[bc82645e] | 1 | <sect1 id="ch06-adjustingtoolchain">
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[1f30432] | 2 | <title>Re-adjusting the toolchain</title>
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[bc82645e] | 3 | <?dbhtml filename="adjustingtoolchain.html" dir="chapter06"?>
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| 4 |
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[1f30432] | 5 | <para>Now that the new C libraries have been installed, it's time to re-adjust
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| 6 | our toolchain. We'll adjust it so that it will link any newly compiled program
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| 7 | against the new C libraries. Basically, this is the reverse of what we did
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| 8 | in the "Locking in" stage in the beginning of the previous chapter.</para>
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[460ac758] | 9 |
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[d1391f0] | 10 | <para>The first thing to do is to adjust the linker. For this we retained the
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| 11 | source and build directories from the second pass over Binutils. Install the
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| 12 | adjusted linker by running the following from within the
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[1f30432] | 13 | <filename class="directory">binutils-build</filename> directory:</para>
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[460ac758] | 14 |
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[21ba4e3] | 15 | <screen><userinput>make -C ld INSTALL=/tools/bin/install install</userinput></screen>
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[460ac758] | 16 |
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[e4df1fc] | 17 | <note><para>If you somehow missed the earlier warning to retain the Binutils
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| 18 | source and build directories from the second pass in Chapter 5 or otherwise
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| 19 | accidentally deleted them or just don't have access to them, don't worry, all is
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[f57e3d1] | 20 | not lost. Just ignore the above command. The result will be that the next
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| 21 | package, Binutils, will link against the Glibc libraries in
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[e4df1fc] | 22 | <filename class="directory">/tools</filename> rather than
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| 23 | <filename class="directory">/usr</filename>. This is not ideal, however, our
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| 24 | testing has shown that the resulting Binutils program binaries should be
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| 25 | identical.</para></note>
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| 26 |
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[d1391f0] | 27 | <para>From now on every compiled program will link <emphasis>only</emphasis>
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[318e3c8] | 28 | against the libraries in <filename>/usr/lib</filename> and
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| 29 | <filename>/lib</filename>. The extra
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| 30 | <userinput>INSTALL=/tools/bin/install</userinput> is needed because the Makefile
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| 31 | created during the second pass still contains the reference to
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| 32 | <filename>/usr/bin/install</filename>, which we obviously haven't installed yet.
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| 33 | Some host distributions contain a <filename class="symlink">ginstall</filename>
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| 34 | symbolic link which takes precedence in the Makefile and thus can cause a
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| 35 | problem here. The above command takes care of this also.</para>
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[460ac758] | 36 |
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| 37 | <para>You can now remove the Binutils source and build directories.</para>
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[a5b2aa9] | 38 |
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[460ac758] | 39 | <para>The next thing to do is to amend our GCC specs file so that it points
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| 40 | to the new dynamic linker. Just like earlier on, we use a sed to accomplish
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| 41 | this:</para>
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| 42 |
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[d5f8a8f] | 43 | <!-- Ampersands are needed to allow cut and paste -->
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| 44 |
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| 45 | <screen><userinput>SPECFILE=/tools/lib/gcc-lib/*/*/specs &&
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[f57e3d1] | 46 | sed -e 's@/tools/lib/ld-linux.so.2@/lib/ld-linux.so.2@g' \
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[d5f8a8f] | 47 | $SPECFILE > newspecfile &&
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| 48 | mv -f newspecfile $SPECFILE &&
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[21ba4e3] | 49 | unset SPECFILE</userinput></screen>
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[bc82645e] | 50 |
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[460ac758] | 51 | <para>Again, cutting and pasting the above is recommended. And just like
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[d1391f0] | 52 | before, it is a good idea to check the specs file to ensure the intended
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| 53 | changes were actually made.</para>
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[460ac758] | 54 |
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[f57e3d1] | 55 | <important><para>If you are working on a platform where the name of the dynamic
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| 56 | linker is something other than <filename>ld-linux.so.2</filename>, you
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| 57 | <emphasis>must</emphasis> substitute <filename>ld-linux.so.2</filename> with the
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[cd40510a] | 58 | name of your platform's dynamic linker in the above commands. Refer back to
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| 59 | <xref linkend="ch05-toolchaintechnotes"/> if necessary.</para></important>
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[f57e3d1] | 60 |
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[e3a72b1] | 61 | <!-- HACK - Force some whitespace to appease tidy -->
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| 62 | <literallayout></literallayout>
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| 63 |
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[1f53626] | 64 | <caution><para>It is imperative at this point to stop and ensure that the
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[76d113f] | 65 | basic functions (compiling and linking) of the adjusted toolchain are working
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| 66 | as expected. For this we are going to perform a simple sanity check:</para>
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[1f53626] | 67 |
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[21ba4e3] | 68 | <screen><userinput>echo 'main(){}' > dummy.c
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[1f53626] | 69 | gcc dummy.c
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[21ba4e3] | 70 | readelf -l a.out | grep ': /lib'</userinput></screen>
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[1f53626] | 71 |
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[76d113f] | 72 | <para>If everything is working correctly, there should be no errors, and the
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| 73 | output of the last command will be:</para>
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[1f53626] | 74 |
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[7e602eab] | 75 | <blockquote><screen>[Requesting program interpreter: /lib/ld-linux.so.2]</screen></blockquote>
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[1f53626] | 76 |
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[6267e8e] | 77 | <para>If you did not receive the output as shown above, or received no output at
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| 78 | all, then something is seriously wrong. You will need to investigate and retrace
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| 79 | your steps to find out where the problem is and correct it. There is no point in
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| 80 | continuing until this is done. Most likely something went wrong with the specs
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| 81 | file amendment above. Note especially that <filename>/lib</filename> now appears
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| 82 | as the prefix of our dynamic linker. Of course, if you are working on a platform
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[3993087] | 83 | where the name of the dynamic linker is something other than
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| 84 | <filename>ld-linux.so.2</filename>, then the output will be slightly
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| 85 | different.</para>
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[1f53626] | 86 |
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| 87 | <para>Once you are satisfied that all is well, clean up the test files:</para>
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| 88 |
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[21ba4e3] | 89 | <screen><userinput>rm dummy.c a.out</userinput></screen>
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[1f53626] | 90 | </caution>
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| 91 |
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[e3a72b1] | 92 | <!-- HACK - Force some whitespace to appease tidy -->
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| 93 | <literallayout></literallayout>
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| 94 |
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[bc82645e] | 95 | </sect1>
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| 96 |
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