mirror of
https://git.linuxfromscratch.org/lfs.git
synced 2025-01-18 21:17:38 +00:00
673b0d84ba
git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@3435 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689
81 lines
3.5 KiB
XML
81 lines
3.5 KiB
XML
<?xml version="1.0" encoding="ISO-8859-1"?>
|
|
<!DOCTYPE sect1 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;
|
|
]>
|
|
<sect1 id="ch-system-kernel-headers">
|
|
<title>Linux-&linux-version; headers</title>
|
|
<?dbhtml filename="kernelheaders.html"?>
|
|
|
|
<indexterm zone="ch-system-kernel-headers">
|
|
<primary sortas="a-Linux">Linux</primary>
|
|
<secondary>system, headers</secondary></indexterm>
|
|
|
|
<screen>&buildtime; 0.1 SBU
|
|
&diskspace; 186 MB</screen>
|
|
|
|
|
|
<sect2>
|
|
<title>Installation of the kernel headers</title>
|
|
|
|
<para>We won't be compiling a new kernel yet -- we'll do that when we have
|
|
finished the installation of all the packages. But the libraries installed in
|
|
the next section need to refer to the kernel header files in order to know how
|
|
to interface with the kernel. Instead of unpacking the kernel sources again,
|
|
making the version file and the symlinks and so on, we will simply copy the
|
|
headers from the temporary tools directory in one swoop:</para>
|
|
|
|
<screen><userinput>cp -a /tools/include/{asm,asm-generic,linux} /usr/include</userinput></screen>
|
|
|
|
<para>A few kernel header files refer to the <filename>autoconf.h</filename>
|
|
header file. Since we have not yet configured the kernel, we need to create
|
|
this file ourselves in order to avoid a compilation failure of Sysklogd.
|
|
Create an empty <filename>autoconf.h</filename> file with:</para>
|
|
|
|
<screen><userinput>touch /usr/include/linux/autoconf.h</userinput></screen>
|
|
|
|
</sect2>
|
|
|
|
|
|
<sect2>
|
|
<title>Why we copy the kernel headers</title>
|
|
|
|
<para>In the past it was common practice to symlink the
|
|
<filename class="directory">/usr/include/{linux,asm}</filename> directories
|
|
to <filename class="directory">/usr/src/linux/include/{linux,asm}</filename>.
|
|
This was a <emphasis>bad</emphasis> practice, as the following extract from a
|
|
post by Linus Torvalds to the Linux Kernel Mailing List points out:</para>
|
|
|
|
<screen>I would suggest that people who compile new kernels should:
|
|
|
|
- not have a single symbolic link in sight (except the one that the
|
|
kernel build itself sets up, namely the <quote>linux/include/asm</quote>
|
|
symlink that is only used for the internal kernel compile itself)
|
|
|
|
And yes, this is what I do. My /usr/src/linux still has the old 2.2.13
|
|
header files, even though I haven't run a 2.2.13 kernel in a _loong_
|
|
time. But those headers were what Glibc was compiled against, so those
|
|
headers are what matches the library object files.
|
|
|
|
And this is actually what has been the suggested environment for at
|
|
least the last five years. I don't know why the symlink business keeps
|
|
on living on, like a bad zombie. Pretty much every distribution still
|
|
has that broken symlink, and people still remember that the linux
|
|
sources should go into <quote>/usr/src/linux</quote> even though that hasn't
|
|
been true in a _loong_ time.</screen>
|
|
|
|
<para>The essential part is where Linus states that the header files should be
|
|
<emphasis>the ones which Glibc was compiled against</emphasis>. These are
|
|
the headers that should be used when you later compile other packages, as they
|
|
are the ones that match the object-code library files. By copying the headers,
|
|
we ensure that they remain available if later you upgrade your kernel.</para>
|
|
|
|
<para>Note, by the way, that it is perfectly all right to have the kernel sources
|
|
in <filename class="directory">/usr/src/linux</filename>, as long as you don't
|
|
have the <filename class="directory">/usr/include/{linux,asm}</filename>
|
|
symlinks.</para>
|
|
|
|
</sect2>
|
|
|
|
</sect1>
|