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| <hr> |
| <a name="Relocations-3"></a> |
| <h4 class="subsubsection">9.41.3.4 Relocations</h4> |
| <a name="index-Sparc-relocations"></a> |
| <a name="index-relocations_002c-Sparc"></a> |
| |
| <p>ELF relocations are available as defined in the 32-bit and 64-bit |
| Sparc ELF specifications. |
| </p> |
| <p><code>R_SPARC_HI22</code> is obtained using ‘<samp>%hi</samp>’ and <code>R_SPARC_LO10</code> |
| is obtained using ‘<samp>%lo</samp>’. Likewise <code>R_SPARC_HIX22</code> is |
| obtained from ‘<samp>%hix</samp>’ and <code>R_SPARC_LOX10</code> is obtained |
| using ‘<samp>%lox</samp>’. For example: |
| </p> |
| <div class="example"> |
| <pre class="example">sethi %hi(symbol), %g1 |
| or %g1, %lo(symbol), %g1 |
| |
| sethi %hix(symbol), %g1 |
| xor %g1, %lox(symbol), %g1 |
| </pre></div> |
| |
| <p>These “high” mnemonics extract bits 31:10 of their operand, |
| and the “low” mnemonics extract bits 9:0 of their operand. |
| </p> |
| <p>V9 code model relocations can be requested as follows: |
| </p> |
| <ul> |
| <li> <code>R_SPARC_HH22</code> is requested using ‘<samp>%hh</samp>’. It can |
| also be generated using ‘<samp>%uhi</samp>’. |
| </li><li> <code>R_SPARC_HM10</code> is requested using ‘<samp>%hm</samp>’. It can |
| also be generated using ‘<samp>%ulo</samp>’. |
| </li><li> <code>R_SPARC_LM22</code> is requested using ‘<samp>%lm</samp>’. |
| |
| </li><li> <code>R_SPARC_H44</code> is requested using ‘<samp>%h44</samp>’. |
| </li><li> <code>R_SPARC_M44</code> is requested using ‘<samp>%m44</samp>’. |
| </li><li> <code>R_SPARC_L44</code> is requested using ‘<samp>%l44</samp>’ or ‘<samp>%l34</samp>’. |
| </li><li> <code>R_SPARC_H34</code> is requested using ‘<samp>%h34</samp>’. |
| </li></ul> |
| |
| <p>The ‘<samp>%l34</samp>’ generates a <code>R_SPARC_L44</code> relocation because it |
| calculates the necessary value, and therefore no explicit |
| <code>R_SPARC_L34</code> relocation needed to be created for this purpose. |
| </p> |
| <p>The ‘<samp>%h34</samp>’ and ‘<samp>%l34</samp>’ relocations are used for the abs34 code |
| model. Here is an example abs34 address generation sequence: |
| </p> |
| <div class="example"> |
| <pre class="example">sethi %h34(symbol), %g1 |
| sllx %g1, 2, %g1 |
| or %g1, %l34(symbol), %g1 |
| </pre></div> |
| |
| <p>The PC relative relocation <code>R_SPARC_PC22</code> can be obtained by |
| enclosing an operand inside of ‘<samp>%pc22</samp>’. Likewise, the |
| <code>R_SPARC_PC10</code> relocation can be obtained using ‘<samp>%pc10</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: |
| </p> |
| <div class="example"> |
| <pre class="example">sethi %pc22(_GLOBAL_OFFSET_TABLE_-4), %l7 |
| add %l7, %pc10(_GLOBAL_OFFSET_TABLE_+4), %l7 |
| </pre></div> |
| |
| <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>%gdop_hix22</samp>’. The <code>R_SPARC_GOTDATA_OP_LOX10</code> |
| relocation can obtained by enclosing an operand inside of |
| ‘<samp>%gdop_lox10</samp>’. Likewise, <code>R_SPARC_GOTDATA_OP</code> can be |
| obtained by enclosing an operand inside of ‘<samp>%gdop</samp>’. |
| For example, assuming the GOT base is in register <code>%l7</code>: |
| </p> |
| <div class="example"> |
| <pre class="example">sethi %gdop_hix22(symbol), %l1 |
| xor %l1, %gdop_lox10(symbol), %l1 |
| ld [%l7 + %l1], %l2, %gdop(symbol) |
| </pre></div> |
| |
| <p>There are many relocations that can be requested for access to |
| thread local storage variables. All of the Sparc TLS mnemonics |
| are supported: |
| </p> |
| <ul> |
| <li> <code>R_SPARC_TLS_GD_HI22</code> is requested using ‘<samp>%tgd_hi22</samp>’. |
| </li><li> <code>R_SPARC_TLS_GD_LO10</code> is requested using ‘<samp>%tgd_lo10</samp>’. |
| </li><li> <code>R_SPARC_TLS_GD_ADD</code> is requested using ‘<samp>%tgd_add</samp>’. |
| </li><li> <code>R_SPARC_TLS_GD_CALL</code> is requested using ‘<samp>%tgd_call</samp>’. |
| |
| </li><li> <code>R_SPARC_TLS_LDM_HI22</code> is requested using ‘<samp>%tldm_hi22</samp>’. |
| </li><li> <code>R_SPARC_TLS_LDM_LO10</code> is requested using ‘<samp>%tldm_lo10</samp>’. |
| </li><li> <code>R_SPARC_TLS_LDM_ADD</code> is requested using ‘<samp>%tldm_add</samp>’. |
| </li><li> <code>R_SPARC_TLS_LDM_CALL</code> is requested using ‘<samp>%tldm_call</samp>’. |
| |
| </li><li> <code>R_SPARC_TLS_LDO_HIX22</code> is requested using ‘<samp>%tldo_hix22</samp>’. |
| </li><li> <code>R_SPARC_TLS_LDO_LOX10</code> is requested using ‘<samp>%tldo_lox10</samp>’. |
| </li><li> <code>R_SPARC_TLS_LDO_ADD</code> is requested using ‘<samp>%tldo_add</samp>’. |
| |
| </li><li> <code>R_SPARC_TLS_IE_HI22</code> is requested using ‘<samp>%tie_hi22</samp>’. |
| </li><li> <code>R_SPARC_TLS_IE_LO10</code> is requested using ‘<samp>%tie_lo10</samp>’. |
| </li><li> <code>R_SPARC_TLS_IE_LD</code> is requested using ‘<samp>%tie_ld</samp>’. |
| </li><li> <code>R_SPARC_TLS_IE_LDX</code> is requested using ‘<samp>%tie_ldx</samp>’. |
| </li><li> <code>R_SPARC_TLS_IE_ADD</code> is requested using ‘<samp>%tie_add</samp>’. |
| |
| </li><li> <code>R_SPARC_TLS_LE_HIX22</code> is requested using ‘<samp>%tle_hix22</samp>’. |
| </li><li> <code>R_SPARC_TLS_LE_LOX10</code> is requested using ‘<samp>%tle_lox10</samp>’. |
| </li></ul> |
| |
| <p>Here are some example TLS model sequences. |
| </p> |
| <p>First, General Dynamic: |
| </p> |
| <div class="example"> |
| <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></div> |
| |
| <p>Local Dynamic: |
| </p> |
| <div class="example"> |
| <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></div> |
| |
| <p>Initial Exec: |
| </p> |
| <div class="example"> |
| <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></div> |
| |
| <p>And finally, Local Exec: |
| </p> |
| <div class="example"> |
| <pre class="example">sethi %tle_hix22(symbol), %l1 |
| add %l1, %tle_lox10(symbol), %l1 |
| add %g7, %l1, %l1 |
| </pre></div> |
| |
| <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. |
| </p> |
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