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98 lines
4.6 KiB
XML
98 lines
4.6 KiB
XML
<sect1 id="ch05-locking-glibc">
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<title>"Locking in" Glibc</title>
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<?dbhtml filename="lockingglibc.html" dir="chapter05"?>
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<para>Now that the temporary C libraries have been installed, we want all
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the tools compiled in the rest of this chapter to be linked against these
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libraries. To accomplish this, we need to adjust the linker and the compiler's
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specs file.</para>
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<para>First install the adjusted linker by running the following from within
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the <filename class="directory">binutils-build</filename> directory:</para>
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<screen><userinput>make -C ld install</userinput></screen>
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<para>The linker was adjusted a little while back, at the end of the first
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pass of Binutils. From this point onwards everything will link <emphasis>only
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</emphasis> against the libraries in <filename>/tools/lib</filename>.</para>
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<note><para>If you somehow missed the earlier warning to retain the Binutils
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source and build directories from the first pass or otherwise accidentally
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deleted them or just don't have access to them, don't worry, all is not lost.
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Just ignore the above command. The result is a small chance of subsequent
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programs linking against libraries on the host. This is not ideal, however,
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it's not a major problem. The situation is corrected when we install the
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second pass of Binutils later on.</para></note>
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<para>Now that the adjusted linker is installed, you have to remove the
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Binutils build and source directories.</para>
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<para>The next thing to do is to amend our GCC specs file so that it points
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to the new dynamic linker. A simple sed will accomplish this:</para>
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<!-- Ampersands are needed to allow cut and paste -->
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<screen><userinput>SPECFILE=/tools/lib/gcc-lib/*/*/specs &&
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sed -e 's@/lib/ld-linux.so.2@/tools/lib/ld-linux.so.2@g' \
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$SPECFILE > tempspecfile &&
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mv -f tempspecfile $SPECFILE &&
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unset SPECFILE</userinput></screen>
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<para>We recommend that you cut-and-paste the above rather than try and type it
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all in. Or you can edit the specs file by hand if you want to: just replace any
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occurrence of "/lib/ld-linux.so.2" with "/tools/lib/ld-linux.so.2".</para>
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<important><para>If you are working on a platform where the name of the dynamic
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linker is something other than <filename>ld-linux.so.2</filename>, you
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<emphasis>must</emphasis> substitute <filename>ld-linux.so.2</filename> with the
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name of your platform's dynamic linker in the above commands. Refer back to
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<xref linkend="ch05-toolchaintechnotes"/> if necessary.</para></important>
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<para>Lastly, there is a possibility that some include files from the host
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system have found their way into GCC's private include dir. This can happen
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because of GCC's "fixincludes" process which runs as part of the GCC build.
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We'll explain more about this further on in this chapter. For now, run the
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following commands to eliminate this possibility:</para>
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<screen><userinput>rm -f /tools/lib/gcc-lib/*/*/include/{pthread.h,bits/sigthread.h}</userinput></screen>
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<!-- HACK - Force some whitespace to appease tidy -->
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<literallayout></literallayout>
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<caution><para>It is imperative at this point to stop and ensure that the basic
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functions (compiling and linking) of the new toolchain are working as expected.
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For this we are going to perform a simple sanity check:</para>
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<screen><userinput>echo 'main(){}' > dummy.c
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gcc dummy.c
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readelf -l a.out | grep ': /tools'</userinput></screen>
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<para>If everything is working correctly, there should be no errors, and the
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output of the last command will be:</para>
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<blockquote><screen>[Requesting program interpreter: /tools/lib/ld-linux.so.2]</screen></blockquote>
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<para>If you did not receive the output as shown above, or received no output at
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all, then something is seriously wrong. You will need to investigate and retrace
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your steps to find out where the problem is and correct it. There is no point in
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continuing until this is done. Most likely something went wrong with the specs
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file amendment above. Note especially that <filename>/tools/lib</filename>
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appears as the prefix of our dynamic linker. Of course, if you are working on a
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platform where the name of the dynamic linker is something other than
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<filename>ld-linux.so.2</filename>, then the output will be slightly
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different.</para>
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<para>Once you are satisfied that all is well, clean up the test files:</para>
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<screen><userinput>rm dummy.c a.out</userinput></screen>
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</caution>
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<!-- HACK - Force some whitespace to appease tidy -->
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<literallayout></literallayout>
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<para>This completes the installation of the self-contained toolchain, and it
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can now be used to build the rest of the temporary tools.</para>
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</sect1>
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