98 lines
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98 lines
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<!--
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This file documents the GNU linker LD
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(GNU Binutils)
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version 2.19.
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Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000,
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2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.1
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or any later version published by the Free Software Foundation;
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<a name="PowerPC-ELF32"></a>Next: <a rel="next" accesskey="n" href="PowerPC64-ELF64.html#PowerPC64-ELF64">PowerPC64 ELF64</a>,
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Previous: <a rel="previous" accesskey="p" href="M68HC11_002f68HC12.html#M68HC11_002f68HC12">M68HC11/68HC12</a>,
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<h3 class="section">4.9 <span class="command">ld</span> and PowerPC 32-bit ELF Support</h3>
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<p><a name="index-PowerPC-long-branches-567"></a><a name="index-_002d_002drelax-on-PowerPC-568"></a>Branches on PowerPC processors are limited to a signed 26-bit
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displacement, which may result in <span class="command">ld</span> giving
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<span class="samp">relocation truncated to fit</span> errors with very large programs.
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<span class="samp">--relax</span> enables the generation of trampolines that can access
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the entire 32-bit address space. These trampolines are inserted at
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section boundaries, so may not themselves be reachable if an input
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section exceeds 33M in size.
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<p><a name="index-PowerPC-ELF32-options-569"></a>
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<a name="index-PowerPC-PLT-570"></a>
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<a name="index-_002d_002dbss_002dplt-571"></a>
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<dl><dt><span class="option">--bss-plt</span><dd>Current PowerPC GCC accepts a <span class="samp">-msecure-plt</span> option that
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generates code capable of using a newer PLT and GOT layout that has
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the security advantage of no executable section ever needing to be
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writable and no writable section ever being executable. PowerPC
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<span class="command">ld</span> will generate this layout, including stubs to access the
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PLT, if all input files (including startup and static libraries) were
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compiled with <span class="samp">-msecure-plt</span>. <span class="samp">--bss-plt</span> forces the old
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BSS PLT (and GOT layout) which can give slightly better performance.
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<p><a name="index-_002d_002dsecure_002dplt-572"></a><br><dt><span class="option">--secure-plt</span><dd><span class="command">ld</span> will use the new PLT and GOT layout if it is linking new
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<span class="samp">-fpic</span> or <span class="samp">-fPIC</span> code, but does not do so automatically
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when linking non-PIC code. This option requests the new PLT and GOT
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layout. A warning will be given if some object file requires the old
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style BSS PLT.
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<p><a name="index-PowerPC-GOT-573"></a><a name="index-_002d_002dsdata_002dgot-574"></a><br><dt><span class="option">--sdata-got</span><dd>The new secure PLT and GOT are placed differently relative to other
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sections compared to older BSS PLT and GOT placement. The location of
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<code>.plt</code> must change because the new secure PLT is an initialized
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section while the old PLT is uninitialized. The reason for the
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<code>.got</code> change is more subtle: The new placement allows
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<code>.got</code> to be read-only in applications linked with
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<span class="samp">-z relro -z now</span>. However, this placement means that
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<code>.sdata</code> cannot always be used in shared libraries, because the
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PowerPC ABI accesses <code>.sdata</code> in shared libraries from the GOT
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pointer. <span class="samp">--sdata-got</span> forces the old GOT placement. PowerPC
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GCC doesn't use <code>.sdata</code> in shared libraries, so this option is
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really only useful for other compilers that may do so.
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<p><a name="index-PowerPC-stub-symbols-575"></a><a name="index-_002d_002demit_002dstub_002dsyms-576"></a><br><dt><span class="option">--emit-stub-syms</span><dd>This option causes <span class="command">ld</span> to label linker stubs with a local
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symbol that encodes the stub type and destination.
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<p><a name="index-PowerPC-TLS-optimization-577"></a><a name="index-_002d_002dno_002dtls_002doptimize-578"></a><br><dt><span class="option">--no-tls-optimize</span><dd>PowerPC <span class="command">ld</span> normally performs some optimization of code
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sequences used to access Thread-Local Storage. Use this option to
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disable the optimization.
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</dl>
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</body></html>
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