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git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@3435 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689
102 lines
4.9 KiB
XML
102 lines
4.9 KiB
XML
<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN" "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [
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<!ENTITY % general-entities SYSTEM "../general.ent">
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%general-entities;
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]>
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<sect1 id="ch-system-readjusting">
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<title>Re-adjusting the toolchain</title>
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<?dbhtml filename="readjusting.html"?>
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<para>Now that the new and final C libraries have been installed, it's time to
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adjust our toolchain again. We'll adjust it so that it will link any newly
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compiled program against these new libraries. This is in fact the same thing we
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did in the <quote>Adjusting</quote> phase in the beginning of the previous
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chapter, even though it looks like the reverse: then we guided the chain from
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the host's <filename class="directory">/{,usr/}lib</filename> to the new
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<filename class="directory">/tools/lib</filename>, now we guide it from that
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same <filename class="directory">/tools/lib</filename> to the LFS's <filename
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class="directory">/{,usr/}lib</filename>.</para>
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<para>First we 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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<screen><userinput>make -C ld INSTALL=/tools/bin/install install</userinput></screen>
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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 second pass in
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<xref linkend="chapter-temporary-tools"/>, or otherwise accidentally deleted them or just
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don't have access to them, don't worry, all is not lost. Just ignore the above
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command. The result will be that the next package, Binutils, will link against
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the C libraries in <filename class="directory">/tools</filename> rather
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than in <filename class="directory">/{,usr/}lib</filename>. This is not ideal,
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however, our testing has shown that the resulting Binutils program binaries
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should be identical.</para></note>
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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
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<filename>/lib</filename>. The extra
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<emphasis>INSTALL=/tools/bin/install</emphasis> is needed because the Makefile
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created during the second pass still contains the reference to
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<filename>/usr/bin/install</filename>, which we obviously haven't installed yet.
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Some host distributions contain a <filename class="symlink">ginstall</filename>
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symbolic link which takes precedence in the Makefile and thus can cause a
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problem here. The above command takes care of this also.</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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<!-- 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@ /tools/lib/ld-linux.so.2@ /lib/ld-linux.so.2@g' \
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$SPECFILE > newspecfile &&
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mv -f newspecfile $SPECFILE &&
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unset SPECFILE</userinput></screen>
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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 visually inspect the specs file to verify the
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intended change was actually made.</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="ch-tools-toolchaintechnotes"/> if necessary.</para></important>
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<caution><para>It is imperative at this point to stop and ensure that the
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basic functions (compiling and linking) of the adjusted toolchain are working
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as expected. 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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cc dummy.c
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readelf -l a.out | grep ': /lib'</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 (allowing for platform specific differences
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in dynamic linker name):</para>
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<blockquote><screen>[Requesting program interpreter: /lib/ld-linux.so.2]</screen></blockquote>
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<para>Note especially that <filename class="directory">/lib</filename> is now
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the prefix of our dynamic linker.</para>
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<para> If you did not receive the output
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as shown above, or received no output at all, then something is seriously wrong.
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You will need to investigate and retrace your steps to find out where the
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problem is and correct it. There is no point in continuing until this is done.
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Most likely something went wrong with the specs file amendment above.</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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</sect1>
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