~ubuntu-branches/ubuntu/raring/linux-nexus7/raring

	Linux kernel release 3.x <http://kernel.org/>

These are the release notes for Linux version 3.  Read them carefully,

as they tell you what this is all about, explain how to install the

kernel, and what to do if something goes wrong. 

WHAT IS LINUX?

  Linux is a clone of the operating system Unix, written from scratch by

  Linus Torvalds with assistance from a loosely-knit team of hackers across

  the Net. It aims towards POSIX and Single UNIX Specification compliance.

  It has all the features you would expect in a modern fully-fledged Unix,

  including true multitasking, virtual memory, shared libraries, demand

  loading, shared copy-on-write executables, proper memory management,

  and multistack networking including IPv4 and IPv6.

  It is distributed under the GNU General Public License - see the

  accompanying COPYING file for more details. 

ON WHAT HARDWARE DOES IT RUN?

  Although originally developed first for 32-bit x86-based PCs (386 or higher),

  today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and

  UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell,

  IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS,

  Xtensa, Tilera TILE, AVR32 and Renesas M32R architectures.

  Linux is easily portable to most general-purpose 32- or 64-bit architectures

  as long as they have a paged memory management unit (PMMU) and a port of the

  GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has

  also been ported to a number of architectures without a PMMU, although

  functionality is then obviously somewhat limited.

  Linux has also been ported to itself. You can now run the kernel as a

  userspace application - this is called UserMode Linux (UML).

DOCUMENTATION:

 - There is a lot of documentation available both in electronic form on

   the Internet and in books, both Linux-specific and pertaining to

   general UNIX questions.  I'd recommend looking into the documentation

   subdirectories on any Linux FTP site for the LDP (Linux Documentation

   Project) books.  This README is not meant to be documentation on the

   system: there are much better sources available.

 - There are various README files in the Documentation/ subdirectory:

   these typically contain kernel-specific installation notes for some 

   drivers for example. See Documentation/00-INDEX for a list of what

   is contained in each file.  Please read the Changes file, as it

   contains information about the problems, which may result by upgrading

   your kernel.

 - The Documentation/DocBook/ subdirectory contains several guides for

   kernel developers and users.  These guides can be rendered in a

   number of formats:  PostScript (.ps), PDF, HTML, & man-pages, among others.

   After installation, "make psdocs", "make pdfdocs", "make htmldocs",

   or "make mandocs" will render the documentation in the requested format.

INSTALLING the kernel source:

 - If you install the full sources, put the kernel tarball in a

   directory where you have permissions (eg. your home directory) and

   unpack it:

		gzip -cd linux-3.X.tar.gz | tar xvf -

   or

		bzip2 -dc linux-3.X.tar.bz2 | tar xvf -

   Replace "XX" with the version number of the latest kernel.

   Do NOT use the /usr/src/linux area! This area has a (usually

   incomplete) set of kernel headers that are used by the library header

   files.  They should match the library, and not get messed up by

   whatever the kernel-du-jour happens to be.

 - You can also upgrade between 3.x releases by patching.  Patches are

   distributed in the traditional gzip and the newer bzip2 format.  To

   install by patching, get all the newer patch files, enter the

   top level directory of the kernel source (linux-3.x) and execute:

		gzip -cd ../patch-3.x.gz | patch -p1

   or

		bzip2 -dc ../patch-3.x.bz2 | patch -p1

   (repeat xx for all versions bigger than the version of your current

   source tree, _in_order_) and you should be ok.  You may want to remove

   the backup files (xxx~ or xxx.orig), and make sure that there are no

   failed patches (xxx# or xxx.rej). If there are, either you or me has

   made a mistake.

   Unlike patches for the 3.x kernels, patches for the 3.x.y kernels

   (also known as the -stable kernels) are not incremental but instead apply

   directly to the base 3.x kernel.  Please read

   Documentation/applying-patches.txt for more information.

   Alternatively, the script patch-kernel can be used to automate this

   process.  It determines the current kernel version and applies any

   patches found.

		linux/scripts/patch-kernel linux

   The first argument in the command above is the location of the

   kernel source.  Patches are applied from the current directory, but

   an alternative directory can be specified as the second argument.

 - If you are upgrading between releases using the stable series patches

   (for example, patch-3.x.y), note that these "dot-releases" are

   not incremental and must be applied to the 3.x base tree. For

   example, if your base kernel is 3.0 and you want to apply the

   3.0.3 patch, you do not and indeed must not first apply the

   3.0.1 and 3.0.2 patches. Similarly, if you are running kernel

   version 3.0.2 and want to jump to 3.0.3, you must first

   reverse the 3.0.2 patch (that is, patch -R) _before_ applying

   the 3.0.3 patch.

   You can read more on this in Documentation/applying-patches.txt

 - Make sure you have no stale .o files and dependencies lying around:

		cd linux

		make mrproper

   You should now have the sources correctly installed.

SOFTWARE REQUIREMENTS

   Compiling and running the 3.x kernels requires up-to-date

   versions of various software packages.  Consult

   Documentation/Changes for the minimum version numbers required

   and how to get updates for these packages.  Beware that using

   excessively old versions of these packages can cause indirect

   errors that are very difficult to track down, so don't assume that

   you can just update packages when obvious problems arise during

   build or operation.

BUILD directory for the kernel:

   When compiling the kernel all output files will per default be

   stored together with the kernel source code.

   Using the option "make O=output/dir" allow you to specify an alternate

   place for the output files (including .config).

   Example:

     kernel source code:	/usr/src/linux-3.N

     build directory:		/home/name/build/kernel

   To configure and build the kernel use:

   cd /usr/src/linux-3.N

   make O=/home/name/build/kernel menuconfig

   make O=/home/name/build/kernel

   sudo make O=/home/name/build/kernel modules_install install

   Please note: If the 'O=output/dir' option is used then it must be

   used for all invocations of make.

CONFIGURING the kernel:

   Do not skip this step even if you are only upgrading one minor

   version.  New configuration options are added in each release, and

   odd problems will turn up if the configuration files are not set up

   as expected.  If you want to carry your existing configuration to a

   new version with minimal work, use "make oldconfig", which will

   only ask you for the answers to new questions.

 - Alternate configuration commands are:

	"make config"      Plain text interface.

	"make menuconfig"  Text based color menus, radiolists & dialogs.

	"make nconfig"     Enhanced text based color menus.

	"make xconfig"     X windows (Qt) based configuration tool.

	"make gconfig"     X windows (Gtk) based configuration tool.

	"make oldconfig"   Default all questions based on the contents of

			   your existing ./.config file and asking about

			   new config symbols.

	"make silentoldconfig"

			   Like above, but avoids cluttering the screen

			   with questions already answered.

			   Additionally updates the dependencies.

	"make defconfig"   Create a ./.config file by using the default

			   symbol values from either arch/$ARCH/defconfig

			   or arch/$ARCH/configs/${PLATFORM}_defconfig,

			   depending on the architecture.

	"make ${PLATFORM}_defconfig"

			  Create a ./.config file by using the default

			  symbol values from

			  arch/$ARCH/configs/${PLATFORM}_defconfig.

			  Use "make help" to get a list of all available

			  platforms of your architecture.

	"make allyesconfig"

			   Create a ./.config file by setting symbol

			   values to 'y' as much as possible.

	"make allmodconfig"

			   Create a ./.config file by setting symbol

			   values to 'm' as much as possible.

	"make allnoconfig" Create a ./.config file by setting symbol

			   values to 'n' as much as possible.

	"make randconfig"  Create a ./.config file by setting symbol

			   values to random values.

   You can find more information on using the Linux kernel config tools

   in Documentation/kbuild/kconfig.txt.

	NOTES on "make config":

	- having unnecessary drivers will make the kernel bigger, and can

	  under some circumstances lead to problems: probing for a

	  nonexistent controller card may confuse your other controllers

	- compiling the kernel with "Processor type" set higher than 386

	  will result in a kernel that does NOT work on a 386.  The

	  kernel will detect this on bootup, and give up.

	- A kernel with math-emulation compiled in will still use the

	  coprocessor if one is present: the math emulation will just

	  never get used in that case.  The kernel will be slightly larger,

	  but will work on different machines regardless of whether they

	  have a math coprocessor or not. 

	- the "kernel hacking" configuration details usually result in a

	  bigger or slower kernel (or both), and can even make the kernel

	  less stable by configuring some routines to actively try to

	  break bad code to find kernel problems (kmalloc()).  Thus you

	  should probably answer 'n' to the questions for

          "development", "experimental", or "debugging" features.

COMPILING the kernel:

 - Make sure you have at least gcc 3.2 available.

   For more information, refer to Documentation/Changes.

   Please note that you can still run a.out user programs with this kernel.

 - Do a "make" to create a compressed kernel image. It is also

   possible to do "make install" if you have lilo installed to suit the

   kernel makefiles, but you may want to check your particular lilo setup first.

   To do the actual install you have to be root, but none of the normal

   build should require that. Don't take the name of root in vain.

 - If you configured any of the parts of the kernel as `modules', you

   will also have to do "make modules_install".

 - Verbose kernel compile/build output:

   Normally the kernel build system runs in a fairly quiet mode (but not

   totally silent).  However, sometimes you or other kernel developers need

   to see compile, link, or other commands exactly as they are executed.

   For this, use "verbose" build mode.  This is done by inserting

   "V=1" in the "make" command.  E.g.:

	make V=1 all

   To have the build system also tell the reason for the rebuild of each

   target, use "V=2".  The default is "V=0".

 - Keep a backup kernel handy in case something goes wrong.  This is 

   especially true for the development releases, since each new release

   contains new code which has not been debugged.  Make sure you keep a

   backup of the modules corresponding to that kernel, as well.  If you

   are installing a new kernel with the same version number as your

   working kernel, make a backup of your modules directory before you

   do a "make modules_install".

   Alternatively, before compiling, use the kernel config option

   "LOCALVERSION" to append a unique suffix to the regular kernel version.

   LOCALVERSION can be set in the "General Setup" menu.

 - In order to boot your new kernel, you'll need to copy the kernel

   image (e.g. .../linux/arch/i386/boot/bzImage after compilation)

   to the place where your regular bootable kernel is found. 

 - Booting a kernel directly from a floppy without the assistance of a

   bootloader such as LILO, is no longer supported.

   If you boot Linux from the hard drive, chances are you use LILO which

   uses the kernel image as specified in the file /etc/lilo.conf.  The

   kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or

   /boot/bzImage.  To use the new kernel, save a copy of the old image

   and copy the new image over the old one.  Then, you MUST RERUN LILO

   to update the loading map!! If you don't, you won't be able to boot

   the new kernel image.

   Reinstalling LILO is usually a matter of running /sbin/lilo. 

   You may wish to edit /etc/lilo.conf to specify an entry for your

   old kernel image (say, /vmlinux.old) in case the new one does not

   work.  See the LILO docs for more information. 

   After reinstalling LILO, you should be all set.  Shutdown the system,

   reboot, and enjoy!

   If you ever need to change the default root device, video mode,

   ramdisk size, etc.  in the kernel image, use the 'rdev' program (or

   alternatively the LILO boot options when appropriate).  No need to

   recompile the kernel to change these parameters. 

 - Reboot with the new kernel and enjoy. 

IF SOMETHING GOES WRONG:

 - If you have problems that seem to be due to kernel bugs, please check

   the file MAINTAINERS to see if there is a particular person associated

   with the part of the kernel that you are having trouble with. If there

   isn't anyone listed there, then the second best thing is to mail

   them to me (torvalds@linux-foundation.org), and possibly to any other

   relevant mailing-list or to the newsgroup.

 - In all bug-reports, *please* tell what kernel you are talking about,

   how to duplicate the problem, and what your setup is (use your common

   sense).  If the problem is new, tell me so, and if the problem is

   old, please try to tell me when you first noticed it.

 - If the bug results in a message like

	unable to handle kernel paging request at address C0000010

	Oops: 0002

	EIP:   0010:XXXXXXXX

	eax: xxxxxxxx   ebx: xxxxxxxx   ecx: xxxxxxxx   edx: xxxxxxxx

	esi: xxxxxxxx   edi: xxxxxxxx   ebp: xxxxxxxx

	ds: xxxx  es: xxxx  fs: xxxx  gs: xxxx

	Pid: xx, process nr: xx

	xx xx xx xx xx xx xx xx xx xx

   or similar kernel debugging information on your screen or in your

   system log, please duplicate it *exactly*.  The dump may look

   incomprehensible to you, but it does contain information that may

   help debugging the problem.  The text above the dump is also

   important: it tells something about why the kernel dumped code (in

   the above example it's due to a bad kernel pointer). More information

   on making sense of the dump is in Documentation/oops-tracing.txt

 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump

   as is, otherwise you will have to use the "ksymoops" program to make

   sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).

   This utility can be downloaded from

   ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .

   Alternately you can do the dump lookup by hand:

 - In debugging dumps like the above, it helps enormously if you can

   look up what the EIP value means.  The hex value as such doesn't help

   me or anybody else very much: it will depend on your particular

   kernel setup.  What you should do is take the hex value from the EIP

   line (ignore the "0010:"), and look it up in the kernel namelist to

   see which kernel function contains the offending address.

   To find out the kernel function name, you'll need to find the system

   binary associated with the kernel that exhibited the symptom.  This is

   the file 'linux/vmlinux'.  To extract the namelist and match it against

   the EIP from the kernel crash, do:

		nm vmlinux | sort | less

   This will give you a list of kernel addresses sorted in ascending

   order, from which it is simple to find the function that contains the

   offending address.  Note that the address given by the kernel

   debugging messages will not necessarily match exactly with the

   function addresses (in fact, that is very unlikely), so you can't

   just 'grep' the list: the list will, however, give you the starting

   point of each kernel function, so by looking for the function that

   has a starting address lower than the one you are searching for but

   is followed by a function with a higher address you will find the one

   you want.  In fact, it may be a good idea to include a bit of

   "context" in your problem report, giving a few lines around the

   interesting one. 

   If you for some reason cannot do the above (you have a pre-compiled

   kernel image or similar), telling me as much about your setup as

   possible will help.  Please read the REPORTING-BUGS document for details.

 - Alternately, you can use gdb on a running kernel. (read-only; i.e. you

   cannot change values or set break points.) To do this, first compile the

   kernel with -g; edit arch/i386/Makefile appropriately, then do a "make

   clean". You'll also need to enable CONFIG_PROC_FS (via "make config").

   After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".

   You can now use all the usual gdb commands. The command to look up the

   point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes

   with the EIP value.)

   gdb'ing a non-running kernel currently fails because gdb (wrongly)

   disregards the starting offset for which the kernel is compiled.