<html lang="en"> <head> <title>PowerPC ELF32 - Untitled</title> <meta http-equiv="Content-Type" content="text/html"> <meta name="description" content="Untitled"> <meta name="generator" content="makeinfo 4.13"> <link title="Top" rel="start" href="index.html#Top"> <link rel="up" href="Machine-Dependent.html#Machine-Dependent" title="Machine Dependent"> <link rel="prev" href="Nios-II.html#Nios-II" title="Nios II"> <link rel="next" href="PowerPC64-ELF64.html#PowerPC64-ELF64" title="PowerPC64 ELF64"> <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> <!-- This file documents the GNU linker LD (GNU Binutils) version 2.26. Copyright (C) 1991-2015 Free Software Foundation, Inc. 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A copy of the license is included in the section entitled ``GNU Free Documentation License''.--> <meta http-equiv="Content-Style-Type" content="text/css"> <style type="text/css"><!-- pre.display { font-family:inherit } pre.format { font-family:inherit } pre.smalldisplay { font-family:inherit; font-size:smaller } pre.smallformat { font-family:inherit; font-size:smaller } pre.smallexample { font-size:smaller } pre.smalllisp { font-size:smaller } span.sc { font-variant:small-caps } span.roman { font-family:serif; font-weight:normal; } span.sansserif { font-family:sans-serif; font-weight:normal; } --></style> </head> <body> <div class="node"> <a name="PowerPC-ELF32"></a> <p> Next: <a rel="next" accesskey="n" href="PowerPC64-ELF64.html#PowerPC64-ELF64">PowerPC64 ELF64</a>, Previous: <a rel="previous" accesskey="p" href="Nios-II.html#Nios-II">Nios II</a>, Up: <a rel="up" accesskey="u" href="Machine-Dependent.html#Machine-Dependent">Machine Dependent</a> <hr> </div> <h3 class="section">4.12 <samp><span class="command">ld</span></samp> and PowerPC 32-bit ELF Support</h3> <p><a name="index-PowerPC-long-branches-663"></a><a name="index-g_t_002d_002drelax-on-PowerPC-664"></a>Branches on PowerPC processors are limited to a signed 26-bit displacement, which may result in <samp><span class="command">ld</span></samp> giving ‘<samp><span class="samp">relocation truncated to fit</span></samp>’ errors with very large programs. ‘<samp><span class="samp">--relax</span></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><span class="samp">-r</span></samp>’ and ‘<samp><span class="samp">--relax</span></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-665"></a> <a name="index-PowerPC-PLT-666"></a> <a name="index-g_t_002d_002dbss_002dplt-667"></a> <dl><dt><samp><span class="option">--bss-plt</span></samp><dd>Current PowerPC GCC accepts a ‘<samp><span class="samp">-msecure-plt</span></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 <samp><span class="command">ld</span></samp> will generate this layout, including stubs to access the PLT, if all input files (including startup and static libraries) were compiled with ‘<samp><span class="samp">-msecure-plt</span></samp>’. ‘<samp><span class="samp">--bss-plt</span></samp>’ forces the old BSS PLT (and GOT layout) which can give slightly better performance. <p><a name="index-g_t_002d_002dsecure_002dplt-668"></a><br><dt><samp><span class="option">--secure-plt</span></samp><dd><samp><span class="command">ld</span></samp> will use the new PLT and GOT layout if it is linking new ‘<samp><span class="samp">-fpic</span></samp>’ or ‘<samp><span class="samp">-fPIC</span></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-669"></a><a name="index-g_t_002d_002dsdata_002dgot-670"></a><br><dt><samp><span class="option">--sdata-got</span></samp><dd>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><span class="samp">-z relro -z now</span></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><span class="samp">--sdata-got</span></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-671"></a><a name="index-g_t_002d_002demit_002dstub_002dsyms-672"></a><br><dt><samp><span class="option">--emit-stub-syms</span></samp><dd>This option causes <samp><span class="command">ld</span></samp> to label linker stubs with a local symbol that encodes the stub type and destination. <p><a name="index-PowerPC-TLS-optimization-673"></a><a name="index-g_t_002d_002dno_002dtls_002doptimize-674"></a><br><dt><samp><span class="option">--no-tls-optimize</span></samp><dd>PowerPC <samp><span class="command">ld</span></samp> normally performs some optimization of code sequences used to access Thread-Local Storage. Use this option to disable the optimization. </dl> </body></html>