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179 lines
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<title>Sparc-Relocs - Using as</title>
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<!--
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This file documents the GNU Assembler "as".
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Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
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2006, 2007 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 1.1
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or any later version published by the Free Software Foundation;
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<p>
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<a name="Sparc_002dRelocs"></a>Next: <a rel="next" accesskey="n" href="Sparc_002dSize_002dTranslations.html#Sparc_002dSize_002dTranslations">Sparc-Size-Translations</a>,
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Previous: <a rel="previous" accesskey="p" href="Sparc_002dConstants.html#Sparc_002dConstants">Sparc-Constants</a>,
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Up: <a rel="up" accesskey="u" href="Sparc_002dSyntax.html#Sparc_002dSyntax">Sparc-Syntax</a>
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<hr><br>
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</div>
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<h5 class="subsubsection">9.30.3.4 Relocations</h5>
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<p><a name="index-Sparc-relocations-1518"></a><a name="index-relocations_002c-Sparc-1519"></a>
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ELF relocations are available as defined in the 32-bit and 64-bit
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Sparc ELF specifications.
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<p><code>R_SPARC_HI22</code> is obtained using <span class="samp">%hi</span> and <code>R_SPARC_LO10</code>
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is obtained using <span class="samp">%lo</span>. Likewise <code>R_SPARC_HIX22</code> is
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obtained from <span class="samp">%hix</span> and <code>R_SPARC_LOX10</code> is obtained
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using <span class="samp">%lox</span>. For example:
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<pre class="example"> sethi %hi(symbol), %g1
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or %g1, %lo(symbol), %g1
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sethi %hix(symbol), %g1
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xor %g1, %lox(symbol), %g1
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</pre>
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<p>These “high” mnemonics extract bits 31:10 of their operand,
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and the “low” mnemonics extract bits 9:0 of their operand.
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<p>V9 code model relocations can be requested as follows:
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<ul>
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<li><code>R_SPARC_HH22</code> is requested using <span class="samp">%hh</span>. It can
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also be generated using <span class="samp">%uhi</span>.
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<li><code>R_SPARC_HM10</code> is requested using <span class="samp">%hm</span>. It can
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also be generated using <span class="samp">%ulo</span>.
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<li><code>R_SPARC_LM22</code> is requested using <span class="samp">%lm</span>.
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<li><code>R_SPARC_H44</code> is requested using <span class="samp">%h44</span>.
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<li><code>R_SPARC_M44</code> is requested using <span class="samp">%m44</span>.
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<li><code>R_SPARC_L44</code> is requested using <span class="samp">%l44</span>.
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</ul>
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<p>The PC relative relocation <code>R_SPARC_PC22</code> can be obtained by
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enclosing an operand inside of <span class="samp">%pc22</span>. Likewise, the
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<code>R_SPARC_PC10</code> relocation can be obtained using <span class="samp">%pc10</span>.
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These are mostly used when assembling PIC code. For example, the
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standard PIC sequence on Sparc to get the base of the global offset
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table, PC relative, into a register, can be performed as:
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<pre class="example"> sethi %pc22(_GLOBAL_OFFSET_TABLE_-4), %l7
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add %l7, %pc10(_GLOBAL_OFFSET_TABLE_+4), %l7
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</pre>
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<p>Several relocations exist to allow the link editor to potentially
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optimize GOT data references. The <code>R_SPARC_GOTDATA_OP_HIX22</code>
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relocation can obtained by enclosing an operand inside of
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<span class="samp">%gdop_hix22</span>. The <code>R_SPARC_GOTDATA_OP_LOX10</code>
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relocation can obtained by enclosing an operand inside of
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<span class="samp">%gdop_lox10</span>. Likewise, <code>R_SPARC_GOTDATA_OP</code> can be
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obtained by enclosing an operand inside of <span class="samp">%gdop</span>.
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For example, assuming the GOT base is in register <code>%l7</code>:
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<pre class="example"> sethi %gdop_hix22(symbol), %l1
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xor %l1, %gdop_lox10(symbol), %l1
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ld [%l7 + %l1], %l2, %gdop(symbol)
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</pre>
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<p>There are many relocations that can be requested for access to
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thread local storage variables. All of the Sparc TLS mnemonics
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are supported:
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<ul>
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<li><code>R_SPARC_TLS_GD_HI22</code> is requested using <span class="samp">%tgd_hi22</span>.
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<li><code>R_SPARC_TLS_GD_LO10</code> is requested using <span class="samp">%tgd_lo10</span>.
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<li><code>R_SPARC_TLS_GD_ADD</code> is requested using <span class="samp">%tgd_add</span>.
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<li><code>R_SPARC_TLS_GD_CALL</code> is requested using <span class="samp">%tgd_call</span>.
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<li><code>R_SPARC_TLS_LDM_HI22</code> is requested using <span class="samp">%tldm_hi22</span>.
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<li><code>R_SPARC_TLS_LDM_LO10</code> is requested using <span class="samp">%tldm_lo10</span>.
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<li><code>R_SPARC_TLS_LDM_ADD</code> is requested using <span class="samp">%tldm_add</span>.
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<li><code>R_SPARC_TLS_LDM_CALL</code> is requested using <span class="samp">%tldm_call</span>.
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<li><code>R_SPARC_TLS_LDO_HIX22</code> is requested using <span class="samp">%tldo_hix22</span>.
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<li><code>R_SPARC_TLS_LDO_LOX10</code> is requested using <span class="samp">%tldo_lox10</span>.
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<li><code>R_SPARC_TLS_LDO_ADD</code> is requested using <span class="samp">%tldo_add</span>.
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<li><code>R_SPARC_TLS_IE_HI22</code> is requested using <span class="samp">%tie_hi22</span>.
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<li><code>R_SPARC_TLS_IE_LO10</code> is requested using <span class="samp">%tie_lo10</span>.
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<li><code>R_SPARC_TLS_IE_LD</code> is requested using <span class="samp">%tie_ld</span>.
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<li><code>R_SPARC_TLS_IE_LDX</code> is requested using <span class="samp">%tie_ldx</span>.
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<li><code>R_SPARC_TLS_IE_ADD</code> is requested using <span class="samp">%tie_add</span>.
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<li><code>R_SPARC_TLS_LE_HIX22</code> is requested using <span class="samp">%tle_hix22</span>.
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<li><code>R_SPARC_TLS_LE_LOX10</code> is requested using <span class="samp">%tle_lox10</span>.
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</ul>
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<p>Here are some example TLS model sequences.
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<p>First, General Dynamic:
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<pre class="example"> sethi %tgd_hi22(symbol), %l1
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add %l1, %tgd_lo10(symbol), %l1
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add %l7, %l1, %o0, %tgd_add(symbol)
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call __tls_get_addr, %tgd_call(symbol)
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nop
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</pre>
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<p>Local Dynamic:
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<pre class="example"> sethi %tldm_hi22(symbol), %l1
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add %l1, %tldm_lo10(symbol), %l1
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add %l7, %l1, %o0, %tldm_add(symbol)
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call __tls_get_addr, %tldm_call(symbol)
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nop
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sethi %tldo_hix22(symbol), %l1
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xor %l1, %tldo_lox10(symbol), %l1
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add %o0, %l1, %l1, %tldo_add(symbol)
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</pre>
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<p>Initial Exec:
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<pre class="example"> sethi %tie_hi22(symbol), %l1
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add %l1, %tie_lo10(symbol), %l1
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ld [%l7 + %l1], %o0, %tie_ld(symbol)
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add %g7, %o0, %o0, %tie_add(symbol)
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sethi %tie_hi22(symbol), %l1
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add %l1, %tie_lo10(symbol), %l1
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ldx [%l7 + %l1], %o0, %tie_ldx(symbol)
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add %g7, %o0, %o0, %tie_add(symbol)
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</pre>
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<p>And finally, Local Exec:
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<pre class="example"> sethi %tle_hix22(symbol), %l1
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add %l1, %tle_lox10(symbol), %l1
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add %g7, %l1, %l1
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</pre>
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<p>When assembling for 64-bit, and a secondary constant addend is
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specified in an address expression that would normally generate
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an <code>R_SPARC_LO10</code> relocation, the assembler will emit an
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<code>R_SPARC_OLO10</code> instead.
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</body></html>
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