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Rearrange "How things are going to be done" section. Simplify seds in "Locking in Glibc" and "Re-adjusting the toolchain" sections. Miscellaneous other fixes.
git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@2931 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689
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Greg Schafer
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@ -95,6 +95,10 @@
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</itemizedlist>
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</para></listitem>
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<listitem><para>October 6th, 2003 [greg]: Simplify seds in "Locking in Glibc"
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and "Re-adjusting the toolchain" sections. Rearrange "How things are going to be
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done" section.</para></listitem>
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<listitem><para>October 5th, 2003 [greg]: Chapter 5: Add new section "Toolchain
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technical notes". Integrate and scale back the old "Why we use static linking"
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section. Closes Bug 658.</para></listitem>
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@ -9,15 +9,15 @@ programs like a compiler, linker and shell to build the new system. Normally
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all the required tools are available if you selected <quote>development</quote>
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as one of the options when you installed your distribution.</para>
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<para>In Chapter 3 you will first create a new Linux native partition and
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filesystem, the place where your new LFS system will be compiled and installed.
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Then in Chapter 4 you download all the packages and patches required to build
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an LFS system, and store them on the new filesystem.</para>
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<para>In Chapter 3 you will first create a new Linux native partition and file
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system, the place where your new LFS system will be compiled and installed. Then
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in Chapter 4 you download all the packages and patches required to build an LFS
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system, and store them on the new file system.</para>
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<para>Chapter 5 will then discuss the installation of a number of packages that
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will form the basic development suite (or tool-set) which is used to build the
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actual system in Chapter 6. Some of these packages are needed to resolve
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circular dependencies. For example, to compile a compiler you need a
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<para>Chapter 5 will then discuss the installation of a number of packages that
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will form the basic development suite (or toolchain) which is used to build the
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actual system in Chapter 6. Some of these packages are needed to resolve
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circular dependencies. For example, to compile a compiler you need a
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compiler.</para>
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<para>The first thing to be done in Chapter 5 is build a first pass of the
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@ -25,35 +25,17 @@ toolchain, which is made up of Binutils and GCC. The programs from these
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packages will be linked statically in order for them to be used independently
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of the host system. The second thing to do is build Glibc, the C library. Glibc
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will be compiled by the toolchain programs we just built in the first
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pass.</para>
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pass. The third thing to do is build a second pass of the toolchain. This time
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the toolchain will be dynamically linked against the newly built Glibc. The
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remaining Chapter 5 packages are all built using this second pass toolchain and
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dynamically linked against the new host-independent Glibc. When this is done,
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the LFS installation process will no longer depend on the host distribution,
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with the exception of the running kernel.</para>
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<para>The third thing to do is build a second pass of the toolchain. This time
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the toolchain will be dynamically linked against the newly built Glibc. The
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remaining Chapter 5 packages are all built using this second pass toolchain and
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dynamically linked against the new host-independent Glibc. When this is done,
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the LFS installation process will no longer depend on the host distribution,
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with the exception of the running kernel. This is known as <quote>self
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contained</quote> and <quote>self hosted</quote>. There is a discussion of the
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differences between statically and dynamically linked programs at the beginning
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of Chapter 5.</para>
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<para>You may be asking yourself <quote>that seems like a lot of work, just to
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get away from my host distribution</quote>. Let us take a few minutes to
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discuss this question. The work involved in building the packages in Chapter 5
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is to ensure that as little information as possible from your host makes it into
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your brand new LFS system. When you build the first two packages in Chapter 5,
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Binutils and GCC, they will be compiled statically. This means that the
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version of the C library on your host distribution will be embedded inside all
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the binary programs you just compiled. This has the potential to cause
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problems for you down the road. The host's Glibc is usually an unknown
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quantity and might even contain bugs or anything else we don't know about
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until it is too late. A well known issue is that statically linked binaries
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compiled on a Glibc-2.2.x based system that contain calls to the
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<emphasis>getpwuid()</emphasis> function crash when run on a Glibc-2.3.x based
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system. Seeing as we are about to build a Glibc-2.3.x based system, we need to
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shield ourselves from problems of this nature. The procedure employed in
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Chapter 5 achieves this goal. With all these things in mind, you can see that
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the extra effort to compile Binutils and GCC twice is well worth it.</para>
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<para>You may be asking yourself <quote>that seems like a lot of work, just to
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get away from my host distribution?</quote>. A full technical and in-depth
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explanation is provided at the start of Chapter 5, including some notes on the
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differences between statically and dynamically linked programs.</para>
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<para>In Chapter 6 your real LFS system will be built. The chroot (change root)
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program is used to enter a virtual environment and start a new shell whose root
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@ -155,7 +155,7 @@ to continue on.</para>
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<note><para>At this point it is strongly recommended to repeat the sanity check
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we performed earlier in the chapter. Refer back to the "Locking in" Glibc section
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and repeat the check. If the results are wrong then most likely, you forgot to
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apply the abovementioned GCC Specs patch.</para></note>
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apply the above mentioned GCC Specs patch.</para></note>
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</sect2>
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@ -23,16 +23,20 @@ Binutils build and source directories.</para>
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to the new dynamic linker. A simple sed will accomplish this:</para>
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<para><screen><userinput>SPECFILE=/tools/lib/gcc-lib/*/*/specs
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sed -e 's@/lib/ld.so.1@/tools/lib/ld.so.1@g' \
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-e 's@/lib/ld-linux.so.2@/tools/lib/ld-linux.so.2@g' \
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sed -e 's@/lib/ld-linux.so.2@/tools/lib/ld-linux.so.2@g' \
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$SPECFILE > tempspecfile
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mv tempspecfile $SPECFILE
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unset SPECFILE</userinput></screen></para>
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<para>We recommend that you cut-and-paste the above rather than try and type it
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all in. Or you can edit the specs file by hand if you want to: just replace
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"/lib/ld-linux.so.2" with "/tools/lib/ld-linux.so.2" and "/lib/ld.so.1" with
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"/tools/lib/ld.so.1".</para>
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<para>We recommend that you cut-and-paste the above rather than try and type it
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all in. Or you can edit the specs file by hand if you want to: just replace any
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occurrence of "/lib/ld-linux.so.2" with "/tools/lib/ld-linux.so.2".</para>
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<important><para>If you are working on a platform where the name of the dynamic
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linker is something other than <filename>ld-linux.so.2</filename>, you
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<emphasis>must</emphasis> substitute <filename>ld-linux.so.2</filename> with the
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name of your platform's dynamic linker in the above commands. Refer back to the
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"Toolchain technical notes" section if necessary.</para></important>
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<para>Lastly, there is a possibility that some include files from the host
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system have found their way into GCC's private include dir. This can happen
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@ -122,8 +122,8 @@ adjusted ld, which has a hard-wired search path limited to
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file to point to our new dynamic linker in
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<filename class="directory">/tools/lib</filename>. This last step is
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<emphasis>vital</emphasis> to the whole process. As mentioned above, a
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hard-wired path to a dynamic linker is embedded into every executable binary.
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You can inspect this by running:
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hard-wired path to a dynamic linker is embedded into every ELF shared
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executable. You can inspect this by running:
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<userinput>`readelf -l <name of binary> | grep interpreter`</userinput>.
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By amending the GCC specs file, we are ensuring that every program compiled from
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here through the end of Chapter 5 will use our new dynamic linker in
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@ -17,8 +17,8 @@ adjusted linker by running the following from within the
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<note><para>If you somehow missed the earlier warning to retain the Binutils
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source and build directories from the second pass in Chapter 5 or otherwise
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accidentally deleted them or just don't have access to them, don't worry, all is
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not lost. Just ignore this step. The result will be that the next package,
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Binutils, will link against the Glibc libraries in
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not lost. Just ignore the above command. The result will be that the next
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package, Binutils, will link against the Glibc libraries in
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<filename class="directory">/tools</filename> rather than
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<filename class="directory">/usr</filename>. This is not ideal, however, our
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testing has shown that the resulting Binutils program binaries should be
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@ -41,8 +41,7 @@ to the new dynamic linker. Just like earlier on, we use a sed to accomplish
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this:</para>
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<para><screen><userinput>SPECFILE=/tools/lib/gcc-lib/*/*/specs
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sed -e 's@/tools/lib/ld.so.1@/lib/ld.so.1@g' \
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-e 's@/tools/lib/ld-linux.so.2@/lib/ld-linux.so.2@g' \
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sed -e 's@/tools/lib/ld-linux.so.2@/lib/ld-linux.so.2@g' \
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$SPECFILE > newspecfile
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mv newspecfile $SPECFILE
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unset SPECFILE</userinput></screen></para>
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@ -51,6 +50,12 @@ unset SPECFILE</userinput></screen></para>
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before, it is a good idea to check the specs file to ensure the intended
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changes were actually made.</para>
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<important><para>If you are working on a platform where the name of the dynamic
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linker is something other than <filename>ld-linux.so.2</filename>, you
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<emphasis>must</emphasis> substitute <filename>ld-linux.so.2</filename> with the
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name of your platform's dynamic linker in the above commands. Refer back to the
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"Toolchain technical notes" section if necessary.</para></important>
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<caution><para>It is imperative at this point to stop and ensure that the
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basic functions (compiling and linking) of the adjusted toolchain are working
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as expected. For this we are going to perform a simple sanity check:</para>
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@ -24,7 +24,9 @@ compilers. Instructions for building these can be found at
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patch -Np1 -i ../gcc-&gcc-suppress-libiberty-patch-version;.patch</userinput></screen></para>
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<para>The second patch here suppresses the installation of libiberty from GCC,
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as we will use the one provided by binutils instead.</para>
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as we will use the one provided by binutils instead. Be careful
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<emphasis>not</emphasis> to apply the GCC specs patch from Chapter 5
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here.</para>
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<para>The GCC documentation recommends building GCC outside of the source
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directory in a dedicated build directory:</para>
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