></a>
<a name="l50"></a></span><span class=cF5>Call</span><span class=cF0>(_HELLO_WORLD);
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