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68 lines
2.9 KiB
XML
68 lines
2.9 KiB
XML
<sect1 id="ch06-adjustingtoolchain">
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<title>Re-adjusting the toolchain</title>
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<?dbhtml filename="adjustingtoolchain.html" dir="chapter06"?>
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<para>Now that the new C libraries have been installed, it's time to re-adjust
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our toolchain. We'll adjust it so that it will link any newly compiled program
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against the new C libraries. Basically, this is the reverse of what we did
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in the "Locking in" stage in the beginning of the previous chapter.</para>
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<para>The first thing to do is to adjust the linker. For this we retained the
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source and build directories from the second pass over Binutils. Install the
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adjusted linker by running the following from within the
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<filename class="directory">binutils-build</filename> directory:</para>
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<para><screen><userinput>make -C ld install</userinput></screen></para>
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<para>From now on every compiled program will link <emphasis>only</emphasis>
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against the libraries in <filename>/usr/lib</filename> and <filename>/lib
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</filename>.</para>
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<para>You can now remove the Binutils source and build 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. Just like earlier on, we use a sed to accomplish
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this:</para>
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<para><screen><userinput>SPECFILE=/tools/lib/gcc-lib/*/*/specs
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sed -e 's@/tools/lib/ld.so.1@/lib/ld.so.1@g' \
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-e 's@/tools/lib/ld-linux.so.2@/lib/ld-linux.so.2@g' \
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$SPECFILE > newspecfile
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mv newspecfile $SPECFILE
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unset SPECFILE</userinput></screen></para>
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<para>Again, cutting and pasting the above is recommended. And just like
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before, it is a good idea to check the specs file to ensure the intended
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changes were actually made.</para>
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<caution><para>It is imperative at this point to stop and ensure that the
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basic functionality of the adjusted toolchain is working as expected. We are
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going to perform a simple sanity check:</para>
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<para><screen><userinput>echo 'main(){}' > dummy.c
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gcc dummy.c
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readelf -l a.out | grep ': /lib'</userinput></screen></para>
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<para>If everything is working correctly, the output of the last command will
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be:</para>
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<para><screen>[Requesting program interpreter: /lib/ld-linux.so.2]
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</screen></para>
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<para>If you did not receive the output as shown above then something is
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seriously wrong. You will need to investigate and retrace your steps to find
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out where the problem is and correct it. There is no point in continuing
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until this is done. Most likely, something went wrong with the specs file
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amendment above. Note especially that <filename>/lib</filename> now appears as
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the prefix of our dynamic linker. Of course, if you are working on a platform
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where the name of the dynamic linker is something other than <filename>
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ld-linux.so.2</filename> then the output will be slightly 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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<para><screen><userinput>rm dummy.c a.out</userinput></screen></para>
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</caution>
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</sect1>
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