source: chapter10/kernel.xml@ cfc0780

xry111/arm64 xry111/arm64-12.0
Last change on this file since cfc0780 was cfc0780, checked in by Xi Ruoyao <xry111@…>, 20 months ago

arm64: update arch-specific path to kernel image

"vmlinuz" is a little puzzling as the kernel image is not compressed.
But let's not deviate too much from trunk...
  • Property mode set to 100644
File size: 18.9 KB
Line 
1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
4 <!ENTITY % general-entities SYSTEM "../general.ent">
5 %general-entities;
6]>
7
8<sect1 id="ch-bootable-kernel" role="wrap">
9 <?dbhtml filename="kernel.html"?>
10
11 <sect1info condition="script">
12 <productname>kernel</productname>
13 <productnumber>&linux-version;</productnumber>
14 <address>&linux-url;</address>
15 </sect1info>
16
17 <title>Linux-&linux-version;</title>
18
19 <indexterm zone="ch-bootable-kernel">
20 <primary sortas="a-Linux">Linux</primary>
21 </indexterm>
22
23 <sect2 role="package">
24 <title/>
25
26 <para>The Linux package contains the Linux kernel.</para>
27
28 <segmentedlist>
29 <segtitle>&buildtime;</segtitle>
30 <segtitle>&diskspace;</segtitle>
31
32 <seglistitem>
33 <seg>&linux-knl-sbu;</seg>
34 <seg>&linux-knl-du;</seg>
35 </seglistitem>
36 </segmentedlist>
37
38 </sect2>
39
40 <sect2 role="installation">
41 <title>Installation of the kernel</title>
42
43 <para>Building the kernel involves a few steps&mdash;configuration,
44 compilation, and installation. Read the <filename>README</filename> file
45 in the kernel source tree for alternative methods to the way this book
46 configures the kernel.</para>
47
48 <para>Prepare for compilation by running the following command:</para>
49
50<screen><userinput remap="pre">make mrproper</userinput></screen>
51
52 <para>This ensures that the kernel tree is absolutely clean. The
53 kernel team recommends that this command be issued prior to each
54 kernel compilation. Do not rely on the source tree being clean after
55 un-tarring.</para>
56
57 <para>There are several ways to configure the kernel options. Usually,
58 This is done through a menu-driven interface, for example:</para>
59
60<screen role="nodump"><userinput>make menuconfig</userinput></screen>
61
62 <variablelist>
63 <title>The meaning of optional make environment variables:</title>
64
65 <varlistentry>
66 <term><parameter>LANG=&lt;host_LANG_value&gt; LC_ALL=</parameter></term>
67 <listitem>
68 <para>This establishes the locale setting to the one used on the
69 host. This may be needed for a proper menuconfig ncurses interface
70 line drawing on a UTF-8 linux text console.</para>
71
72 <para>If used, be sure to replace
73 <replaceable>&lt;host_LANG_value&gt;</replaceable> by the value of
74 the <envar>$LANG</envar> variable from your host. You can
75 alternatively use instead the host's value of <envar>$LC_ALL</envar>
76 or <envar>$LC_CTYPE</envar>.</para>
77 </listitem>
78 </varlistentry>
79
80 <varlistentry>
81 <term><command>make menuconfig</command></term>
82 <listitem>
83 <para>This launches an ncurses menu-driven interface. For other
84 (graphical) interfaces, type <command>make help</command>.</para>
85 </listitem>
86 </varlistentry>
87 </variablelist>
88
89 <!-- Support for compiling a keymap into the kernel is deliberately removed -->
90
91 <para>For general information on kernel configuration see <ulink
92 url="&hints-root;kernel-configuration.txt"/>. BLFS has some information
93 regarding particular kernel configuration requirements of packages outside
94 of LFS at <ulink
95 url="&blfs-book;longindex.html#kernel-config-index"/>. Additional
96 information about configuring and building the kernel can be found at
97 <ulink url="http://www.kroah.com/lkn/"/> </para>
98
99 <note>
100 <para>A good starting place for setting up the kernel configuration is to
101 run <command>make defconfig</command>. This will set the base
102 configuration to a good state that takes your current system architecture
103 into account.</para>
104
105 <para>Be sure to enable/disable/set the following features or the system might
106 not work correctly or boot at all:</para>
107
108 <screen role="nodump" revision="sysv">General setup -->
109 [ ] Compile the kernel with warnings as errors [CONFIG_WERROR]
110 &lt; &gt; Enable kernel headers through /sys/kernel/kheaders.tar.xz [CONFIG_IKHEADERS]
111Device Drivers ---&gt;
112 Graphics support ---&gt;
113 Frame buffer Devices ---&gt;
114 [*] Support for frame buffer devices ----
115 Generic Driver Options ---&gt;
116 [ ] Support for uevent helper [CONFIG_UEVENT_HELPER]
117 [*] Maintain a devtmpfs filesystem to mount at /dev [CONFIG_DEVTMPFS]
118 [*] Automount devtmpfs at /dev, after the kernel mounted the rootfs [CONFIG_DEVTMPFS_MOUNT]</screen>
119
120 <screen role="nodump" revision="systemd">General setup -->
121 [ ] Compile the kernel with warnings as errors [CONFIG_WERROR]
122 [ ] Auditing Support [CONFIG_AUDIT]
123 CPU/Task time and stats accounting ---&gt;
124 [*] Pressure stall information tracking [CONFIG_PSI]
125 &lt; &gt; Enable kernel headers through /sys/kernel/kheaders.tar.xz [CONFIG_IKHEADERS]
126 [*] Control Group support [CONFIG_CGROUPS] ---&gt;
127 [*] Memory controller [CONFIG_MEMCG]
128 [ ] Enable deprecated sysfs features to support old userspace tools [CONFIG_SYSFS_DEPRECATED]
129 [*] Configure standard kernel features (expert users) [CONFIG_EXPERT] ---&gt;
130 [*] open by fhandle syscalls [CONFIG_FHANDLE]
131General architecture-dependent options ---&gt;
132 [*] Enable seccomp to safely compute untrusted bytecode [CONFIG_SECCOMP]
133Networking support ---&gt;
134 Networking options ---&gt;
135 &lt;*&gt; The IPv6 protocol [CONFIG_IPV6]
136Device Drivers ---&gt;
137 Generic Driver Options ---&gt;
138 [ ] Support for uevent helper [CONFIG_UEVENT_HELPER]
139 [*] Maintain a devtmpfs filesystem to mount at /dev [CONFIG_DEVTMPFS]
140 [*] Automount devtmpfs at /dev, after the kernel mounted the rootfs [CONFIG_DEVTMPFS_MOUNT]
141 Firmware Loader ---&gt;
142 [ ] Enable the firmware sysfs fallback mechanism [CONFIG_FW_LOADER_USER_HELPER]
143 Firmware Drivers ---&gt;
144 [*] Export DMI identification via sysfs to userspace [CONFIG_DMIID]
145 Graphics support ---&gt;
146 Frame buffer Devices ---&gt;
147 &lt;*&gt; Support for frame buffer devices ---&gt;
148File systems ---&gt;
149 [*] Inotify support for userspace [CONFIG_INOTIFY_USER]
150 Pseudo filesystems ---&gt;
151 [*] Tmpfs POSIX Access Control Lists [CONFIG_TMPFS_POSIX_ACL]</screen>
152
153 <para>Disable a feature which is security compromised in this kernel
154 release:</para>
155
156 <screen role="nodump">Memory Management options ---&gt;
157 [ ] Enable userfaultfd() system call [CONFIG_USERFAULTFD]</screen>
158 </note>
159
160 <note revision="systemd">
161 <para>While "The IPv6 Protocol" is not strictly
162 required, it is highly recommended by the systemd developers.</para>
163 </note>
164
165 <para revision="sysv">There are several other options that may be desired
166 depending on the requirements for the system. For a list of options needed
167 for BLFS packages, see the <ulink
168 url="&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index">BLFS
169 Index of Kernel Settings</ulink>
170 (&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index).</para>
171
172 <note>
173 <para>If your host hardware is using UEFI and you wish to boot the
174 LFS system with it, you should adjust some kernel configuration
175 following <ulink url="&blfs-book;postlfs/grub-setup.html#uefi-kernel">
176 the BLFS page</ulink>.</para>
177 </note>
178
179 <variablelist>
180 <title>The rationale for the above configuration items:</title>
181
182 <varlistentry>
183 <term>
184 <parameter>
185 Compile the kernel with warnings as errors
186 </parameter>
187 </term>
188 <listitem>
189 <para>This may cause building failure if the compiler and/or
190 configuration are different from those of the kernel
191 developers.</para>
192 </listitem>
193 </varlistentry>
194
195 <varlistentry>
196 <term>
197 <parameter>
198 Enable kernel headers through /sys/kernel/kheaders.tar.xz
199 </parameter>
200 </term>
201 <listitem>
202 <para>This will require <command>cpio</command> building the kernel.
203 <command>cpio</command> is not installed by LFS.</para>
204 </listitem>
205 </varlistentry>
206
207 <varlistentry>
208 <term><parameter>Support for uevent helper</parameter></term>
209 <listitem>
210 <para>Having this option set may interfere with device
211 management when using Udev/Eudev. </para>
212 </listitem>
213 </varlistentry>
214
215 <varlistentry>
216 <term><parameter>Maintain a devtmpfs</parameter></term>
217 <listitem>
218 <para>This will create automated device nodes which are populated by the
219 kernel, even without Udev running. Udev then runs on top of this,
220 managing permissions and adding symlinks. This configuration
221 item is required for all users of Udev/Eudev.</para>
222 </listitem>
223 </varlistentry>
224
225 <varlistentry>
226 <term><parameter>Automount devtmpfs at /dev</parameter></term>
227 <listitem>
228 <para>This will mount the kernel view of the devices on /dev
229 upon switching to root filesystem just before starting
230 init.</para>
231 </listitem>
232 </varlistentry>
233
234 <varlistentry>
235 <term><parameter>Enable userfaultfd() system call</parameter></term>
236 <listitem>
237 <para>If this option is enabled, a security vulnerability not
238 resolved in Linux-&linux-version; yet will be exploitable.
239 Disable this option to avoid the vulnerability. This system call
240 is not used by any part of LFS or BLFS.</para>
241 </listitem>
242 </varlistentry>
243
244 </variablelist>
245
246 <para>Alternatively, <command>make oldconfig</command> may be more
247 appropriate in some situations. See the <filename>README</filename>
248 file for more information.</para>
249
250 <para>If desired, skip kernel configuration by copying the kernel
251 config file, <filename>.config</filename>, from the host system
252 (assuming it is available) to the unpacked <filename
253 class="directory">linux-&linux-version;</filename> directory. However,
254 we do not recommend this option. It is often better to explore all the
255 configuration menus and create the kernel configuration from
256 scratch.</para>
257
258 <para>Compile the kernel image and modules:</para>
259
260<screen><userinput remap="make">make</userinput></screen>
261
262 <para>If using kernel modules, module configuration in <filename
263 class="directory">/etc/modprobe.d</filename> may be required.
264 Information pertaining to modules and kernel configuration is
265 located in <xref linkend="ch-config-udev"/> and in the kernel
266 documentation in the <filename
267 class="directory">linux-&linux-version;/Documentation</filename> directory.
268 Also, <filename>modprobe.d(5)</filename> may be of interest.</para>
269
270 <para>Unless module support has been disabled in the kernel configuration,
271 install the modules with:</para>
272
273<screen><userinput remap="install">make modules_install</userinput></screen>
274
275 <para>After kernel compilation is complete, additional steps are
276 required to complete the installation. Some files need to be copied to
277 the <filename class="directory">/boot</filename> directory.</para>
278
279 <caution>
280 <para>If the host system has a separate /boot partition, the files copied
281 below should go there. The easiest way to do that is to bind /boot on the
282 host (outside chroot) to /mnt/lfs/boot before proceeding. As the
283 &root; user in the <emphasis>host system</emphasis>:</para>
284
285<screen role="nodump"><userinput>mount --bind /boot /mnt/lfs/boot</userinput></screen>
286 </caution>
287
288 <para>The path to the kernel image may vary depending on the platform being
289 used. The filename below can be changed to suit your taste, but the stem of
290 the filename should be <emphasis>vmlinuz</emphasis> to be compatible with
291 the automatic setup of the boot process described in the next section. The
292 following command assumes an x86 architecture:</para>
293
294<screen><userinput remap="install">cp -iv arch/arm64/boot/Image /boot/vmlinuz-&linux-version;-lfs-&version;</userinput></screen>
295
296 <para><filename>System.map</filename> is a symbol file for the kernel.
297 It maps the function entry points of every function in the kernel API,
298 as well as the addresses of the kernel data structures for the running
299 kernel. It is used as a resource when investigating kernel problems.
300 Issue the following command to install the map file:</para>
301
302<screen><userinput remap="install">cp -iv System.map /boot/System.map-&linux-version;</userinput></screen>
303
304 <para>The kernel configuration file <filename>.config</filename>
305 produced by the <command>make menuconfig</command> step
306 above contains all the configuration selections for the kernel
307 that was just compiled. It is a good idea to keep this file for future
308 reference:</para>
309
310<screen><userinput remap="install">cp -iv .config /boot/config-&linux-version;</userinput></screen>
311
312 <para>Install the documentation for the Linux kernel:</para>
313
314<screen><userinput remap="install">install -d /usr/share/doc/linux-&linux-version;
315cp -r Documentation/* /usr/share/doc/linux-&linux-version;</userinput></screen>
316
317 <para>It is important to note that the files in the kernel source
318 directory are not owned by <emphasis>root</emphasis>. Whenever a
319 package is unpacked as user <emphasis>root</emphasis> (like we did
320 inside chroot), the files have the user and group IDs of whatever
321 they were on the packager's computer. This is usually not a problem
322 for any other package to be installed because the source tree is
323 removed after the installation. However, the Linux source tree is
324 often retained for a long time. Because of this, there is a chance
325 that whatever user ID the packager used will be assigned to somebody
326 on the machine. That person would then have write access to the kernel
327 source.</para>
328
329 <note>
330 <para>In many cases, the configuration of the kernel will need to be
331 updated for packages that will be installed later in BLFS. Unlike
332 other packages, it is not necessary to remove the kernel source tree
333 after the newly built kernel is installed.</para>
334
335 <para>If the kernel source tree is going to be retained, run
336 <command>chown -R 0:0</command> on the <filename
337 class="directory">linux-&linux-version;</filename> directory to ensure
338 all files are owned by user <emphasis>root</emphasis>.</para>
339 </note>
340
341 <warning>
342 <para>Some kernel documentation recommends creating a symlink from
343 <filename class="symlink">/usr/src/linux</filename> pointing to the kernel
344 source directory. This is specific to kernels prior to the 2.6 series and
345 <emphasis>must not</emphasis> be created on an LFS system as it can cause
346 problems for packages you may wish to build once your base LFS system is
347 complete.</para>
348 </warning>
349
350 <warning>
351 <para>The headers in the system's <filename
352 class="directory">include</filename> directory (<filename
353 class="directory">/usr/include</filename>) should
354 <emphasis>always</emphasis> be the ones against which Glibc was compiled,
355 that is, the sanitised headers installed in <xref
356 linkend="ch-tools-linux-headers"/>. Therefore, they should
357 <emphasis>never</emphasis> be replaced by either the raw kernel headers
358 or any other kernel sanitized headers.</para>
359 </warning>
360
361 </sect2>
362
363 <sect2 id="conf-modprobe" role="configuration">
364 <title>Configuring Linux Module Load Order</title>
365
366 <indexterm zone="conf-modprobe">
367 <primary sortas="e-/etc/modprobe.d/usb.conf">/etc/modprobe.d/usb.conf</primary>
368 </indexterm>
369
370 <para>Most of the time Linux modules are loaded automatically, but
371 sometimes it needs some specific direction. The program that loads
372 modules, <command>modprobe</command> or <command>insmod</command>, uses
373 <filename>/etc/modprobe.d/usb.conf</filename> for this purpose. This file
374 needs to be created so that if the USB drivers (ehci_hcd, ohci_hcd and
375 uhci_hcd) have been built as modules, they will be loaded in the correct
376 order; ehci_hcd needs to be loaded prior to ohci_hcd and uhci_hcd in order
377 to avoid a warning being output at boot time.</para>
378
379 <para>Create a new file <filename>/etc/modprobe.d/usb.conf</filename> by running
380 the following:</para>
381
382<screen><userinput>install -v -m755 -d /etc/modprobe.d
383cat &gt; /etc/modprobe.d/usb.conf &lt;&lt; "EOF"
384<literal># Begin /etc/modprobe.d/usb.conf
385
386install ohci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i ohci_hcd ; true
387install uhci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i uhci_hcd ; true
388
389# End /etc/modprobe.d/usb.conf</literal>
390EOF</userinput></screen>
391
392 </sect2>
393
394 <sect2 id="contents-kernel" role="content">
395 <title>Contents of Linux</title>
396
397 <segmentedlist>
398 <segtitle>Installed files</segtitle>
399 <segtitle>Installed directories</segtitle>
400
401 <seglistitem>
402 <seg>config-&linux-version;,
403 vmlinuz-&linux-version;-lfs-&version;,
404 and System.map-&linux-version;</seg>
405 <seg>/lib/modules, /usr/share/doc/linux-&linux-version;</seg>
406 </seglistitem>
407 </segmentedlist>
408
409 <variablelist>
410 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
411 <?dbfo list-presentation="list"?>
412 <?dbhtml list-presentation="table"?>
413
414 <varlistentry id="config">
415 <term><filename>config-&linux-version;</filename></term>
416 <listitem>
417 <para>Contains all the configuration selections for the kernel</para>
418 <indexterm zone="ch-bootable-kernel config">
419 <primary sortas="e-/boot/config">/boot/config-&linux-version;</primary>
420 </indexterm>
421 </listitem>
422 </varlistentry>
423
424 <varlistentry id="lfskernel">
425 <term><filename>vmlinuz-&linux-version;-lfs-&version;</filename></term>
426 <listitem>
427 <para>The engine of the Linux system. When turning on the computer,
428 the kernel is the first part of the operating system that gets loaded.
429 It detects and initializes all components of the computer's hardware,
430 then makes these components available as a tree of files to the
431 software and turns a single CPU into a multitasking machine capable
432 of running scores of programs seemingly at the same time</para>
433 <indexterm zone="ch-bootable-kernel lfskernel">
434 <primary sortas="b-lfskernel">lfskernel-&linux-version;</primary>
435 </indexterm>
436 </listitem>
437 </varlistentry>
438
439 <varlistentry id="System.map">
440 <term><filename>System.map-&linux-version;</filename></term>
441 <listitem>
442 <para>A list of addresses and symbols; it maps the entry points and
443 addresses of all the functions and data structures in the
444 kernel</para>
445 <indexterm zone="ch-bootable-kernel System.map">
446 <primary sortas="e-/boot/System.map">/boot/System.map-&linux-version;</primary>
447 </indexterm>
448 </listitem>
449 </varlistentry>
450
451 </variablelist>
452
453 </sect2>
454
455</sect1>
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