source: chapter06/adjusting.xml@ 2a975935

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Last change on this file since 2a975935 was 2a975935, checked in by Bruce Dubbs <bdubbs@…>, 5 years ago

Add a fix (embeeded patch) to shadow to fix an upstream bug.
Minor text change in adjusting toolchanin.

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@11189 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

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1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
4 <!ENTITY % general-entities SYSTEM "../general.ent">
5 %general-entities;
6]>
7
8<sect1 id="ch-system-adjusting">
9 <?dbhtml filename="adjusting.html"?>
10
11 <title>Adjusting the Toolchain</title>
12
13 <para>Now that the final C libraries have been installed, it is time to adjust
14 the toolchain so that it will link any
15 newly compiled program against these new libraries.</para>
16
17 <para>First, backup the <filename class="directory">/tools</filename> linker,
18 and replace it with the adjusted linker we made in chapter 5. We'll also create
19 a link to its counterpart in
20 <filename class="directory">/tools/$(uname -m)-pc-linux-gnu/bin</filename>:</para>
21
22<screen><userinput>mv -v /tools/bin/{ld,ld-old}
23mv -v /tools/$(uname -m)-pc-linux-gnu/bin/{ld,ld-old}
24mv -v /tools/bin/{ld-new,ld}
25ln -sv /tools/bin/ld /tools/$(uname -m)-pc-linux-gnu/bin/ld</userinput></screen>
26
27 <para>Next, amend the GCC specs file so that it points to the new
28 dynamic linker. Simply deleting all instances of <quote>/tools</quote> should
29 leave us with the correct path to the dynamic linker. Also adjust the specs file
30 so that GCC knows where to find the correct headers and Glibc start files.
31 A <command>sed</command> command accomplishes this:</para>
32
33<screen><userinput>gcc -dumpspecs | sed -e 's@/tools@@g' \
34 -e '/\*startfile_prefix_spec:/{n;s@.*@/usr/lib/ @}' \
35 -e '/\*cpp:/{n;s@$@ -isystem /usr/include@}' &gt; \
36 `dirname $(gcc --print-libgcc-file-name)`/specs</userinput></screen>
37
38 <para>It is a good idea to visually inspect the specs file to verify the
39 intended change was actually made.</para>
40
41 <para>It is imperative at this point to ensure that the basic
42 functions (compiling and linking) of the adjusted toolchain are working
43 as expected. To do this, perform the following sanity checks:</para>
44
45<screen os="a"><userinput>echo 'int main(){}' &gt; dummy.c
46cc dummy.c -v -Wl,--verbose &amp;&gt; dummy.log
47readelf -l a.out | grep ': /lib'</userinput></screen>
48
49 <para os="b">There should be no errors,
50 and the output of the last command will be (allowing for
51 platform-specific differences in dynamic linker name):</para>
52
53<screen os="c"><computeroutput>[Requesting program interpreter: /lib64/ld-linux-x86-64.so.2]</computeroutput></screen>
54
55 <para>Note that on 64-bit systems <filename class="directory">/lib</filename> is
56 the location of our dynamic linker, but is accessed via a symbolic link
57 in /lib64.</para>
58
59 <note><para>On 32-bit systems the interpreter should be
60 /lib/ld-linux.so.2.</para></note>
61
62 <para os="d">Now make sure that we're setup to use the correct start files:</para>
63
64<screen os="e"><userinput>grep -o '/usr/lib.*/crt[1in].*succeeded' dummy.log</userinput></screen>
65
66 <para os="f">The output of the last command should be:</para>
67
68<screen><computeroutput>/usr/lib/../lib/crt1.o succeeded
69/usr/lib/../lib/crti.o succeeded
70/usr/lib/../lib/crtn.o succeeded</computeroutput></screen>
71
72 <para os="g">Verify that the compiler is searching for the correct header
73 files:</para>
74
75<screen><userinput>grep -B1 '^ /usr/include' dummy.log</userinput></screen>
76
77 <para os="h">This command should return the following output:</para>
78
79<screen><computeroutput>#include &lt;...&gt; search starts here:
80 /usr/include</computeroutput></screen>
81
82 <para os="i">Next, verify that the new linker is being used with the correct search paths:</para>
83
84<screen os="j"><userinput>grep 'SEARCH.*/usr/lib' dummy.log |sed 's|; |\n|g'</userinput></screen>
85
86 <para os="k">References to paths that have components with '-linux-gnu' should
87 be ignored, but otherwise the output of the last command should be:</para>
88
89<screen><computeroutput>SEARCH_DIR("/usr/lib")
90SEARCH_DIR("/lib")</computeroutput></screen>
91
92 <para os="l">Next make sure that we're using the correct libc:</para>
93
94<screen os="m"><userinput>grep "/lib.*/libc.so.6 " dummy.log</userinput></screen>
95
96 <para os="n">The output of the last command should be:</para>
97
98<screen os="o"><computeroutput>attempt to open /lib/libc.so.6 succeeded</computeroutput></screen>
99
100 <para os="p">Lastly, make sure GCC is using the correct dynamic linker:</para>
101
102<screen os="q"><userinput>grep found dummy.log</userinput></screen>
103
104 <para os="r">The output of the last command should be (allowing for
105 platform-specific differences in dynamic linker name):</para>
106
107<screen os="s"><computeroutput>found ld-linux-x86-64.so.2 at /lib/ld-linux-x86-64.so.2</computeroutput></screen>
108
109 <para os="t">If the output does not appear as shown above or is not received
110 at all, then something is seriously wrong. Investigate and retrace the
111 steps to find out where the problem is and correct it. The most likely
112 reason is that something went wrong with the specs file adjustment. Any
113 issues will need to be resolved before continuing on with the process.</para>
114
115 <para os="u">Once everything is working correctly, clean up the test files:</para>
116
117<screen os="v"><userinput>rm -v dummy.c a.out dummy.log</userinput></screen>
118
119</sect1>
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