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| <a name="PowerPC-ELF32"></a> |
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| Next: <a href="PowerPC64-ELF64.html#PowerPC64-ELF64" accesskey="n" rel="next">PowerPC64 ELF64</a>, Previous: <a href="MSP430.html#MSP430" accesskey="p" rel="prev">MSP430</a>, Up: <a href="Machine-Dependent.html#Machine-Dependent" accesskey="u" rel="up">Machine Dependent</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="LD-Index.html#LD-Index" title="Index" rel="index">Index</a>]</p> |
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| <hr> |
| <a name="ld-and-PowerPC-32_002dbit-ELF-Support"></a> |
| <h3 class="section">4.10 <code>ld</code> and PowerPC 32-bit ELF Support</h3> |
| <a name="index-PowerPC-long-branches"></a> |
| <a name="index-_002d_002drelax-on-PowerPC"></a> |
| <p>Branches on PowerPC processors are limited to a signed 26-bit |
| displacement, which may result in <code>ld</code> giving |
| ‘<samp>relocation truncated to fit</samp>’ errors with very large programs. |
| ‘<samp>--relax</samp>’ enables the generation of trampolines that can access |
| the entire 32-bit address space. These trampolines are inserted at |
| section boundaries, so may not themselves be reachable if an input |
| section exceeds 33M in size. You may combine ‘<samp>-r</samp>’ and |
| ‘<samp>--relax</samp>’ to add trampolines in a partial link. In that case |
| both branches to undefined symbols and inter-section branches are also |
| considered potentially out of range, and trampolines inserted. |
| </p> |
| <a name="index-PowerPC-ELF32-options"></a> |
| <dl compact="compact"> |
| <dd><a name="index-PowerPC-PLT"></a> |
| <a name="index-_002d_002dbss_002dplt"></a> |
| </dd> |
| <dt><samp>--bss-plt</samp></dt> |
| <dd><p>Current PowerPC GCC accepts a ‘<samp>-msecure-plt</samp>’ option that |
| generates code capable of using a newer PLT and GOT layout that has |
| the security advantage of no executable section ever needing to be |
| writable and no writable section ever being executable. PowerPC |
| <code>ld</code> will generate this layout, including stubs to access the |
| PLT, if all input files (including startup and static libraries) were |
| compiled with ‘<samp>-msecure-plt</samp>’. ‘<samp>--bss-plt</samp>’ forces the old |
| BSS PLT (and GOT layout) which can give slightly better performance. |
| </p> |
| <a name="index-_002d_002dsecure_002dplt"></a> |
| </dd> |
| <dt><samp>--secure-plt</samp></dt> |
| <dd><p><code>ld</code> will use the new PLT and GOT layout if it is linking new |
| ‘<samp>-fpic</samp>’ or ‘<samp>-fPIC</samp>’ code, but does not do so automatically |
| when linking non-PIC code. This option requests the new PLT and GOT |
| layout. A warning will be given if some object file requires the old |
| style BSS PLT. |
| </p> |
| <a name="index-PowerPC-GOT"></a> |
| <a name="index-_002d_002dsdata_002dgot"></a> |
| </dd> |
| <dt><samp>--sdata-got</samp></dt> |
| <dd><p>The new secure PLT and GOT are placed differently relative to other |
| sections compared to older BSS PLT and GOT placement. The location of |
| <code>.plt</code> must change because the new secure PLT is an initialized |
| section while the old PLT is uninitialized. The reason for the |
| <code>.got</code> change is more subtle: The new placement allows |
| <code>.got</code> to be read-only in applications linked with |
| ‘<samp>-z relro -z now</samp>’. However, this placement means that |
| <code>.sdata</code> cannot always be used in shared libraries, because the |
| PowerPC ABI accesses <code>.sdata</code> in shared libraries from the GOT |
| pointer. ‘<samp>--sdata-got</samp>’ forces the old GOT placement. PowerPC |
| GCC doesn’t use <code>.sdata</code> in shared libraries, so this option is |
| really only useful for other compilers that may do so. |
| </p> |
| <a name="index-PowerPC-stub-symbols"></a> |
| <a name="index-_002d_002demit_002dstub_002dsyms"></a> |
| </dd> |
| <dt><samp>--emit-stub-syms</samp></dt> |
| <dd><p>This option causes <code>ld</code> to label linker stubs with a local |
| symbol that encodes the stub type and destination. |
| </p> |
| <a name="index-PowerPC-TLS-optimization"></a> |
| <a name="index-_002d_002dno_002dtls_002doptimize"></a> |
| </dd> |
| <dt><samp>--no-tls-optimize</samp></dt> |
| <dd><p>PowerPC <code>ld</code> normally performs some optimization of code |
| sequences used to access Thread-Local Storage. Use this option to |
| disable the optimization. |
| </p></dd> |
| </dl> |
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| Next: <a href="PowerPC64-ELF64.html#PowerPC64-ELF64" accesskey="n" rel="next">PowerPC64 ELF64</a>, Previous: <a href="MSP430.html#MSP430" accesskey="p" rel="prev">MSP430</a>, Up: <a href="Machine-Dependent.html#Machine-Dependent" accesskey="u" rel="up">Machine Dependent</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="LD-Index.html#LD-Index" title="Index" rel="index">Index</a>]</p> |
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