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