diff options
author | Alex Gronenwoud <alex@linuxfromscratch.org> | 2003-11-13 22:31:08 +0000 |
---|---|---|
committer | Alex Gronenwoud <alex@linuxfromscratch.org> | 2003-11-13 22:31:08 +0000 |
commit | cfabeeda7b517f8b7a202113d4c3c645c81579af (patch) | |
tree | e657971b3423813c400dd5bd71d7c36af1b8aa08 /chapter05 | |
parent | 0ba2766b69ef1911d436eaf6cd6be684be50fc74 (diff) |
Moving chapter 5 intermezzos into a single file.
git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@3080 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689
Diffstat (limited to 'chapter05')
-rw-r--r-- | chapter05/adding-user.xml | 36 | ||||
-rw-r--r-- | chapter05/chapter05.xml | 504 | ||||
-rw-r--r-- | chapter05/creatingstage1dir.xml | 38 | ||||
-rw-r--r-- | chapter05/introduction.xml | 58 | ||||
-rw-r--r-- | chapter05/lockingglibc.xml | 97 | ||||
-rw-r--r-- | chapter05/setting-environment.xml | 58 | ||||
-rw-r--r-- | chapter05/toolchaintechnotes.xml | 200 |
7 files changed, 498 insertions, 493 deletions
diff --git a/chapter05/adding-user.xml b/chapter05/adding-user.xml deleted file mode 100644 index 4f6f487c5..000000000 --- a/chapter05/adding-user.xml +++ /dev/null @@ -1,36 +0,0 @@ -<sect1 id="ch05-addinguser"> -<title>Adding the user lfs</title> -<?dbhtml filename="addinguser.html" dir="chapter05"?> - -<para>When logged in as <emphasis>root</emphasis>, making a single mistake -can damage or even wreck your system. Therefore we recommend that you -build the packages in this chapter as an unprivileged user. You could -of course use your own user name, but to make it easier to set up a clean -work environment we'll create a new user <emphasis>lfs</emphasis> and -use this one during the installation process. As <emphasis>root</emphasis>, -issue the following commands to add the new user:</para> - -<screen><userinput>useradd -s /bin/bash -m lfs -passwd lfs</userinput></screen> - -<para>Now grant this new user <emphasis>lfs</emphasis> full access to -<filename class="directory">$LFS/tools</filename> by giving it ownership -of the directory:</para> - -<screen><userinput>chown lfs $LFS/tools</userinput></screen> - -<para>If you made a separate working directory as suggested, give user -<emphasis>lfs</emphasis> ownership of this directory too:</para> - -<screen><userinput>chown lfs $LFS/sources</userinput></screen> - -<para>Next, login as user <emphasis>lfs</emphasis>. This can be done via a -virtual console, through a display manager, or with the following substitute -user command:</para> - -<screen><userinput>su - lfs</userinput></screen> - -<para>The "<userinput>-</userinput>" instructs <userinput>su</userinput> to -start a new, clean shell.</para> - -</sect1> diff --git a/chapter05/chapter05.xml b/chapter05/chapter05.xml index 44cbf189f..ae7976fd4 100644 --- a/chapter05/chapter05.xml +++ b/chapter05/chapter05.xml @@ -2,21 +2,513 @@ <title>Constructing a temporary system</title> <?dbhtml filename="chapter05.html" dir="chapter05"?> -&c5-introduction; -&c5-toolchaintechnotes; -&c5-creatingtoolsdir; -&c5-addinguser; -&c5-settingenviron; + +<sect1 id="ch05-introduction"> +<title>Introduction</title> +<?dbhtml filename="introduction.html" dir="chapter05"?> + +<para>In this chapter we will compile and install a minimal +Linux system. This system will contain just enough tools to be able +to start constructing the final LFS system in the next chapter.</para> + +<para>The building of this minimal system is done in two steps: first we +build a brand-new and host-independent toolchain (compiler, assembler, +linker and libraries), and then use this to build all the other essential +tools.</para> + +<para>The files compiled in this chapter will be installed under the +<filename class="directory">$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>The key to learning what makes a Linux system work is to know +what each package is used for and why the user or the system needs it. +For this purpose a short summary of the content of each package is given +before the actual installation instructions. For a short description of +each program in a package, please refer to the corresponding section in +<xref linkend="appendixa"/>.</para> + +<para>The build instructions assume that you are using the bash shell. There +is also a general expectation that you have already unpacked the sources for a +package and have performed a <userinput>cd</userinput> into the unpacked source +directory before issuing the build commands.</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.</para> + +<para>During the installation of most packages you will +see all kinds of compiler warnings scroll by on your screen. These are +normal and can be safely 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><emphasis>Unless</emphasis> told not to, you should normally delete the +source and build directories after installing each package -- for cleanness +sake and to save space.</para> + +<para>Before continuing, make sure the LFS environment variable is set up +properly by executing the following:</para> + +<screen><userinput>echo $LFS</userinput></screen> + +<para>Make sure the output shows the path to your LFS partition's mount +point, which is <filename class="directory">/mnt/lfs</filename> if you +followed our example.</para> + +</sect1> + + +<sect1 id="ch05-toolchaintechnotes"> +<title>Toolchain technical notes</title> +<?dbhtml filename="toolchaintechnotes.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="chapter05"/> 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="chapter06"/>. 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 be, for example: +<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="chapter05"/> 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 <userinput>gcc</userinput>'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 +<userinput>./configure</userinput> 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 <userinput>ld</userinput> by passing it the <emphasis>--verbose</emphasis> +flag. For example: <userinput>'ld --verbose | grep SEARCH'</userinput> will +show you the current search paths and their order. You can see what files are +actually linked by <userinput>ld</userinput> by compiling a dummy program and +passing the <emphasis>--verbose</emphasis> switch. For example: +<userinput>'gcc dummy.c -Wl,--verbose 2>&1 | grep succeeded'</userinput> +will show you all the files successfully opened during the link.</para> + +<para>The next package installed is GCC and during its run of +<userinput>./configure</userinput> 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 <userinput>gcc</userinput> +itself, the same search paths are not necessarily used. You can find out which +standard linker <userinput>gcc</userinput> will use by running: +<userinput>'gcc -print-prog-name=ld'</userinput>. +Detailed information can be obtained from <userinput>gcc</userinput> by passing +it the <emphasis>-v</emphasis> flag while compiling a dummy program. For +example: <userinput>'gcc -v dummy.c'</userinput> will show you detailed +information about the preprocessor, compilation and assembly stages, including +<userinput>gcc</userinput>'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 <userinput>gcc</userinput> +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 +<userinput>./configure</userinput> 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 +<userinput>CC="gcc -B/tools/bin/"</userinput> 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 <userinput>ld</userinput>, which has a hard-wired +search path limited to <filename class="directory">/tools/lib</filename>. Then +we amend <userinput>gcc</userinput>'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: +<userinput>'readelf -l <name of binary> | grep interpreter'</userinput>. +By amending <userinput>gcc</userinput>'s specs file, we are ensuring that every +program compiled from here through the end of <xref linkend="chapter05"/> 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 +<userinput>ld</userinput>'s library search path. From this point onwards, the +core toolchain is self-contained and self-hosted. The remainder of the +<xref linkend="chapter05"/> 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="chapter06"/>, 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 <xref linkend="chapter06"/> LFS system.</para> + +<sect2> +<title>Notes on static linking</title> + +<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> + +</sect2> + +</sect1> + + +<sect1 id="ch05-creatingtoolsdir"> +<title>Creating the $LFS/tools directory</title> +<?dbhtml filename="creatingtoolsdir.html" dir="chapter05"?> + +<para>All programs compiled in this chapter will be installed under <filename +class="directory">$LFS/tools</filename> to keep them separate from the +programs compiled in the next chapter. The programs compiled here are only +temporary tools and won't be a part of the final LFS system and by keeping them +in a separate directory, we can later easily throw them away.</para> + +<para>If later you wish to search through the binaries of your system to see +what files they make use of or link against, then to make this searching easier +you may want to choose a unique name. Instead of the simple "tools" you could +use something like "tools-for-lfs".</para> + +<para>Create the required directory by running the following:</para> + +<screen><userinput>mkdir $LFS/tools</userinput></screen> + +<para>The next step is to create a <filename>/tools</filename> symlink on +your host system. It will point to the directory we just created on the LFS +partition:</para> + +<screen><userinput>ln -s $LFS/tools /</userinput></screen> + +<para>This symlink enables us to compile our toolchain so that it always +refers to <filename>/tools</filename>, meaning that the compiler, assembler +and linker will work both in this chapter (when we are still using some tools +from the host) <emphasis>and</emphasis> in the next (when we are chrooted to +the LFS partition).</para> + +<note><para>Study the above command closely. It can be confusing at first +glance. The <userinput>ln</userinput> command has several syntax variations, +so be sure to check the ln man page before reporting what you may think is an +error.</para></note> + +</sect1> + + +<sect1 id="ch05-addinguser"> +<title>Adding the user lfs</title> +<?dbhtml filename="addinguser.html" dir="chapter05"?> + +<para>When logged in as <emphasis>root</emphasis>, making a single mistake +can damage or even wreck your system. Therefore we recommend that you +build the packages in this chapter as an unprivileged user. You could +of course use your own user name, but to make it easier to set up a clean +work environment we'll create a new user <emphasis>lfs</emphasis> and +use this one during the installation process. As <emphasis>root</emphasis>, +issue the following commands to add the new user:</para> + +<screen><userinput>useradd -s /bin/bash -m lfs +passwd lfs</userinput></screen> + +<para>Now grant this new user <emphasis>lfs</emphasis> full access to +<filename class="directory">$LFS/tools</filename> by giving it ownership +of the directory:</para> + +<screen><userinput>chown lfs $LFS/tools</userinput></screen> + +<para>If you made a separate working directory as suggested, give user +<emphasis>lfs</emphasis> ownership of this directory too:</para> + +<screen><userinput>chown lfs $LFS/sources</userinput></screen> + +<para>Next, login as user <emphasis>lfs</emphasis>. This can be done via a +virtual console, through a display manager, or with the following substitute +user command:</para> + +<screen><userinput>su - lfs</userinput></screen> + +<para>The "<userinput>-</userinput>" instructs <userinput>su</userinput> to +start a new, clean shell.</para> + +</sect1> + + +<sect1 id="ch05-settingenviron"> +<title>Setting up the environment</title> +<?dbhtml filename="settingenvironment.html" dir="chapter05"?> + +<para>While logged in as user <emphasis>lfs</emphasis>, issue the +following commands to set up a good work environment:</para> + +<screen><userinput>cat > ~/.bash_profile << "EOF"</userinput> +set +h +umask 022 +LFS=/mnt/lfs +LC_ALL=POSIX +PATH=/tools/bin:$PATH +export LFS LC_ALL PATH +unset CC CXX CPP LD_LIBRARY_PATH LD_PRELOAD +<userinput>EOF + +source ~/.bash_profile</userinput></screen> + +<para>The <userinput>set +h</userinput> command turns off +<userinput>bash</userinput>'s hash function. Normally hashing is a useful +feature: <userinput>bash</userinput> uses a hash table to remember the +full pathnames of executable files to avoid searching the PATH time and time +again to find the same executable. However, we'd like the new tools to be +used as soon as they are installed. By switching off the hash function, our +"interactive" commands (<userinput>make</userinput>, +<userinput>patch</userinput>, <userinput>sed</userinput>, +<userinput>cp</userinput> and so forth) will always use +the newest available version during the build process.</para> + +<para>Setting the user file-creation mask to 022 ensures that newly created +files and directories are only writable for their owner, but readable and +executable for anyone.</para> + +<para>The LFS variable should of course be set to the mount point you +chose.</para> + +<para>The LC_ALL variable controls the localization of certain programs, +making their messages follow the conventions of a specified country. If your +host system uses a version of Glibc older than 2.2.4, +having LC_ALL set to something other than "POSIX" or "C" during this chapter +may cause trouble if you exit the chroot environment and wish to return later. +By setting LC_ALL to "POSIX" (or "C", the two are equivalent) we ensure that +everything will work as expected in the chroot environment.</para> + +<para>We prepend <filename>/tools/bin</filename> to the standard PATH so +that, as we move along through this chapter, the tools we build will get used +during the rest of the building process.</para> + +<para>The CC, CXX, CPP, LD_LIBRARY_PATH and LD_PRELOAD environment variables all +have the potential to cause havoc with our Chapter 5 toolchain. We therefore +unset them to prevent any chance of this happening.</para> + +<para>Now, after sourcing the just-created profile, we're all set to begin +building the temporary tools that will support us in later chapters.</para> + +</sect1> + + &c5-binutils-pass1; &c5-gcc-pass1; &c5-kernelheaders; &c5-glibc; -&c5-lockingglibc; + + +<sect1 id="ch05-locking-glibc"> +<title>"Locking in" Glibc</title> +<?dbhtml filename="lockingglibc.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.</para> + +<para>First install the adjusted linker by running the following from within +the <filename class="directory">binutils-build</filename> directory:</para> + +<screen><userinput>make -C ld install</userinput></screen> + +<para>The linker was adjusted a little while back, at the end of the first +pass of Binutils. 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 subsequent +programs linking against libraries on the host. This is not ideal, however, +it's not a major problem. The situation is corrected when we install the +second pass of Binutils later on.</para></note> + +<para>Now that the adjusted linker is installed, you have to remove 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 any +occurrence of "/lib/ld-linux.so.2" with "/tools/lib/ld-linux.so.2".</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="ch05-toolchaintechnotes"/> 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 +gcc 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:</para> + +<blockquote><screen>[Requesting program interpreter: /tools/lib/ld-linux.so.2]</screen></blockquote> + +<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. Most likely something went wrong with the specs +file amendment above. Note especially that <filename>/tools/lib</filename> +appears as the prefix of our dynamic linker. Of course, if you are working on a +platform where the name of the dynamic linker is something other than +<filename>ld-linux.so.2</filename>, then the output will be slightly +different.</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> + +<para>This completes the installation of the self-contained toolchain, and it +can now be used to build the rest of the temporary tools.</para> + +</sect1> + + &c5-tcl; &c5-expect; &c5-dejagnu; &c5-gcc-pass2; &c5-binutils-pass2; + &c5-gawk; &c5-coreutils; &c5-bzip2; diff --git a/chapter05/creatingstage1dir.xml b/chapter05/creatingstage1dir.xml deleted file mode 100644 index 2621ec6b3..000000000 --- a/chapter05/creatingstage1dir.xml +++ /dev/null @@ -1,38 +0,0 @@ -<sect1 id="ch05-creatingtoolsdir"> -<title>Creating the $LFS/tools directory</title> -<?dbhtml filename="creatingtoolsdir.html" dir="chapter05"?> - -<para>All programs compiled in this chapter will be installed under <filename -class="directory">$LFS/tools</filename> to keep them separate from the -programs compiled in the next chapter. The programs compiled here are only -temporary tools and won't be a part of the final LFS system and by keeping them -in a separate directory, we can later easily throw them away.</para> - -<para>If later you wish to search through the binaries of your system to see -what files they make use of or link against, then to make this searching easier -you may want to choose a unique name. Instead of the simple "tools" you could -use something like "tools-for-lfs".</para> - -<para>Create the required directory by running the following:</para> - -<screen><userinput>mkdir $LFS/tools</userinput></screen> - -<para>The next step is to create a <filename>/tools</filename> symlink on -your host system. It will point to the directory we just created on the LFS -partition:</para> - -<screen><userinput>ln -s $LFS/tools /</userinput></screen> - -<para>This symlink enables us to compile our toolchain so that it always -refers to <filename>/tools</filename>, meaning that the compiler, assembler -and linker will work both in this chapter (when we are still using some tools -from the host) <emphasis>and</emphasis> in the next (when we are chrooted to -the LFS partition).</para> - -<note><para>Study the above command closely. It can be confusing at first -glance. The <userinput>ln</userinput> command has several syntax variations, -so be sure to check the ln man page before reporting what you may think is an -error.</para></note> - -</sect1> - diff --git a/chapter05/introduction.xml b/chapter05/introduction.xml deleted file mode 100644 index 5335b8be2..000000000 --- a/chapter05/introduction.xml +++ /dev/null @@ -1,58 +0,0 @@ -<sect1 id="ch05-introduction"> -<title>Introduction</title> -<?dbhtml filename="introduction.html" dir="chapter05"?> - -<para>In this chapter we will compile and install a minimal -Linux system. This system will contain just enough tools to be able -to start constructing the final LFS system in the next chapter.</para> - -<para>The building of this minimal system is done in two steps: first we -build a brand-new and host-independent toolchain (compiler, assembler, -linker and libraries), and then use this to build all the other essential -tools.</para> - -<para>The files compiled in this chapter will be installed under the -<filename class="directory">$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>The key to learning what makes a Linux system work is to know -what each package is used for and why the user or the system needs it. -For this purpose a short summary of the content of each package is given -before the actual installation instructions. For a short description of -each program in a package, please refer to the corresponding section in -<xref linkend="appendixa"/>.</para> - -<para>The build instructions assume that you are using the bash shell. There -is also a general expectation that you have already unpacked the sources for a -package and have performed a <userinput>cd</userinput> into the unpacked source -directory before issuing the build commands.</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.</para> - -<para>During the installation of most packages you will -see all kinds of compiler warnings scroll by on your screen. These are -normal and can be safely 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><emphasis>Unless</emphasis> told not to, you should normally delete the -source and build directories after installing each package -- for cleanness -sake and to save space.</para> - -<para>Before continuing, make sure the LFS environment variable is set up -properly by executing the following:</para> - -<screen><userinput>echo $LFS</userinput></screen> - -<para>Make sure the output shows the path to your LFS partition's mount -point, which is <filename class="directory">/mnt/lfs</filename> if you -followed our example.</para> - -</sect1> - diff --git a/chapter05/lockingglibc.xml b/chapter05/lockingglibc.xml deleted file mode 100644 index eb2f1c7d1..000000000 --- a/chapter05/lockingglibc.xml +++ /dev/null @@ -1,97 +0,0 @@ -<sect1 id="ch05-locking-glibc"> -<title>"Locking in" Glibc</title> -<?dbhtml filename="lockingglibc.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.</para> - -<para>First install the adjusted linker by running the following from within -the <filename class="directory">binutils-build</filename> directory:</para> - -<screen><userinput>make -C ld install</userinput></screen> - -<para>The linker was adjusted a little while back, at the end of the first -pass of Binutils. 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 subsequent -programs linking against libraries on the host. This is not ideal, however, -it's not a major problem. The situation is corrected when we install the -second pass of Binutils later on.</para></note> - -<para>Now that the adjusted linker is installed, you have to remove 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 any -occurrence of "/lib/ld-linux.so.2" with "/tools/lib/ld-linux.so.2".</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="ch05-toolchaintechnotes"/> 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 -gcc 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:</para> - -<blockquote><screen>[Requesting program interpreter: /tools/lib/ld-linux.so.2]</screen></blockquote> - -<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. Most likely something went wrong with the specs -file amendment above. Note especially that <filename>/tools/lib</filename> -appears as the prefix of our dynamic linker. Of course, if you are working on a -platform where the name of the dynamic linker is something other than -<filename>ld-linux.so.2</filename>, then the output will be slightly -different.</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> - -<para>This completes the installation of the self-contained toolchain, and it -can now be used to build the rest of the temporary tools.</para> - -</sect1> - diff --git a/chapter05/setting-environment.xml b/chapter05/setting-environment.xml deleted file mode 100644 index 413908917..000000000 --- a/chapter05/setting-environment.xml +++ /dev/null @@ -1,58 +0,0 @@ -<sect1 id="ch05-settingenviron"> -<title>Setting up the environment</title> -<?dbhtml filename="settingenvironment.html" dir="chapter05"?> - -<para>While logged in as user <emphasis>lfs</emphasis>, issue the -following commands to set up a good work environment:</para> - -<screen><userinput>cat > ~/.bash_profile << "EOF"</userinput> -set +h -umask 022 -LFS=/mnt/lfs -LC_ALL=POSIX -PATH=/tools/bin:$PATH -export LFS LC_ALL PATH -unset CC CXX CPP LD_LIBRARY_PATH LD_PRELOAD -<userinput>EOF - -source ~/.bash_profile</userinput></screen> - -<para>The <userinput>set +h</userinput> command turns off -<userinput>bash</userinput>'s hash function. Normally hashing is a useful -feature: <userinput>bash</userinput> uses a hash table to remember the -full pathnames of executable files to avoid searching the PATH time and time -again to find the same executable. However, we'd like the new tools to be -used as soon as they are installed. By switching off the hash function, our -"interactive" commands (<userinput>make</userinput>, -<userinput>patch</userinput>, <userinput>sed</userinput>, -<userinput>cp</userinput> and so forth) will always use -the newest available version during the build process.</para> - -<para>Setting the user file-creation mask to 022 ensures that newly created -files and directories are only writable for their owner, but readable and -executable for anyone.</para> - -<para>The LFS variable should of course be set to the mount point you -chose.</para> - -<para>The LC_ALL variable controls the localization of certain programs, -making their messages follow the conventions of a specified country. If your -host system uses a version of Glibc older than 2.2.4, -having LC_ALL set to something other than "POSIX" or "C" during this chapter -may cause trouble if you exit the chroot environment and wish to return later. -By setting LC_ALL to "POSIX" (or "C", the two are equivalent) we ensure that -everything will work as expected in the chroot environment.</para> - -<para>We prepend <filename>/tools/bin</filename> to the standard PATH so -that, as we move along through this chapter, the tools we build will get used -during the rest of the building process.</para> - -<para>The CC, CXX, CPP, LD_LIBRARY_PATH and LD_PRELOAD environment variables all -have the potential to cause havoc with our Chapter 5 toolchain. We therefore -unset them to prevent any chance of this happening.</para> - -<para>Now, after sourcing the just-created profile, we're all set to begin -building the temporary tools that will support us in later chapters.</para> - -</sect1> - diff --git a/chapter05/toolchaintechnotes.xml b/chapter05/toolchaintechnotes.xml deleted file mode 100644 index 5cca86e2b..000000000 --- a/chapter05/toolchaintechnotes.xml +++ /dev/null @@ -1,200 +0,0 @@ -<sect1 id="ch05-toolchaintechnotes"> -<title>Toolchain technical notes</title> -<?dbhtml filename="toolchaintechnotes.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="chapter05"/> 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="chapter06"/>. 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 be, for example: -<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="chapter05"/> 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 <userinput>gcc</userinput>'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 -<userinput>./configure</userinput> 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 <userinput>ld</userinput> by passing it the <emphasis>--verbose</emphasis> -flag. For example: <userinput>'ld --verbose | grep SEARCH'</userinput> will -show you the current search paths and their order. You can see what files are -actually linked by <userinput>ld</userinput> by compiling a dummy program and -passing the <emphasis>--verbose</emphasis> switch. For example: -<userinput>'gcc dummy.c -Wl,--verbose 2>&1 | grep succeeded'</userinput> -will show you all the files successfully opened during the link.</para> - -<para>The next package installed is GCC and during its run of -<userinput>./configure</userinput> 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 <userinput>gcc</userinput> -itself, the same search paths are not necessarily used. You can find out which -standard linker <userinput>gcc</userinput> will use by running: -<userinput>'gcc -print-prog-name=ld'</userinput>. -Detailed information can be obtained from <userinput>gcc</userinput> by passing -it the <emphasis>-v</emphasis> flag while compiling a dummy program. For -example: <userinput>'gcc -v dummy.c'</userinput> will show you detailed -information about the preprocessor, compilation and assembly stages, including -<userinput>gcc</userinput>'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 <userinput>gcc</userinput> -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 -<userinput>./configure</userinput> 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 -<userinput>CC="gcc -B/tools/bin/"</userinput> 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 <userinput>ld</userinput>, which has a hard-wired -search path limited to <filename class="directory">/tools/lib</filename>. Then -we amend <userinput>gcc</userinput>'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: -<userinput>'readelf -l <name of binary> | grep interpreter'</userinput>. -By amending <userinput>gcc</userinput>'s specs file, we are ensuring that every -program compiled from here through the end of <xref linkend="chapter05"/> 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 -<userinput>ld</userinput>'s library search path. From this point onwards, the -core toolchain is self-contained and self-hosted. The remainder of the -<xref linkend="chapter05"/> 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="chapter06"/>, 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 <xref linkend="chapter06"/> LFS system.</para> - -<sect2> -<title>Notes on static linking</title> - -<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> - -</sect2> - -</sect1> - |