401 lines
18 KiB
Plaintext
401 lines
18 KiB
Plaintext
Linux kernel release 4.x <http://kernel.org/>
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These are the release notes for Linux version 4. Read them carefully,
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as they tell you what this is all about, explain how to install the
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kernel, and what to do if something goes wrong.
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WHAT IS LINUX?
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Linux is a clone of the operating system Unix, written from scratch by
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Linus Torvalds with assistance from a loosely-knit team of hackers across
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the Net. It aims towards POSIX and Single UNIX Specification compliance.
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It has all the features you would expect in a modern fully-fledged Unix,
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including true multitasking, virtual memory, shared libraries, demand
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loading, shared copy-on-write executables, proper memory management,
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and multistack networking including IPv4 and IPv6.
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It is distributed under the GNU General Public License - see the
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accompanying COPYING file for more details.
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ON WHAT HARDWARE DOES IT RUN?
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Although originally developed first for 32-bit x86-based PCs (386 or higher),
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today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and
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UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell,
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IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS,
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Xtensa, Tilera TILE, AVR32, ARC and Renesas M32R architectures.
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Linux is easily portable to most general-purpose 32- or 64-bit architectures
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as long as they have a paged memory management unit (PMMU) and a port of the
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GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has
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also been ported to a number of architectures without a PMMU, although
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functionality is then obviously somewhat limited.
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Linux has also been ported to itself. You can now run the kernel as a
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userspace application - this is called UserMode Linux (UML).
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DOCUMENTATION:
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- There is a lot of documentation available both in electronic form on
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the Internet and in books, both Linux-specific and pertaining to
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general UNIX questions. I'd recommend looking into the documentation
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subdirectories on any Linux FTP site for the LDP (Linux Documentation
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Project) books. This README is not meant to be documentation on the
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system: there are much better sources available.
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- There are various README files in the Documentation/ subdirectory:
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these typically contain kernel-specific installation notes for some
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drivers for example. See Documentation/00-INDEX for a list of what
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is contained in each file. Please read the Changes file, as it
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contains information about the problems, which may result by upgrading
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your kernel.
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- The Documentation/DocBook/ subdirectory contains several guides for
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kernel developers and users. These guides can be rendered in a
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number of formats: PostScript (.ps), PDF, HTML, & man-pages, among others.
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After installation, "make psdocs", "make pdfdocs", "make htmldocs",
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or "make mandocs" will render the documentation in the requested format.
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INSTALLING the kernel source:
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- If you install the full sources, put the kernel tarball in a
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directory where you have permissions (e.g. your home directory) and
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unpack it:
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xz -cd linux-4.X.tar.xz | tar xvf -
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Replace "X" with the version number of the latest kernel.
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Do NOT use the /usr/src/linux area! This area has a (usually
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incomplete) set of kernel headers that are used by the library header
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files. They should match the library, and not get messed up by
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whatever the kernel-du-jour happens to be.
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- You can also upgrade between 4.x releases by patching. Patches are
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distributed in the xz format. To install by patching, get all the
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newer patch files, enter the top level directory of the kernel source
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(linux-4.X) and execute:
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xz -cd ../patch-4.x.xz | patch -p1
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Replace "x" for all versions bigger than the version "X" of your current
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source tree, _in_order_, and you should be ok. You may want to remove
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the backup files (some-file-name~ or some-file-name.orig), and make sure
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that there are no failed patches (some-file-name# or some-file-name.rej).
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If there are, either you or I have made a mistake.
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Unlike patches for the 4.x kernels, patches for the 4.x.y kernels
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(also known as the -stable kernels) are not incremental but instead apply
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directly to the base 4.x kernel. For example, if your base kernel is 4.0
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and you want to apply the 4.0.3 patch, you must not first apply the 4.0.1
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and 4.0.2 patches. Similarly, if you are running kernel version 4.0.2 and
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want to jump to 4.0.3, you must first reverse the 4.0.2 patch (that is,
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patch -R) _before_ applying the 4.0.3 patch. You can read more on this in
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Documentation/applying-patches.txt
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Alternatively, the script patch-kernel can be used to automate this
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process. It determines the current kernel version and applies any
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patches found.
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linux/scripts/patch-kernel linux
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The first argument in the command above is the location of the
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kernel source. Patches are applied from the current directory, but
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an alternative directory can be specified as the second argument.
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- Make sure you have no stale .o files and dependencies lying around:
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cd linux
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make mrproper
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You should now have the sources correctly installed.
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SOFTWARE REQUIREMENTS
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Compiling and running the 4.x kernels requires up-to-date
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versions of various software packages. Consult
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Documentation/Changes for the minimum version numbers required
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and how to get updates for these packages. Beware that using
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excessively old versions of these packages can cause indirect
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errors that are very difficult to track down, so don't assume that
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you can just update packages when obvious problems arise during
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build or operation.
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BUILD directory for the kernel:
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When compiling the kernel, all output files will per default be
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stored together with the kernel source code.
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Using the option "make O=output/dir" allows you to specify an alternate
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place for the output files (including .config).
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Example:
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kernel source code: /usr/src/linux-4.X
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build directory: /home/name/build/kernel
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To configure and build the kernel, use:
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cd /usr/src/linux-4.X
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make O=/home/name/build/kernel menuconfig
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make O=/home/name/build/kernel
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sudo make O=/home/name/build/kernel modules_install install
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Please note: If the 'O=output/dir' option is used, then it must be
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used for all invocations of make.
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CONFIGURING the kernel:
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Do not skip this step even if you are only upgrading one minor
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version. New configuration options are added in each release, and
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odd problems will turn up if the configuration files are not set up
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as expected. If you want to carry your existing configuration to a
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new version with minimal work, use "make oldconfig", which will
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only ask you for the answers to new questions.
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- Alternative configuration commands are:
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"make config" Plain text interface.
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"make menuconfig" Text based color menus, radiolists & dialogs.
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"make nconfig" Enhanced text based color menus.
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"make xconfig" Qt based configuration tool.
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"make gconfig" GTK+ based configuration tool.
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"make oldconfig" Default all questions based on the contents of
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your existing ./.config file and asking about
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new config symbols.
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"make silentoldconfig"
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Like above, but avoids cluttering the screen
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with questions already answered.
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Additionally updates the dependencies.
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"make olddefconfig"
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Like above, but sets new symbols to their default
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values without prompting.
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"make defconfig" Create a ./.config file by using the default
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symbol values from either arch/$ARCH/defconfig
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or arch/$ARCH/configs/${PLATFORM}_defconfig,
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depending on the architecture.
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"make ${PLATFORM}_defconfig"
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Create a ./.config file by using the default
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symbol values from
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arch/$ARCH/configs/${PLATFORM}_defconfig.
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Use "make help" to get a list of all available
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platforms of your architecture.
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"make allyesconfig"
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Create a ./.config file by setting symbol
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values to 'y' as much as possible.
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"make allmodconfig"
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Create a ./.config file by setting symbol
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values to 'm' as much as possible.
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"make allnoconfig" Create a ./.config file by setting symbol
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values to 'n' as much as possible.
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"make randconfig" Create a ./.config file by setting symbol
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values to random values.
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"make localmodconfig" Create a config based on current config and
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loaded modules (lsmod). Disables any module
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option that is not needed for the loaded modules.
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To create a localmodconfig for another machine,
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store the lsmod of that machine into a file
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and pass it in as a LSMOD parameter.
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target$ lsmod > /tmp/mylsmod
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target$ scp /tmp/mylsmod host:/tmp
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host$ make LSMOD=/tmp/mylsmod localmodconfig
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The above also works when cross compiling.
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"make localyesconfig" Similar to localmodconfig, except it will convert
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all module options to built in (=y) options.
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You can find more information on using the Linux kernel config tools
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in Documentation/kbuild/kconfig.txt.
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- NOTES on "make config":
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- Having unnecessary drivers will make the kernel bigger, and can
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under some circumstances lead to problems: probing for a
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nonexistent controller card may confuse your other controllers
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- A kernel with math-emulation compiled in will still use the
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coprocessor if one is present: the math emulation will just
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never get used in that case. The kernel will be slightly larger,
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but will work on different machines regardless of whether they
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have a math coprocessor or not.
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- The "kernel hacking" configuration details usually result in a
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bigger or slower kernel (or both), and can even make the kernel
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less stable by configuring some routines to actively try to
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break bad code to find kernel problems (kmalloc()). Thus you
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should probably answer 'n' to the questions for "development",
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"experimental", or "debugging" features.
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COMPILING the kernel:
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- Make sure you have at least gcc 3.2 available.
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For more information, refer to Documentation/Changes.
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Please note that you can still run a.out user programs with this kernel.
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- Do a "make" to create a compressed kernel image. It is also
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possible to do "make install" if you have lilo installed to suit the
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kernel makefiles, but you may want to check your particular lilo setup first.
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To do the actual install, you have to be root, but none of the normal
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build should require that. Don't take the name of root in vain.
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- If you configured any of the parts of the kernel as `modules', you
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will also have to do "make modules_install".
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- Verbose kernel compile/build output:
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Normally, the kernel build system runs in a fairly quiet mode (but not
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totally silent). However, sometimes you or other kernel developers need
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to see compile, link, or other commands exactly as they are executed.
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For this, use "verbose" build mode. This is done by passing
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"V=1" to the "make" command, e.g.
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make V=1 all
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To have the build system also tell the reason for the rebuild of each
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target, use "V=2". The default is "V=0".
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- Keep a backup kernel handy in case something goes wrong. This is
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especially true for the development releases, since each new release
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contains new code which has not been debugged. Make sure you keep a
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backup of the modules corresponding to that kernel, as well. If you
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are installing a new kernel with the same version number as your
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working kernel, make a backup of your modules directory before you
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do a "make modules_install".
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Alternatively, before compiling, use the kernel config option
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"LOCALVERSION" to append a unique suffix to the regular kernel version.
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LOCALVERSION can be set in the "General Setup" menu.
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- In order to boot your new kernel, you'll need to copy the kernel
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image (e.g. .../linux/arch/x86/boot/bzImage after compilation)
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to the place where your regular bootable kernel is found.
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- Booting a kernel directly from a floppy without the assistance of a
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bootloader such as LILO, is no longer supported.
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If you boot Linux from the hard drive, chances are you use LILO, which
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uses the kernel image as specified in the file /etc/lilo.conf. The
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kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
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/boot/bzImage. To use the new kernel, save a copy of the old image
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and copy the new image over the old one. Then, you MUST RERUN LILO
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to update the loading map! If you don't, you won't be able to boot
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the new kernel image.
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Reinstalling LILO is usually a matter of running /sbin/lilo.
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You may wish to edit /etc/lilo.conf to specify an entry for your
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old kernel image (say, /vmlinux.old) in case the new one does not
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work. See the LILO docs for more information.
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After reinstalling LILO, you should be all set. Shutdown the system,
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reboot, and enjoy!
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If you ever need to change the default root device, video mode,
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ramdisk size, etc. in the kernel image, use the 'rdev' program (or
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alternatively the LILO boot options when appropriate). No need to
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recompile the kernel to change these parameters.
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- Reboot with the new kernel and enjoy.
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IF SOMETHING GOES WRONG:
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- If you have problems that seem to be due to kernel bugs, please check
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the file MAINTAINERS to see if there is a particular person associated
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with the part of the kernel that you are having trouble with. If there
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isn't anyone listed there, then the second best thing is to mail
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them to me (torvalds@linux-foundation.org), and possibly to any other
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relevant mailing-list or to the newsgroup.
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- In all bug-reports, *please* tell what kernel you are talking about,
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how to duplicate the problem, and what your setup is (use your common
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sense). If the problem is new, tell me so, and if the problem is
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old, please try to tell me when you first noticed it.
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- If the bug results in a message like
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unable to handle kernel paging request at address C0000010
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Oops: 0002
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EIP: 0010:XXXXXXXX
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eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
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esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
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ds: xxxx es: xxxx fs: xxxx gs: xxxx
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Pid: xx, process nr: xx
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xx xx xx xx xx xx xx xx xx xx
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or similar kernel debugging information on your screen or in your
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system log, please duplicate it *exactly*. The dump may look
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incomprehensible to you, but it does contain information that may
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help debugging the problem. The text above the dump is also
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important: it tells something about why the kernel dumped code (in
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the above example, it's due to a bad kernel pointer). More information
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on making sense of the dump is in Documentation/oops-tracing.txt
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- If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
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as is, otherwise you will have to use the "ksymoops" program to make
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sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
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This utility can be downloaded from
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ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .
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Alternatively, you can do the dump lookup by hand:
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- In debugging dumps like the above, it helps enormously if you can
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look up what the EIP value means. The hex value as such doesn't help
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me or anybody else very much: it will depend on your particular
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kernel setup. What you should do is take the hex value from the EIP
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line (ignore the "0010:"), and look it up in the kernel namelist to
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see which kernel function contains the offending address.
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To find out the kernel function name, you'll need to find the system
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binary associated with the kernel that exhibited the symptom. This is
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the file 'linux/vmlinux'. To extract the namelist and match it against
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the EIP from the kernel crash, do:
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nm vmlinux | sort | less
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This will give you a list of kernel addresses sorted in ascending
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order, from which it is simple to find the function that contains the
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offending address. Note that the address given by the kernel
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debugging messages will not necessarily match exactly with the
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function addresses (in fact, that is very unlikely), so you can't
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just 'grep' the list: the list will, however, give you the starting
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point of each kernel function, so by looking for the function that
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has a starting address lower than the one you are searching for but
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is followed by a function with a higher address you will find the one
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you want. In fact, it may be a good idea to include a bit of
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"context" in your problem report, giving a few lines around the
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interesting one.
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If you for some reason cannot do the above (you have a pre-compiled
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kernel image or similar), telling me as much about your setup as
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possible will help. Please read the REPORTING-BUGS document for details.
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- Alternatively, you can use gdb on a running kernel. (read-only; i.e. you
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cannot change values or set break points.) To do this, first compile the
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kernel with -g; edit arch/x86/Makefile appropriately, then do a "make
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clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
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After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
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You can now use all the usual gdb commands. The command to look up the
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point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
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with the EIP value.)
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gdb'ing a non-running kernel currently fails because gdb (wrongly)
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disregards the starting offset for which the kernel is compiled.
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