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-system-readjusting">
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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/$(gcc
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28 | -dumpmachine)/bin</filename>.</para>
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29 |
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30 | <screen><userinput>mv -v /tools/bin/{ld,ld-old}
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31 | mv -v /tools/$(gcc -dumpmachine)/bin/{ld,ld-old}
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32 | mv -v /tools/bin/{ld-new,ld}
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33 | ln -sv /tools/bin/ld /tools/$(gcc -dumpmachine)/bin/ld</userinput></screen>
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34 |
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35 | <para>Next, amend the GCC specs file so that it points to the new
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36 | dynamic linker, and so that GCC knows where to find its start files.
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37 | A <command>perl</command> command accomplishes this:</para>
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38 |
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39 | <screen><userinput>gcc -dumpspecs | \
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40 | perl -p -e 's@/tools/lib/ld-linux.so.2@/lib/ld-linux.so.2@g;' \
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41 | -e 's@\*startfile_prefix_spec:\n@$_/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 | <para>It is imperative at this point to ensure that the basic
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56 | functions (compiling and linking) of the adjusted toolchain are working
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57 | as expected. To do this, perform the following sanity checks:</para>
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58 |
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59 | <screen role="nodump" os="a"><userinput>echo 'main(){}' > dummy.c
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60 | cc dummy.c -Wl,--verbose &> dummy.log
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61 | readelf -l a.out | grep ': /lib'</userinput></screen>
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62 |
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63 | <para os="b">If everything is working correctly, there should be no errors,
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64 | and the output of the last command will be (allowing for
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65 | platform-specific differences in dynamic linker name):</para>
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66 |
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67 | <screen os="c"><computeroutput>[Requesting program interpreter: /lib/ld-linux.so.2]</computeroutput></screen>
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68 |
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69 | <para>Note that <filename class="directory">/lib</filename> is now
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70 | the prefix of our dynamic linker.</para>
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71 |
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72 | <para os="d">Now make sure that we're setup to use the correct startfiles:</para>
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73 |
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74 | <screen role="nodump" os="e"><userinput>grep -o '/usr/lib.*/crt[1in].* .*' dummy.log</userinput></screen>
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75 |
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76 | <para os="f">If everything is working correctly, there should be no errors,
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77 | and the output of the last command will be:</para>
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78 |
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79 | <screen><computeroutput>/usr/lib/crt1.o succeeded
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80 | /usr/lib/crti.o succeeded
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81 | /usr/lib/crtn.o succeeded</computeroutput></screen>
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82 |
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83 | <para os="g">Next, verify that the new linker is being used with the correct search paths:</para>
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84 |
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85 | <screen role="nodump" os="h"><userinput>grep 'SEARCH.*/usr/lib' dummy.log |sed 's|; |\n|g'</userinput></screen>
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86 |
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87 | <para os="i">If everything is working correctly, there should be no errors,
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88 | and the output of the last command will be:</para>
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89 |
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90 | <screen><computeroutput>SEARCH_DIR("/tools/i686-pc-linux-gnu/lib")
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91 | SEARCH_DIR("/usr/lib")
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92 | SEARCH_DIR("/lib");</computeroutput></screen>
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93 |
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94 | <para os="j">Next make sure that we're using the correct libc:</para>
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95 |
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96 | <screen role="nodump" os="k"><userinput>grep "/lib/libc.so.6 " dummy.log</userinput></screen>
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97 |
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98 | <para os="l">If everything is working correctly, there should be no errors,
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99 | and the output of the last command will be:</para>
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100 |
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101 | <screen os="m"><computeroutput>attempt to open /lib/libc.so.6 succeeded</computeroutput></screen>
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102 |
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103 | <para os="n">Lastly, make sure GCC is using the correct dynamic linker:</para>
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104 |
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105 | <screen role="nodump" os="o"><userinput>grep found dummy.log</userinput></screen>
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106 |
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107 | <para os="p">If everything is working correctly, there should be no errors,
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108 | and the output of the last command will be (allowing for
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109 | platform-specific differences in dynamic linker name):</para>
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110 |
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111 | <screen os="q"><computeroutput>found ld-linux.so.2 at /lib/ld-linux.so.2</computeroutput></screen>
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112 |
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113 | <para os="r">If the output does not appear as shown above or is not received
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114 | at all, then something is seriously wrong. Investigate and retrace the
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115 | steps to find out where the problem is and correct it. The most likely
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116 | reason is that something went wrong with the specs file adjustment. Any
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117 | issues will need to be resolved before continuing on with the process.</para>
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118 |
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119 | <para os="s">Once everything is working correctly, clean up the test files:</para>
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120 |
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121 | <screen role="nodump" os="t"><userinput>rm -v dummy.c a.out dummy.log</userinput></screen>
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122 |
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123 | </sect1>
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