[bc82645e] | 1 | <sect1 id="ch05-locking-glibc">
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| 2 | <title>"Locking in" Glibc</title>
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| 3 | <?dbhtml filename="lockingglibc.html" dir="chapter05"?>
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| 4 |
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[1f30432] | 5 | <para>Now that the temporary C libraries have been installed, we want all
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| 6 | the tools compiled in the rest of this chapter to be linked against these
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[d1391f0] | 7 | libraries. To accomplish this, we need to adjust the linker and the compiler's
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| 8 | specs file.</para>
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[bc82645e] | 9 |
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[d1391f0] | 10 | <para>First install the adjusted linker by running the following from within
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| 11 | the <filename class="directory">binutils-build</filename> directory:</para>
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[2cff2cc] | 12 |
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[21ba4e3] | 13 | <screen><userinput>make -C ld install</userinput></screen>
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[bc82645e] | 14 |
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[d1391f0] | 15 | <para>The linker was adjusted a little while back, at the end of the first
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| 16 | pass of Binutils. From this point onwards everything will link <emphasis>only
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| 17 | </emphasis> against the libraries in <filename>/tools/lib</filename>.</para>
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[78deb7d] | 18 |
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[a6505d9] | 19 | <note><para>If you somehow missed the earlier warning to retain the Binutils
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| 20 | source and build directories from the first pass or otherwise accidentally
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| 21 | deleted them or just don't have access to them, don't worry, all is not lost.
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| 22 | Just ignore the above command. The result is a small chance of subsequent
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| 23 | programs linking against libraries on the host. This is not ideal, however,
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| 24 | it's not a major problem. The situation is corrected when we install the
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| 25 | second pass of Binutils later on.</para></note>
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| 26 |
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[d1391f0] | 27 | <para>Now that the adjusted linker is installed, you have to remove the
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| 28 | Binutils build and source directories.</para>
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[66e4325] | 29 |
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[c9398bc] | 30 | <para>The next thing to do is to amend our GCC specs file so that it points
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[66e4325] | 31 | to the new dynamic linker. A simple sed will accomplish this:</para>
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[d5f8a8f] | 32 |
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| 33 | <!-- Ampersands are needed to allow cut and paste -->
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[66e4325] | 34 |
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[d5f8a8f] | 35 | <screen><userinput>SPECFILE=/tools/lib/gcc-lib/*/*/specs &&
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[65e5785] | 36 | sed -e 's@ /lib/ld-linux.so.2@ /tools/lib/ld-linux.so.2@g' \
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[360e2c4] | 37 | $SPECFILE > tempspecfile &&
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[d5f8a8f] | 38 | mv -f tempspecfile $SPECFILE &&
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[21ba4e3] | 39 | unset SPECFILE</userinput></screen>
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[bc82645e] | 40 |
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[f57e3d1] | 41 | <para>We recommend that you cut-and-paste the above rather than try and type it
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| 42 | all in. Or you can edit the specs file by hand if you want to: just replace any
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| 43 | occurrence of "/lib/ld-linux.so.2" with "/tools/lib/ld-linux.so.2".</para>
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| 44 |
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| 45 | <important><para>If you are working on a platform where the name of the dynamic
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| 46 | linker is something other than <filename>ld-linux.so.2</filename>, you
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| 47 | <emphasis>must</emphasis> substitute <filename>ld-linux.so.2</filename> with the
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[cd40510a] | 48 | name of your platform's dynamic linker in the above commands. Refer back to
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| 49 | <xref linkend="ch05-toolchaintechnotes"/> if necessary.</para></important>
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[66e4325] | 50 |
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[be2dd91] | 51 | <para>Lastly, there is a possibility that some include files from the host
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[1e163254] | 52 | system have found their way into GCC's private include dir. This can happen
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[fa2e693] | 53 | because of GCC's "fixincludes" process which runs as part of the GCC build.
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| 54 | We'll explain more about this further on in this chapter. For now, run the
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[783c041] | 55 | following commands to eliminate this possibility:</para>
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[be2dd91] | 56 |
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[21ba4e3] | 57 | <screen><userinput>rm -f /tools/lib/gcc-lib/*/*/include/{pthread.h,bits/sigthread.h}</userinput></screen>
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[40b88c2] | 58 |
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[0594698] | 59 | <!-- HACK - Force some whitespace to appease tidy -->
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| 60 | <literallayout></literallayout>
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| 61 |
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[783c041] | 62 | <caution><para>It is imperative at this point to stop and ensure that the basic
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| 63 | functions (compiling and linking) of the new toolchain are working as expected.
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| 64 | For this we are going to perform a simple sanity check:</para>
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[1f53626] | 65 |
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[360e2c4] | 66 | <screen><userinput>echo 'main(){}' > dummy.c
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[1f53626] | 67 | gcc dummy.c
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[21ba4e3] | 68 | readelf -l a.out | grep ': /tools'</userinput></screen>
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[1f53626] | 69 |
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[783c041] | 70 | <para>If everything is working correctly, there should be no errors, and the
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| 71 | output of the last command will be:</para>
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[1f53626] | 72 |
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[7e602eab] | 73 | <blockquote><screen>[Requesting program interpreter: /tools/lib/ld-linux.so.2]</screen></blockquote>
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[1f53626] | 74 |
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[6267e8e] | 75 | <para>If you did not receive the output as shown above, or received no output at
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| 76 | all, then something is seriously wrong. You will need to investigate and retrace
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| 77 | your steps to find out where the problem is and correct it. There is no point in
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| 78 | continuing until this is done. Most likely something went wrong with the specs
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| 79 | file amendment above. Note especially that <filename>/tools/lib</filename>
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| 80 | appears as the prefix of our dynamic linker. Of course, if you are working on a
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[1f53626] | 81 | platform where the name of the dynamic linker is something other than
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[6267e8e] | 82 | <filename>ld-linux.so.2</filename>, then the output will be slightly
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| 83 | different.</para>
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[1f53626] | 84 |
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| 85 | <para>Once you are satisfied that all is well, clean up the test files:</para>
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| 86 |
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[21ba4e3] | 87 | <screen><userinput>rm dummy.c a.out</userinput></screen>
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[1f53626] | 88 | </caution>
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| 89 |
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[e3a72b1] | 90 | <!-- HACK - Force some whitespace to appease tidy -->
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| 91 | <literallayout></literallayout>
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| 92 |
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[783c041] | 93 | <para>This completes the installation of the self-contained toolchain, and it
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[66e4325] | 94 | can now be used to build the rest of the temporary tools.</para>
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| 95 |
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[bc82645e] | 96 | </sect1>
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| 97 |
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