[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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[d1391f0] | 13 | <para><screen><userinput>make -C ld install</userinput></screen></para>
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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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[d1391f0] | 19 | <para>Now that the adjusted linker is installed, you have to remove the
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| 20 | Binutils build and source directories.</para>
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[66e4325] | 21 |
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[c9398bc] | 22 | <para>The next thing to do is to amend our GCC specs file so that it points
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[66e4325] | 23 | to the new dynamic linker. A simple sed will accomplish this:</para>
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| 24 |
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[148bb04] | 25 | <para><screen><userinput>SPECFILE=/tools/lib/gcc-lib/*/*/specs
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| 26 | sed -e 's@/lib/ld.so.1@/tools/lib/ld.so.1@g' \
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| 27 | -e 's@/lib/ld-linux.so.2@/tools/lib/ld-linux.so.2@g' \
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[1f30432] | 28 | $SPECFILE > tempspecfile
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| 29 | mv tempspecfile $SPECFILE
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[585ce08] | 30 | unset SPECFILE</userinput></screen></para>
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[bc82645e] | 31 |
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[7064daf] | 32 | <para>We recommend that you cut-and-paste the above rather than try and type it
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| 33 | all in. Or you can edit the specs file by hand if you want to: just replace
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| 34 | "/lib/ld-linux.so.2" with "/tools/lib/ld-linux.so.2" and "/lib/ld.so.1" with
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| 35 | "/tools/lib/ld.so.1".</para>
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[66e4325] | 36 |
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[be2dd91] | 37 | <para>Lastly, there is a possibility that some include files from the host
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[1e163254] | 38 | system have found their way into GCC's private include dir. This can happen
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[fa2e693] | 39 | because of GCC's "fixincludes" process which runs as part of the GCC build.
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| 40 | We'll explain more about this further on in this chapter. For now, run the
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[783c041] | 41 | following commands to eliminate this possibility:</para>
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[be2dd91] | 42 |
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[148bb04] | 43 | <para><screen><userinput>rm -f /tools/lib/gcc-lib/*/*/include/{pthread.h,bits/sigthread.h}</userinput></screen></para>
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[40b88c2] | 44 |
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[783c041] | 45 | <caution><para>It is imperative at this point to stop and ensure that the basic
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| 46 | functions (compiling and linking) of the new toolchain are working as expected.
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| 47 | For this we are going to perform a simple sanity check:</para>
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[1f53626] | 48 |
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| 49 | <para><screen><userinput>echo 'main(){}' > dummy.c
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| 50 | gcc dummy.c
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| 51 | readelf -l a.out | grep ': /tools'</userinput></screen></para>
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| 52 |
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[783c041] | 53 | <para>If everything is working correctly, there should be no errors, and the
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| 54 | output of the last command will be:</para>
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[1f53626] | 55 |
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[7e602eab] | 56 | <blockquote><screen>[Requesting program interpreter: /tools/lib/ld-linux.so.2]</screen></blockquote>
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[1f53626] | 57 |
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[783c041] | 58 | <para>If you did not receive the output as shown above, then something is
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[1f53626] | 59 | seriously wrong. You will need to investigate and retrace your steps to find
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| 60 | out where the problem is and correct it. There is no point in continuing
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[783c041] | 61 | until this is done. Most likely something went wrong with the specs file
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[1f53626] | 62 | amendment above. Note especially that <filename>/tools/lib</filename> appears
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| 63 | as the prefix of our dynamic linker. Of course, if you are working on a
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| 64 | platform where the name of the dynamic linker is something other than
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[783c041] | 65 | <filename>ld-linux.so.2</filename>, then the output will be slightly different.
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[1f53626] | 66 | </para>
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| 67 |
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| 68 | <para>Once you are satisfied that all is well, clean up the test files:</para>
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| 69 |
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| 70 | <para><screen><userinput>rm dummy.c a.out</userinput></screen></para>
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| 71 | </caution>
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| 72 |
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[783c041] | 73 | <para>This completes the installation of the self-contained toolchain, and it
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[66e4325] | 74 | can now be used to build the rest of the temporary tools.</para>
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| 75 |
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[bc82645e] | 76 | </sect1>
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| 77 |
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