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diff --git a/prologue/multilib.xml b/prologue/multilib.xml new file mode 100644 index 000000000..b4bf7975d --- /dev/null +++ b/prologue/multilib.xml @@ -0,0 +1,128 @@ +<?xml version="1.0" encoding="ISO-8859-1"?> +<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" + "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [ + <!ENTITY % general-entities SYSTEM "../general.ent"> + %general-entities; +]> + +<sect1 arch="ml_32,ml_x32,ml_all" id="pre-multilib"> + <?dbhtml filename="multilib.html"?> + + <title>About the Multilib Edition</title> + + <sect2><title>What is Multilib</title> + + <para>Today, most systems in the x86 world have a word size of 64 + bit. The word size is a number of bits which can be used at once + in the most efficient way. Previous architectures of x86 processors + had a word size of 32 bit which means they have a different + understanding of what is the best alignment of data in memory as + well as they have a different mechanism to address a different size + of memory. Even the instruction set of the 64 bit processors is + quite simmilar to the instructions of 32 bit processors, binaries + (objects compiled to machine code) cannot directly be executed on + 64 bit systems.</para> + + <para>Multilib is a mechanism to provide support for the 32 bit + binaries so that they can be executed of modern 64 bit CPUs.</para> + + </sect2> + + <sect2><title>Why doing Multilib?</title> + + <para>From an educational point of view, LFS in its 'native' form is + probably the best way to see how a Linux system is built from source. + There is no need to confuse with different architectures. But when + there is a need to run 32 binaries and you don't want to build the + whole system in 32 bit (which would be waste of ressources + nowadays) then LFS-multilib is an option. Examples for such a + need could be + <itemizedlist> + <listitem><para>Closed-source software without source only + available for 32 bit. That may be the case for printer driver + or any other kind of hardware drivers, the company provides + the binaries. If you have such a driver, LFS-multilib + may help you getting the stuff running</para> + </listitem> + <listitem><para>If you want to go far beyond LFS and setup a + virtualization platform like <application>VirtualBox</application>, + you will need multilib support</para> + </listitem> + <listitem><para>or even just because you can</para> + </listitem> + </itemizedlist> + + </para> + + <para>The multilib edition of LFS goes a small step beyond and a + small step back to what has been said in the previous section + when talking about target architectures. On one hand, the multilib + edition is focused and <emphasis>limited</emphasis> to x86_64 + architectures only, on the other hand, it <emphasis>expands</emphasis> + the instructions to utilize both possible architectures, namely + 32-bit as well as 64-bit.</para> + + <para>It also goes a bit beyond the basic educational + approach of LFS which is to show you how to build a Linux system. + To achieve this, no support for additional architectures than + the default one for your system is required. If you haven't + previously built by the standard LFS book, you are encouraged to + do so before using this edition.</para> + + </sect2> + + <sect2><title>Building a Multilib System</title> + + <para>Building a multilib system is not that much different from + building a system by using the 'native' LFS book. Beside some + tweaks here and there the most prominent difference is that + multilib requires compiling some applications up to three times: + one for the primary 64-bit architecture, + one for the 32-bit architecture (m32), + and once again for the 32-bit architecture with is 32-bit memory + access and 64 bit instruction set (mx32).</para> + + <para>Continue only if you and your system meets the following + requirements: + <itemizedlist> + <listitem> + <para>you have a x86_64 compatible machine</para> + <note><para> + If you have access to the kernel config for your system, + you will need to have + <parameter>CONFIG_IA32_EMULATION=y</parameter> + set in order to build for <parameter>m32</parameter> and + <parameter>CONFIG_X86_X32=y</parameter> set in order to + build for <parameter>mx32</parameter>. + </para> + <para> + If you do not have access to the kernel config for your system, + you may be able to test for compatability by running the + following commands: + </para> +<screen><userinput>echo 'int main(){}' > dummy.c +gcc -m32 dummy.c +./a.out + +gcc -mx32 dummy.c +./a.out</userinput></screen> + <para> + If either of the <command>./a.out</command> commands results in an + "Exec format error" message, then you do not have a system kernel + capable of building for that architecture within LFS, and so you + should probably look to build an LFS system without Multilib, but + with the required kernel capabilities, and use that to build a + Multilib system. + </para></note> + </listitem> + <listitem><para>you already have some experience with LFS</para></listitem> + <listitem><para>you have a need for 32-bit support</para></listitem> + </itemizedlist> + </para> + + <para>If you passed all three requirements, go ahead and build LFS + in multilib mode.</para> + + </sect2> + +</sect1> |