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. For this we retained the
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11 | source and build directories from the second pass over Binutils. Install the
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12 | adjusted linker 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</userinput></screen></para>
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16 |
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17 | <para>From now on every compiled program will link <emphasis>only</emphasis>
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18 | against the libraries in <filename>/usr/lib</filename> and <filename>/lib
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19 | </filename>.</para>
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20 |
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21 | <para>You can now remove the Binutils source and build directories.</para>
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22 |
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23 | <para>The next thing to do is to amend our GCC specs file so that it points
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24 | to the new dynamic linker. Just like earlier on, we use a sed to accomplish
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25 | this:</para>
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26 |
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27 | <para><screen><userinput>SPECFILE=/tools/lib/gcc-lib/*/*/specs
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28 | sed -e 's@/tools/lib/ld.so.1@/lib/ld.so.1@g' \
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29 | -e 's@/tools/lib/ld-linux.so.2@/lib/ld-linux.so.2@g' \
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30 | $SPECFILE > newspecfile
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31 | mv newspecfile $SPECFILE
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32 | unset SPECFILE</userinput></screen></para>
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33 |
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34 | <para>Again, cutting and pasting the above is recommended. And just like
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35 | before, it is a good idea to check the specs file to ensure the intended
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36 | changes were actually made.</para>
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37 |
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38 | <caution><para>It is imperative at this point to stop and ensure that the
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39 | basic functions (compiling and linking) of the adjusted toolchain are working
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40 | as expected. For this we are going to perform a simple sanity check:</para>
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41 |
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42 | <para><screen><userinput>echo 'main(){}' > dummy.c
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43 | gcc dummy.c
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44 | readelf -l a.out | grep ': /lib'</userinput></screen></para>
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45 |
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46 | <para>If everything is working correctly, there should be no errors, and the
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47 | output of the last command will be:</para>
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48 |
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49 | <para><screen>[Requesting program interpreter: /lib/ld-linux.so.2]
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50 | </screen></para>
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51 |
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52 | <para>If you did not receive the output as shown above, then something is
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53 | seriously wrong. You will need to investigate and retrace your steps to find
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54 | out where the problem is and correct it. There is no point in continuing
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55 | until this is done. Most likely something went wrong with the specs file
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56 | amendment above. Note especially that <filename>/lib</filename> now appears as
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57 | the prefix of our dynamic linker. Of course, if you are working on a platform
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58 | where the name of the dynamic linker is something other than <filename>
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59 | ld-linux.so.2</filename>, then the output will be slightly different.</para>
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60 |
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61 | <para>Once you are satisfied that all is well, clean up the test files:</para>
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62 |
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63 | <para><screen><userinput>rm dummy.c a.out</userinput></screen></para>
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64 | </caution>
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65 |
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66 | </sect1>
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67 |
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