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| <a name="CFI-directives"></a> |
| <div class="header"> |
| <p> |
| Next: <a href="Comm.html#Comm" accesskey="n" rel="next">Comm</a>, Previous: <a href="Byte.html#Byte" accesskey="p" rel="prev">Byte</a>, Up: <a href="Pseudo-Ops.html#Pseudo-Ops" accesskey="u" rel="up">Pseudo Ops</a> [<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="g_t_002ecfi_005fsections-section_005flist"></a> |
| <h3 class="section">7.11 <code>.cfi_sections <var>section_list</var></code></h3> |
| <a name="index-cfi_005fsections-directive"></a> |
| <p><code>.cfi_sections</code> may be used to specify whether CFI directives |
| should emit <code>.eh_frame</code> section and/or <code>.debug_frame</code> section. |
| If <var>section_list</var> is <code>.eh_frame</code>, <code>.eh_frame</code> is emitted, |
| if <var>section_list</var> is <code>.debug_frame</code>, <code>.debug_frame</code> is emitted. |
| To emit both use <code>.eh_frame, .debug_frame</code>. The default if this |
| directive is not used is <code>.cfi_sections .eh_frame</code>. |
| </p> |
| <a name="g_t_002ecfi_005fstartproc-_005bsimple_005d"></a> |
| <h3 class="section">7.12 <code>.cfi_startproc [simple]</code></h3> |
| <a name="index-cfi_005fstartproc-directive"></a> |
| <p><code>.cfi_startproc</code> is used at the beginning of each function that |
| should have an entry in <code>.eh_frame</code>. It initializes some internal |
| data structures. Don’t forget to close the function by |
| <code>.cfi_endproc</code>. |
| </p> |
| <p>Unless <code>.cfi_startproc</code> is used along with parameter <code>simple</code> |
| it also emits some architecture dependent initial CFI instructions. |
| </p> |
| <a name="g_t_002ecfi_005fendproc"></a> |
| <h3 class="section">7.13 <code>.cfi_endproc</code></h3> |
| <a name="index-cfi_005fendproc-directive"></a> |
| <p><code>.cfi_endproc</code> is used at the end of a function where it closes its |
| unwind entry previously opened by |
| <code>.cfi_startproc</code>, and emits it to <code>.eh_frame</code>. |
| </p> |
| <a name="g_t_002ecfi_005fpersonality-encoding-_005b_002c-exp_005d"></a> |
| <h3 class="section">7.14 <code>.cfi_personality <var>encoding</var> [, <var>exp</var>]</code></h3> |
| <p><code>.cfi_personality</code> defines personality routine and its encoding. |
| <var>encoding</var> must be a constant determining how the personality |
| should be encoded. If it is 255 (<code>DW_EH_PE_omit</code>), second |
| argument is not present, otherwise second argument should be |
| a constant or a symbol name. When using indirect encodings, |
| the symbol provided should be the location where personality |
| can be loaded from, not the personality routine itself. |
| The default after <code>.cfi_startproc</code> is <code>.cfi_personality 0xff</code>, |
| no personality routine. |
| </p> |
| <a name="g_t_002ecfi_005flsda-encoding-_005b_002c-exp_005d"></a> |
| <h3 class="section">7.15 <code>.cfi_lsda <var>encoding</var> [, <var>exp</var>]</code></h3> |
| <p><code>.cfi_lsda</code> defines LSDA and its encoding. |
| <var>encoding</var> must be a constant determining how the LSDA |
| should be encoded. If it is 255 (<code>DW_EH_PE_omit</code>), second |
| argument is not present, otherwise second argument should be a constant |
| or a symbol name. The default after <code>.cfi_startproc</code> is <code>.cfi_lsda 0xff</code>, |
| no LSDA. |
| </p> |
| <a name="g_t_002ecfi_005fdef_005fcfa-register_002c-offset"></a> |
| <h3 class="section">7.16 <code>.cfi_def_cfa <var>register</var>, <var>offset</var></code></h3> |
| <p><code>.cfi_def_cfa</code> defines a rule for computing CFA as: <i>take |
| address from <var>register</var> and add <var>offset</var> to it</i>. |
| </p> |
| <a name="g_t_002ecfi_005fdef_005fcfa_005fregister-register"></a> |
| <h3 class="section">7.17 <code>.cfi_def_cfa_register <var>register</var></code></h3> |
| <p><code>.cfi_def_cfa_register</code> modifies a rule for computing CFA. From |
| now on <var>register</var> will be used instead of the old one. Offset |
| remains the same. |
| </p> |
| <a name="g_t_002ecfi_005fdef_005fcfa_005foffset-offset"></a> |
| <h3 class="section">7.18 <code>.cfi_def_cfa_offset <var>offset</var></code></h3> |
| <p><code>.cfi_def_cfa_offset</code> modifies a rule for computing CFA. Register |
| remains the same, but <var>offset</var> is new. Note that it is the |
| absolute offset that will be added to a defined register to compute |
| CFA address. |
| </p> |
| <a name="g_t_002ecfi_005fadjust_005fcfa_005foffset-offset"></a> |
| <h3 class="section">7.19 <code>.cfi_adjust_cfa_offset <var>offset</var></code></h3> |
| <p>Same as <code>.cfi_def_cfa_offset</code> but <var>offset</var> is a relative |
| value that is added/substracted from the previous offset. |
| </p> |
| <a name="g_t_002ecfi_005foffset-register_002c-offset"></a> |
| <h3 class="section">7.20 <code>.cfi_offset <var>register</var>, <var>offset</var></code></h3> |
| <p>Previous value of <var>register</var> is saved at offset <var>offset</var> from |
| CFA. |
| </p> |
| <a name="g_t_002ecfi_005frel_005foffset-register_002c-offset"></a> |
| <h3 class="section">7.21 <code>.cfi_rel_offset <var>register</var>, <var>offset</var></code></h3> |
| <p>Previous value of <var>register</var> is saved at offset <var>offset</var> from |
| the current CFA register. This is transformed to <code>.cfi_offset</code> |
| using the known displacement of the CFA register from the CFA. |
| This is often easier to use, because the number will match the |
| code it’s annotating. |
| </p> |
| <a name="g_t_002ecfi_005fregister-register1_002c-register2"></a> |
| <h3 class="section">7.22 <code>.cfi_register <var>register1</var>, <var>register2</var></code></h3> |
| <p>Previous value of <var>register1</var> is saved in register <var>register2</var>. |
| </p> |
| <a name="g_t_002ecfi_005frestore-register"></a> |
| <h3 class="section">7.23 <code>.cfi_restore <var>register</var></code></h3> |
| <p><code>.cfi_restore</code> says that the rule for <var>register</var> is now the |
| same as it was at the beginning of the function, after all initial |
| instruction added by <code>.cfi_startproc</code> were executed. |
| </p> |
| <a name="g_t_002ecfi_005fundefined-register"></a> |
| <h3 class="section">7.24 <code>.cfi_undefined <var>register</var></code></h3> |
| <p>From now on the previous value of <var>register</var> can’t be restored anymore. |
| </p> |
| <a name="g_t_002ecfi_005fsame_005fvalue-register"></a> |
| <h3 class="section">7.25 <code>.cfi_same_value <var>register</var></code></h3> |
| <p>Current value of <var>register</var> is the same like in the previous frame, |
| i.e. no restoration needed. |
| </p> |
| <a name="g_t_002ecfi_005fremember_005fstate_002c"></a> |
| <h3 class="section">7.26 <code>.cfi_remember_state</code>,</h3> |
| <p>First save all current rules for all registers by <code>.cfi_remember_state</code>, |
| then totally screw them up by subsequent <code>.cfi_*</code> directives and when |
| everything is hopelessly bad, use <code>.cfi_restore_state</code> to restore |
| the previous saved state. |
| </p> |
| <a name="g_t_002ecfi_005freturn_005fcolumn-register"></a> |
| <h3 class="section">7.27 <code>.cfi_return_column <var>register</var></code></h3> |
| <p>Change return column <var>register</var>, i.e. the return address is either |
| directly in <var>register</var> or can be accessed by rules for <var>register</var>. |
| </p> |
| <a name="g_t_002ecfi_005fsignal_005fframe"></a> |
| <h3 class="section">7.28 <code>.cfi_signal_frame</code></h3> |
| <p>Mark current function as signal trampoline. |
| </p> |
| <a name="g_t_002ecfi_005fwindow_005fsave"></a> |
| <h3 class="section">7.29 <code>.cfi_window_save</code></h3> |
| <p>SPARC register window has been saved. |
| </p> |
| <a name="g_t_002ecfi_005fescape-expression_005b_002c-_2026_005d"></a> |
| <h3 class="section">7.30 <code>.cfi_escape</code> <var>expression</var>[, …]</h3> |
| <p>Allows the user to add arbitrary bytes to the unwind info. One |
| might use this to add OS-specific CFI opcodes, or generic CFI |
| opcodes that GAS does not yet support. |
| </p> |
| <a name="g_t_002ecfi_005fval_005fencoded_005faddr-register_002c-encoding_002c-label"></a> |
| <h3 class="section">7.31 <code>.cfi_val_encoded_addr <var>register</var>, <var>encoding</var>, <var>label</var></code></h3> |
| <p>The current value of <var>register</var> is <var>label</var>. The value of <var>label</var> |
| will be encoded in the output file according to <var>encoding</var>; see the |
| description of <code>.cfi_personality</code> for details on this encoding. |
| </p> |
| <p>The usefulness of equating a register to a fixed label is probably |
| limited to the return address register. Here, it can be useful to |
| mark a code segment that has only one return address which is reached |
| by a direct branch and no copy of the return address exists in memory |
| or another register. |
| </p> |
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