Merge branch 'misc' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6
* 'misc' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6: (39 commits) Revert "namespace: add source file location exceptions" Coccinelle: Add contextual message Coccinelle: Fix documentation Coccinelle: Find doubled arguments to boolean or bit operators. Coccinelle: Find nested lock+irqsave functions that use the same flags variables. namespace: add source file location exceptions scripts/extract-ikconfig: add support for bzip2, lzma and lzo kbuild: check return value of asprintf() scripts/namespace.pl: improve to get more correct results scripts/namespace.pl: some bug fixes scripts/namespace.pl: update file exclusion list scripts/namespace.pl: fix wrong source path Coccinelle: Use the -no_show_diff option for org and report mode Coccinelle: Add a new mode named 'chain' Coccinelle: Use new comment format to explain kfree.cocci Coccinelle: Improve user information with a new kind of comment Coccinelle: Update documentation MAINTAINERS: Coccinelle: Update email address Documentation/kbuild: modules.txt cleanup Documentation/kbuild: major edit of modules.txt sections 5-8 ...
This commit is contained in:
Linus Torvalds
@@ -24,6 +24,9 @@ of many distributions, e.g. :
|
||||
You can get the latest version released from the Coccinelle homepage at
|
||||
http://coccinelle.lip6.fr/
|
||||
|
||||
Information and tips about Coccinelle are also provided on the wiki
|
||||
pages at http://cocci.ekstranet.diku.dk/wiki/doku.php
|
||||
|
||||
Once you have it, run the following command:
|
||||
|
||||
./configure
|
||||
@@ -41,20 +44,22 @@ A Coccinelle-specific target is defined in the top level
|
||||
Makefile. This target is named 'coccicheck' and calls the 'coccicheck'
|
||||
front-end in the 'scripts' directory.
|
||||
|
||||
Four modes are defined: report, patch, context, and org. The mode to
|
||||
Four modes are defined: patch, report, context, and org. The mode to
|
||||
use is specified by setting the MODE variable with 'MODE=<mode>'.
|
||||
|
||||
'patch' proposes a fix, when possible.
|
||||
|
||||
'report' generates a list in the following format:
|
||||
file:line:column-column: message
|
||||
|
||||
'patch' proposes a fix, when possible.
|
||||
|
||||
'context' highlights lines of interest and their context in a
|
||||
diff-like style.Lines of interest are indicated with '-'.
|
||||
|
||||
'org' generates a report in the Org mode format of Emacs.
|
||||
|
||||
Note that not all semantic patches implement all modes.
|
||||
Note that not all semantic patches implement all modes. For easy use
|
||||
of Coccinelle, the default mode is "chain" which tries the previous
|
||||
modes in the order above until one succeeds.
|
||||
|
||||
To make a report for every semantic patch, run the following command:
|
||||
|
||||
@@ -68,9 +73,9 @@ To produce patches, run:
|
||||
|
||||
|
||||
The coccicheck target applies every semantic patch available in the
|
||||
subdirectories of 'scripts/coccinelle' to the entire Linux kernel.
|
||||
sub-directories of 'scripts/coccinelle' to the entire Linux kernel.
|
||||
|
||||
For each semantic patch, a changelog message is proposed. It gives a
|
||||
For each semantic patch, a commit message is proposed. It gives a
|
||||
description of the problem being checked by the semantic patch, and
|
||||
includes a reference to Coccinelle.
|
||||
|
||||
@@ -93,12 +98,35 @@ or
|
||||
make coccicheck COCCI=<my_SP.cocci> MODE=report
|
||||
|
||||
|
||||
Using Coccinelle on (modified) files
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
To apply Coccinelle on a file basis, instead of a directory basis, the
|
||||
following command may be used:
|
||||
|
||||
make C=1 CHECK="scripts/coccicheck"
|
||||
|
||||
To check only newly edited code, use the value 2 for the C flag, i.e.
|
||||
|
||||
make C=2 CHECK="scripts/coccicheck"
|
||||
|
||||
This runs every semantic patch in scripts/coccinelle by default. The
|
||||
COCCI variable may additionally be used to only apply a single
|
||||
semantic patch as shown in the previous section.
|
||||
|
||||
The "chain" mode is the default. You can select another one with the
|
||||
MODE variable explained above.
|
||||
|
||||
In this mode, there is no information about semantic patches
|
||||
displayed, and no commit message proposed.
|
||||
|
||||
|
||||
Proposing new semantic patches
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
New semantic patches can be proposed and submitted by kernel
|
||||
developers. For sake of clarity, they should be organized in the
|
||||
subdirectories of 'scripts/coccinelle/'.
|
||||
sub-directories of 'scripts/coccinelle/'.
|
||||
|
||||
|
||||
Detailed description of the 'report' mode
|
||||
@@ -111,7 +139,7 @@ Example:
|
||||
|
||||
Running
|
||||
|
||||
make coccicheck MODE=report COCCI=scripts/coccinelle/err_cast.cocci
|
||||
make coccicheck MODE=report COCCI=scripts/coccinelle/api/err_cast.cocci
|
||||
|
||||
will execute the following part of the SmPL script.
|
||||
|
||||
@@ -149,7 +177,7 @@ identified.
|
||||
Example:
|
||||
|
||||
Running
|
||||
make coccicheck MODE=patch COCCI=scripts/coccinelle/err_cast.cocci
|
||||
make coccicheck MODE=patch COCCI=scripts/coccinelle/api/err_cast.cocci
|
||||
|
||||
will execute the following part of the SmPL script.
|
||||
|
||||
@@ -193,7 +221,7 @@ NOTE: The diff-like output generated is NOT an applicable patch. The
|
||||
Example:
|
||||
|
||||
Running
|
||||
make coccicheck MODE=context COCCI=scripts/coccinelle/err_cast.cocci
|
||||
make coccicheck MODE=context COCCI=scripts/coccinelle/api/err_cast.cocci
|
||||
|
||||
will execute the following part of the SmPL script.
|
||||
|
||||
@@ -228,7 +256,7 @@ diff -u -p /home/user/linux/crypto/ctr.c /tmp/nothing
|
||||
Example:
|
||||
|
||||
Running
|
||||
make coccicheck MODE=org COCCI=scripts/coccinelle/err_cast.cocci
|
||||
make coccicheck MODE=org COCCI=scripts/coccinelle/api/err_cast.cocci
|
||||
|
||||
will execute the following part of the SmPL script.
|
||||
|
||||
|
||||
+356
-367
@@ -1,215 +1,185 @@
|
||||
Building External Modules
|
||||
|
||||
In this document you will find information about:
|
||||
- how to build external modules
|
||||
- how to make your module use the kbuild infrastructure
|
||||
- how kbuild will install a kernel
|
||||
- how to install modules in a non-standard location
|
||||
This document describes how to build an out-of-tree kernel module.
|
||||
|
||||
=== Table of Contents
|
||||
|
||||
=== 1 Introduction
|
||||
=== 2 How to build external modules
|
||||
--- 2.1 Building external modules
|
||||
--- 2.2 Available targets
|
||||
--- 2.3 Available options
|
||||
--- 2.4 Preparing the kernel tree for module build
|
||||
--- 2.5 Building separate files for a module
|
||||
=== 3. Example commands
|
||||
=== 4. Creating a kbuild file for an external module
|
||||
=== 5. Include files
|
||||
--- 5.1 How to include files from the kernel include dir
|
||||
--- 5.2 External modules using an include/ dir
|
||||
--- 5.3 External modules using several directories
|
||||
=== 6. Module installation
|
||||
--- 6.1 INSTALL_MOD_PATH
|
||||
--- 6.2 INSTALL_MOD_DIR
|
||||
=== 7. Module versioning & Module.symvers
|
||||
--- 7.1 Symbols from the kernel (vmlinux + modules)
|
||||
--- 7.2 Symbols and external modules
|
||||
--- 7.3 Symbols from another external module
|
||||
=== 8. Tips & Tricks
|
||||
--- 8.1 Testing for CONFIG_FOO_BAR
|
||||
=== 2 How to Build External Modules
|
||||
--- 2.1 Command Syntax
|
||||
--- 2.2 Options
|
||||
--- 2.3 Targets
|
||||
--- 2.4 Building Separate Files
|
||||
=== 3. Creating a Kbuild File for an External Module
|
||||
--- 3.1 Shared Makefile
|
||||
--- 3.2 Separate Kbuild file and Makefile
|
||||
--- 3.3 Binary Blobs
|
||||
--- 3.4 Building Multiple Modules
|
||||
=== 4. Include Files
|
||||
--- 4.1 Kernel Includes
|
||||
--- 4.2 Single Subdirectory
|
||||
--- 4.3 Several Subdirectories
|
||||
=== 5. Module Installation
|
||||
--- 5.1 INSTALL_MOD_PATH
|
||||
--- 5.2 INSTALL_MOD_DIR
|
||||
=== 6. Module Versioning
|
||||
--- 6.1 Symbols From the Kernel (vmlinux + modules)
|
||||
--- 6.2 Symbols and External Modules
|
||||
--- 6.3 Symbols From Another External Module
|
||||
=== 7. Tips & Tricks
|
||||
--- 7.1 Testing for CONFIG_FOO_BAR
|
||||
|
||||
|
||||
|
||||
=== 1. Introduction
|
||||
|
||||
kbuild includes functionality for building modules both
|
||||
within the kernel source tree and outside the kernel source tree.
|
||||
The latter is usually referred to as external or "out-of-tree"
|
||||
modules and is used both during development and for modules that
|
||||
are not planned to be included in the kernel tree.
|
||||
"kbuild" is the build system used by the Linux kernel. Modules must use
|
||||
kbuild to stay compatible with changes in the build infrastructure and
|
||||
to pick up the right flags to "gcc." Functionality for building modules
|
||||
both in-tree and out-of-tree is provided. The method for building
|
||||
either is similar, and all modules are initially developed and built
|
||||
out-of-tree.
|
||||
|
||||
What is covered within this file is mainly information to authors
|
||||
of modules. The author of an external module should supply
|
||||
a makefile that hides most of the complexity, so one only has to type
|
||||
'make' to build the module. A complete example will be presented in
|
||||
chapter 4, "Creating a kbuild file for an external module".
|
||||
Covered in this document is information aimed at developers interested
|
||||
in building out-of-tree (or "external") modules. The author of an
|
||||
external module should supply a makefile that hides most of the
|
||||
complexity, so one only has to type "make" to build the module. This is
|
||||
easily accomplished, and a complete example will be presented in
|
||||
section 3.
|
||||
|
||||
|
||||
=== 2. How to build external modules
|
||||
=== 2. How to Build External Modules
|
||||
|
||||
kbuild offers functionality to build external modules, with the
|
||||
prerequisite that there is a pre-built kernel available with full source.
|
||||
A subset of the targets available when building the kernel is available
|
||||
when building an external module.
|
||||
To build external modules, you must have a prebuilt kernel available
|
||||
that contains the configuration and header files used in the build.
|
||||
Also, the kernel must have been built with modules enabled. If you are
|
||||
using a distribution kernel, there will be a package for the kernel you
|
||||
are running provided by your distribution.
|
||||
|
||||
--- 2.1 Building external modules
|
||||
An alternative is to use the "make" target "modules_prepare." This will
|
||||
make sure the kernel contains the information required. The target
|
||||
exists solely as a simple way to prepare a kernel source tree for
|
||||
building external modules.
|
||||
|
||||
Use the following command to build an external module:
|
||||
NOTE: "modules_prepare" will not build Module.symvers even if
|
||||
CONFIG_MODVERSIONS is set; therefore, a full kernel build needs to be
|
||||
executed to make module versioning work.
|
||||
|
||||
make -C <path-to-kernel> M=`pwd`
|
||||
--- 2.1 Command Syntax
|
||||
|
||||
For the running kernel use:
|
||||
The command to build an external module is:
|
||||
|
||||
make -C /lib/modules/`uname -r`/build M=`pwd`
|
||||
$ make -C <path_to_kernel_src> M=$PWD
|
||||
|
||||
For the above command to succeed, the kernel must have been
|
||||
built with modules enabled.
|
||||
The kbuild system knows that an external module is being built
|
||||
due to the "M=<dir>" option given in the command.
|
||||
|
||||
To install the modules that were just built:
|
||||
To build against the running kernel use:
|
||||
|
||||
make -C <path-to-kernel> M=`pwd` modules_install
|
||||
$ make -C /lib/modules/`uname -r`/build M=$PWD
|
||||
|
||||
More complex examples will be shown later, the above should
|
||||
be enough to get you started.
|
||||
Then to install the module(s) just built, add the target
|
||||
"modules_install" to the command:
|
||||
|
||||
--- 2.2 Available targets
|
||||
$ make -C /lib/modules/`uname -r`/build M=$PWD modules_install
|
||||
|
||||
$KDIR refers to the path to the kernel source top-level directory
|
||||
--- 2.2 Options
|
||||
|
||||
make -C $KDIR M=`pwd`
|
||||
Will build the module(s) located in current directory.
|
||||
All output files will be located in the same directory
|
||||
as the module source.
|
||||
No attempts are made to update the kernel source, and it is
|
||||
a precondition that a successful make has been executed
|
||||
for the kernel.
|
||||
($KDIR refers to the path of the kernel source directory.)
|
||||
|
||||
make -C $KDIR M=`pwd` modules
|
||||
The modules target is implied when no target is given.
|
||||
Same functionality as if no target was specified.
|
||||
See description above.
|
||||
make -C $KDIR M=$PWD
|
||||
|
||||
make -C $KDIR M=`pwd` modules_install
|
||||
Install the external module(s).
|
||||
Installation default is in /lib/modules/<kernel-version>/extra,
|
||||
but may be prefixed with INSTALL_MOD_PATH - see separate
|
||||
chapter.
|
||||
-C $KDIR
|
||||
The directory where the kernel source is located.
|
||||
"make" will actually change to the specified directory
|
||||
when executing and will change back when finished.
|
||||
|
||||
make -C $KDIR M=`pwd` clean
|
||||
Remove all generated files for the module - the kernel
|
||||
source directory is not modified.
|
||||
M=$PWD
|
||||
Informs kbuild that an external module is being built.
|
||||
The value given to "M" is the absolute path of the
|
||||
directory where the external module (kbuild file) is
|
||||
located.
|
||||
|
||||
make -C $KDIR M=`pwd` help
|
||||
help will list the available target when building external
|
||||
modules.
|
||||
--- 2.3 Targets
|
||||
|
||||
--- 2.3 Available options:
|
||||
When building an external module, only a subset of the "make"
|
||||
targets are available.
|
||||
|
||||
$KDIR refers to the path to the kernel source top-level directory
|
||||
make -C $KDIR M=$PWD [target]
|
||||
|
||||
make -C $KDIR
|
||||
Used to specify where to find the kernel source.
|
||||
'$KDIR' represent the directory where the kernel source is.
|
||||
Make will actually change directory to the specified directory
|
||||
when executed but change back when finished.
|
||||
The default will build the module(s) located in the current
|
||||
directory, so a target does not need to be specified. All
|
||||
output files will also be generated in this directory. No
|
||||
attempts are made to update the kernel source, and it is a
|
||||
precondition that a successful "make" has been executed for the
|
||||
kernel.
|
||||
|
||||
make -C $KDIR M=`pwd`
|
||||
M= is used to tell kbuild that an external module is
|
||||
being built.
|
||||
The option given to M= is the directory where the external
|
||||
module (kbuild file) is located.
|
||||
When an external module is being built only a subset of the
|
||||
usual targets are available.
|
||||
modules
|
||||
The default target for external modules. It has the
|
||||
same functionality as if no target was specified. See
|
||||
description above.
|
||||
|
||||
make -C $KDIR SUBDIRS=`pwd`
|
||||
Same as M=. The SUBDIRS= syntax is kept for backwards
|
||||
compatibility.
|
||||
modules_install
|
||||
Install the external module(s). The default location is
|
||||
/lib/modules/<kernel_release>/extra/, but a prefix may
|
||||
be added with INSTALL_MOD_PATH (discussed in section 5).
|
||||
|
||||
--- 2.4 Preparing the kernel tree for module build
|
||||
clean
|
||||
Remove all generated files in the module directory only.
|
||||
|
||||
To make sure the kernel contains the information required to
|
||||
build external modules the target 'modules_prepare' must be used.
|
||||
'modules_prepare' exists solely as a simple way to prepare
|
||||
a kernel source tree for building external modules.
|
||||
Note: modules_prepare will not build Module.symvers even if
|
||||
CONFIG_MODVERSIONS is set. Therefore a full kernel build
|
||||
needs to be executed to make module versioning work.
|
||||
help
|
||||
List the available targets for external modules.
|
||||
|
||||
--- 2.5 Building separate files for a module
|
||||
It is possible to build single files which are part of a module.
|
||||
This works equally well for the kernel, a module and even for
|
||||
--- 2.4 Building Separate Files
|
||||
|
||||
It is possible to build single files that are part of a module.
|
||||
This works equally well for the kernel, a module, and even for
|
||||
external modules.
|
||||
Examples (module foo.ko, consist of bar.o, baz.o):
|
||||
make -C $KDIR M=`pwd` bar.lst
|
||||
make -C $KDIR M=`pwd` bar.o
|
||||
make -C $KDIR M=`pwd` foo.ko
|
||||
make -C $KDIR M=`pwd` /
|
||||
|
||||
Example (The module foo.ko, consist of bar.o and baz.o):
|
||||
make -C $KDIR M=$PWD bar.lst
|
||||
make -C $KDIR M=$PWD baz.o
|
||||
make -C $KDIR M=$PWD foo.ko
|
||||
make -C $KDIR M=$PWD /
|
||||
|
||||
|
||||
=== 3. Example commands
|
||||
=== 3. Creating a Kbuild File for an External Module
|
||||
|
||||
This example shows the actual commands to be executed when building
|
||||
an external module for the currently running kernel.
|
||||
In the example below, the distribution is supposed to use the
|
||||
facility to locate output files for a kernel compile in a different
|
||||
directory than the kernel source - but the examples will also work
|
||||
when the source and the output files are mixed in the same directory.
|
||||
In the last section we saw the command to build a module for the
|
||||
running kernel. The module is not actually built, however, because a
|
||||
build file is required. Contained in this file will be the name of
|
||||
the module(s) being built, along with the list of requisite source
|
||||
files. The file may be as simple as a single line:
|
||||
|
||||
# Kernel source
|
||||
/lib/modules/<kernel-version>/source -> /usr/src/linux-<version>
|
||||
obj-m := <module_name>.o
|
||||
|
||||
# Output from kernel compile
|
||||
/lib/modules/<kernel-version>/build -> /usr/src/linux-<version>-up
|
||||
The kbuild system will build <module_name>.o from <module_name>.c,
|
||||
and, after linking, will result in the kernel module <module_name>.ko.
|
||||
The above line can be put in either a "Kbuild" file or a "Makefile."
|
||||
When the module is built from multiple sources, an additional line is
|
||||
needed listing the files:
|
||||
|
||||
Change to the directory where the kbuild file is located and execute
|
||||
the following commands to build the module:
|
||||
<module_name>-y := <src1>.o <src2>.o ...
|
||||
|
||||
cd /home/user/src/module
|
||||
make -C /usr/src/`uname -r`/source \
|
||||
O=/lib/modules/`uname-r`/build \
|
||||
M=`pwd`
|
||||
NOTE: Further documentation describing the syntax used by kbuild is
|
||||
located in Documentation/kbuild/makefiles.txt.
|
||||
|
||||
Then, to install the module use the following command:
|
||||
The examples below demonstrate how to create a build file for the
|
||||
module 8123.ko, which is built from the following files:
|
||||
|
||||
make -C /usr/src/`uname -r`/source \
|
||||
O=/lib/modules/`uname-r`/build \
|
||||
M=`pwd` \
|
||||
modules_install
|
||||
|
||||
If you look closely you will see that this is the same command as
|
||||
listed before - with the directories spelled out.
|
||||
|
||||
The above are rather long commands, and the following chapter
|
||||
lists a few tricks to make it all easier.
|
||||
|
||||
|
||||
=== 4. Creating a kbuild file for an external module
|
||||
|
||||
kbuild is the build system for the kernel, and external modules
|
||||
must use kbuild to stay compatible with changes in the build system
|
||||
and to pick up the right flags to gcc etc.
|
||||
|
||||
The kbuild file used as input shall follow the syntax described
|
||||
in Documentation/kbuild/makefiles.txt. This chapter will introduce a few
|
||||
more tricks to be used when dealing with external modules.
|
||||
|
||||
In the following a Makefile will be created for a module with the
|
||||
following files:
|
||||
8123_if.c
|
||||
8123_if.h
|
||||
8123_pci.c
|
||||
8123_bin.o_shipped <= Binary blob
|
||||
|
||||
--- 4.1 Shared Makefile for module and kernel
|
||||
--- 3.1 Shared Makefile
|
||||
|
||||
An external module always includes a wrapper Makefile supporting
|
||||
building the module using 'make' with no arguments.
|
||||
The Makefile provided will most likely include additional
|
||||
functionality such as test targets etc. and this part shall
|
||||
be filtered away from kbuild since it may impact kbuild if
|
||||
name clashes occurs.
|
||||
An external module always includes a wrapper makefile that
|
||||
supports building the module using "make" with no arguments.
|
||||
This target is not used by kbuild; it is only for convenience.
|
||||
Additional functionality, such as test targets, can be included
|
||||
but should be filtered out from kbuild due to possible name
|
||||
clashes.
|
||||
|
||||
Example 1:
|
||||
--> filename: Makefile
|
||||
@@ -219,11 +189,11 @@ following files:
|
||||
8123-y := 8123_if.o 8123_pci.o 8123_bin.o
|
||||
|
||||
else
|
||||
# Normal Makefile
|
||||
# normal makefile
|
||||
KDIR ?= /lib/modules/`uname -r`/build
|
||||
|
||||
KERNELDIR := /lib/modules/`uname -r`/build
|
||||
all::
|
||||
$(MAKE) -C $(KERNELDIR) M=`pwd` $@
|
||||
default:
|
||||
$(MAKE) -C $(KDIR) M=$$PWD
|
||||
|
||||
# Module specific targets
|
||||
genbin:
|
||||
@@ -231,15 +201,20 @@ following files:
|
||||
|
||||
endif
|
||||
|
||||
In example 1, the check for KERNELRELEASE is used to separate
|
||||
the two parts of the Makefile. kbuild will only see the two
|
||||
assignments whereas make will see everything except the two
|
||||
kbuild assignments.
|
||||
The check for KERNELRELEASE is used to separate the two parts
|
||||
of the makefile. In the example, kbuild will only see the two
|
||||
assignments, whereas "make" will see everything except these
|
||||
two assignments. This is due to two passes made on the file:
|
||||
the first pass is by the "make" instance run on the command
|
||||
line; the second pass is by the kbuild system, which is
|
||||
initiated by the parameterized "make" in the default target.
|
||||
|
||||
In recent versions of the kernel, kbuild will look for a file named
|
||||
Kbuild and as second option look for a file named Makefile.
|
||||
Utilising the Kbuild file makes us split up the Makefile in example 1
|
||||
into two files as shown in example 2:
|
||||
--- 3.2 Separate Kbuild File and Makefile
|
||||
|
||||
In newer versions of the kernel, kbuild will first look for a
|
||||
file named "Kbuild," and only if that is not found, will it
|
||||
then look for a makefile. Utilizing a "Kbuild" file allows us
|
||||
to split up the makefile from example 1 into two files:
|
||||
|
||||
Example 2:
|
||||
--> filename: Kbuild
|
||||
@@ -247,20 +222,21 @@ following files:
|
||||
8123-y := 8123_if.o 8123_pci.o 8123_bin.o
|
||||
|
||||
--> filename: Makefile
|
||||
KERNELDIR := /lib/modules/`uname -r`/build
|
||||
all::
|
||||
$(MAKE) -C $(KERNELDIR) M=`pwd` $@
|
||||
KDIR ?= /lib/modules/`uname -r`/build
|
||||
|
||||
default:
|
||||
$(MAKE) -C $(KDIR) M=$$PWD
|
||||
|
||||
# Module specific targets
|
||||
genbin:
|
||||
echo "X" > 8123_bin.o_shipped
|
||||
|
||||
The split in example 2 is questionable due to the simplicity of
|
||||
each file; however, some external modules use makefiles
|
||||
consisting of several hundred lines, and here it really pays
|
||||
off to separate the kbuild part from the rest.
|
||||
|
||||
In example 2, we are down to two fairly simple files and for simple
|
||||
files as used in this example the split is questionable. But some
|
||||
external modules use Makefiles of several hundred lines and here it
|
||||
really pays off to separate the kbuild part from the rest.
|
||||
Example 3 shows a backward compatible version.
|
||||
The next example shows a backward compatible version.
|
||||
|
||||
Example 3:
|
||||
--> filename: Kbuild
|
||||
@@ -269,13 +245,15 @@ following files:
|
||||
|
||||
--> filename: Makefile
|
||||
ifneq ($(KERNELRELEASE),)
|
||||
# kbuild part of makefile
|
||||
include Kbuild
|
||||
else
|
||||
# Normal Makefile
|
||||
|
||||
KERNELDIR := /lib/modules/`uname -r`/build
|
||||
all::
|
||||
$(MAKE) -C $(KERNELDIR) M=`pwd` $@
|
||||
else
|
||||
# normal makefile
|
||||
KDIR ?= /lib/modules/`uname -r`/build
|
||||
|
||||
default:
|
||||
$(MAKE) -C $(KDIR) M=$$PWD
|
||||
|
||||
# Module specific targets
|
||||
genbin:
|
||||
@@ -283,260 +261,271 @@ following files:
|
||||
|
||||
endif
|
||||
|
||||
The trick here is to include the Kbuild file from Makefile, so
|
||||
if an older version of kbuild picks up the Makefile, the Kbuild
|
||||
file will be included.
|
||||
Here the "Kbuild" file is included from the makefile. This
|
||||
allows an older version of kbuild, which only knows of
|
||||
makefiles, to be used when the "make" and kbuild parts are
|
||||
split into separate files.
|
||||
|
||||
--- 4.2 Binary blobs included in a module
|
||||
--- 3.3 Binary Blobs
|
||||
|
||||
Some external modules needs to include a .o as a blob. kbuild
|
||||
has support for this, but requires the blob file to be named
|
||||
<filename>_shipped. In our example the blob is named
|
||||
8123_bin.o_shipped and when the kbuild rules kick in the file
|
||||
8123_bin.o is created as a simple copy off the 8213_bin.o_shipped file
|
||||
with the _shipped part stripped of the filename.
|
||||
This allows the 8123_bin.o filename to be used in the assignment to
|
||||
the module.
|
||||
Some external modules need to include an object file as a blob.
|
||||
kbuild has support for this, but requires the blob file to be
|
||||
named <filename>_shipped. When the kbuild rules kick in, a copy
|
||||
of <filename>_shipped is created with _shipped stripped off,
|
||||
giving us <filename>. This shortened filename can be used in
|
||||
the assignment to the module.
|
||||
|
||||
Throughout this section, 8123_bin.o_shipped has been used to
|
||||
build the kernel module 8123.ko; it has been included as
|
||||
8123_bin.o.
|
||||
|
||||
Example 4:
|
||||
obj-m := 8123.o
|
||||
8123-y := 8123_if.o 8123_pci.o 8123_bin.o
|
||||
|
||||
In example 4, there is no distinction between the ordinary .c/.h files
|
||||
and the binary file. But kbuild will pick up different rules to create
|
||||
the .o file.
|
||||
Although there is no distinction between the ordinary source
|
||||
files and the binary file, kbuild will pick up different rules
|
||||
when creating the object file for the module.
|
||||
|
||||
--- 3.4 Building Multiple Modules
|
||||
|
||||
kbuild supports building multiple modules with a single build
|
||||
file. For example, if you wanted to build two modules, foo.ko
|
||||
and bar.ko, the kbuild lines would be:
|
||||
|
||||
obj-m := foo.o bar.o
|
||||
foo-y := <foo_srcs>
|
||||
bar-y := <bar_srcs>
|
||||
|
||||
It is that simple!
|
||||
|
||||
|
||||
=== 5. Include files
|
||||
=== 4. Include Files
|
||||
|
||||
Include files are a necessity when a .c file uses something from other .c
|
||||
files (not strictly in the sense of C, but if good programming practice is
|
||||
used). Any module that consists of more than one .c file will have a .h file
|
||||
for one of the .c files.
|
||||
Within the kernel, header files are kept in standard locations
|
||||
according to the following rule:
|
||||
|
||||
- If the .h file only describes a module internal interface, then the .h file
|
||||
shall be placed in the same directory as the .c files.
|
||||
- If the .h files describe an interface used by other parts of the kernel
|
||||
located in different directories, the .h files shall be located in
|
||||
include/linux/ or other include/ directories as appropriate.
|
||||
* If the header file only describes the internal interface of a
|
||||
module, then the file is placed in the same directory as the
|
||||
source files.
|
||||
* If the header file describes an interface used by other parts
|
||||
of the kernel that are located in different directories, then
|
||||
the file is placed in include/linux/.
|
||||
|
||||
One exception for this rule is larger subsystems that have their own directory
|
||||
under include/ such as include/scsi. Another exception is arch-specific
|
||||
.h files which are located under include/asm-$(ARCH)/*.
|
||||
NOTE: There are two notable exceptions to this rule: larger
|
||||
subsystems have their own directory under include/, such as
|
||||
include/scsi; and architecture specific headers are located
|
||||
under arch/$(ARCH)/include/.
|
||||
|
||||
External modules have a tendency to locate include files in a separate include/
|
||||
directory and therefore need to deal with this in their kbuild file.
|
||||
--- 4.1 Kernel Includes
|
||||
|
||||
--- 5.1 How to include files from the kernel include dir
|
||||
To include a header file located under include/linux/, simply
|
||||
use:
|
||||
|
||||
When a module needs to include a file from include/linux/, then one
|
||||
just uses:
|
||||
#include <linux/module.h>
|
||||
|
||||
#include <linux/modules.h>
|
||||
kbuild will add options to "gcc" so the relevant directories
|
||||
are searched.
|
||||
|
||||
kbuild will make sure to add options to gcc so the relevant
|
||||
directories are searched.
|
||||
Likewise for .h files placed in the same directory as the .c file.
|
||||
--- 4.2 Single Subdirectory
|
||||
|
||||
#include "8123_if.h"
|
||||
External modules tend to place header files in a separate
|
||||
include/ directory where their source is located, although this
|
||||
is not the usual kernel style. To inform kbuild of the
|
||||
directory, use either ccflags-y or CFLAGS_<filename>.o.
|
||||
|
||||
will do the job.
|
||||
|
||||
--- 5.2 External modules using an include/ dir
|
||||
|
||||
External modules often locate their .h files in a separate include/
|
||||
directory although this is not usual kernel style. When an external
|
||||
module uses an include/ dir then kbuild needs to be told so.
|
||||
The trick here is to use either EXTRA_CFLAGS (take effect for all .c
|
||||
files) or CFLAGS_$F.o (take effect only for a single file).
|
||||
|
||||
In our example, if we move 8123_if.h to a subdirectory named include/
|
||||
the resulting Kbuild file would look like:
|
||||
Using the example from section 3, if we moved 8123_if.h to a
|
||||
subdirectory named include, the resulting kbuild file would
|
||||
look like:
|
||||
|
||||
--> filename: Kbuild
|
||||
obj-m := 8123.o
|
||||
obj-m := 8123.o
|
||||
|
||||
EXTRA_CFLAGS := -Iinclude
|
||||
ccflags-y := -Iinclude
|
||||
8123-y := 8123_if.o 8123_pci.o 8123_bin.o
|
||||
|
||||
Note that in the assignment there is no space between -I and the path.
|
||||
This is a kbuild limitation: there must be no space present.
|
||||
Note that in the assignment there is no space between -I and
|
||||
the path. This is a limitation of kbuild: there must be no
|
||||
space present.
|
||||
|
||||
--- 5.3 External modules using several directories
|
||||
|
||||
If an external module does not follow the usual kernel style, but
|
||||
decides to spread files over several directories, then kbuild can
|
||||
handle this too.
|
||||
--- 4.3 Several Subdirectories
|
||||
|
||||
kbuild can handle files that are spread over several directories.
|
||||
Consider the following example:
|
||||
|
||||
|
|
||||
+- src/complex_main.c
|
||||
| +- hal/hardwareif.c
|
||||
| +- hal/include/hardwareif.h
|
||||
+- include/complex.h
|
||||
.
|
||||
|__ src
|
||||
| |__ complex_main.c
|
||||
| |__ hal
|
||||
| |__ hardwareif.c
|
||||
| |__ include
|
||||
| |__ hardwareif.h
|
||||
|__ include
|
||||
|__ complex.h
|
||||
|
||||
To build a single module named complex.ko, we then need the following
|
||||
To build the module complex.ko, we then need the following
|
||||
kbuild file:
|
||||
|
||||
Kbuild:
|
||||
--> filename: Kbuild
|
||||
obj-m := complex.o
|
||||
complex-y := src/complex_main.o
|
||||
complex-y += src/hal/hardwareif.o
|
||||
|
||||
EXTRA_CFLAGS := -I$(src)/include
|
||||
EXTRA_CFLAGS += -I$(src)src/hal/include
|
||||
ccflags-y := -I$(src)/include
|
||||
ccflags-y += -I$(src)/src/hal/include
|
||||
|
||||
As you can see, kbuild knows how to handle object files located
|
||||
in other directories. The trick is to specify the directory
|
||||
relative to the kbuild file's location. That being said, this
|
||||
is NOT recommended practice.
|
||||
|
||||
For the header files, kbuild must be explicitly told where to
|
||||
look. When kbuild executes, the current directory is always the
|
||||
root of the kernel tree (the argument to "-C") and therefore an
|
||||
absolute path is needed. $(src) provides the absolute path by
|
||||
pointing to the directory where the currently executing kbuild
|
||||
file is located.
|
||||
|
||||
|
||||
kbuild knows how to handle .o files located in another directory -
|
||||
although this is NOT recommended practice. The syntax is to specify
|
||||
the directory relative to the directory where the Kbuild file is
|
||||
located.
|
||||
=== 5. Module Installation
|
||||
|
||||
To find the .h files, we have to explicitly tell kbuild where to look
|
||||
for the .h files. When kbuild executes, the current directory is always
|
||||
the root of the kernel tree (argument to -C) and therefore we have to
|
||||
tell kbuild how to find the .h files using absolute paths.
|
||||
$(src) will specify the absolute path to the directory where the
|
||||
Kbuild file are located when being build as an external module.
|
||||
Therefore -I$(src)/ is used to point out the directory of the Kbuild
|
||||
file and any additional path are just appended.
|
||||
Modules which are included in the kernel are installed in the
|
||||
directory:
|
||||
|
||||
=== 6. Module installation
|
||||
/lib/modules/$(KERNELRELEASE)/kernel/
|
||||
|
||||
Modules which are included in the kernel are installed in the directory:
|
||||
And external modules are installed in:
|
||||
|
||||
/lib/modules/$(KERNELRELEASE)/kernel
|
||||
/lib/modules/$(KERNELRELEASE)/extra/
|
||||
|
||||
External modules are installed in the directory:
|
||||
--- 5.1 INSTALL_MOD_PATH
|
||||
|
||||
/lib/modules/$(KERNELRELEASE)/extra
|
||||
|
||||
--- 6.1 INSTALL_MOD_PATH
|
||||
|
||||
Above are the default directories, but as always, some level of
|
||||
customization is possible. One can prefix the path using the variable
|
||||
INSTALL_MOD_PATH:
|
||||
Above are the default directories but as always some level of
|
||||
customization is possible. A prefix can be added to the
|
||||
installation path using the variable INSTALL_MOD_PATH:
|
||||
|
||||
$ make INSTALL_MOD_PATH=/frodo modules_install
|
||||
=> Install dir: /frodo/lib/modules/$(KERNELRELEASE)/kernel
|
||||
=> Install dir: /frodo/lib/modules/$(KERNELRELEASE)/kernel/
|
||||
|
||||
INSTALL_MOD_PATH may be set as an ordinary shell variable or as in the
|
||||
example above, can be specified on the command line when calling make.
|
||||
INSTALL_MOD_PATH has effect both when installing modules included in
|
||||
the kernel as well as when installing external modules.
|
||||
INSTALL_MOD_PATH may be set as an ordinary shell variable or,
|
||||
as shown above, can be specified on the command line when
|
||||
calling "make." This has effect when installing both in-tree
|
||||
and out-of-tree modules.
|
||||
|
||||
--- 6.2 INSTALL_MOD_DIR
|
||||
--- 5.2 INSTALL_MOD_DIR
|
||||
|
||||
When installing external modules they are by default installed to a
|
||||
directory under /lib/modules/$(KERNELRELEASE)/extra, but one may wish
|
||||
to locate modules for a specific functionality in a separate
|
||||
directory. For this purpose, one can use INSTALL_MOD_DIR to specify an
|
||||
alternative name to 'extra'.
|
||||
External modules are by default installed to a directory under
|
||||
/lib/modules/$(KERNELRELEASE)/extra/, but you may wish to
|
||||
locate modules for a specific functionality in a separate
|
||||
directory. For this purpose, use INSTALL_MOD_DIR to specify an
|
||||
alternative name to "extra."
|
||||
|
||||
$ make INSTALL_MOD_DIR=gandalf -C KERNELDIR \
|
||||
M=`pwd` modules_install
|
||||
=> Install dir: /lib/modules/$(KERNELRELEASE)/gandalf
|
||||
$ make INSTALL_MOD_DIR=gandalf -C $KDIR \
|
||||
M=$PWD modules_install
|
||||
=> Install dir: /lib/modules/$(KERNELRELEASE)/gandalf/
|
||||
|
||||
|
||||
=== 7. Module versioning & Module.symvers
|
||||
=== 6. Module Versioning
|
||||
|
||||
Module versioning is enabled by the CONFIG_MODVERSIONS tag.
|
||||
Module versioning is enabled by the CONFIG_MODVERSIONS tag, and is used
|
||||
as a simple ABI consistency check. A CRC value of the full prototype
|
||||
for an exported symbol is created. When a module is loaded/used, the
|
||||
CRC values contained in the kernel are compared with similar values in
|
||||
the module; if they are not equal, the kernel refuses to load the
|
||||
module.
|
||||
|
||||
Module versioning is used as a simple ABI consistency check. The Module
|
||||
versioning creates a CRC value of the full prototype for an exported symbol and
|
||||
when a module is loaded/used then the CRC values contained in the kernel are
|
||||
compared with similar values in the module. If they are not equal, then the
|
||||
kernel refuses to load the module.
|
||||
Module.symvers contains a list of all exported symbols from a kernel
|
||||
build.
|
||||
|
||||
Module.symvers contains a list of all exported symbols from a kernel build.
|
||||
--- 6.1 Symbols From the Kernel (vmlinux + modules)
|
||||
|
||||
--- 7.1 Symbols from the kernel (vmlinux + modules)
|
||||
|
||||
During a kernel build, a file named Module.symvers will be generated.
|
||||
Module.symvers contains all exported symbols from the kernel and
|
||||
compiled modules. For each symbols, the corresponding CRC value
|
||||
is stored too.
|
||||
During a kernel build, a file named Module.symvers will be
|
||||
generated. Module.symvers contains all exported symbols from
|
||||
the kernel and compiled modules. For each symbol, the
|
||||
corresponding CRC value is also stored.
|
||||
|
||||
The syntax of the Module.symvers file is:
|
||||
<CRC> <Symbol> <module>
|
||||
Sample:
|
||||
<CRC> <Symbol> <module>
|
||||
|
||||
0x2d036834 scsi_remove_host drivers/scsi/scsi_mod
|
||||
|
||||
For a kernel build without CONFIG_MODVERSIONS enabled, the crc
|
||||
would read: 0x00000000
|
||||
For a kernel build without CONFIG_MODVERSIONS enabled, the CRC
|
||||
would read 0x00000000.
|
||||
|
||||
Module.symvers serves two purposes:
|
||||
1) It lists all exported symbols both from vmlinux and all modules
|
||||
2) It lists the CRC if CONFIG_MODVERSIONS is enabled
|
||||
1) It lists all exported symbols from vmlinux and all modules.
|
||||
2) It lists the CRC if CONFIG_MODVERSIONS is enabled.
|
||||
|
||||
--- 7.2 Symbols and external modules
|
||||
--- 6.2 Symbols and External Modules
|
||||
|
||||
When building an external module, the build system needs access to
|
||||
the symbols from the kernel to check if all external symbols are
|
||||
defined. This is done in the MODPOST step and to obtain all
|
||||
symbols, modpost reads Module.symvers from the kernel.
|
||||
If a Module.symvers file is present in the directory where
|
||||
the external module is being built, this file will be read too.
|
||||
During the MODPOST step, a new Module.symvers file will be written
|
||||
containing all exported symbols that were not defined in the kernel.
|
||||
When building an external module, the build system needs access
|
||||
to the symbols from the kernel to check if all external symbols
|
||||
are defined. This is done in the MODPOST step. modpost obtains
|
||||
the symbols by reading Module.symvers from the kernel source
|
||||
tree. If a Module.symvers file is present in the directory
|
||||
where the external module is being built, this file will be
|
||||
read too. During the MODPOST step, a new Module.symvers file
|
||||
will be written containing all exported symbols that were not
|
||||
defined in the kernel.
|
||||
|
||||
--- 7.3 Symbols from another external module
|
||||
--- 6.3 Symbols From Another External Module
|
||||
|
||||
Sometimes, an external module uses exported symbols from another
|
||||
external module. Kbuild needs to have full knowledge on all symbols
|
||||
to avoid spitting out warnings about undefined symbols.
|
||||
Three solutions exist to let kbuild know all symbols of more than
|
||||
one external module.
|
||||
The method with a top-level kbuild file is recommended but may be
|
||||
impractical in certain situations.
|
||||
Sometimes, an external module uses exported symbols from
|
||||
another external module. kbuild needs to have full knowledge of
|
||||
all symbols to avoid spitting out warnings about undefined
|
||||
symbols. Three solutions exist for this situation.
|
||||
|
||||
Use a top-level Kbuild file
|
||||
If you have two modules: 'foo' and 'bar', and 'foo' needs
|
||||
symbols from 'bar', then one can use a common top-level kbuild
|
||||
file so both modules are compiled in same build.
|
||||
NOTE: The method with a top-level kbuild file is recommended
|
||||
but may be impractical in certain situations.
|
||||
|
||||
Consider following directory layout:
|
||||
./foo/ <= contains the foo module
|
||||
./bar/ <= contains the bar module
|
||||
The top-level Kbuild file would then look like:
|
||||
Use a top-level kbuild file
|
||||
If you have two modules, foo.ko and bar.ko, where
|
||||
foo.ko needs symbols from bar.ko, you can use a
|
||||
common top-level kbuild file so both modules are
|
||||
compiled in the same build. Consider the following
|
||||
directory layout:
|
||||
|
||||
#./Kbuild: (this file may also be named Makefile)
|
||||
./foo/ <= contains foo.ko
|
||||
./bar/ <= contains bar.ko
|
||||
|
||||
The top-level kbuild file would then look like:
|
||||
|
||||
#./Kbuild (or ./Makefile):
|
||||
obj-y := foo/ bar/
|
||||
|
||||
Executing:
|
||||
make -C $KDIR M=`pwd`
|
||||
And executing
|
||||
|
||||
will then do the expected and compile both modules with full
|
||||
knowledge on symbols from both modules.
|
||||
$ make -C $KDIR M=$PWD
|
||||
|
||||
will then do the expected and compile both modules with
|
||||
full knowledge of symbols from either module.
|
||||
|
||||
Use an extra Module.symvers file
|
||||
When an external module is built, a Module.symvers file is
|
||||
generated containing all exported symbols which are not
|
||||
defined in the kernel.
|
||||
To get access to symbols from module 'bar', one can copy the
|
||||
Module.symvers file from the compilation of the 'bar' module
|
||||
to the directory where the 'foo' module is built.
|
||||
During the module build, kbuild will read the Module.symvers
|
||||
file in the directory of the external module and when the
|
||||
build is finished, a new Module.symvers file is created
|
||||
containing the sum of all symbols defined and not part of the
|
||||
kernel.
|
||||
When an external module is built, a Module.symvers file
|
||||
is generated containing all exported symbols which are
|
||||
not defined in the kernel. To get access to symbols
|
||||
from bar.ko, copy the Module.symvers file from the
|
||||
compilation of bar.ko to the directory where foo.ko is
|
||||
built. During the module build, kbuild will read the
|
||||
Module.symvers file in the directory of the external
|
||||
module, and when the build is finished, a new
|
||||
Module.symvers file is created containing the sum of
|
||||
all symbols defined and not part of the kernel.
|
||||
|
||||
Use make variable KBUILD_EXTRA_SYMBOLS in the Makefile
|
||||
If it is impractical to copy Module.symvers from another
|
||||
module, you can assign a space separated list of files to
|
||||
KBUILD_EXTRA_SYMBOLS in your Makfile. These files will be
|
||||
loaded by modpost during the initialisation of its symbol
|
||||
tables.
|
||||
Use "make" variable KBUILD_EXTRA_SYMBOLS
|
||||
If it is impractical to copy Module.symvers from
|
||||
another module, you can assign a space separated list
|
||||
of files to KBUILD_EXTRA_SYMBOLS in your build file.
|
||||
These files will be loaded by modpost during the
|
||||
initialization of its symbol tables.
|
||||
|
||||
=== 8. Tips & Tricks
|
||||
|
||||
--- 8.1 Testing for CONFIG_FOO_BAR
|
||||
=== 7. Tips & Tricks
|
||||
|
||||
Modules often need to check for certain CONFIG_ options to decide if
|
||||
a specific feature shall be included in the module. When kbuild is used
|
||||
this is done by referencing the CONFIG_ variable directly.
|
||||
--- 7.1 Testing for CONFIG_FOO_BAR
|
||||
|
||||
Modules often need to check for certain CONFIG_ options to
|
||||
decide if a specific feature is included in the module. In
|
||||
kbuild this is done by referencing the CONFIG_ variable
|
||||
directly.
|
||||
|
||||
#fs/ext2/Makefile
|
||||
obj-$(CONFIG_EXT2_FS) += ext2.o
|
||||
@@ -544,9 +533,9 @@ Module.symvers contains a list of all exported symbols from a kernel build.
|
||||
ext2-y := balloc.o bitmap.o dir.o
|
||||
ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o
|
||||
|
||||
External modules have traditionally used grep to check for specific
|
||||
CONFIG_ settings directly in .config. This usage is broken.
|
||||
As introduced before, external modules shall use kbuild when building
|
||||
and therefore can use the same methods as in-kernel modules when
|
||||
testing for CONFIG_ definitions.
|
||||
External modules have traditionally used "grep" to check for
|
||||
specific CONFIG_ settings directly in .config. This usage is
|
||||
broken. As introduced before, external modules should use
|
||||
kbuild for building and can therefore use the same methods as
|
||||
in-tree modules when testing for CONFIG_ definitions.
|
||||
|
||||
|
||||
Reference in New Issue
Block a user