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106 lines
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HTML
106 lines
4.0 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- This file documents the GNU Assembler "as".
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Copyright (C) 1991-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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Back-Cover Texts. A copy of the license is included in the
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>ARM Mapping Symbols (Using as)</title>
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<meta name="description" content="ARM Mapping Symbols (Using as)">
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<meta name="keywords" content="ARM Mapping Symbols (Using as)">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="AS-Index.html#AS-Index" rel="index" title="AS Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="ARM_002dDependent.html#ARM_002dDependent" rel="up" title="ARM-Dependent">
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<link href="ARM-Unwinding-Tutorial.html#ARM-Unwinding-Tutorial" rel="next" title="ARM Unwinding Tutorial">
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<link href="ARM-Opcodes.html#ARM-Opcodes" rel="prev" title="ARM Opcodes">
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</head>
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<body lang="en">
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<a name="ARM-Mapping-Symbols"></a>
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<div class="header">
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<p>
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Next: <a href="ARM-Unwinding-Tutorial.html#ARM-Unwinding-Tutorial" accesskey="n" rel="next">ARM Unwinding Tutorial</a>, Previous: <a href="ARM-Opcodes.html#ARM-Opcodes" accesskey="p" rel="prev">ARM Opcodes</a>, Up: <a href="ARM_002dDependent.html#ARM_002dDependent" accesskey="u" rel="up">ARM-Dependent</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Mapping-Symbols-1"></a>
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<h4 class="subsection">9.4.6 Mapping Symbols</h4>
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<p>The ARM ELF specification requires that special symbols be inserted
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into object files to mark certain features:
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</p>
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<dl compact="compact">
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<dd>
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<a name="index-_0024a"></a>
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</dd>
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<dt><code>$a</code></dt>
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<dd><p>At the start of a region of code containing ARM instructions.
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</p>
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<a name="index-_0024t"></a>
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</dd>
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<dt><code>$t</code></dt>
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<dd><p>At the start of a region of code containing THUMB instructions.
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</p>
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<a name="index-_0024d-1"></a>
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</dd>
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<dt><code>$d</code></dt>
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<dd><p>At the start of a region of data.
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</p>
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</dd>
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</dl>
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<p>The assembler will automatically insert these symbols for you - there
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is no need to code them yourself. Support for tagging symbols ($b,
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$f, $p and $m) which is also mentioned in the current ARM ELF
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specification is not implemented. This is because they have been
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dropped from the new EABI and so tools cannot rely upon their
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presence.
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</p>
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</body>
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</html>
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