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author | Matthew Burgess <matthew@linuxfromscratch.org> | 2004-05-03 10:59:46 +0000 |
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committer | Matthew Burgess <matthew@linuxfromscratch.org> | 2004-05-03 10:59:46 +0000 |
commit | 673b0d84ba9591e07c0bdf0ee49d92eba10f502c (patch) | |
tree | 129e27a1450727b440da4378e0117a468eb9c25e /chapter05/chapter05.xml | |
parent | 287ea55da70ceb1f0990554b7db921d525fef816 (diff) |
* Merged newxml into HEAD
git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@3435 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689
Diffstat (limited to 'chapter05/chapter05.xml')
-rw-r--r-- | chapter05/chapter05.xml | 462 |
1 files changed, 38 insertions, 424 deletions
diff --git a/chapter05/chapter05.xml b/chapter05/chapter05.xml index f8724b46b..9a939e00e 100644 --- a/chapter05/chapter05.xml +++ b/chapter05/chapter05.xml @@ -1,428 +1,42 @@ +<?xml version="1.0" encoding="ISO-8859-1"?> +<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN" "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [ + <!ENTITY % general-entities SYSTEM "../general.ent"> + %general-entities; +]> <chapter id="chapter-temporary-tools" xreflabel="Chapter 5"> +<?dbhtml dir="chapter05"?> <title>Constructing a temporary system</title> -<?dbhtml filename="chapter05.html" dir="chapter05"?> - - -<sect1 id="ch-tools-introduction"> -<title>Introduction</title> -<?dbhtml filename="introduction.html" dir="chapter05"?> - -<para>In this chapter we will compile and install a minimal -Linux system. This system will contain just enough tools to be able -to start constructing the final LFS system in the next chapter.</para> - -<para>The building of this minimal system is done in two steps: first we -build a brand-new and host-independent toolchain (compiler, assembler, -linker and libraries), and then use this to build all the other essential -tools.</para> - -<para>The files compiled in this chapter will be installed under the -<filename class="directory">$LFS/tools</filename> directory -to keep them separate from the files installed in the next chapter. -Since the packages compiled here are merely temporary, we don't want -them to pollute the soon-to-be LFS system.</para> - -<para>Before issuing the build instructions for a package you are expected to -have already unpacked it as user <emphasis>lfs</emphasis>, and to have -performed a <userinput>cd</userinput> into the created directory. The build -instructions assume that you are using the <command>bash</command> -shell.</para> - -<para>Several of the packages are patched before compilation, but only when -the patch is needed to circumvent a problem. Often the patch is needed in -both this and the next chapter, but sometimes in only one of them. Therefore, -don't worry when instructions for a downloaded patch seem to be missing. Also, -when applying a patch, you'll occasionally see warning messages about -<emphasis>offset</emphasis> or <emphasis>fuzz</emphasis>. These warnings are -nothing to worry about, as the patch was still successfully applied.</para> - -<para>During the compilation of most packages you will see many warnings -scroll by on your screen. These are normal and can safely be ignored. They are -just what they say they are: warnings -- mostly about deprecated, but not -invalid, use of the C or C++ syntax. It's just that C standards have changed -rather often and some packages still use the older standard, which is not -really a problem.</para> - -<para>After installing each package you should delete its source and build -directories, <emphasis>unless</emphasis> told otherwise. Deleting the sources -saves space, but also prevents misconfiguration when the same package is -reinstalled further on. Only for three packages you will need to keep the -source and build directories around for a while, so their contents can be used -by later commands. Do not miss the reminders.</para> - -</sect1> - - -<sect1 id="tools-technicalnotes"> -<title>Technical notes</title> -<?dbhtml filename="technicalnotes.html" dir="chapter05"?> - -<para>This section attempts to explain some of the rationale and technical -details behind the overall build method. It's not essential that you understand -everything here immediately. Most of it will make sense once you have performed -an actual build. Feel free to refer back here at any time.</para> - -<para>The overall goal of <xref linkend="chapter-temporary-tools"/> is to provide a sane, -temporary environment that we can chroot into, and from which we can produce a -clean, trouble-free build of the target LFS system in -<xref linkend="chapter-building-system"/>. Along the way, we attempt to divorce ourselves -from the host system as much as possible, and in so doing build a -self-contained and self-hosted toolchain. It should be noted that the -build process has been designed in such a way so as to minimize the risks for -new readers and provide maximum educational value at the same time. In other -words, more advanced techniques could be used to build the system.</para> - -<important> -<para>Before continuing, you really should be aware of the name of your working -platform, often also referred to as the <emphasis>target triplet</emphasis>. For -many folks the target triplet will probably be -<emphasis>i686-pc-linux-gnu</emphasis>. A simple way to determine your target -triplet is to run the <filename>config.guess</filename> script that comes with -the source for many packages. Unpack the Binutils sources and run the script: -<userinput>./config.guess</userinput> and note the output.</para> - -<para>You'll also need to be aware of the name of your platform's -<emphasis>dynamic linker</emphasis>, often also referred to as the -<emphasis>dynamic loader</emphasis>, not to be confused with the standard linker -<emphasis>ld</emphasis> that is part of Binutils. The dynamic linker is provided -by Glibc and has the job of finding and loading the shared libraries needed by a -program, preparing the program to run and then running it. For most folks the -name of the dynamic linker will be <emphasis>ld-linux.so.2</emphasis>. On -platforms that are less prevalent, the name might be -<emphasis>ld.so.1</emphasis> and newer 64 bit platforms might even have -something completely different. You should be able to determine the name -of your platform's dynamic linker by looking in the -<filename class="directory">/lib</filename> directory on your host system. A -surefire way is to inspect a random binary from your host system by running: -<userinput>readelf -l <name of binary> | grep interpreter</userinput> -and noting the output. The authoritative reference covering all platforms is in -the <filename>shlib-versions</filename> file in the root of the Glibc source -tree.</para> -</important> - -<para>Some key technical points of how the <xref linkend="chapter-temporary-tools"/> build -method works:</para> - -<itemizedlist> -<listitem><para>Similar in principle to cross compiling whereby tools installed -into the same prefix work in cooperation and thus utilize a little GNU -"magic".</para></listitem> - -<listitem><para>Careful manipulation of the standard linker's library search -path to ensure programs are linked only against libraries we -choose.</para></listitem> - -<listitem><para>Careful manipulation of <command>gcc</command>'s -<emphasis>specs</emphasis> file to tell the compiler which target dynamic -linker will be used.</para></listitem> -</itemizedlist> - -<para>Binutils is installed first because both GCC and Glibc perform various -feature tests on the assembler and linker during their respective runs of -<command>./configure</command> to determine which software features to enable -or disable. This is more important than one might first realize. An incorrectly -configured GCC or Glibc can result in a subtly broken toolchain where the impact -of such breakage might not show up until near the end of the build of a whole -distribution. Thankfully, a test suite failure will usually alert us before too -much time is wasted.</para> - -<para>Binutils installs its assembler and linker into two locations, -<filename class="directory">/tools/bin</filename> and -<filename class="directory">/tools/$TARGET_TRIPLET/bin</filename>. In reality, -the tools in one location are hard linked to the other. An important facet of -the linker is its library search order. Detailed information can be obtained -from <command>ld</command> by passing it the <emphasis>--verbose</emphasis> -flag. For example: <command>ld --verbose | grep SEARCH</command> will -show you the current search paths and their order. You can see what files are -actually linked by <command>ld</command> by compiling a dummy program and -passing the <emphasis>--verbose</emphasis> switch to the linker. For example: -<command>gcc dummy.c -Wl,--verbose 2>&1 | grep succeeded</command> -will show you all the files successfully opened during the linking.</para> - -<para>The next package installed is GCC and during its run of -<command>./configure</command> you'll see, for example:</para> - -<blockquote><screen>checking what assembler to use... /tools/i686-pc-linux-gnu/bin/as -checking what linker to use... /tools/i686-pc-linux-gnu/bin/ld</screen></blockquote> - -<para>This is important for the reasons mentioned above. It also demonstrates -that GCC's configure script does not search the PATH directories to find which -tools to use. However, during the actual operation of <command>gcc</command> -itself, the same search paths are not necessarily used. You can find out which -standard linker <command>gcc</command> will use by running: -<command>gcc -print-prog-name=ld</command>. -Detailed information can be obtained from <command>gcc</command> by passing -it the <emphasis>-v</emphasis> flag while compiling a dummy program. For -example: <command>gcc -v dummy.c</command> will show you detailed -information about the preprocessor, compilation and assembly stages, including -<command>gcc</command>'s include search paths and their order.</para> - -<para>The next package installed is Glibc. The most important considerations for -building Glibc are the compiler, binary tools and kernel headers. The compiler -is generally no problem as Glibc will always use the <command>gcc</command> -found in a PATH directory. The binary tools and kernel headers can be a little -more troublesome. Therefore we take no risks and use the available configure -switches to enforce the correct selections. After the run of -<command>./configure</command> you can check the contents of the -<filename>config.make</filename> file in the -<filename class="directory">glibc-build</filename> directory for all the -important details. You'll note some interesting items like the use of -<emphasis>CC="gcc -B/tools/bin/"</emphasis> to control which binary tools are -used, and also the use of the <emphasis>-nostdinc</emphasis> and -<emphasis>-isystem</emphasis> flags to control the compiler's include search -path. These items help to highlight an important aspect of the Glibc package: -it is very self-sufficient in terms of its build machinery and generally does -not rely on toolchain defaults.</para> - -<para>After the Glibc installation, we make some adjustments to ensure that -searching and linking take place only within our <filename>/tools</filename> -prefix. We install an adjusted <command>ld</command>, which has a hard-wired -search path limited to <filename class="directory">/tools/lib</filename>. Then -we amend <command>gcc</command>'s specs file to point to our new dynamic -linker in <filename class="directory">/tools/lib</filename>. This last step is -<emphasis>vital</emphasis> to the whole process. As mentioned above, a -hard-wired path to a dynamic linker is embedded into every ELF shared -executable. You can inspect this by running: -<command>readelf -l <name of binary> | grep interpreter</command>. -By amending <command>gcc</command>'s specs file, we are ensuring that every -program compiled from here through the end of this chapter will use our new -dynamic linker in <filename class="directory">/tools/lib</filename>.</para> - -<para>The need to use the new dynamic linker is also the reason why we apply the -Specs patch for the second pass of GCC. Failure to do so will result in the GCC -programs themselves having the name of the dynamic linker from the host system's -<filename class="directory">/lib</filename> directory embedded into them, which -would defeat our goal of getting away from the host.</para> - -<para>During the second pass of Binutils, we are able to utilize the -<emphasis>--with-lib-path</emphasis> configure switch to control -<command>ld</command>'s library search path. From this point onwards, the -core toolchain is self-contained and self-hosted. The remainder of the -<xref linkend="chapter-temporary-tools"/> packages all build against the new Glibc in -<filename class="directory">/tools</filename> and all is well.</para> - -<para>Upon entering the chroot environment in <xref linkend="chapter-building-system"/>, the -first major package we install is Glibc, due to its self-sufficient nature that -we mentioned above. Once this Glibc is installed into -<filename class="directory">/usr</filename>, we perform a quick changeover of -the toolchain defaults, then proceed for real in building the rest of the -target LFS system.</para> - -</sect1> - - -<sect1 id="tools-aboutlinking"> -<title>Notes on static linking</title> -<?dbhtml filename="aboutlinking.html" dir="chapter05"?> - -<para>Most programs have to perform, beside their specific task, many rather -common and sometimes trivial operations. These include allocating memory, -searching directories, reading and writing files, string handling, pattern -matching, arithmetic and many other tasks. Instead of obliging each program to -reinvent the wheel, the GNU system provides all these basic functions in -ready-made libraries. The major library on any Linux system is -<emphasis>Glibc</emphasis>.</para> - -<para>There are two primary ways of linking the functions from a library to a -program that uses them: statically or dynamically. When a program is linked -statically, the code of the used functions is included in the executable, -resulting in a rather bulky program. When a program is dynamically linked, what -is included is a reference to the dynamic linker, the name of the library, and -the name of the function, resulting in a much smaller executable. (A third way -is to use the programming interface of the dynamic linker. See the -<emphasis>dlopen</emphasis> man page for more information.)</para> - -<para>Dynamic linking is the default on Linux and has three major advantages -over static linking. First, you need only one copy of the executable library -code on your hard disk, instead of having many copies of the same code included -into a whole bunch of programs -- thus saving disk space. Second, when several -programs use the same library function at the same time, only one copy of the -function's code is required in core -- thus saving memory space. Third, when a -library function gets a bug fixed or is otherwise improved, you only need to -recompile this one library, instead of having to recompile all the programs that -make use of the improved function.</para> - -<para>If dynamic linking has several advantages, why then do we statically link -the first two packages in this chapter? The reasons are threefold: historical, -educational, and technical. Historical, because earlier versions of LFS -statically linked every program in this chapter. Educational, because knowing -the difference is useful. Technical, because we gain an element of independence -from the host in doing so, meaning that those programs can be used -independently of the host system. However, it's worth noting that an overall -successful LFS build can still be achieved when the first two packages are -built dynamically.</para> - -</sect1> - - -&c5-binutils-pass1; -&c5-gcc-pass1; -&c5-kernelheaders; -&c5-glibc; - - -<sect1 id="ch-tools-adjusting"> -<title>Adjusting the toolchain</title> -<?dbhtml filename="adjusting.html" dir="chapter05"?> - -<para>Now that the temporary C libraries have been installed, we want all -the tools compiled in the rest of this chapter to be linked against these -libraries. To accomplish this, we need to adjust the linker and the compiler's -specs file. Some people would say that it is <emphasis>"black magic juju below -this line"</emphasis>, but it is really very simple.</para> - -<para>First install the adjusted linker (adjusted at the end of the first pass -of Binutils) by running the following command from within -the <filename class="directory">binutils-build</filename> directory:</para> - -<screen><userinput>make -C ld install</userinput></screen> - -<para>From this point onwards everything will link <emphasis>only</emphasis> -against the libraries in <filename>/tools/lib</filename>.</para> - -<note><para>If you somehow missed the earlier warning to retain the Binutils -source and build directories from the first pass or otherwise accidentally -deleted them or just don't have access to them, don't worry, all is not lost. -Just ignore the above command. The result is a small chance of the subsequent -testing programs linking against libraries on the host. This is not ideal, but -it's not a major problem. The situation is corrected when we install the -second pass of Binutils a bit further on.</para></note> - -<para>Now that the adjusted linker is installed, you have to -<emphasis>remove</emphasis> the Binutils build and source directories.</para> - -<para>The next thing to do is to amend our GCC specs file so that it points -to the new dynamic linker. A simple sed will accomplish this:</para> - -<!-- Ampersands are needed to allow cut and paste --> - -<screen><userinput>SPECFILE=/tools/lib/gcc-lib/*/*/specs && -sed -e 's@ /lib/ld-linux.so.2@ /tools/lib/ld-linux.so.2@g' \ - $SPECFILE > tempspecfile && -mv -f tempspecfile $SPECFILE && -unset SPECFILE</userinput></screen> - -<para>We recommend that you cut-and-paste the above rather than try and type it -all in. Or you can edit the specs file by hand if you want to: just replace the -occurrence of "/lib/ld-linux.so.2" with "/tools/lib/ld-linux.so.2". Be sure to -visually inspect the specs file to verify the intended change was actually -made.</para> - -<important><para>If you are working on a platform where the name of the dynamic -linker is something other than <filename>ld-linux.so.2</filename>, you -<emphasis>must</emphasis> substitute <filename>ld-linux.so.2</filename> with the -name of your platform's dynamic linker in the above commands. Refer back to -<xref linkend="tools-technicalnotes"/> if necessary.</para></important> - -<para>Lastly, there is a possibility that some include files from the host -system have found their way into GCC's private include dir. This can happen -because of GCC's "fixincludes" process which runs as part of the GCC build. -We'll explain more about this further on in this chapter. For now, run the -following commands to eliminate this possibility:</para> - -<screen><userinput>rm -f /tools/lib/gcc-lib/*/*/include/{pthread.h,bits/sigthread.h}</userinput></screen> - -<!-- HACK - Force some whitespace to appease tidy --> -<literallayout></literallayout> - -<caution><para>It is imperative at this point to stop and ensure that the basic -functions (compiling and linking) of the new toolchain are working as expected. -For this we are going to perform a simple sanity check:</para> - -<screen><userinput>echo 'main(){}' > dummy.c -cc dummy.c -readelf -l a.out | grep ': /tools'</userinput></screen> - -<para>If everything is working correctly, there should be no errors, and the -output of the last command will be (allowing for platform specific differences -in dynamic linker name):</para> - -<blockquote><screen>[Requesting program interpreter: /tools/lib/ld-linux.so.2]</screen></blockquote> - -<para>Note especially that <filename class="directory">/tools/lib</filename> -appears as the prefix of our dynamic linker.</para> - -<para>If you did not receive the output -as shown above, or received no output at all, then something is seriously wrong. -You will need to investigate and retrace your steps to find out where the -problem is and correct it. There is no point in continuing until this is done. -First, redo the sanity check using <command>gcc</command> instead of -<command>cc</command>. If this works it means the -<filename class="symlink">/tools/bin/cc</filename> symlink is missing. Revisit -<xref linkend="ch-tools-gcc-pass1"/> and fix the symlink. Second, ensure your PATH -is correct. You can check this by running <userinput>echo $PATH</userinput> and -verifying that <filename class="directory">/tools/bin</filename> is at the head -of the list. If the PATH is wrong it could mean you're not logged in as user -<emphasis>lfs</emphasis> or something went wrong back in <xref -linkend="prepare-settingenvironment"/>. Third, something may have gone wrong -with the specs file amendment above. In this case redo the specs file amendment -ensuring to cut-and-paste the commands as was recommended.</para> - -<para>Once you are satisfied that all is well, clean up the test files:</para> - -<screen><userinput>rm dummy.c a.out</userinput></screen> -</caution> - -<!-- HACK - Force some whitespace to appease tidy --> -<literallayout></literallayout> - -</sect1> - - -&c5-tcl; -&c5-expect; -&c5-dejagnu; -&c5-gcc-pass2; -&c5-binutils-pass2; - -&c5-gawk; -&c5-coreutils; -&c5-bzip2; -&c5-gzip; -&c5-diffutils; -&c5-findutils; -&c5-make; -&c5-grep; -&c5-sed; -&c5-gettext; -&c5-ncurses; -&c5-patch; -&c5-tar; -&c5-texinfo; -&c5-bash; -&c5-perl; - - -<sect1 id="ch-tools-stripping"> -<title>Stripping</title> -<?dbhtml filename="stripping.html" dir="chapter05"?> - -<para>The steps in this section are optional, but if your LFS partition is -rather small, you will be glad to learn that you can remove some unnecessary -things. The executables and libraries you have built so far contain about 130 -MB of unneeded debugging symbols. Remove those symbols with:</para> - -<screen><userinput>strip --strip-debug /tools/lib/* -strip --strip-unneeded /tools/{,s}bin/*</userinput></screen> - -<para>The last of the above commands will skip some twenty files, reporting -that it doesn't recognize their file format. Most of them are scripts instead -of binaries.</para> - -<para>Take care <emphasis>not</emphasis> to use -<emphasis>--strip-unneeded</emphasis> on the libraries -- the static ones -would be destroyed and you would have to build the three toolchain packages -all over again.</para> - -<para>To save another 30 MB, you can remove all the documentation:</para> - -<screen><userinput>rm -rf /tools/{doc,info,man}</userinput></screen> - -<para>You will now need to have at least 850 MB of free space on your LFS -file system to be able to build and install Glibc in the next phase. If you can -build and install Glibc, you can build and install the rest too.</para> - -</sect1> +<?dbhtml filename="chapter05.html"?> + +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="introduction.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="toolchaintechnotes.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="binutils-pass1.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="gcc-pass1.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="kernel-headers.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="glibc.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="adjusting.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="tcl.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="expect.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="dejagnu.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="gcc-pass2.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="binutils-pass2.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="gawk.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="coreutils.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="bzip2.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="gzip.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="diffutils.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="findutils.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="make.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="grep.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="sed.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="gettext.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="ncurses.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="patch.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="tar.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="texinfo.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="bash.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="util-linux.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="perl.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="stripping.xml"/> </chapter> - |