[519ee45] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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| 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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| 4 | <!ENTITY % general-entities SYSTEM "../general.ent">
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| 5 | %general-entities;
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| 6 | ]>
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| 7 |
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| 8 | <sect1 id="ch-tools-adjusting">
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| 9 | <?dbhtml filename="adjusting.html"?>
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| 10 |
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| 11 | <title>Adjusting the Toolchain</title>
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| 12 |
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| 13 | <para>Now that the temporary C libraries have been installed, all
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| 14 | tools compiled in the rest of this chapter should be linked against
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| 15 | these libraries. In order to accomplish this, the linker and the
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| 16 | compiler's specs file need to be adjusted.</para>
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| 17 |
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| 18 | <para>The linker, adjusted at the end of the first pass of Binutils, needs
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| 19 | to be renamed so that it can be properly found and used. First, backup the
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| 20 | original linker, then replace it with the adjusted linker. We'll also
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| 21 | create a link to its counterpart in <filename class="directory">
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| 22 | /tools/$(gcc -dumpmachine)/bin</filename></para>
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| 23 |
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| 24 | <screen><userinput>mv -v /tools/bin/{ld,ld-old}
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| 25 | mv -v /tools/$(gcc -dumpmachine)/bin/{ld,ld-old}
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| 26 | mv -v /tools/bin/{ld-new,ld}
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| 27 | ln -sv /tools/bin/ld /tools/$(gcc -dumpmachine)/bin/ld</userinput></screen>
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| 28 |
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| 29 | <para>From this point onwards, everything will link only against the
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| 30 | libraries in <filename class="directory">/tools/lib</filename>.</para>
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| 31 |
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| 32 | <para>The next task is to point GCC to the new dynamic linker. This is done by
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| 33 | dumping GCC's <quote>specs</quote> file to a location where GCC will look for it
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| 34 | by default. A simple <command>sed</command> substitution then alters the
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| 35 | dynamic linker that GCC will use:</para>
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| 36 |
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| 37 | <!-- Ampersands are needed to allow copy and paste -->
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| 38 | <screen><userinput>SPECFILE=`dirname $(gcc -print-libgcc-file-name)`/specs &&
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| 39 | gcc -dumpspecs > $SPECFILE &&
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| 40 | sed 's@^/lib/ld-linux.so.2@/tools&@g' $SPECFILE > tempspecfile &&
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| 41 | mv -vf tempspecfile $SPECFILE &&
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| 42 | unset SPECFILE</userinput></screen>
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| 43 |
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| 44 | <para>It is recommended that the above command be copy-and-pasted in order to
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| 45 | ensure accuracy. Alternatively, the specs file can be edited by hand. This is
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| 46 | done by replacing every occurrence of <quote>/lib/ld-linux.so.2</quote> with
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| 47 | <quote>/tools/lib/ld-linux.so.2</quote></para>
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| 48 |
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| 49 | <para>Be sure to visually inspect the specs file in order to verify the
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| 50 | intended changes have been made.</para>
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| 51 |
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| 52 | <important>
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| 53 | <para>If working on a platform where the name of the dynamic linker is
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| 54 | something other than <filename class="libraryfile">ld-linux.so.2</filename>,
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| 55 | replace <quote>ld-linux.so.2</quote> with the name of the platform's
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| 56 | dynamic linker in the above commands. Refer back to <xref
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| 57 | linkend="ch-tools-toolchaintechnotes" role=","/> if necessary.</para>
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| 58 | </important>
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| 59 |
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| 60 | <para>During the build process, GCC runs a script
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| 61 | (<command>fixincludes</command>) that scans the system for header files
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| 62 | that may need to be fixed (they might contain syntax errors, for example),
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| 63 | and installs the fixed versions in a private include directory. There is a
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| 64 | possibility that, as a result of this process, some header files from the
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| 65 | host system have found their way into GCC's private include directory. As
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| 66 | the rest of this chapter only requires the headers from GCC and Glibc,
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| 67 | which have both been installed at this point, any <quote>fixed</quote>
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| 68 | headers can safely be removed. This helps to avoid any host headers
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| 69 | polluting the build environment. Run the following commands to remove the
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| 70 | header files in GCC's private include directory (you may find it easier to
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| 71 | copy and paste these commands, rather than typing them by hand, due to
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| 72 | their length):</para>
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| 73 |
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| 74 | <!-- && used to ease copy and pasting -->
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| 75 | <screen><userinput>GCC_INCLUDEDIR=`dirname $(gcc -print-libgcc-file-name)`/include &&
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| 76 | find ${GCC_INCLUDEDIR}/* -maxdepth 0 -xtype d -exec rm -rvf '{}' \; &&
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| 77 | rm -vf `grep -l "DO NOT EDIT THIS FILE" ${GCC_INCLUDEDIR}/*` &&
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| 78 | unset GCC_INCLUDEDIR</userinput></screen>
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| 79 |
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| 80 | <caution>
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| 81 | <para>At this point, it is imperative to stop and ensure that the basic
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| 82 | functions (compiling and linking) of the new toolchain are working as
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| 83 | expected. To perform a sanity check, run the following commands:</para>
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| 84 |
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| 85 | <screen><userinput>echo 'main(){}' > dummy.c
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| 86 | cc dummy.c
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| 87 | readelf -l a.out | grep ': /tools'</userinput></screen>
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| 88 |
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| 89 | <para>If everything is working correctly, there should be no errors,
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| 90 | and the output of the last command will be of the form:</para>
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| 91 |
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| 92 | <screen><computeroutput>[Requesting program interpreter:
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| 93 | /tools/lib/ld-linux.so.2]</computeroutput></screen>
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| 94 |
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| 95 | <para>Note that <filename class="directory">/tools/lib</filename>
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| 96 | appears as the prefix of the dynamic linker.</para>
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| 97 |
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| 98 | <para>If the output is not shown as above or there was no output at all,
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| 99 | then something is wrong. Investigate and retrace the steps to find out
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| 100 | where the problem is and correct it. This issue must be resolved before
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| 101 | continuing on. First, perform the sanity check again, using
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| 102 | <command>gcc</command> instead of <command>cc</command>. If this works,
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| 103 | then the <filename class="symlink">/tools/bin/cc</filename> symlink is
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| 104 | missing. Revisit <xref linkend="ch-tools-gcc-pass1" role=","/> and install
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| 105 | the symlink. Next, ensure that the <envar>PATH</envar> is correct. This
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| 106 | can be checked by running <command>echo $PATH</command> and verifying that
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| 107 | <filename class="directory">/tools/bin</filename> is at the head of the
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| 108 | list. If the <envar>PATH</envar> is wrong it could mean that you are not
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| 109 | logged in as user <systemitem class="username">lfs</systemitem> or that
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| 110 | something went wrong back in <xref linkend="ch-tools-settingenviron"
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| 111 | role="."/> Another option is that something may have gone wrong with the
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| 112 | specs file amendment above. In this case, redo the specs file amendment,
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| 113 | being careful to copy-and-paste the commands.</para>
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| 114 |
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| 115 | <para>Once all is well, clean up the test files:</para>
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| 116 |
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| 117 | <screen><userinput>rm -v dummy.c a.out</userinput></screen>
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| 118 |
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| 119 | </caution>
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| 120 |
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| 121 | <note><para>Building TCL in the next section will serve as an additional check that
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| 122 | the toolchain has been built properly. If TCL fails to build, it is an
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| 123 | indication that something has gone wrong with the Binutils, GCC, or Glibc
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| 124 | installation, but not with TCL itself.</para></note>
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| 125 |
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| 126 | </sect1>
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