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154 lines
7.2 KiB
HTML
154 lines
7.2 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- This file documents the GNU linker LD
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(SiFive Binutils 2.32.0-2020.04.1)
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version 2.32.
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Copyright (C) 1991-2019 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 1.3
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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Back-Cover Texts. A copy of the license is included in the
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section entitled "GNU Free Documentation License". -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>PowerPC ELF32 (LD)</title>
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<meta name="description" content="PowerPC ELF32 (LD)">
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<meta name="keywords" content="PowerPC ELF32 (LD)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="LD-Index.html#LD-Index" rel="index" title="LD Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Machine-Dependent.html#Machine-Dependent" rel="up" title="Machine Dependent">
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<link href="PowerPC64-ELF64.html#PowerPC64-ELF64" rel="next" title="PowerPC64 ELF64">
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<link href="Nios-II.html#Nios-II" rel="prev" title="Nios II">
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<style type="text/css">
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-->
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</style>
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</head>
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<body lang="en">
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<a name="PowerPC-ELF32"></a>
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<div class="header">
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<p>
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Next: <a href="PowerPC64-ELF64.html#PowerPC64-ELF64" accesskey="n" rel="next">PowerPC64 ELF64</a>, Previous: <a href="Nios-II.html#Nios-II" accesskey="p" rel="prev">Nios II</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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</div>
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<hr>
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<a name="ld-and-PowerPC-32_002dbit-ELF-Support"></a>
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<h3 class="section">4.11 <code>ld</code> and PowerPC 32-bit ELF Support</h3>
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<a name="index-PowerPC-long-branches"></a>
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<a name="index-_002d_002drelax-on-PowerPC"></a>
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<p>Branches on PowerPC processors are limited to a signed 26-bit
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displacement, which may result in <code>ld</code> giving
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‘<samp>relocation truncated to fit</samp>’ errors with very large programs.
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‘<samp>--relax</samp>’ 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. You may combine ‘<samp>-r</samp>’ and
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‘<samp>--relax</samp>’ to add trampolines in a partial link. In that case
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both branches to undefined symbols and inter-section branches are also
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considered potentially out of range, and trampolines inserted.
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</p>
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<a name="index-PowerPC-ELF32-options"></a>
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<dl compact="compact">
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<dd><a name="index-PowerPC-PLT"></a>
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<a name="index-_002d_002dbss_002dplt"></a>
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</dd>
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<dt><samp>--bss-plt</samp></dt>
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<dd><p>Current PowerPC GCC accepts a ‘<samp>-msecure-plt</samp>’ 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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<code>ld</code> 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 ‘<samp>-msecure-plt</samp>’. ‘<samp>--bss-plt</samp>’ forces the old
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BSS PLT (and GOT layout) which can give slightly better performance.
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</p>
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<a name="index-_002d_002dsecure_002dplt"></a>
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</dd>
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<dt><samp>--secure-plt</samp></dt>
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<dd><p><code>ld</code> will use the new PLT and GOT layout if it is linking new
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‘<samp>-fpic</samp>’ or ‘<samp>-fPIC</samp>’ 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>
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<a name="index-PowerPC-GOT"></a>
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<a name="index-_002d_002dsdata_002dgot"></a>
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</dd>
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<dt><samp>--sdata-got</samp></dt>
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<dd><p>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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‘<samp>-z relro -z now</samp>’. 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. ‘<samp>--sdata-got</samp>’ 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>
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<a name="index-PowerPC-stub-symbols"></a>
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<a name="index-_002d_002demit_002dstub_002dsyms"></a>
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</dd>
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<dt><samp>--emit-stub-syms</samp></dt>
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<dd><p>This option causes <code>ld</code> to label linker stubs with a local
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symbol that encodes the stub type and destination.
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</p>
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<a name="index-PowerPC-TLS-optimization"></a>
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<a name="index-_002d_002dno_002dtls_002doptimize"></a>
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</dd>
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<dt><samp>--no-tls-optimize</samp></dt>
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<dd><p>PowerPC <code>ld</code> 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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</p></dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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Next: <a href="PowerPC64-ELF64.html#PowerPC64-ELF64" accesskey="n" rel="next">PowerPC64 ELF64</a>, Previous: <a href="Nios-II.html#Nios-II" accesskey="p" rel="prev">Nios II</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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</div>
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</body>
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</html>
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