[673b0d8] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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[1770019] | 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN" "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
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[673b0d8] | 3 | <!ENTITY % general-entities SYSTEM "../general.ent">
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| 4 | %general-entities;
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| 5 | ]>
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| 6 | <sect1 id="ch-system-readjusting">
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[d72e04a] | 7 | <title>Re-adjusting the Toolchain</title>
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[673b0d8] | 8 | <?dbhtml filename="readjusting.html"?>
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| 9 |
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[2645ec6] | 10 | <para>Now that the final C libraries have been installed, it is time to adjust
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| 11 | the toolchain again. The toolchain will be adjusted so that it will link any
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[e6ab4b5] | 12 | newly compiled program against these new libraries. This is a similar process
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[2645ec6] | 13 | used in the <quote>Adjusting</quote> phase in the beginning of <xref
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| 14 | linkend="chapter-temporary-tools"/>, but with the adjustments reversed. In <xref
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| 15 | linkend="chapter-temporary-tools"/>, the chain was guided from the host's
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| 16 | <filename class="directory">/{,usr/}lib</filename> directories to the new
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| 17 | <filename class="directory">/tools/lib</filename> directory. Now, the chain will
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| 18 | be guided from that same <filename class="directory">/tools/lib</filename>
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| 19 | directory to the LFS <filename class="directory">/{,usr/}lib</filename>
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| 20 | directories.</para>
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[81fd230] | 21 |
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[e6ab4b5] | 22 | <para>First, backup the <filename class="directory">/tools</filename> linker, and
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| 23 | replace it with the adjusted linker we made in chapter 5. We'll also create a
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| 24 | link to its counterpart in <filename class="directory">/tools/$(gcc -dumpmachine)/bin</filename>.</para>
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| 25 |
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| 26 | <screen><userinput>mv -v /tools/bin/{ld,ld-old}
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| 27 | mv -v /tools/$(gcc -dumpmachine)/bin/{ld,ld-old}
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| 28 | mv -v /tools/bin/{ld-new,ld}
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| 29 | ln -sv /tools/bin/ld /tools/$(gcc -dumpmachine)/bin/ld</userinput></screen>
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[81fd230] | 30 |
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| 31 | <para>Next, amend the GCC specs file so that it points to the new
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[e6ab4b5] | 32 | dynamic linker, and so that GCC knows where to find its start files.
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| 33 | A <command>perl</command> command accomplishes this:</para>
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[673b0d8] | 34 |
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[e6ab4b5] | 35 | <screen><userinput>gcc -dumpspecs | \
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| 36 | perl -p -e 's@/tools/lib/ld-linux.so.2@/lib/ld-linux.so.2@g;' \
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| 37 | -e 's@\*startfile_prefix_spec:\n@$_/usr/lib/ @g;' > \
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| 38 | `dirname $(gcc --print-libgcc-file-name)`/specs
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| 39 | </userinput></screen>
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[673b0d8] | 40 |
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[81fd230] | 41 | <para>It is a good idea to visually inspect the specs file to verify the intended
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| 42 | change was actually made.</para>
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| 43 |
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| 44 | <important><para>If working on a platform where the name of the
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| 45 | dynamic linker is something other than
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| 46 | <filename class="libraryfile">ld-linux.so.2</filename>, substitute
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| 47 | <quote>ld-linux.so.2</quote> with the name of the platform's
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| 48 | dynamic linker in the above commands. Refer back to <xref
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| 49 | linkend="ch-tools-toolchaintechnotes" role=","/> if
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| 50 | necessary.</para></important>
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| 51 |
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| 52 | <caution><para>It is imperative at this point to stop and ensure that
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| 53 | the basic functions (compiling and linking) of the adjusted toolchain
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| 54 | are working as expected. To do this, perform a sanity
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| 55 | check:</para>
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[673b0d8] | 56 |
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| 57 | <screen><userinput>echo 'main(){}' > dummy.c
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[e6ab4b5] | 58 | cc dummy.c -Wl,--verbose &> dummy.log
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[673b0d8] | 59 | readelf -l a.out | grep ': /lib'</userinput></screen>
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| 60 |
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[81fd230] | 61 | <para>If everything is working correctly, there should be no errors,
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| 62 | and the output of the last command will be (allowing for
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| 63 | platform-specific differences in dynamic linker name):</para>
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[673b0d8] | 64 |
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[8ad7980] | 65 | <screen><computeroutput>[Requesting program interpreter: /lib/ld-linux.so.2]</computeroutput></screen>
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[673b0d8] | 66 |
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[81fd230] | 67 | <para>Note that <filename class="directory">/lib</filename> is now
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| 68 | the prefix of our dynamic linker.</para>
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[673b0d8] | 69 |
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[e6ab4b5] | 70 | <para>Now make sure that we're setup to use the correct start files:</para>
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| 71 |
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| 72 | <screen><userinput>grep "/usr/lib/crt.* " dummy.log</userinput></screen>
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| 73 |
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| 74 | <para>If everything is working correctly, there should be no errors,
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| 75 | and the output of the last command will be:</para>
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| 76 |
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| 77 | <screen><computeroutput>attempt to open /usr/lib/crt1.o succeeded
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| 78 | attempt to open /usr/lib/crti.o succeeded
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| 79 | attempt to open /usr/lib/crtn.o succeeded</computeroutput></screen>
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| 80 |
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| 81 | <para>Next make sure that we're using the correct libc:</para>
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| 82 |
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| 83 | <screen><userinput>grep "/lib/libc.so.6 " dummy.log</userinput></screen>
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| 84 |
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| 85 | <para>If everything is working correctly, there should be no errors,
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| 86 | and the output of the last command will be:</para>
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| 87 |
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| 88 | <screen><computeroutput>attempt to open /lib/libc.so.6 succeeded</computeroutput></screen>
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| 89 |
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| 90 | <para>Lastly, make sure GCC is using the correct dynamic linker:</para>
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| 91 |
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| 92 | <screen><userinput>grep found dummy.log</userinput></screen>
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| 93 |
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| 94 | <para>If everything is working correctly, there should be no errors,
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| 95 | and the output of the last command will be (allowing for
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| 96 | platform-specific differences in dynamic linker name):</para>
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| 97 |
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| 98 | <screen><computeroutput>found ld-linux.so.2 at /lib/ld-linux.so.2</computeroutput></screen>
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| 99 |
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[81fd230] | 100 | <para>If the output does not appear as shown above or is not received
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| 101 | at all, then something is seriously wrong. Investigate and retrace the
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| 102 | steps to find out where the problem is and correct it. The most likely
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| 103 | reason is that something went wrong with the specs file amendment
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| 104 | above. Any issues will need to be resolved before continuing on with
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| 105 | the process.</para>
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[673b0d8] | 106 |
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[81fd230] | 107 | <para>Once everything is working correctly, clean up the test
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| 108 | files:</para>
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| 109 |
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[e6ab4b5] | 110 | <screen><userinput>rm -v dummy.c a.out dummy.log</userinput></screen></caution>
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[673b0d8] | 111 |
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| 112 | </sect1>
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[81fd230] | 113 |
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