[7f1fcd8] | 1 | <chapter id="chapter05" xreflabel="Chapter 5">
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[35c2fa60] | 2 | <title>Constructing a temporary system</title>
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[9ac3d35] | 3 | <?dbhtml filename="chapter05.html" dir="chapter05"?>
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[6370fa6] | 4 |
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[cfabeed] | 5 |
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| 6 | <sect1 id="ch05-introduction">
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| 7 | <title>Introduction</title>
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| 8 | <?dbhtml filename="introduction.html" dir="chapter05"?>
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| 9 |
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| 10 | <para>In this chapter we will compile and install a minimal
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| 11 | Linux system. This system will contain just enough tools to be able
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| 12 | to start constructing the final LFS system in the next chapter.</para>
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| 13 |
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| 14 | <para>The building of this minimal system is done in two steps: first we
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| 15 | build a brand-new and host-independent toolchain (compiler, assembler,
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| 16 | linker and libraries), and then use this to build all the other essential
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| 17 | tools.</para>
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| 18 |
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| 19 | <para>The files compiled in this chapter will be installed under the
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| 20 | <filename class="directory">$LFS/tools</filename> directory
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| 21 | to keep them separate from the files installed in the next chapter.
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| 22 | Since the packages compiled here are merely temporary, we don't want
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| 23 | them to pollute the soon-to-be LFS system.</para>
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| 24 |
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[5888299] | 25 | <para>The build instructions assume that you are using the
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| 26 | <userinput>bash</userinput> shell. It is also expected that you have already
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[b05a831] | 27 | unpacked a source package (while logged in as user <emphasis>lfs</emphasis> --
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| 28 | explained shortly) and performed a <userinput>cd</userinput> into the source
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[5888299] | 29 | directory of a package before issuing its build commands.</para>
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[cfabeed] | 30 |
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| 31 | <para>Several of the packages are patched before compilation, but only when
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| 32 | the patch is needed to circumvent a problem. Often the patch is needed in
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| 33 | both this and the next chapter, but sometimes in only one of them. Therefore,
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[b05a831] | 34 | don't worry when instructions for a downloaded patch seem to be missing. When
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| 35 | applying a patch you'll occasionally see a warning message about
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| 36 | <emphasis>offset</emphasis> or <emphasis>fuzz</emphasis>. These warnings are
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| 37 | nothing to worry about as the patch was still successfully applied.</para>
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[cfabeed] | 38 |
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| 39 | <para>During the installation of most packages you will
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| 40 | see all kinds of compiler warnings scroll by on your screen. These are
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| 41 | normal and can be safely ignored. They are just what they say they are:
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| 42 | warnings -- mostly about deprecated, but not invalid, use of the C or C++
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| 43 | syntax. It's just that C standards have changed rather often and some
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| 44 | packages still use the older standard, which is not really a problem.</para>
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| 45 |
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| 46 | <para><emphasis>Unless</emphasis> told not to, you should normally delete the
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| 47 | source and build directories after installing each package -- for cleanness
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| 48 | sake and to save space.</para>
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| 49 |
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| 50 | <para>Before continuing, make sure the LFS environment variable is set up
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| 51 | properly by executing the following:</para>
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| 52 |
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| 53 | <screen><userinput>echo $LFS</userinput></screen>
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| 54 |
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| 55 | <para>Make sure the output shows the path to your LFS partition's mount
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| 56 | point, which is <filename class="directory">/mnt/lfs</filename> if you
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| 57 | followed our example.</para>
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| 58 |
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| 59 | </sect1>
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| 60 |
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| 61 |
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| 62 | <sect1 id="ch05-toolchaintechnotes">
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| 63 | <title>Toolchain technical notes</title>
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| 64 | <?dbhtml filename="toolchaintechnotes.html" dir="chapter05"?>
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| 65 |
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| 66 | <para>This section attempts to explain some of the rationale and technical
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| 67 | details behind the overall build method. It's not essential that you understand
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| 68 | everything here immediately. Most of it will make sense once you have performed
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| 69 | an actual build. Feel free to refer back here at any time.</para>
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| 70 |
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| 71 | <para>The overall goal of <xref linkend="chapter05"/> is to provide a sane,
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| 72 | temporary environment that we can chroot into, and from which we can produce a
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| 73 | clean, trouble-free build of the target LFS system in
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| 74 | <xref linkend="chapter06"/>. Along the way, we attempt to divorce ourselves
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| 75 | from the host system as much as possible, and in so doing build a
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| 76 | self-contained and self-hosted toolchain. It should be noted that the
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| 77 | build process has been designed in such a way so as to minimize the risks for
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| 78 | new readers and provide maximum educational value at the same time. In other
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| 79 | words, more advanced techniques could be used to build the system.</para>
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| 80 |
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| 81 | <important>
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| 82 | <para>Before continuing, you really should be aware of the name of your working
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| 83 | platform, often also referred to as the <emphasis>target triplet</emphasis>. For
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[f4993cf] | 84 | many folks the target triplet will probably be
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[cfabeed] | 85 | <emphasis>i686-pc-linux-gnu</emphasis>. A simple way to determine your target
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| 86 | triplet is to run the <filename>config.guess</filename> script that comes with
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| 87 | the source for many packages. Unpack the Binutils sources and run the script:
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| 88 | <userinput>./config.guess</userinput> and note the output.</para>
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| 89 |
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| 90 | <para>You'll also need to be aware of the name of your platform's
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| 91 | <emphasis>dynamic linker</emphasis>, often also referred to as the
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| 92 | <emphasis>dynamic loader</emphasis>, not to be confused with the standard linker
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| 93 | <emphasis>ld</emphasis> that is part of Binutils. The dynamic linker is provided
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| 94 | by Glibc and has the job of finding and loading the shared libraries needed by a
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[f4993cf] | 95 | program, preparing the program to run and then running it. For most folks the
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[cfabeed] | 96 | name of the dynamic linker will be <emphasis>ld-linux.so.2</emphasis>. On
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| 97 | platforms that are less prevalent, the name might be
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| 98 | <emphasis>ld.so.1</emphasis> and newer 64 bit platforms might even have
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| 99 | something completely different. You should be able to determine the name
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| 100 | of your platform's dynamic linker by looking in the
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| 101 | <filename class="directory">/lib</filename> directory on your host system. A
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| 102 | surefire way is to inspect a random binary from your host system by running:
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| 103 | <userinput>'readelf -l <name of binary> | grep interpreter'</userinput>
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| 104 | and noting the output. The authoritative reference covering all platforms is in
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| 105 | the <filename>shlib-versions</filename> file in the root of the Glibc source
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| 106 | tree.</para>
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| 107 | </important>
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| 108 |
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| 109 | <para>Some key technical points of how the <xref linkend="chapter05"/> build
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| 110 | method works:</para>
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| 111 |
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| 112 | <itemizedlist>
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| 113 | <listitem><para>Similar in principle to cross compiling whereby tools installed
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| 114 | into the same prefix work in cooperation and thus utilize a little GNU
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| 115 | "magic".</para></listitem>
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| 116 |
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| 117 | <listitem><para>Careful manipulation of the standard linker's library search
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| 118 | path to ensure programs are linked only against libraries we
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| 119 | choose.</para></listitem>
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| 120 |
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| 121 | <listitem><para>Careful manipulation of <userinput>gcc</userinput>'s
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| 122 | <emphasis>specs</emphasis> file to tell the compiler which target dynamic
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| 123 | linker will be used.</para></listitem>
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| 124 | </itemizedlist>
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| 125 |
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| 126 | <para>Binutils is installed first because both GCC and Glibc perform various
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| 127 | feature tests on the assembler and linker during their respective runs of
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| 128 | <userinput>./configure</userinput> to determine which software features to enable
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| 129 | or disable. This is more important than one might first realize. An incorrectly
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| 130 | configured GCC or Glibc can result in a subtly broken toolchain where the impact
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| 131 | of such breakage might not show up until near the end of the build of a whole
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| 132 | distribution. Thankfully, a test suite failure will usually alert us before too
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| 133 | much time is wasted.</para>
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| 134 |
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| 135 | <para>Binutils installs its assembler and linker into two locations,
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| 136 | <filename class="directory">/tools/bin</filename> and
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| 137 | <filename class="directory">/tools/$TARGET_TRIPLET/bin</filename>. In reality,
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| 138 | the tools in one location are hard linked to the other. An important facet of
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| 139 | the linker is its library search order. Detailed information can be obtained
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| 140 | from <userinput>ld</userinput> by passing it the <emphasis>--verbose</emphasis>
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| 141 | flag. For example: <userinput>'ld --verbose | grep SEARCH'</userinput> will
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| 142 | show you the current search paths and their order. You can see what files are
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| 143 | actually linked by <userinput>ld</userinput> by compiling a dummy program and
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| 144 | passing the <emphasis>--verbose</emphasis> switch. For example:
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| 145 | <userinput>'gcc dummy.c -Wl,--verbose 2>&1 | grep succeeded'</userinput>
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| 146 | will show you all the files successfully opened during the link.</para>
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| 147 |
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| 148 | <para>The next package installed is GCC and during its run of
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| 149 | <userinput>./configure</userinput> you'll see, for example:</para>
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| 150 |
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| 151 | <blockquote><screen>checking what assembler to use... /tools/i686-pc-linux-gnu/bin/as
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| 152 | checking what linker to use... /tools/i686-pc-linux-gnu/bin/ld</screen></blockquote>
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| 153 |
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| 154 | <para>This is important for the reasons mentioned above. It also demonstrates
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| 155 | that GCC's configure script does not search the $PATH directories to find which
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| 156 | tools to use. However, during the actual operation of <userinput>gcc</userinput>
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| 157 | itself, the same search paths are not necessarily used. You can find out which
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| 158 | standard linker <userinput>gcc</userinput> will use by running:
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| 159 | <userinput>'gcc -print-prog-name=ld'</userinput>.
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| 160 | Detailed information can be obtained from <userinput>gcc</userinput> by passing
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| 161 | it the <emphasis>-v</emphasis> flag while compiling a dummy program. For
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| 162 | example: <userinput>'gcc -v dummy.c'</userinput> will show you detailed
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| 163 | information about the preprocessor, compilation and assembly stages, including
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| 164 | <userinput>gcc</userinput>'s include search paths and their order.</para>
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| 165 |
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| 166 | <para>The next package installed is Glibc. The most important considerations for
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| 167 | building Glibc are the compiler, binary tools and kernel headers. The compiler
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| 168 | is generally no problem as Glibc will always use the <userinput>gcc</userinput>
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| 169 | found in a $PATH directory. The binary tools and kernel headers can be a little
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| 170 | more troublesome. Therefore we take no risks and use the available configure
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| 171 | switches to enforce the correct selections. After the run of
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| 172 | <userinput>./configure</userinput> you can check the contents of the
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| 173 | <filename>config.make</filename> file in the
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| 174 | <filename class="directory">glibc-build</filename> directory for all the
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| 175 | important details. You'll note some interesting items like the use of
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| 176 | <userinput>CC="gcc -B/tools/bin/"</userinput> to control which binary tools are
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| 177 | used, and also the use of the <emphasis>-nostdinc</emphasis> and
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| 178 | <emphasis>-isystem</emphasis> flags to control the compiler's include search
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| 179 | path. These items help to highlight an important aspect of the Glibc package:
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| 180 | it is very self-sufficient in terms of its build machinery and generally does
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| 181 | not rely on toolchain defaults.</para>
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| 182 |
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| 183 | <para>After the Glibc installation, we make some adjustments to ensure that
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| 184 | searching and linking take place only within our <filename>/tools</filename>
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| 185 | prefix. We install an adjusted <userinput>ld</userinput>, which has a hard-wired
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| 186 | search path limited to <filename class="directory">/tools/lib</filename>. Then
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| 187 | we amend <userinput>gcc</userinput>'s specs file to point to our new dynamic
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| 188 | linker in <filename class="directory">/tools/lib</filename>. This last step is
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| 189 | <emphasis>vital</emphasis> to the whole process. As mentioned above, a
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| 190 | hard-wired path to a dynamic linker is embedded into every ELF shared
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| 191 | executable. You can inspect this by running:
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| 192 | <userinput>'readelf -l <name of binary> | grep interpreter'</userinput>.
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| 193 | By amending <userinput>gcc</userinput>'s specs file, we are ensuring that every
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| 194 | program compiled from here through the end of <xref linkend="chapter05"/> will
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| 195 | use our new dynamic linker in
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| 196 | <filename class="directory">/tools/lib</filename>.</para>
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| 197 |
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| 198 | <para>The need to use the new dynamic linker is also the reason why we apply the
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| 199 | Specs patch for the second pass of GCC. Failure to do so will result in the GCC
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| 200 | programs themselves having the name of the dynamic linker from the host system's
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| 201 | <filename class="directory">/lib</filename> directory embedded into them, which
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| 202 | would defeat our goal of getting away from the host.</para>
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| 203 |
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| 204 | <para>During the second pass of Binutils, we are able to utilize the
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| 205 | <emphasis>--with-lib-path</emphasis> configure switch to control
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| 206 | <userinput>ld</userinput>'s library search path. From this point onwards, the
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| 207 | core toolchain is self-contained and self-hosted. The remainder of the
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| 208 | <xref linkend="chapter05"/> packages all build against the new Glibc in
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| 209 | <filename class="directory">/tools</filename> and all is well.</para>
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| 210 |
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| 211 | <para>Upon entering the chroot environment in <xref linkend="chapter06"/>, the
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| 212 | first major package we install is Glibc, due to its self-sufficient nature that
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| 213 | we mentioned above. Once this Glibc is installed into
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| 214 | <filename class="directory">/usr</filename>, we perform a quick changeover of
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| 215 | the toolchain defaults, then proceed for real in building the rest of the
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| 216 | target <xref linkend="chapter06"/> LFS system.</para>
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| 217 |
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| 218 | <sect2>
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| 219 | <title>Notes on static linking</title>
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| 220 |
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| 221 | <para>Most programs have to perform, beside their specific task, many rather
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| 222 | common and sometimes trivial operations. These include allocating memory,
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| 223 | searching directories, reading and writing files, string handling, pattern
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| 224 | matching, arithmetic and many other tasks. Instead of obliging each program to
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| 225 | reinvent the wheel, the GNU system provides all these basic functions in
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| 226 | ready-made libraries. The major library on any Linux system is
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| 227 | <emphasis>Glibc</emphasis>.</para>
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| 228 |
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| 229 | <para>There are two primary ways of linking the functions from a library to a
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| 230 | program that uses them: statically or dynamically. When a program is linked
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| 231 | statically, the code of the used functions is included in the executable,
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| 232 | resulting in a rather bulky program. When a program is dynamically linked, what
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| 233 | is included is a reference to the dynamic linker, the name of the library, and
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| 234 | the name of the function, resulting in a much smaller executable. (A third way
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| 235 | is to use the programming interface of the dynamic linker. See the
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| 236 | <emphasis>dlopen</emphasis> man page for more information.)</para>
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| 237 |
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| 238 | <para>Dynamic linking is the default on Linux and has three major advantages
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| 239 | over static linking. First, you need only one copy of the executable library
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| 240 | code on your hard disk, instead of having many copies of the same code included
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| 241 | into a whole bunch of programs -- thus saving disk space. Second, when several
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| 242 | programs use the same library function at the same time, only one copy of the
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| 243 | function's code is required in core -- thus saving memory space. Third, when a
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| 244 | library function gets a bug fixed or is otherwise improved, you only need to
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| 245 | recompile this one library, instead of having to recompile all the programs that
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| 246 | make use of the improved function.</para>
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| 247 |
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| 248 | <para>If dynamic linking has several advantages, why then do we statically link
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| 249 | the first two packages in this chapter? The reasons are threefold: historical,
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| 250 | educational, and technical. Historical, because earlier versions of LFS
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| 251 | statically linked every program in this chapter. Educational, because knowing
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| 252 | the difference is useful. Technical, because we gain an element of independence
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| 253 | from the host in doing so, meaning that those programs can be used
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| 254 | independently of the host system. However, it's worth noting that an overall
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| 255 | successful LFS build can still be achieved when the first two packages are
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| 256 | built dynamically.</para>
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| 257 |
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| 258 | </sect2>
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| 259 |
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| 260 | </sect1>
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| 261 |
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| 262 |
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| 263 | <sect1 id="ch05-creatingtoolsdir">
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| 264 | <title>Creating the $LFS/tools directory</title>
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| 265 | <?dbhtml filename="creatingtoolsdir.html" dir="chapter05"?>
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| 266 |
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| 267 | <para>All programs compiled in this chapter will be installed under <filename
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| 268 | class="directory">$LFS/tools</filename> to keep them separate from the
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| 269 | programs compiled in the next chapter. The programs compiled here are only
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| 270 | temporary tools and won't be a part of the final LFS system and by keeping them
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| 271 | in a separate directory, we can later easily throw them away.</para>
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| 272 |
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[f4993cf] | 273 | <para>Later on you might wish to search through the binaries of your system to
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| 274 | see what files they make use of or link against. To make this searching easier
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| 275 | you may want to choose a unique name for the directory in which the temporary
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| 276 | tools are stored. Instead of the simple "tools" you could use something like
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| 277 | "tools-for-lfs". However, you'll need to be careful to adjust all references to
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| 278 | "tools" throughout the book -- including those in any patches, notably the
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| 279 | GCC Specs Patch.</para>
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[cfabeed] | 280 |
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| 281 | <para>Create the required directory by running the following:</para>
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| 282 |
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| 283 | <screen><userinput>mkdir $LFS/tools</userinput></screen>
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| 284 |
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| 285 | <para>The next step is to create a <filename>/tools</filename> symlink on
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| 286 | your host system. It will point to the directory we just created on the LFS
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| 287 | partition:</para>
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| 288 |
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| 289 | <screen><userinput>ln -s $LFS/tools /</userinput></screen>
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| 290 |
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[f4993cf] | 291 | <note><para>The above command is correct. The <userinput>ln</userinput> command
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| 292 | has a few syntactic variations, so be sure to check the info page before
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| 293 | reporting what you may think is an error.</para></note>
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| 294 |
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| 295 | <para>The created symlink enables us to compile our toolchain so that it always
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[cfabeed] | 296 | refers to <filename>/tools</filename>, meaning that the compiler, assembler
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| 297 | and linker will work both in this chapter (when we are still using some tools
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| 298 | from the host) <emphasis>and</emphasis> in the next (when we are chrooted to
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| 299 | the LFS partition).</para>
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| 300 |
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| 301 | </sect1>
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| 302 |
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| 303 |
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| 304 | <sect1 id="ch05-addinguser">
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| 305 | <title>Adding the user lfs</title>
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| 306 | <?dbhtml filename="addinguser.html" dir="chapter05"?>
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| 307 |
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| 308 | <para>When logged in as <emphasis>root</emphasis>, making a single mistake
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| 309 | can damage or even wreck your system. Therefore we recommend that you
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| 310 | build the packages in this chapter as an unprivileged user. You could
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| 311 | of course use your own user name, but to make it easier to set up a clean
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| 312 | work environment we'll create a new user <emphasis>lfs</emphasis> and
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| 313 | use this one during the installation process. As <emphasis>root</emphasis>,
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| 314 | issue the following commands to add the new user:</para>
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| 315 |
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| 316 | <screen><userinput>useradd -s /bin/bash -m lfs
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| 317 | passwd lfs</userinput></screen>
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| 318 |
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| 319 | <para>Now grant this new user <emphasis>lfs</emphasis> full access to
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| 320 | <filename class="directory">$LFS/tools</filename> by giving it ownership
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| 321 | of the directory:</para>
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| 322 |
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| 323 | <screen><userinput>chown lfs $LFS/tools</userinput></screen>
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| 324 |
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| 325 | <para>If you made a separate working directory as suggested, give user
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| 326 | <emphasis>lfs</emphasis> ownership of this directory too:</para>
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| 327 |
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| 328 | <screen><userinput>chown lfs $LFS/sources</userinput></screen>
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| 329 |
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| 330 | <para>Next, login as user <emphasis>lfs</emphasis>. This can be done via a
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| 331 | virtual console, through a display manager, or with the following substitute
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| 332 | user command:</para>
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| 333 |
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| 334 | <screen><userinput>su - lfs</userinput></screen>
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| 335 |
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| 336 | <para>The "<userinput>-</userinput>" instructs <userinput>su</userinput> to
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[f4993cf] | 337 | start a <emphasis>login</emphasis> shell.</para>
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[cfabeed] | 338 |
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| 339 | </sect1>
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| 340 |
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| 341 |
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| 342 | <sect1 id="ch05-settingenviron">
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| 343 | <title>Setting up the environment</title>
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| 344 | <?dbhtml filename="settingenvironment.html" dir="chapter05"?>
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| 345 |
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[538aa7a] | 346 | <para>We're going to set up a good working environment by creating two new
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[f4993cf] | 347 | startup files for the <userinput>bash</userinput> shell. While logged in as
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| 348 | user <emphasis>lfs</emphasis>, issue the following command to create a new
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[538aa7a] | 349 | <filename>.bash_profile</filename>:</para>
|
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[cfabeed] | 350 |
|
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| 351 | <screen><userinput>cat > ~/.bash_profile << "EOF"</userinput>
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[07ecae2] | 352 | exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash
|
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[538aa7a] | 353 | <userinput>EOF</userinput></screen>
|
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| 354 |
|
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[f4993cf] | 355 | <para>Normally, when you log on as user <emphasis>lfs</emphasis>,
|
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| 356 | the initial shell is a <emphasis>login</emphasis> shell which reads the
|
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| 357 | <filename>/etc/profile</filename> of your host (probably containing some
|
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| 358 | settings of environment variables) and then <filename>.bash_profile</filename>.
|
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| 359 | The <userinput>exec env -i ... /bin/bash</userinput> command in the latter file
|
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| 360 | replaces the running shell with a new one with a completely empty environment,
|
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| 361 | except for the HOME, TERM and PS1 variables. This ensures that no unwanted and
|
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| 362 | potentially hazardous environment variables from the host system leak into our
|
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| 363 | build environment. The technique used here is a little strange, but it achieves
|
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| 364 | the goal of enforcing a clean environment.</para>
|
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| 365 |
|
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| 366 | <para>The new instance of the shell is a <emphasis>non-login</emphasis> shell,
|
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| 367 | which doesn't read the <filename>/etc/profile</filename> or
|
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| 368 | <filename>.bash_profile</filename> files, but reads the
|
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| 369 | <filename>.bashrc</filename> file instead. Create this latter file now:</para>
|
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[538aa7a] | 370 |
|
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| 371 | <screen><userinput>cat > ~/.bashrc << "EOF"</userinput>
|
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[cfabeed] | 372 | set +h
|
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| 373 | umask 022
|
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| 374 | LFS=/mnt/lfs
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| 375 | LC_ALL=POSIX
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[538aa7a] | 376 | PATH=/tools/bin:/bin:/usr/bin
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[cfabeed] | 377 | export LFS LC_ALL PATH
|
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[538aa7a] | 378 | <userinput>EOF</userinput></screen>
|
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[cfabeed] | 379 |
|
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| 380 | <para>The <userinput>set +h</userinput> command turns off
|
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| 381 | <userinput>bash</userinput>'s hash function. Normally hashing is a useful
|
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| 382 | feature: <userinput>bash</userinput> uses a hash table to remember the
|
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| 383 | full pathnames of executable files to avoid searching the PATH time and time
|
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| 384 | again to find the same executable. However, we'd like the new tools to be
|
---|
| 385 | used as soon as they are installed. By switching off the hash function, our
|
---|
| 386 | "interactive" commands (<userinput>make</userinput>,
|
---|
| 387 | <userinput>patch</userinput>, <userinput>sed</userinput>,
|
---|
| 388 | <userinput>cp</userinput> and so forth) will always use
|
---|
| 389 | the newest available version during the build process.</para>
|
---|
| 390 |
|
---|
| 391 | <para>Setting the user file-creation mask to 022 ensures that newly created
|
---|
| 392 | files and directories are only writable for their owner, but readable and
|
---|
| 393 | executable for anyone.</para>
|
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[07ecae2] | 394 |
|
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[cfabeed] | 395 | <para>The LFS variable should of course be set to the mount point you
|
---|
| 396 | chose.</para>
|
---|
| 397 |
|
---|
| 398 | <para>The LC_ALL variable controls the localization of certain programs,
|
---|
| 399 | making their messages follow the conventions of a specified country. If your
|
---|
| 400 | host system uses a version of Glibc older than 2.2.4,
|
---|
| 401 | having LC_ALL set to something other than "POSIX" or "C" during this chapter
|
---|
| 402 | may cause trouble if you exit the chroot environment and wish to return later.
|
---|
| 403 | By setting LC_ALL to "POSIX" (or "C", the two are equivalent) we ensure that
|
---|
| 404 | everything will work as expected in the chroot environment.</para>
|
---|
| 405 |
|
---|
| 406 | <para>We prepend <filename>/tools/bin</filename> to the standard PATH so
|
---|
| 407 | that, as we move along through this chapter, the tools we build will get used
|
---|
| 408 | during the rest of the building process.</para>
|
---|
| 409 |
|
---|
[f4993cf] | 410 | <para>Finally, to have our environment fully prepared for building the
|
---|
| 411 | temporary tools, source the just-created profile:</para>
|
---|
[cfabeed] | 412 |
|
---|
[538aa7a] | 413 | <screen><userinput>source ~/.bash_profile</userinput></screen>
|
---|
| 414 |
|
---|
[cfabeed] | 415 | </sect1>
|
---|
| 416 |
|
---|
| 417 |
|
---|
[bc82645e] | 418 | &c5-binutils-pass1;
|
---|
| 419 | &c5-gcc-pass1;
|
---|
| 420 | &c5-kernelheaders;
|
---|
[37ad07a] | 421 | &c5-glibc;
|
---|
[cfabeed] | 422 |
|
---|
| 423 |
|
---|
| 424 | <sect1 id="ch05-locking-glibc">
|
---|
| 425 | <title>"Locking in" Glibc</title>
|
---|
| 426 | <?dbhtml filename="lockingglibc.html" dir="chapter05"?>
|
---|
| 427 |
|
---|
| 428 | <para>Now that the temporary C libraries have been installed, we want all
|
---|
| 429 | the tools compiled in the rest of this chapter to be linked against these
|
---|
| 430 | libraries. To accomplish this, we need to adjust the linker and the compiler's
|
---|
| 431 | specs file.</para>
|
---|
| 432 |
|
---|
| 433 | <para>First install the adjusted linker by running the following from within
|
---|
| 434 | the <filename class="directory">binutils-build</filename> directory:</para>
|
---|
| 435 |
|
---|
| 436 | <screen><userinput>make -C ld install</userinput></screen>
|
---|
| 437 |
|
---|
| 438 | <para>The linker was adjusted a little while back, at the end of the first
|
---|
| 439 | pass of Binutils. From this point onwards everything will link <emphasis>only
|
---|
| 440 | </emphasis> against the libraries in <filename>/tools/lib</filename>.</para>
|
---|
| 441 |
|
---|
| 442 | <note><para>If you somehow missed the earlier warning to retain the Binutils
|
---|
| 443 | source and build directories from the first pass or otherwise accidentally
|
---|
| 444 | deleted them or just don't have access to them, don't worry, all is not lost.
|
---|
[f4993cf] | 445 | Just ignore the above command. The result is a small chance of the subsequent
|
---|
| 446 | testing programs linking against libraries on the host. This is not ideal, but
|
---|
[cfabeed] | 447 | it's not a major problem. The situation is corrected when we install the
|
---|
[f4993cf] | 448 | second pass of Binutils a bit further on.</para></note>
|
---|
[cfabeed] | 449 |
|
---|
| 450 | <para>Now that the adjusted linker is installed, you have to remove the
|
---|
| 451 | Binutils build and source directories.</para>
|
---|
| 452 |
|
---|
| 453 | <para>The next thing to do is to amend our GCC specs file so that it points
|
---|
| 454 | to the new dynamic linker. A simple sed will accomplish this:</para>
|
---|
| 455 |
|
---|
| 456 | <!-- Ampersands are needed to allow cut and paste -->
|
---|
| 457 |
|
---|
| 458 | <screen><userinput>SPECFILE=/tools/lib/gcc-lib/*/*/specs &&
|
---|
| 459 | sed -e 's@ /lib/ld-linux.so.2@ /tools/lib/ld-linux.so.2@g' \
|
---|
| 460 | $SPECFILE > tempspecfile &&
|
---|
| 461 | mv -f tempspecfile $SPECFILE &&
|
---|
| 462 | unset SPECFILE</userinput></screen>
|
---|
| 463 |
|
---|
| 464 | <para>We recommend that you cut-and-paste the above rather than try and type it
|
---|
| 465 | all in. Or you can edit the specs file by hand if you want to: just replace any
|
---|
| 466 | occurrence of "/lib/ld-linux.so.2" with "/tools/lib/ld-linux.so.2".</para>
|
---|
| 467 |
|
---|
| 468 | <important><para>If you are working on a platform where the name of the dynamic
|
---|
| 469 | linker is something other than <filename>ld-linux.so.2</filename>, you
|
---|
| 470 | <emphasis>must</emphasis> substitute <filename>ld-linux.so.2</filename> with the
|
---|
| 471 | name of your platform's dynamic linker in the above commands. Refer back to
|
---|
| 472 | <xref linkend="ch05-toolchaintechnotes"/> if necessary.</para></important>
|
---|
| 473 |
|
---|
| 474 | <para>Lastly, there is a possibility that some include files from the host
|
---|
| 475 | system have found their way into GCC's private include dir. This can happen
|
---|
| 476 | because of GCC's "fixincludes" process which runs as part of the GCC build.
|
---|
| 477 | We'll explain more about this further on in this chapter. For now, run the
|
---|
| 478 | following commands to eliminate this possibility:</para>
|
---|
| 479 |
|
---|
| 480 | <screen><userinput>rm -f /tools/lib/gcc-lib/*/*/include/{pthread.h,bits/sigthread.h}</userinput></screen>
|
---|
| 481 |
|
---|
| 482 | <!-- HACK - Force some whitespace to appease tidy -->
|
---|
| 483 | <literallayout></literallayout>
|
---|
| 484 |
|
---|
| 485 | <caution><para>It is imperative at this point to stop and ensure that the basic
|
---|
| 486 | functions (compiling and linking) of the new toolchain are working as expected.
|
---|
| 487 | For this we are going to perform a simple sanity check:</para>
|
---|
| 488 |
|
---|
| 489 | <screen><userinput>echo 'main(){}' > dummy.c
|
---|
| 490 | gcc dummy.c
|
---|
| 491 | readelf -l a.out | grep ': /tools'</userinput></screen>
|
---|
| 492 |
|
---|
| 493 | <para>If everything is working correctly, there should be no errors, and the
|
---|
| 494 | output of the last command will be:</para>
|
---|
| 495 |
|
---|
| 496 | <blockquote><screen>[Requesting program interpreter: /tools/lib/ld-linux.so.2]</screen></blockquote>
|
---|
| 497 |
|
---|
| 498 | <para>If you did not receive the output as shown above, or received no output at
|
---|
| 499 | all, then something is seriously wrong. You will need to investigate and retrace
|
---|
| 500 | your steps to find out where the problem is and correct it. There is no point in
|
---|
| 501 | continuing until this is done. Most likely something went wrong with the specs
|
---|
| 502 | file amendment above. Note especially that <filename>/tools/lib</filename>
|
---|
| 503 | appears as the prefix of our dynamic linker. Of course, if you are working on a
|
---|
| 504 | platform where the name of the dynamic linker is something other than
|
---|
| 505 | <filename>ld-linux.so.2</filename>, then the output will be slightly
|
---|
| 506 | different.</para>
|
---|
| 507 |
|
---|
| 508 | <para>Once you are satisfied that all is well, clean up the test files:</para>
|
---|
| 509 |
|
---|
| 510 | <screen><userinput>rm dummy.c a.out</userinput></screen>
|
---|
| 511 | </caution>
|
---|
| 512 |
|
---|
| 513 | <!-- HACK - Force some whitespace to appease tidy -->
|
---|
| 514 | <literallayout></literallayout>
|
---|
| 515 |
|
---|
| 516 | <para>This completes the installation of the self-contained toolchain, and it
|
---|
| 517 | can now be used to build the rest of the temporary tools.</para>
|
---|
| 518 |
|
---|
| 519 | </sect1>
|
---|
| 520 |
|
---|
| 521 |
|
---|
[37ad07a] | 522 | &c5-tcl;
|
---|
| 523 | &c5-expect;
|
---|
| 524 | &c5-dejagnu;
|
---|
[bc82645e] | 525 | &c5-gcc-pass2;
|
---|
| 526 | &c5-binutils-pass2;
|
---|
[cfabeed] | 527 |
|
---|
[bc82645e] | 528 | &c5-gawk;
|
---|
| 529 | &c5-coreutils;
|
---|
[abbd27a5] | 530 | &c5-bzip2;
|
---|
[bc82645e] | 531 | &c5-gzip;
|
---|
[abbd27a5] | 532 | &c5-diffutils;
|
---|
[5e2cb65] | 533 | &c5-findutils;
|
---|
[abbd27a5] | 534 | &c5-make;
|
---|
[bc82645e] | 535 | &c5-grep;
|
---|
[abbd27a5] | 536 | &c5-sed;
|
---|
[bc82645e] | 537 | &c5-gettext;
|
---|
| 538 | &c5-ncurses;
|
---|
| 539 | &c5-patch;
|
---|
[abbd27a5] | 540 | &c5-tar;
|
---|
| 541 | &c5-texinfo;
|
---|
[bc82645e] | 542 | &c5-bash;
|
---|
[5e2cb65] | 543 | &c5-utillinux;
|
---|
[bc82645e] | 544 | &c5-perl;
|
---|
[6370fa6] | 545 |
|
---|
[503e1a6] | 546 |
|
---|
[69a52c1] | 547 | <sect1 id="ch05-stripping">
|
---|
| 548 | <title>Stripping</title>
|
---|
| 549 | <?dbhtml filename="stripping.html" dir="chapter05"?>
|
---|
| 550 |
|
---|
[1cb7ced] | 551 | <para>The steps in this section are optional. If your LFS partition is rather
|
---|
| 552 | small, you will be glad to learn that you can throw away some unnecessary
|
---|
| 553 | things. The executables and libraries you have built so far contain about 130 MB
|
---|
| 554 | of unneeded debugging symbols. Remove those symbols like this:</para>
|
---|
[69a52c1] | 555 |
|
---|
[21ba4e3] | 556 | <screen><userinput>strip --strip-unneeded /tools/{,s}bin/*
|
---|
| 557 | strip --strip-debug /tools/lib/*</userinput></screen>
|
---|
[69a52c1] | 558 |
|
---|
| 559 | <para>The first of the above commands will skip some twenty files, reporting
|
---|
| 560 | that it doesn't recognize their file format. Most of them are scripts instead
|
---|
| 561 | of binaries.</para>
|
---|
| 562 |
|
---|
| 563 | <para>Take care <emphasis>not</emphasis> to use
|
---|
| 564 | <userinput>--strip-unneeded</userinput> on the libraries -- they would be
|
---|
| 565 | destroyed and you would have to build Glibc all over again.</para>
|
---|
| 566 |
|
---|
[238527e] | 567 | <para>To save another couple of megabytes, you can throw away all the
|
---|
| 568 | documentation:</para>
|
---|
[69a52c1] | 569 |
|
---|
[21ba4e3] | 570 | <screen><userinput>rm -rf /tools/{,share/}{doc,info,man}</userinput></screen>
|
---|
[69a52c1] | 571 |
|
---|
[a6505d9] | 572 | <para>You will now need to have at least 850 MB of free space on your LFS
|
---|
[1668d8e] | 573 | filesystem to be able to build and install Glibc in the next phase. If you can
|
---|
| 574 | build and install Glibc, you can build and install the rest too.</para>
|
---|
[69a52c1] | 575 |
|
---|
| 576 | </sect1>
|
---|
| 577 |
|
---|
[6370fa6] | 578 | </chapter>
|
---|
| 579 |
|
---|