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dev-manual, kernel-dev, sdk-manual: Moved patching kernel section

Browse Source 
Moved the "Patching the Kernel" section, which was in the
dev-manual to the kernel-dev manual.  During the move,
renamed the section to "Using devtool to Patch the Kernel".

This move bothered a lot of links so I had to fix them in
various manuals.

(From yocto-docs rev: a000be1eddf33e4d7de8f350e076d48e27ca4b98)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark
2017-08-15 15:52:21 -07:00
committed by Richard Purdie
parent 2c0c962dd9
commit a99c2c5581
5 changed files with 366 additions and 358 deletions
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documentation/dev-manual/dev-manual-common-tasks.xml
-341
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@@ -6625,347 +6625,6 @@ Some notes from Cal:
</section> </section>
</section> </section>
<section id="patching-the-kernel">
<title>Patching the Kernel</title>
<para>
Patching the kernel involves changing or adding configurations to an existing kernel,
changing or adding recipes to the kernel that are needed to support specific hardware features,
or even altering the source code itself.
<note>
You can use the <filename>yocto-kernel</filename> script
found in the <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
under <filename>scripts</filename> to manage kernel patches and configuration.
See the "<ulink url='&YOCTO_DOCS_BSP_URL;#managing-kernel-patches-and-config-items-with-yocto-kernel'>Managing kernel Patches and Config Items with yocto-kernel</ulink>"
section in the Yocto Project Board Support Packages (BSP) Developer's Guide for
more information.</note>
</para>
<para>
This example creates a simple patch by adding some QEMU emulator console
output at boot time through <filename>printk</filename> statements in the kernel's
<filename>calibrate.c</filename> source code file.
Applying the patch and booting the modified image causes the added
messages to appear on the emulator's console.
</para>
<para>
The example assumes a clean build exists for the <filename>qemux86</filename>
machine in a
<ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
named <filename>poky</filename>.
Furthermore, the
<ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>
is <filename>build</filename> and is located in
<filename>poky</filename> and the kernel is based on the
Linux 3.4 kernel.
</para>
<para>
Also, for more information on patching the kernel, see the
"<ulink url='&YOCTO_DOCS_KERNEL_DEV_URL;#applying-patches'>Applying Patches</ulink>"
section in the Yocto Project Linux Kernel Development Manual.
</para>
<section id='create-a-layer-for-your-changes'>
<title>Create a Layer for your Changes</title>
<para>
The first step is to create a layer so you can isolate your
changes.
Rather than use the <filename>yocto-layer</filename> script
to create the layer, this example steps through the process
by hand.
If you want information on the script that creates a general
layer, see the
"<link linkend='creating-a-general-layer-using-the-yocto-layer-script'>Creating a General Layer Using the yocto-layer Script</link>"
section.
</para>
<para>
These two commands create a directory you can use for your
layer:
<literallayout class='monospaced'>
$ cd ~/poky
$ mkdir meta-mylayer
</literallayout>
Creating a directory that follows the Yocto Project layer naming
conventions sets up the layer for your changes.
The layer is where you place your configuration files, append
files, and patch files.
To learn more about creating a layer and filling it with the
files you need, see the "<link linkend='understanding-and-creating-layers'>Understanding
and Creating Layers</link>" section.
</para>
</section>
<section id='finding-the-kernel-source-code'>
<title>Finding the Kernel Source Code</title>
<para>
Each time you build a kernel image, the kernel source code
is fetched and unpacked into the following directory:
<literallayout class='monospaced'>
${S}/linux
</literallayout>
See the "<link linkend='finding-the-temporary-source-code'>Finding Temporary Source Code</link>"
section and the
<ulink url='&YOCTO_DOCS_REF_URL;#var-S'><filename>S</filename></ulink> variable
for more information about where source is kept during a build.
</para>
<para>
For this example, we are going to patch the
<filename>init/calibrate.c</filename> file
by adding some simple console <filename>printk</filename> statements that we can
see when we boot the image using QEMU.
</para>
</section>
<section id='creating-the-patch'>
<title>Creating the Patch</title>
<para>
Two methods exist by which you can create the patch:
<ulink url='&YOCTO_DOCS_SDK_URL;#using-devtool-in-your-sdk-workflow'><filename>devtool</filename></ulink>
and
<link linkend='using-a-quilt-workflow'>Quilt</link>.
For kernel patches, the Git workflow is more appropriate.
This section assumes the Git workflow and shows the steps specific to
this example.
<orderedlist>
<listitem><para><emphasis>Change the working directory</emphasis>:
Change to where the kernel source code is before making
your edits to the <filename>calibrate.c</filename> file:
<literallayout class='monospaced'>
$ cd ~/poky/build/tmp/work/qemux86-poky-linux/linux-yocto-${PV}-${PR}/linux
</literallayout>
Because you are working in an established Git repository,
you must be in this directory in order to commit your changes
and create the patch file.
<note>The <ulink url='&YOCTO_DOCS_REF_URL;#var-PV'><filename>PV</filename></ulink> and
<ulink url='&YOCTO_DOCS_REF_URL;#var-PR'><filename>PR</filename></ulink> variables
represent the version and revision for the
<filename>linux-yocto</filename> recipe.
The <filename>PV</filename> variable includes the Git meta and machine
hashes, which make the directory name longer than you might
expect.
</note></para></listitem>
<listitem><para><emphasis>Edit the source file</emphasis>:
Edit the <filename>init/calibrate.c</filename> file to have the
following changes:
<literallayout class='monospaced'>
void calibrate_delay(void)
{
unsigned long lpj;
static bool printed;
int this_cpu = smp_processor_id();
printk("*************************************\n");
printk("* *\n");
printk("* HELLO YOCTO KERNEL *\n");
printk("* *\n");
printk("*************************************\n");
if (per_cpu(cpu_loops_per_jiffy, this_cpu)) {
.
.
.
</literallayout></para></listitem>
<listitem><para><emphasis>Stage and commit your changes</emphasis>:
These Git commands display the modified file, stage it, and then
commit the file:
<literallayout class='monospaced'>
$ git status
$ git add init/calibrate.c
$ git commit -m "calibrate: Add printk example"
</literallayout></para></listitem>
<listitem><para><emphasis>Generate the patch file</emphasis>:
This Git command creates the a patch file named
<filename>0001-calibrate-Add-printk-example.patch</filename>
in the current directory.
<literallayout class='monospaced'>
$ git format-patch -1
</literallayout>
</para></listitem>
</orderedlist>
</para>
</section>
<section id='set-up-your-layer-for-the-build'>
<title>Set Up Your Layer for the Build</title>
<para>These steps get your layer set up for the build:
<orderedlist>
<listitem><para><emphasis>Create additional structure</emphasis>:
Create the additional layer structure:
<literallayout class='monospaced'>
$ cd ~/poky/meta-mylayer
$ mkdir conf
$ mkdir recipes-kernel
$ mkdir recipes-kernel/linux
$ mkdir recipes-kernel/linux/linux-yocto
</literallayout>
The <filename>conf</filename> directory holds your configuration files, while the
<filename>recipes-kernel</filename> directory holds your append file and
your patch file.</para></listitem>
<listitem><para><emphasis>Create the layer configuration file</emphasis>:
Move to the <filename>meta-mylayer/conf</filename> directory and create
the <filename>layer.conf</filename> file as follows:
<literallayout class='monospaced'>
# We have a conf and classes directory, add to BBPATH
BBPATH .= ":${LAYERDIR}"
# We have recipes-* directories, add to BBFILES
BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
${LAYERDIR}/recipes-*/*/*.bbappend"
BBFILE_COLLECTIONS += "mylayer"
BBFILE_PATTERN_mylayer = "^${LAYERDIR}/"
BBFILE_PRIORITY_mylayer = "5"
</literallayout>
Notice <filename>mylayer</filename> as part of the last three
statements.</para></listitem>
<listitem><para><emphasis>Create the kernel recipe append file</emphasis>:
Move to the <filename>meta-mylayer/recipes-kernel/linux</filename> directory and create
the <filename>linux-yocto_3.4.bbappend</filename> file as follows:
<literallayout class='monospaced'>
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
SRC_URI += "file://0001-calibrate-Add-printk-example.patch"
</literallayout>
The <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink>
and <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
statements enable the OpenEmbedded build system to find the patch file.
For more information on using append files, see the
"<link linkend='using-bbappend-files'>Using .bbappend Files in Your Layer</link>"
section.
</para></listitem>
<listitem><para><emphasis>Put the patch file in your layer</emphasis>:
Move the <filename>0001-calibrate-Add-printk-example.patch</filename> file to
the <filename>meta-mylayer/recipes-kernel/linux/linux-yocto</filename>
directory.</para></listitem>
</orderedlist>
</para>
</section>
<section id='set-up-for-the-build'>
<title>Set Up for the Build</title>
<para>
Do the following to make sure the build parameters are set up for the example.
Once you set up these build parameters, they do not have to change unless you
change the target architecture of the machine you are building:
<itemizedlist>
<listitem><para><emphasis>Build for the correct target architecture:</emphasis> Your
selected <ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE'><filename>MACHINE</filename></ulink>
definition within the <filename>local.conf</filename> file in the
<ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>
specifies the target architecture used when building the Linux kernel.
By default, <filename>MACHINE</filename> is set to
<filename>qemux86</filename>, which specifies a 32-bit
<trademark class='registered'>Intel</trademark> Architecture
target machine suitable for the QEMU emulator.</para></listitem>
<listitem><para><emphasis>Identify your <filename>meta-mylayer</filename>
layer:</emphasis> The
<ulink url='&YOCTO_DOCS_REF_URL;#var-BBLAYERS'><filename>BBLAYERS</filename></ulink>
variable in the
<filename>bblayers.conf</filename> file found in the
<filename>poky/build/conf</filename> directory needs to have the path to your local
<filename>meta-mylayer</filename> layer.
By default, the <filename>BBLAYERS</filename> variable contains paths to
<filename>meta</filename>, <filename>meta-poky</filename>, and
<filename>meta-yocto-bsp</filename> in the
<filename>poky</filename> Git repository.
Add the path to your <filename>meta-mylayer</filename> location:
<literallayout class='monospaced'>
BBLAYERS ?= " \
$HOME/poky/meta \
$HOME/poky/meta-poky \
$HOME/poky/meta-yocto-bsp \
$HOME/poky/meta-mylayer \
"
</literallayout></para></listitem>
</itemizedlist>
</para>
</section>
<section id='build-the-modified-qemu-kernel-image'>
<title>Build the Modified QEMU Kernel Image</title>
<para>
The following steps build your modified kernel image:
<orderedlist>
<listitem><para><emphasis>Be sure your build environment is initialized</emphasis>:
Your environment should be set up since you previously sourced
the
<ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink>
script.
If it is not, source the script again from <filename>poky</filename>.
<literallayout class='monospaced'>
$ cd ~/poky
$ source &OE_INIT_FILE;
</literallayout>
</para></listitem>
<listitem><para><emphasis>Clean up</emphasis>:
Be sure to clean the shared state out by using BitBake
to run from within the Build Directory the
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleansstate'><filename>do_cleansstate</filename></ulink>
task as follows:
<literallayout class='monospaced'>
$ bitbake -c cleansstate linux-yocto
</literallayout></para>
<para>
<note>
Never remove any files by hand from the
<filename>tmp/deploy</filename>
directory inside the
<ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>.
Always use the various BitBake clean tasks to
clear out previous build artifacts.
For information on the clean tasks, see the
"<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-clean'><filename>do_clean</filename></ulink>",
"<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleanall'><filename>do_cleanall</filename></ulink>",
and
"<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleansstate'><filename>do_cleansstate</filename></ulink>"
sections all in the Yocto Project Reference
Manual.
</note>
</para></listitem>
<listitem><para><emphasis>Build the image</emphasis>:
Next, build the kernel image using this command:
<literallayout class='monospaced'>
$ bitbake -k linux-yocto
</literallayout></para></listitem>
</orderedlist>
</para>
</section>
<section id='boot-the-image-and-verify-your-changes'>
<title>Boot the Image and Verify Your Changes</title>
<para>
These steps boot the image and allow you to see the changes
<orderedlist>
<listitem><para><emphasis>Boot the image</emphasis>:
Boot the modified image in the QEMU emulator
using this command:
<literallayout class='monospaced'>
$ runqemu qemux86
</literallayout></para></listitem>
<listitem><para><emphasis>Verify the changes</emphasis>:
Log into the machine using <filename>root</filename> with no password and then
use the following shell command to scroll through the console's boot output.
<literallayout class='monospaced'>
# dmesg | less
</literallayout>
You should see the results of your <filename>printk</filename> statements
as part of the output.</para></listitem>
</orderedlist>
</para>
</section>
</section>
<section id='making-images-more-secure'> <section id='making-images-more-secure'>
<title>Making Images More Secure</title> <title>Making Images More Secure</title>
documentation/kernel-dev/kernel-dev-common.xml
+356 -8
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@@ -75,9 +75,8 @@
See the "<link linkend='creating-and-preparing-a-layer'>Creating and Preparing a Layer</link>" See the "<link linkend='creating-and-preparing-a-layer'>Creating and Preparing a Layer</link>"
section for some general resources. section for some general resources.
You can also see the You can also see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#set-up-your-layer-for-the-build'>Set Up Your Layer for the Build</ulink>" section "<link linkend='set-up-your-layer-for-the-build'>Set Up Your Layer for the Build</link>"
of the Yocto Project Development Manual for a detailed section for a detailed example.
example.
</para> </para>
<section id='creating-the-append-file'> <section id='creating-the-append-file'>
@@ -295,9 +294,10 @@
</para> </para>
<para> <para>
For a detailed example showing how to patch the kernel, see the For a detailed example showing how to patch the kernel using
"<ulink url='&YOCTO_DOCS_DEV_URL;#patching-the-kernel'>Patching the Kernel</ulink>" <filename>devtool</filename>, see the
section in the Yocto Project Development Manual. "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>"
section.
</para> </para>
</section> </section>
@@ -449,6 +449,354 @@
</section> </section>
</section> </section>
<section id="using-devtool-to-patch-the-kernel">
<title>Using <filename>devtool</filename> to Patch the Kernel</title>
<para>
Patching the kernel involves changing or adding configurations to an existing kernel,
changing or adding recipes to the kernel that are needed to support specific hardware features,
or even altering the source code itself.
<note>
You can use the <filename>yocto-kernel</filename> script
found in the <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
under <filename>scripts</filename> to manage kernel patches and configuration.
See the "<ulink url='&YOCTO_DOCS_BSP_URL;#managing-kernel-patches-and-config-items-with-yocto-kernel'>Managing kernel Patches and Config Items with yocto-kernel</ulink>"
section in the Yocto Project Board Support Packages (BSP) Developer's Guide for
more information.</note>
</para>
<para>
This example creates a simple patch by adding some QEMU emulator console
output at boot time through <filename>printk</filename> statements in the kernel's
<filename>calibrate.c</filename> source code file.
Applying the patch and booting the modified image causes the added
messages to appear on the emulator's console.
</para>
<para>
The example assumes a clean build exists for the <filename>qemux86</filename>
machine in a
<ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
named <filename>poky</filename>.
Furthermore, the
<ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>
is <filename>build</filename> and is located in
<filename>poky</filename> and the kernel is based on the
Linux 3.4 kernel.
</para>
<para>
Also, for more information on patching the kernel, see the
"<link linkend='applying-patches'>Applying Patches</link>"
section.
</para>
<section id='create-a-layer-for-your-changes'>
<title>Create a Layer for your Changes</title>
<para>
The first step is to create a layer so you can isolate your
changes.
Rather than use the <filename>yocto-layer</filename> script
to create the layer, this example steps through the process
by hand.
If you want information on the script that creates a general
layer, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#creating-a-general-layer-using-the-yocto-layer-script'>Creating a General Layer Using the yocto-layer Script</ulink>"
section in the Yocto Project Development Manual.
</para>
<para>
These two commands create a directory you can use for your
layer:
<literallayout class='monospaced'>
$ cd ~/poky
$ mkdir meta-mylayer
</literallayout>
Creating a directory that follows the Yocto Project layer naming
conventions sets up the layer for your changes.
The layer is where you place your configuration files, append
files, and patch files.
To learn more about creating a layer and filling it with the
files you need, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>"
section in the Yocto Project Development Manual.
</para>
</section>
<section id='finding-the-kernel-source-code'>
<title>Finding the Kernel Source Code</title>
<para>
Each time you build a kernel image, the kernel source code
is fetched and unpacked into the following directory:
<literallayout class='monospaced'>
${S}/linux
</literallayout>
See the "<ulink url='&YOCTO_DOCS_DEV_URL;#finding-the-temporary-source-code'>Finding Temporary Source Code</ulink>"
section in the Yocto Project Development Manual and the
<ulink url='&YOCTO_DOCS_REF_URL;#var-S'><filename>S</filename></ulink>
variable for more information about where source is kept
during a build.
</para>
<para>
For this example, we are going to patch the
<filename>init/calibrate.c</filename> file
by adding some simple console <filename>printk</filename> statements that we can
see when we boot the image using QEMU.
</para>
</section>
<section id='creating-the-patch'>
<title>Creating the Patch</title>
<para>
Two methods exist by which you can create the patch:
<ulink url='&YOCTO_DOCS_SDK_URL;#using-devtool-in-your-sdk-workflow'><filename>devtool</filename></ulink>
and
<ulink url='&YOCTO_DOCS_DEV_URL;#using-a-quilt-workflow'>Quilt</ulink>.
For kernel patches, the Git workflow is more appropriate.
This section assumes the Git workflow and shows the steps
specific to this example.
<orderedlist>
<listitem><para>
<emphasis>Change the working directory</emphasis>:
Change to where the kernel source code is before making
your edits to the <filename>calibrate.c</filename> file:
<literallayout class='monospaced'>
$ cd ~/poky/build/tmp/work/qemux86-poky-linux/linux-yocto-${PV}-${PR}/linux
</literallayout>
Because you are working in an established Git repository,
you must be in this directory in order to commit your changes
and create the patch file.
<note>The <ulink url='&YOCTO_DOCS_REF_URL;#var-PV'><filename>PV</filename></ulink> and
<ulink url='&YOCTO_DOCS_REF_URL;#var-PR'><filename>PR</filename></ulink> variables
represent the version and revision for the
<filename>linux-yocto</filename> recipe.
The <filename>PV</filename> variable includes the Git meta and machine
hashes, which make the directory name longer than you might
expect.
</note></para></listitem>
<listitem><para>
<emphasis>Edit the source file</emphasis>:
Edit the <filename>init/calibrate.c</filename> file to have the
following changes:
<literallayout class='monospaced'>
void calibrate_delay(void)
{
unsigned long lpj;
static bool printed;
int this_cpu = smp_processor_id();
printk("*************************************\n");
printk("* *\n");
printk("* HELLO YOCTO KERNEL *\n");
printk("* *\n");
printk("*************************************\n");
if (per_cpu(cpu_loops_per_jiffy, this_cpu)) {
.
.
.
</literallayout></para></listitem>
<listitem><para><emphasis>Stage and commit your changes</emphasis>:
These Git commands display the modified file, stage it, and then
commit the file:
<literallayout class='monospaced'>
$ git status
$ git add init/calibrate.c
$ git commit -m "calibrate: Add printk example"
</literallayout></para></listitem>
<listitem><para><emphasis>Generate the patch file</emphasis>:
This Git command creates the a patch file named
<filename>0001-calibrate-Add-printk-example.patch</filename>
in the current directory.
<literallayout class='monospaced'>
$ git format-patch -1
</literallayout>
</para></listitem>
</orderedlist>
</para>
</section>
<section id='set-up-your-layer-for-the-build'>
<title>Set Up Your Layer for the Build</title>
<para>These steps get your layer set up for the build:
<orderedlist>
<listitem><para><emphasis>Create additional structure</emphasis>:
Create the additional layer structure:
<literallayout class='monospaced'>
$ cd ~/poky/meta-mylayer
$ mkdir conf
$ mkdir recipes-kernel
$ mkdir recipes-kernel/linux
$ mkdir recipes-kernel/linux/linux-yocto
</literallayout>
The <filename>conf</filename> directory holds your configuration files, while the
<filename>recipes-kernel</filename> directory holds your append file and
your patch file.</para></listitem>
<listitem><para><emphasis>Create the layer configuration file</emphasis>:
Move to the <filename>meta-mylayer/conf</filename> directory and create
the <filename>layer.conf</filename> file as follows:
<literallayout class='monospaced'>
# We have a conf and classes directory, add to BBPATH
BBPATH .= ":${LAYERDIR}"
# We have recipes-* directories, add to BBFILES
BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
${LAYERDIR}/recipes-*/*/*.bbappend"
BBFILE_COLLECTIONS += "mylayer"
BBFILE_PATTERN_mylayer = "^${LAYERDIR}/"
BBFILE_PRIORITY_mylayer = "5"
</literallayout>
Notice <filename>mylayer</filename> as part of the last three
statements.</para></listitem>
<listitem><para><emphasis>Create the kernel recipe append file</emphasis>:
Move to the <filename>meta-mylayer/recipes-kernel/linux</filename> directory and create
the <filename>linux-yocto_3.4.bbappend</filename> file as follows:
<literallayout class='monospaced'>
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
SRC_URI += "file://0001-calibrate-Add-printk-example.patch"
</literallayout>
The <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink>
and <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
statements enable the OpenEmbedded build system to find the patch file.
For more information on using append files, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#using-bbappend-files'>Using .bbappend Files in Your Layer</ulink>"
section in the Yocto Project Development Manual.
</para></listitem>
<listitem><para>
<emphasis>Put the patch file in your layer</emphasis>:
Move the <filename>0001-calibrate-Add-printk-example.patch</filename> file to
the <filename>meta-mylayer/recipes-kernel/linux/linux-yocto</filename>
directory.</para></listitem>
</orderedlist>
</para>
</section>
<section id='set-up-for-the-build'>
<title>Set Up for the Build</title>
<para>
Do the following to make sure the build parameters are set up for the example.
Once you set up these build parameters, they do not have to change unless you
change the target architecture of the machine you are building:
<itemizedlist>
<listitem><para><emphasis>Build for the correct target architecture:</emphasis> Your
selected <ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE'><filename>MACHINE</filename></ulink>
definition within the <filename>local.conf</filename> file in the
<ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>
specifies the target architecture used when building the Linux kernel.
By default, <filename>MACHINE</filename> is set to
<filename>qemux86</filename>, which specifies a 32-bit
<trademark class='registered'>Intel</trademark> Architecture
target machine suitable for the QEMU emulator.</para></listitem>
<listitem><para><emphasis>Identify your <filename>meta-mylayer</filename>
layer:</emphasis> The
<ulink url='&YOCTO_DOCS_REF_URL;#var-BBLAYERS'><filename>BBLAYERS</filename></ulink>
variable in the
<filename>bblayers.conf</filename> file found in the
<filename>poky/build/conf</filename> directory needs to have the path to your local
<filename>meta-mylayer</filename> layer.
By default, the <filename>BBLAYERS</filename> variable contains paths to
<filename>meta</filename>, <filename>meta-poky</filename>, and
<filename>meta-yocto-bsp</filename> in the
<filename>poky</filename> Git repository.
Add the path to your <filename>meta-mylayer</filename> location:
<literallayout class='monospaced'>
BBLAYERS ?= " \
$HOME/poky/meta \
$HOME/poky/meta-poky \
$HOME/poky/meta-yocto-bsp \
$HOME/poky/meta-mylayer \
"
</literallayout></para></listitem>
</itemizedlist>
</para>
</section>
<section id='build-the-modified-qemu-kernel-image'>
<title>Build the Modified QEMU Kernel Image</title>
<para>
The following steps build your modified kernel image:
<orderedlist>
<listitem><para><emphasis>Be sure your build environment is initialized</emphasis>:
Your environment should be set up since you previously sourced
the
<ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink>
script.
If it is not, source the script again from <filename>poky</filename>.
<literallayout class='monospaced'>
$ cd ~/poky
$ source &OE_INIT_FILE;
</literallayout>
</para></listitem>
<listitem><para>
<emphasis>Clean up</emphasis>:
Be sure to clean the shared state out by using BitBake
to run from within the Build Directory the
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleansstate'><filename>do_cleansstate</filename></ulink>
task as follows:
<literallayout class='monospaced'>
$ bitbake -c cleansstate linux-yocto
</literallayout></para>
<para>
<note>
Never remove any files by hand from the
<filename>tmp/deploy</filename>
directory inside the
<ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>.
Always use the various BitBake clean tasks to
clear out previous build artifacts.
For information on the clean tasks, see the
"<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-clean'><filename>do_clean</filename></ulink>",
"<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleanall'><filename>do_cleanall</filename></ulink>",
and
"<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleansstate'><filename>do_cleansstate</filename></ulink>"
sections all in the Yocto Project Reference
Manual.
</note>
</para></listitem>
<listitem><para>
<emphasis>Build the image</emphasis>:
Next, build the kernel image using this command:
<literallayout class='monospaced'>
$ bitbake -k linux-yocto
</literallayout></para></listitem>
</orderedlist>
</para>
</section>
<section id='boot-the-image-and-verify-your-changes'>
<title>Boot the Image and Verify Your Changes</title>
<para>
These steps boot the image and allow you to see the changes
<orderedlist>
<listitem><para><emphasis>Boot the image</emphasis>:
Boot the modified image in the QEMU emulator
using this command:
<literallayout class='monospaced'>
$ runqemu qemux86
</literallayout></para></listitem>
<listitem><para><emphasis>Verify the changes</emphasis>:
Log into the machine using <filename>root</filename> with no password and then
use the following shell command to scroll through the console's boot output.
<literallayout class='monospaced'>
# dmesg | less
</literallayout>
You should see the results of your <filename>printk</filename> statements
as part of the output.</para></listitem>
</orderedlist>
</para>
</section>
</section>
<section id='using-an-iterative-development-process'> <section id='using-an-iterative-development-process'>
<title>Using an Iterative Development Process</title> <title>Using an Iterative Development Process</title>
@@ -747,8 +1095,8 @@
"<link linkend='applying-patches'>Applying Patches</link>" "<link linkend='applying-patches'>Applying Patches</link>"
section. section.
If you are not familiar with generating patches, refer to the If you are not familiar with generating patches, refer to the
"<ulink url='&YOCTO_DOCS_DEV_URL;#creating-the-patch'>Creating the Patch</ulink>" "<link linkend='creating-the-patch'>Creating the Patch</link>"
section in the Yocto Project Development Manual. section.
</para> </para>
</section> </section>
</section> </section>
documentation/kernel-dev/kernel-dev-concepts-appx.xml
+2 -3
View File
@@ -461,9 +461,8 @@
"<link linkend='yocto-linux-kernel-architecture-and-branching-strategies'>Yocto Linux Kernel Architecture and Branching Strategies</link>" "<link linkend='yocto-linux-kernel-architecture-and-branching-strategies'>Yocto Linux Kernel Architecture and Branching Strategies</link>"
section. section.
You can also reference the You can also reference the
"<ulink url='&YOCTO_DOCS_DEV_URL;#patching-the-kernel'>Patching the Kernel</ulink>" "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>"
section in the Yocto Project Development Manual for a detailed section for a detailed example that modifies the kernel.
example that modifies the kernel.
</para> </para>
</section> </section>
</appendix> </appendix>
documentation/kernel-dev/kernel-dev-intro.xml
+5 -3
View File
@@ -108,12 +108,14 @@
You can find additional information here: You can find additional information here:
<itemizedlist> <itemizedlist>
<listitem><para> <listitem><para>
"<ulink url='&YOCTO_DOCS_DEV_URL;#patching-the-kernel'>Patching the Kernel</ulink>" The
in the Yocto Project Development Manual. "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>"
section.
</para></listitem> </para></listitem>
<listitem><para> <listitem><para>
The
"<ulink url='&YOCTO_DOCS_DEV_URL;#configuring-the-kernel'>Configuring the Kernel</ulink>" "<ulink url='&YOCTO_DOCS_DEV_URL;#configuring-the-kernel'>Configuring the Kernel</ulink>"
in the Yocto Project Development Manual. section in the Yocto Project Development Manual.
</para></listitem> </para></listitem>
</itemizedlist> </itemizedlist>
This illustration and the following list summarizes the kernel This illustration and the following list summarizes the kernel
documentation/sdk-manual/sdk-working-projects.xml
+3 -3
View File
@@ -349,9 +349,9 @@
supported architecture, you can modify the supported architecture, you can modify the
kernel image before you build it. kernel image before you build it.
See the See the
"<ulink url='&YOCTO_DOCS_DEV_URL;#patching-the-kernel'>Patching the Kernel</ulink>" "<ulink url='&YOCTO_DOCS_KERNEL_DEV_URL;#using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</ulink>"
section in the Yocto Project Development section in the Yocto Project Linux Kernel
manual for an example. Development Manual for an example.
</para></listitem> </para></listitem>
</itemizedlist> </itemizedlist>
</para></listitem> </para></listitem>