[673b0d8] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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[3f3931b0] | 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
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| 3 | "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
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[673b0d8] | 4 | <!ENTITY % general-entities SYSTEM "../general.ent">
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| 5 | %general-entities;
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| 6 | ]>
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[3f3931b0] | 7 |
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[673b0d8] | 8 | <sect1 id="ch-system-readjusting">
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[3f3931b0] | 9 | <?dbhtml filename="readjusting.html"?>
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| 10 |
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| 11 | <title>Re-adjusting the Toolchain</title>
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| 12 |
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| 13 | <para>Now that the final C libraries have been installed, it is time to adjust
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| 14 | the toolchain again. The toolchain will be adjusted so that it will link any
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| 15 | newly compiled program against these new libraries. This is a similar process
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| 16 | used in the <quote>Adjusting</quote> phase in the beginning of <xref
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| 17 | linkend="chapter-temporary-tools"/>, but with the adjustments reversed. In <xref
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| 18 | linkend="chapter-temporary-tools"/>, the chain was guided from the host's
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| 19 | <filename class="directory">/{,usr/}lib</filename> directories to the new
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| 20 | <filename class="directory">/tools/lib</filename> directory. Now, the chain will
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| 21 | be guided from that same <filename class="directory">/tools/lib</filename>
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| 22 | directory to the LFS <filename class="directory">/{,usr/}lib</filename>
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| 23 | directories.</para>
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| 24 |
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| 25 | <para>First, backup the <filename class="directory">/tools</filename> linker,
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| 26 | and replace it with the adjusted linker we made in chapter 5. We'll also create
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| 27 | a link to its counterpart in <filename class="directory">/tools/$(gcc
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| 28 | -dumpmachine)/bin</filename>.</para>
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[2914987b] | 29 |
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[1ba726f] | 30 | <screen><userinput>mv -v /tools/bin/{ld,ld-old}
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[62d3362] | 31 | mv -v /tools/$(gcc -dumpmachine)/bin/{ld,ld-old}
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[1ba726f] | 32 | mv -v /tools/bin/{ld-new,ld}
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[62d3362] | 33 | ln -sv /tools/bin/ld /tools/$(gcc -dumpmachine)/bin/ld</userinput></screen>
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[2914987b] | 34 |
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[3f3931b0] | 35 | <para>Next, amend the GCC specs file so that it points to the new
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| 36 | dynamic linker, and so that GCC knows where to find its start files.
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| 37 | A <command>perl</command> command accomplishes this:</para>
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[673b0d8] | 38 |
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[1ba726f] | 39 | <screen><userinput>gcc -dumpspecs | \
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[b87ea87] | 40 | perl -p -e 's@/tools/lib/ld-linux.so.2@/lib/ld-linux.so.2@g;' \
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[3f3931b0] | 41 | -e 's@\*startfile_prefix_spec:\n@$_/usr/lib/ @g;' > \
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| 42 | `dirname $(gcc --print-libgcc-file-name)`/specs</userinput></screen>
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| 43 |
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| 44 | <para>It is a good idea to visually inspect the specs file to verify the
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| 45 | intended change was actually made.</para>
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| 46 |
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| 47 | <important>
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| 48 | <para>If working on a platform where the name of the dynamic linker is
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| 49 | something other than <filename class="libraryfile">ld-linux.so.2</filename>,
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| 50 | substitute <quote>ld-linux.so.2</quote> with the name of the platform's
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| 51 | dynamic linker in the above commands. Refer back to <xref
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| 52 | linkend="ch-tools-toolchaintechnotes" role=","/> if necessary.</para>
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| 53 | </important>
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| 54 |
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| 55 | <caution>
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| 56 | <para>It is imperative at this point to stop and ensure that the basic
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| 57 | functions (compiling and linking) of the adjusted toolchain are working
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| 58 | as expected. To do this, perform a sanity check:</para>
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[673b0d8] | 59 |
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| 60 | <screen><userinput>echo 'main(){}' > dummy.c
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[2914987b] | 61 | cc dummy.c -Wl,--verbose &> dummy.log
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[673b0d8] | 62 | readelf -l a.out | grep ': /lib'</userinput></screen>
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| 63 |
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[3f3931b0] | 64 | <para>If everything is working correctly, there should be no errors,
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| 65 | and the output of the last command will be (allowing for
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| 66 | platform-specific differences in dynamic linker name):</para>
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[673b0d8] | 67 |
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[8ad7980] | 68 | <screen><computeroutput>[Requesting program interpreter: /lib/ld-linux.so.2]</computeroutput></screen>
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[673b0d8] | 69 |
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[3f3931b0] | 70 | <para>Note that <filename class="directory">/lib</filename> is now
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| 71 | the prefix of our dynamic linker.</para>
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[673b0d8] | 72 |
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[3f3931b0] | 73 | <para>Now make sure that we're setup to use the correct start files:</para>
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[2914987b] | 74 |
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| 75 | <screen><userinput>grep "/usr/lib/crt.* " dummy.log</userinput></screen>
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| 76 |
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[3f3931b0] | 77 | <para>If everything is working correctly, there should be no errors,
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| 78 | and the output of the last command will be:</para>
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[2914987b] | 79 |
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| 80 | <screen><computeroutput>attempt to open /usr/lib/crt1.o succeeded
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| 81 | attempt to open /usr/lib/crti.o succeeded
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| 82 | attempt to open /usr/lib/crtn.o succeeded</computeroutput></screen>
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| 83 |
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[3f3931b0] | 84 | <para>Next make sure that we're using the correct libc:</para>
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[2914987b] | 85 |
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| 86 | <screen><userinput>grep "/lib/libc.so.6 " dummy.log</userinput></screen>
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| 87 |
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[3f3931b0] | 88 | <para>If everything is working correctly, there should be no errors,
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| 89 | and the output of the last command will be:</para>
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[2914987b] | 90 |
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| 91 | <screen><computeroutput>attempt to open /lib/libc.so.6 succeeded</computeroutput></screen>
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| 92 |
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[3f3931b0] | 93 | <para>Lastly, make sure GCC is using the correct dynamic linker:</para>
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[2914987b] | 94 |
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| 95 | <screen><userinput>grep found dummy.log</userinput></screen>
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| 96 |
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[3f3931b0] | 97 | <para>If everything is working correctly, there should be no errors,
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| 98 | and the output of the last command will be (allowing for
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| 99 | platform-specific differences in dynamic linker name):</para>
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[2914987b] | 100 |
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| 101 | <screen><computeroutput>found ld-linux.so.2 at /lib/ld-linux.so.2</computeroutput></screen>
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| 102 |
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[3f3931b0] | 103 | <para>If the output does not appear as shown above or is not received
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| 104 | at all, then something is seriously wrong. Investigate and retrace the
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| 105 | steps to find out where the problem is and correct it. The most likely
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| 106 | reason is that something went wrong with the specs file amendment
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| 107 | above. Any issues will need to be resolved before continuing on with
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| 108 | the process.</para>
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[673b0d8] | 109 |
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[3f3931b0] | 110 | <para>Once everything is working correctly, clean up the test
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| 111 | files:</para>
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[81fd230] | 112 |
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[3f3931b0] | 113 | <screen><userinput>rm -v dummy.c a.out dummy.log</userinput></screen>
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| 114 | </caution>
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[673b0d8] | 115 |
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| 116 | </sect1>
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