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<a name="OpenRISC_002dRelocs"></a>
<div class="header">
<p>
Previous: <a href="OpenRISC_002dRegs.html#OpenRISC_002dRegs" accesskey="p" rel="prev">OpenRISC-Regs</a>, Up: <a href="OpenRISC_002dSyntax.html#OpenRISC_002dSyntax" accesskey="u" rel="up">OpenRISC-Syntax</a> &nbsp; [<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>
</div>
<hr>
<a name="Relocations-3"></a>
<h4 class="subsubsection">9.33.1.3 Relocations</h4>
<a name="index-OpenRISC-relocations"></a>
<a name="index-relocations_002c-OpenRISC"></a>

<p>ELF relocations are available as defined in the OpenRISC architecture
specification.
</p>
<p><code>R_OR1K_HI_16_IN_INSN</code> is obtained using &lsquo;<samp>hi</samp>&rsquo; and
<code>R_OR1K_LO_16_IN_INSN</code> and <code>R_OR1K_SLO16</code> are obtained using
&lsquo;<samp>lo</samp>&rsquo;.  For signed offsets <code>R_OR1K_AHI16</code> is obtained from
&lsquo;<samp>ha</samp>&rsquo;.  For example:
</p>
<div class="example">
<pre class="example">l.movhi r5, hi(symbol)
l.ori   r5, r5, lo(symbol)

l.movhi r5, ha(symbol)
l.addi  r5, r5, lo(symbol)
</pre></div>

<p>These &ldquo;high&rdquo; mnemonics extract bits 31:16 of their operand,
and the &ldquo;low&rdquo; mnemonics extract bits 15:0 of their operand.
</p>
<p>The PC relative relocation <code>R_OR1K_GOTPC_HI16</code> can be obtained by
enclosing an operand inside of &lsquo;<samp>gotpchi</samp>&rsquo;.  Likewise, the
<code>R_OR1K_GOTPC_LO16</code> relocation can be obtained using &lsquo;<samp>gotpclo</samp>&rsquo;.
These are mostly used when assembling PIC code.  For example, the
standard PIC sequence on OpenRISC to get the base of the global offset
table, PC relative, into a register, can be performed as:
</p>
<div class="example">
<pre class="example">l.jal   0x8
 l.movhi r17, gotpchi(_GLOBAL_OFFSET_TABLE_-4)
l.ori   r17, r17, gotpclo(_GLOBAL_OFFSET_TABLE_+0)
l.add   r17, r17, r9
</pre></div>

<p>Several relocations exist to allow the link editor to perform GOT data
references.  The <code>R_OR1K_GOT16</code> relocation can obtained by enclosing an
operand inside of &lsquo;<samp>got</samp>&rsquo;.  For example, assuming the GOT base is in
register <code>r17</code>.
</p>
<div class="example">
<pre class="example">l.lwz   r19, got(a)(r17)
l.lwz   r21, 0(r19)
</pre></div>

<p>Also, several relocations exist for local GOT references.  The
<code>R_OR1K_GOTOFF_AHI16</code> relocation can obtained by enclosing an operand
inside of &lsquo;<samp>gotoffha</samp>&rsquo;.  Likewise, <code>R_OR1K_GOTOFF_LO16</code> and
<code>R_OR1K_GOTOFF_SLO16</code> can be obtained by enclosing an operand inside of
&lsquo;<samp>gotofflo</samp>&rsquo;.  For example, assuming the GOT base is in register
<code>rl7</code>:
</p>
<div class="example">
<pre class="example">l.movhi r19, gotoffha(symbol)
l.add   r19, r19, r17
l.lwz   r19, gotofflo(symbol)(r19)
</pre></div>

<p>The above PC relative relocations use a <code>l.jal</code> (jump) instruction
and reading of the link register to load the PC.  OpenRISC also supports
page offset PC relative locations without a jump instruction using the
<code>l.adrp</code> instruction.  By default the <code>l.adrp</code> instruction will
create an <code>R_OR1K_PCREL_PG21</code> relocation.
Likewise, <code>BFD_RELOC_OR1K_LO13</code> and <code>BFD_RELOC_OR1K_SLO13</code> can
be obtained by enclosing an operand inside of &lsquo;<samp>po</samp>&rsquo;.  For example:
</p>
<div class="example">
<pre class="example">l.adrp  r3, symbol
l.ori   r4, r3, po(symbol)
l.lbz   r5, po(symbol)(r3)
l.sb    po(symbol)(r3), r6
</pre></div>

<p>Likewise the page offset relocations can be used with GOT references.  The
relocation <code>R_OR1K_GOT_PG21</code> can be obtained by enclosing an
<code>l.adrp</code> immediate operand inside of &lsquo;<samp>got</samp>&rsquo;.  Likewise,
<code>R_OR1K_GOT_LO13</code> can be obtained by enclosing an operand inside of
&lsquo;<samp>gotpo</samp>&rsquo;.  For example to load the value of a GOT symbol into register
&lsquo;<samp>r5</samp>&rsquo; we can do:
</p>
<div class="example">
<pre class="example">l.adrp  r17, got(_GLOBAL_OFFSET_TABLE_)
l.lwz   r5, gotpo(symbol)(r17)
</pre></div>

<p>There are many relocations that can be requested for access to
thread local storage variables.  All of the OpenRISC TLS mnemonics
are supported:
</p>
<ul>
<li> <code>R_OR1K_TLS_GD_HI16</code> is requested using &lsquo;<samp>tlsgdhi</samp>&rsquo;.
</li><li> <code>R_OR1K_TLS_GD_LO16</code> is requested using &lsquo;<samp>tlsgdlo</samp>&rsquo;.
</li><li> <code>R_OR1K_TLS_GD_PG21</code> is requested using &lsquo;<samp>tldgd</samp>&rsquo;.
</li><li> <code>R_OR1K_TLS_GD_LO13</code> is requested using &lsquo;<samp>tlsgdpo</samp>&rsquo;.

</li><li> <code>R_OR1K_TLS_LDM_HI16</code> is requested using &lsquo;<samp>tlsldmhi</samp>&rsquo;.
</li><li> <code>R_OR1K_TLS_LDM_LO16</code> is requested using &lsquo;<samp>tlsldmlo</samp>&rsquo;.
</li><li> <code>R_OR1K_TLS_LDM_PG21</code> is requested using &lsquo;<samp>tldldm</samp>&rsquo;.
</li><li> <code>R_OR1K_TLS_LDM_LO13</code> is requested using &lsquo;<samp>tlsldmpo</samp>&rsquo;.

</li><li> <code>R_OR1K_TLS_LDO_HI16</code> is requested using &lsquo;<samp>dtpoffhi</samp>&rsquo;.
</li><li> <code>R_OR1K_TLS_LDO_LO16</code> is requested using &lsquo;<samp>dtpofflo</samp>&rsquo;.

</li><li> <code>R_OR1K_TLS_IE_HI16</code> is requested using &lsquo;<samp>gottpoffhi</samp>&rsquo;.
</li><li> <code>R_OR1K_TLS_IE_AHI16</code> is requested using &lsquo;<samp>gottpoffha</samp>&rsquo;.
</li><li> <code>R_OR1K_TLS_IE_LO16</code> is requested using &lsquo;<samp>gottpofflo</samp>&rsquo;.
</li><li> <code>R_OR1K_TLS_IE_PG21</code> is requested using &lsquo;<samp>gottp</samp>&rsquo;.
</li><li> <code>R_OR1K_TLS_IE_LO13</code> is requested using &lsquo;<samp>gottppo</samp>&rsquo;.

</li><li> <code>R_OR1K_TLS_LE_HI16</code> is requested using &lsquo;<samp>tpoffhi</samp>&rsquo;.
</li><li> <code>R_OR1K_TLS_LE_AHI16</code> is requested using &lsquo;<samp>tpoffha</samp>&rsquo;.
</li><li> <code>R_OR1K_TLS_LE_LO16</code> is requested using &lsquo;<samp>tpofflo</samp>&rsquo;.
</li><li> <code>R_OR1K_TLS_LE_SLO16</code> also is requested using &lsquo;<samp>tpofflo</samp>&rsquo;
depending on the instruction format.
</li></ul>

<p>Here are some example TLS model sequences.
</p>
<p>First, General Dynamic:
</p>
<div class="example">
<pre class="example">l.movhi r17, tlsgdhi(symbol)
l.ori   r17, r17, tlsgdlo(symbol)
l.add   r17, r17, r16
l.or    r3, r17, r17
l.jal   plt(__tls_get_addr)
 l.nop
</pre></div>

<p>Initial Exec:
</p>
<div class="example">
<pre class="example">l.movhi r17, gottpoffhi(symbol)
l.add   r17, r17, r16
l.lwz   r17, gottpofflo(symbol)(r17)
l.add   r17, r17, r10
l.lbs   r17, 0(r17)
</pre></div>

<p>And finally, Local Exec:
</p>
<div class="example">
<pre class="example">l.movhi r17, tpoffha(symbol)
l.add   r17, r17, r10
l.addi  r17, r17, tpofflo(symbol)
l.lbs   r17, 0(r17)
</pre></div>

<hr>
<div class="header">
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Previous: <a href="OpenRISC_002dRegs.html#OpenRISC_002dRegs" accesskey="p" rel="prev">OpenRISC-Regs</a>, Up: <a href="OpenRISC_002dSyntax.html#OpenRISC_002dSyntax" accesskey="u" rel="up">OpenRISC-Syntax</a> &nbsp; [<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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