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<h5 class="subsubsection">9.7.4.2 Symbols in position-independent code</h5>

<p><a name="index-Symbols-in-position_002dindependent-code_002c-CRIS-728"></a><a name="index-CRIS-symbols-in-position_002dindependent-code-729"></a><a name="index-Position_002dindependent-code_002c-symbols-in_002c-CRIS-730"></a>
When generating <a name="crispic"></a>position-independent code (SVR4
PIC) for use in cris-axis-linux-gnu or crisv32-axis-linux-gnu
shared libraries, symbol
suffixes are used to specify what kind of run-time symbol lookup
will be used, expressed in the object as different
<em>relocation types</em>.  Usually, all absolute symbol values
must be located in a table, the <em>global offset table</em>,
leaving the code position-independent; independent of values of
global symbols and independent of the address of the code.  The
suffix modifies the value of the symbol, into for example an
index into the global offset table where the real symbol value
is entered, or a PC-relative value, or a value relative to the
start of the global offset table.  All symbol suffixes start
with the character &lsquo;<samp><span class="samp">:</span></samp>&rsquo; (omitted in the list below).  Every
symbol use in code or a read-only section must therefore have a
PIC suffix to enable a useful shared library to be created. 
Usually, these constructs must not be used with an additive
constant offset as is usually allowed, i.e. no 4 as in
<code>symbol + 4</code> is allowed.  This restriction is checked at
link-time, not at assembly-time.

     <dl>
<dt><code>GOT</code><dd>
Attaching this suffix to a symbol in an instruction causes the
symbol to be entered into the global offset table.  The value is
a 32-bit index for that symbol into the global offset table. 
The name of the corresponding relocation is
&lsquo;<samp><span class="samp">R_CRIS_32_GOT</span></samp>&rsquo;.  Example: <code>move.d
[$r0+extsym:GOT],$r9</code>

     <br><dt><code>GOT16</code><dd>
Same as for &lsquo;<samp><span class="samp">GOT</span></samp>&rsquo;, but the value is a 16-bit index into the
global offset table.  The corresponding relocation is
&lsquo;<samp><span class="samp">R_CRIS_16_GOT</span></samp>&rsquo;.  Example: <code>move.d
[$r0+asymbol:GOT16],$r10</code>

     <br><dt><code>PLT</code><dd>
This suffix is used for function symbols.  It causes a
<em>procedure linkage table</em>, an array of code stubs, to be
created at the time the shared object is created or linked
against, together with a global offset table entry.  The value
is a pc-relative offset to the corresponding stub code in the
procedure linkage table.  This arrangement causes the run-time
symbol resolver to be called to look up and set the value of the
symbol the first time the function is called (at latest;
depending environment variables).  It is only safe to leave the
symbol unresolved this way if all references are function calls. 
The name of the relocation is &lsquo;<samp><span class="samp">R_CRIS_32_PLT_PCREL</span></samp>&rsquo;. 
Example: <code>add.d fnname:PLT,$pc</code>

     <br><dt><code>PLTG</code><dd>
Like PLT, but the value is relative to the beginning of the
global offset table.  The relocation is
&lsquo;<samp><span class="samp">R_CRIS_32_PLT_GOTREL</span></samp>&rsquo;.  Example: <code>move.d
fnname:PLTG,$r3</code>

     <br><dt><code>GOTPLT</code><dd>
Similar to &lsquo;<samp><span class="samp">PLT</span></samp>&rsquo;, but the value of the symbol is a 32-bit
index into the global offset table.  This is somewhat of a mix
between the effect of the &lsquo;<samp><span class="samp">GOT</span></samp>&rsquo; and the &lsquo;<samp><span class="samp">PLT</span></samp>&rsquo; suffix;
the difference to &lsquo;<samp><span class="samp">GOT</span></samp>&rsquo; is that there will be a procedure
linkage table entry created, and that the symbol is assumed to
be a function entry and will be resolved by the run-time
resolver as with &lsquo;<samp><span class="samp">PLT</span></samp>&rsquo;.  The relocation is
&lsquo;<samp><span class="samp">R_CRIS_32_GOTPLT</span></samp>&rsquo;.  Example: <code>jsr
[$r0+fnname:GOTPLT]</code>

     <br><dt><code>GOTPLT16</code><dd>
A variant of &lsquo;<samp><span class="samp">GOTPLT</span></samp>&rsquo; giving a 16-bit value.  Its
relocation name is &lsquo;<samp><span class="samp">R_CRIS_16_GOTPLT</span></samp>&rsquo;.  Example: <code>jsr
[$r0+fnname:GOTPLT16]</code>

     <br><dt><code>GOTOFF</code><dd>
This suffix must only be attached to a local symbol, but may be
used in an expression adding an offset.  The value is the
address of the symbol relative to the start of the global offset
table.  The relocation name is &lsquo;<samp><span class="samp">R_CRIS_32_GOTREL</span></samp>&rsquo;. 
Example: <code>move.d [$r0+localsym:GOTOFF],r3</code>
</dl>

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