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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
<!ENTITY % general-entities SYSTEM "../general.ent">
%general-entities;
]>
<sect1 id="ch-system-readjusting">
<?dbhtml filename="readjusting.html"?>
<title>Re-adjusting the Toolchain</title>
<para>Now that the final C libraries have been installed, it is time to adjust
the toolchain again. The toolchain will be adjusted so that it will link any
newly compiled program against these new libraries. This is a similar process
used in the <quote>Adjusting</quote> phase in the beginning of <xref
linkend="chapter-temporary-tools"/>, but with the adjustments reversed. In <xref
linkend="chapter-temporary-tools"/>, the chain was guided from the host's
<filename class="directory">/{,usr/}lib</filename> directories to the new
<filename class="directory">/tools/lib</filename> directory. Now, the chain will
be guided from that same <filename class="directory">/tools/lib</filename>
directory to the LFS <filename class="directory">/{,usr/}lib</filename>
directories.</para>
<para>First, backup the <filename class="directory">/tools</filename> linker,
and replace it with the adjusted linker we made in chapter 5. We'll also create
a link to its counterpart in <filename class="directory">/tools/$(gcc
-dumpmachine)/bin</filename>.</para>
<screen><userinput>mv -v /tools/bin/{ld,ld-old}
mv -v /tools/$(gcc -dumpmachine)/bin/{ld,ld-old}
mv -v /tools/bin/{ld-new,ld}
ln -sv /tools/bin/ld /tools/$(gcc -dumpmachine)/bin/ld</userinput></screen>
<para>Next, amend the GCC specs file so that it points to the new
dynamic linker, and so that GCC knows where to find its start files.
A <command>perl</command> command accomplishes this.</para>
<important>
<para>If working on a platform where the name of the dynamic linker is
something other than <filename class="libraryfile">ld-linux.so.2</filename>,
substitute <quote>ld-linux.so.2</quote> with the name of the platform's
dynamic linker in the following commands. Refer to <xref
linkend="ch-tools-toolchaintechnotes" role=","/> if necessary.</para>
</important>
<screen><userinput>gcc -dumpspecs | \
perl -p -e 's@/tools/lib/ld-linux.so.2@/lib/ld-linux.so.2@g;' \
-e 's@\*startfile_prefix_spec:\n@$_/usr/lib/ @g;' > \
`dirname $(gcc --print-libgcc-file-name)`/specs</userinput></screen>
<para>It is a good idea to visually inspect the specs file to verify the
intended change was actually made.</para>
<para>It is imperative at this point to ensure that the basic
functions (compiling and linking) of the adjusted toolchain are working
as expected. To do this, perform the following sanity checks:</para>
<screen role="nodump" os="a"><userinput>echo 'main(){}' > dummy.c
cc dummy.c -Wl,--verbose &> dummy.log
readelf -l a.out | grep ': /lib'</userinput></screen>
<para os="b">If everything is working correctly, there should be no errors,
and the output of the last command will be (allowing for
platform-specific differences in dynamic linker name):</para>
<screen os="c"><computeroutput>[Requesting program interpreter: /lib/ld-linux.so.2]</computeroutput></screen>
<para>Note that <filename class="directory">/lib</filename> is now
the prefix of our dynamic linker.</para>
<para os="d">Now make sure that we're setup to use the correct startfiles:</para>
<screen role="nodump" os="e"><userinput>grep -o '/usr/lib.*/crt[1in].* .*' dummy.log</userinput></screen>
<para os="f">If everything is working correctly, there should be no errors,
and the output of the last command will be:</para>
<screen><computeroutput>/usr/lib/crt1.o succeeded
/usr/lib/crti.o succeeded
/usr/lib/crtn.o succeeded</computeroutput></screen>
<para os="g">Next, verify that the new linker is being used with the correct search paths:</para>
<screen role="nodump" os="h"><userinput>grep 'SEARCH.*/usr/lib' dummy.log |sed 's|; |\n|g'</userinput></screen>
<para os="i">If everything is working correctly, there should be no errors,
and the output of the last command will be:</para>
<screen><computeroutput>SEARCH_DIR("/tools/i686-pc-linux-gnu/lib")
SEARCH_DIR("/usr/lib")
SEARCH_DIR("/lib");</computeroutput></screen>
<para os="j">Next make sure that we're using the correct libc:</para>
<screen role="nodump" os="k"><userinput>grep "/lib/libc.so.6 " dummy.log</userinput></screen>
<para os="l">If everything is working correctly, there should be no errors,
and the output of the last command will be:</para>
<screen os="m"><computeroutput>attempt to open /lib/libc.so.6 succeeded</computeroutput></screen>
<para os="n">Lastly, make sure GCC is using the correct dynamic linker:</para>
<screen role="nodump" os="o"><userinput>grep found dummy.log</userinput></screen>
<para os="p">If everything is working correctly, there should be no errors,
and the output of the last command will be (allowing for
platform-specific differences in dynamic linker name):</para>
<screen os="q"><computeroutput>found ld-linux.so.2 at /lib/ld-linux.so.2</computeroutput></screen>
<para os="r">If the output does not appear as shown above or is not received
at all, then something is seriously wrong. Investigate and retrace the
steps to find out where the problem is and correct it. The most likely
reason is that something went wrong with the specs file adjustment. Any
issues will need to be resolved before continuing on with the process.</para>
<para os="s">Once everything is working correctly, clean up the test files:</para>
<screen role="nodump" os="t"><userinput>rm -v dummy.c a.out dummy.log</userinput></screen>
</sect1>
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