1 | <sect1 id="ch06-adjustingtoolchain">
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2 | <title>Re-adjusting the toolchain</title>
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3 | <?dbhtml filename="adjustingtoolchain.html" dir="chapter06"?>
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4 |
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5 | <para>Now that the new C libraries have been installed, it's time to re-adjust
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6 | our toolchain. We'll adjust it so that it will link any newly compiled program
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7 | against the new C libraries. Basically, this is the reverse of what we did
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8 | in the "Locking in" stage in the beginning of the previous chapter.</para>
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9 |
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10 | <para>The first thing to do is to adjust the linker scripts. For this we
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11 | retained the source and build directories from the second pass over Binutils.
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12 | Install the adjusted linker scripts by running the following from within the
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13 | <filename class="directory">binutils-build</filename> directory:</para>
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14 |
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15 | <para><screen><userinput>make -C ld install-data-local</userinput></screen></para>
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16 |
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17 | <para>The linker scripts now contain
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18 | no mention of <filename class="directory">/tools/lib</filename> anymore.
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19 | From now on every compiled program will link <emphasis>only</emphasis>
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20 | against the libraries in <filename>/usr/lib</filename> and
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21 | <filename>/lib</filename>.</para>
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22 |
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23 | <para>You can now remove the Binutils source and build directories.</para>
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24 |
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25 | <para>The next thing to do is to amend our GCC specs file so that it points
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26 | to the new dynamic linker. Just like earlier on, we use a sed to accomplish
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27 | this:</para>
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28 |
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29 | <para><screen><userinput>SPECFILE=/tools/lib/gcc-lib/*/*/specs
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30 | sed -e 's@/tools/lib/ld.so.1@/lib/ld.so.1@g' \
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31 | -e 's@/tools/lib/ld-linux.so.2@/lib/ld-linux.so.2@g' \
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32 | $SPECFILE > newspecfile
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33 | mv newspecfile $SPECFILE
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34 | unset SPECFILE</userinput></screen></para>
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35 |
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36 | <para>Again, cutting and pasting the above is recommended. And just like
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37 | before, it is a good idea to check the linker scripts and the specs file to
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38 | ensure the intended changes were actually made.</para>
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39 |
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40 | <para>Note that the linker scripts will still contain a reference to
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41 | <filename class="directory">/tools/i686-pc-linux-gnu/lib</filename>. This
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42 | is unavoidable, but luckily does not present a problem. There are no
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43 | libraries in that location as all the temporary tools libraries are
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44 | located in <filename class="directory">/tools/lib</filename>.</para>
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45 |
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46 | <caution><para>It is imperative at this point to stop and ensure that the
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47 | basic functionality of the adjusted toolchain is working as expected. We are
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48 | going to perform a simple sanity check:</para>
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49 |
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50 | <para><screen><userinput>echo 'main(){}' > dummy.c
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51 | gcc dummy.c
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52 | readelf -l a.out | grep ': /lib'</userinput></screen></para>
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53 |
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54 | <para>If everything is working correctly, the output of the last command will
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55 | be:</para>
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56 |
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57 | <para><screen>[Requesting program interpreter: /lib/ld-linux.so.2]
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58 | </screen></para>
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59 |
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60 | <para>If you did not receive the output as shown above then something is
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61 | seriously wrong. You will need to investigate and retrace your steps to find
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62 | out where the problem is and correct it. There is no point in continuing
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63 | until this is done. Most likely, something went wrong with the specs file
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64 | amendment above. Note especially that <filename>/lib</filename> now appears as
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65 | the prefix of our dynamic linker. Of course, if you are working on a platform
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66 | where the name of the dynamic linker is something other than <filename>
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67 | ld-linux.so.2</filename> then the output will be slightly different.</para>
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68 |
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69 | <para>Once you are satisfied that all is well, clean up the test files:</para>
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70 |
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71 | <para><screen><userinput>rm dummy.c a.out</userinput></screen></para>
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72 | </caution>
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73 |
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74 | </sect1>
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75 |
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