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| <h5 class="subsubsection">9.35.3.4 Relocations</h5> |
| |
| <p><a name="index-Sparc-relocations-1647"></a><a name="index-relocations_002c-Sparc-1648"></a> |
| ELF relocations are available as defined in the 32-bit and 64-bit |
| Sparc ELF specifications. |
| |
| <p><code>R_SPARC_HI22</code> is obtained using ‘<samp><span class="samp">%hi</span></samp>’ and <code>R_SPARC_LO10</code> |
| is obtained using ‘<samp><span class="samp">%lo</span></samp>’. Likewise <code>R_SPARC_HIX22</code> is |
| obtained from ‘<samp><span class="samp">%hix</span></samp>’ and <code>R_SPARC_LOX10</code> is obtained |
| using ‘<samp><span class="samp">%lox</span></samp>’. For example: |
| |
| <pre class="example"> sethi %hi(symbol), %g1 |
| or %g1, %lo(symbol), %g1 |
| |
| sethi %hix(symbol), %g1 |
| xor %g1, %lox(symbol), %g1 |
| </pre> |
| <p>These “high” mnemonics extract bits 31:10 of their operand, |
| and the “low” mnemonics extract bits 9:0 of their operand. |
| |
| <p>V9 code model relocations can be requested as follows: |
| |
| <ul> |
| <li><code>R_SPARC_HH22</code> is requested using ‘<samp><span class="samp">%hh</span></samp>’. It can |
| also be generated using ‘<samp><span class="samp">%uhi</span></samp>’. |
| <li><code>R_SPARC_HM10</code> is requested using ‘<samp><span class="samp">%hm</span></samp>’. It can |
| also be generated using ‘<samp><span class="samp">%ulo</span></samp>’. |
| <li><code>R_SPARC_LM22</code> is requested using ‘<samp><span class="samp">%lm</span></samp>’. |
| |
| <li><code>R_SPARC_H44</code> is requested using ‘<samp><span class="samp">%h44</span></samp>’. |
| <li><code>R_SPARC_M44</code> is requested using ‘<samp><span class="samp">%m44</span></samp>’. |
| <li><code>R_SPARC_L44</code> is requested using ‘<samp><span class="samp">%l44</span></samp>’. |
| </ul> |
| |
| <p>The PC relative relocation <code>R_SPARC_PC22</code> can be obtained by |
| enclosing an operand inside of ‘<samp><span class="samp">%pc22</span></samp>’. Likewise, the |
| <code>R_SPARC_PC10</code> relocation can be obtained using ‘<samp><span class="samp">%pc10</span></samp>’. |
| These are mostly used when assembling PIC code. For example, the |
| standard PIC sequence on Sparc to get the base of the global offset |
| table, PC relative, into a register, can be performed as: |
| |
| <pre class="example"> sethi %pc22(_GLOBAL_OFFSET_TABLE_-4), %l7 |
| add %l7, %pc10(_GLOBAL_OFFSET_TABLE_+4), %l7 |
| </pre> |
| <p>Several relocations exist to allow the link editor to potentially |
| optimize GOT data references. The <code>R_SPARC_GOTDATA_OP_HIX22</code> |
| relocation can obtained by enclosing an operand inside of |
| ‘<samp><span class="samp">%gdop_hix22</span></samp>’. The <code>R_SPARC_GOTDATA_OP_LOX10</code> |
| relocation can obtained by enclosing an operand inside of |
| ‘<samp><span class="samp">%gdop_lox10</span></samp>’. Likewise, <code>R_SPARC_GOTDATA_OP</code> can be |
| obtained by enclosing an operand inside of ‘<samp><span class="samp">%gdop</span></samp>’. |
| For example, assuming the GOT base is in register <code>%l7</code>: |
| |
| <pre class="example"> sethi %gdop_hix22(symbol), %l1 |
| xor %l1, %gdop_lox10(symbol), %l1 |
| ld [%l7 + %l1], %l2, %gdop(symbol) |
| </pre> |
| <p>There are many relocations that can be requested for access to |
| thread local storage variables. All of the Sparc TLS mnemonics |
| are supported: |
| |
| <ul> |
| <li><code>R_SPARC_TLS_GD_HI22</code> is requested using ‘<samp><span class="samp">%tgd_hi22</span></samp>’. |
| <li><code>R_SPARC_TLS_GD_LO10</code> is requested using ‘<samp><span class="samp">%tgd_lo10</span></samp>’. |
| <li><code>R_SPARC_TLS_GD_ADD</code> is requested using ‘<samp><span class="samp">%tgd_add</span></samp>’. |
| <li><code>R_SPARC_TLS_GD_CALL</code> is requested using ‘<samp><span class="samp">%tgd_call</span></samp>’. |
| |
| <li><code>R_SPARC_TLS_LDM_HI22</code> is requested using ‘<samp><span class="samp">%tldm_hi22</span></samp>’. |
| <li><code>R_SPARC_TLS_LDM_LO10</code> is requested using ‘<samp><span class="samp">%tldm_lo10</span></samp>’. |
| <li><code>R_SPARC_TLS_LDM_ADD</code> is requested using ‘<samp><span class="samp">%tldm_add</span></samp>’. |
| <li><code>R_SPARC_TLS_LDM_CALL</code> is requested using ‘<samp><span class="samp">%tldm_call</span></samp>’. |
| |
| <li><code>R_SPARC_TLS_LDO_HIX22</code> is requested using ‘<samp><span class="samp">%tldo_hix22</span></samp>’. |
| <li><code>R_SPARC_TLS_LDO_LOX10</code> is requested using ‘<samp><span class="samp">%tldo_lox10</span></samp>’. |
| <li><code>R_SPARC_TLS_LDO_ADD</code> is requested using ‘<samp><span class="samp">%tldo_add</span></samp>’. |
| |
| <li><code>R_SPARC_TLS_IE_HI22</code> is requested using ‘<samp><span class="samp">%tie_hi22</span></samp>’. |
| <li><code>R_SPARC_TLS_IE_LO10</code> is requested using ‘<samp><span class="samp">%tie_lo10</span></samp>’. |
| <li><code>R_SPARC_TLS_IE_LD</code> is requested using ‘<samp><span class="samp">%tie_ld</span></samp>’. |
| <li><code>R_SPARC_TLS_IE_LDX</code> is requested using ‘<samp><span class="samp">%tie_ldx</span></samp>’. |
| <li><code>R_SPARC_TLS_IE_ADD</code> is requested using ‘<samp><span class="samp">%tie_add</span></samp>’. |
| |
| <li><code>R_SPARC_TLS_LE_HIX22</code> is requested using ‘<samp><span class="samp">%tle_hix22</span></samp>’. |
| <li><code>R_SPARC_TLS_LE_LOX10</code> is requested using ‘<samp><span class="samp">%tle_lox10</span></samp>’. |
| </ul> |
| |
| <p>Here are some example TLS model sequences. |
| |
| <p>First, General Dynamic: |
| |
| <pre class="example"> sethi %tgd_hi22(symbol), %l1 |
| add %l1, %tgd_lo10(symbol), %l1 |
| add %l7, %l1, %o0, %tgd_add(symbol) |
| call __tls_get_addr, %tgd_call(symbol) |
| nop |
| </pre> |
| <p>Local Dynamic: |
| |
| <pre class="example"> sethi %tldm_hi22(symbol), %l1 |
| add %l1, %tldm_lo10(symbol), %l1 |
| add %l7, %l1, %o0, %tldm_add(symbol) |
| call __tls_get_addr, %tldm_call(symbol) |
| nop |
| |
| sethi %tldo_hix22(symbol), %l1 |
| xor %l1, %tldo_lox10(symbol), %l1 |
| add %o0, %l1, %l1, %tldo_add(symbol) |
| </pre> |
| <p>Initial Exec: |
| |
| <pre class="example"> sethi %tie_hi22(symbol), %l1 |
| add %l1, %tie_lo10(symbol), %l1 |
| ld [%l7 + %l1], %o0, %tie_ld(symbol) |
| add %g7, %o0, %o0, %tie_add(symbol) |
| |
| sethi %tie_hi22(symbol), %l1 |
| add %l1, %tie_lo10(symbol), %l1 |
| ldx [%l7 + %l1], %o0, %tie_ldx(symbol) |
| add %g7, %o0, %o0, %tie_add(symbol) |
| </pre> |
| <p>And finally, Local Exec: |
| |
| <pre class="example"> sethi %tle_hix22(symbol), %l1 |
| add %l1, %tle_lox10(symbol), %l1 |
| add %g7, %l1, %l1 |
| </pre> |
| <p>When assembling for 64-bit, and a secondary constant addend is |
| specified in an address expression that would normally generate |
| an <code>R_SPARC_LO10</code> relocation, the assembler will emit an |
| <code>R_SPARC_OLO10</code> instead. |
| |
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