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Jesper Juhl0466dcb2011-07-01 12:46:56 +02001 Linux kernel release 3.x <http://kernel.org/>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002
Jesper Juhl0466dcb2011-07-01 12:46:56 +02003These are the release notes for Linux version 3. Read them carefully,
Linus Torvalds1da177e2005-04-16 15:20:36 -07004as they tell you what this is all about, explain how to install the
5kernel, and what to do if something goes wrong.
6
7WHAT IS LINUX?
8
Xose Vazquez Perez4f4e2dc2006-01-14 19:56:28 +01009 Linux is a clone of the operating system Unix, written from scratch by
10 Linus Torvalds with assistance from a loosely-knit team of hackers across
11 the Net. It aims towards POSIX and Single UNIX Specification compliance.
Linus Torvalds1da177e2005-04-16 15:20:36 -070012
Xose Vazquez Perez4f4e2dc2006-01-14 19:56:28 +010013 It has all the features you would expect in a modern fully-fledged Unix,
14 including true multitasking, virtual memory, shared libraries, demand
15 loading, shared copy-on-write executables, proper memory management,
16 and multistack networking including IPv4 and IPv6.
Linus Torvalds1da177e2005-04-16 15:20:36 -070017
18 It is distributed under the GNU General Public License - see the
19 accompanying COPYING file for more details.
20
21ON WHAT HARDWARE DOES IT RUN?
22
Xose Vazquez Perez4f4e2dc2006-01-14 19:56:28 +010023 Although originally developed first for 32-bit x86-based PCs (386 or higher),
24 today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and
Jesper Juhl620034c2006-12-07 00:45:58 +010025 UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell,
Xose Vazquez Perez4f4e2dc2006-01-14 19:56:28 +010026 IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS,
Tracey Dentcddb5de2010-11-24 06:56:36 -050027 Xtensa, Tilera TILE, AVR32 and Renesas M32R architectures.
Xose Vazquez Perez4f4e2dc2006-01-14 19:56:28 +010028
29 Linux is easily portable to most general-purpose 32- or 64-bit architectures
30 as long as they have a paged memory management unit (PMMU) and a port of the
31 GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has
32 also been ported to a number of architectures without a PMMU, although
33 functionality is then obviously somewhat limited.
Jesper Juhl620034c2006-12-07 00:45:58 +010034 Linux has also been ported to itself. You can now run the kernel as a
35 userspace application - this is called UserMode Linux (UML).
Linus Torvalds1da177e2005-04-16 15:20:36 -070036
37DOCUMENTATION:
38
39 - There is a lot of documentation available both in electronic form on
40 the Internet and in books, both Linux-specific and pertaining to
41 general UNIX questions. I'd recommend looking into the documentation
42 subdirectories on any Linux FTP site for the LDP (Linux Documentation
43 Project) books. This README is not meant to be documentation on the
44 system: there are much better sources available.
45
46 - There are various README files in the Documentation/ subdirectory:
47 these typically contain kernel-specific installation notes for some
48 drivers for example. See Documentation/00-INDEX for a list of what
49 is contained in each file. Please read the Changes file, as it
50 contains information about the problems, which may result by upgrading
51 your kernel.
52
53 - The Documentation/DocBook/ subdirectory contains several guides for
54 kernel developers and users. These guides can be rendered in a
Randy Dunlap2af238e2008-02-29 14:21:53 -080055 number of formats: PostScript (.ps), PDF, HTML, & man-pages, among others.
56 After installation, "make psdocs", "make pdfdocs", "make htmldocs",
57 or "make mandocs" will render the documentation in the requested format.
Linus Torvalds1da177e2005-04-16 15:20:36 -070058
Randy Dunlap2af238e2008-02-29 14:21:53 -080059INSTALLING the kernel source:
Linus Torvalds1da177e2005-04-16 15:20:36 -070060
61 - If you install the full sources, put the kernel tarball in a
62 directory where you have permissions (eg. your home directory) and
63 unpack it:
64
Jesper Juhl0466dcb2011-07-01 12:46:56 +020065 gzip -cd linux-3.X.tar.gz | tar xvf -
Linus Torvalds1da177e2005-04-16 15:20:36 -070066
Hormsb39f72f2005-10-30 15:03:19 -080067 or
Hormsb39f72f2005-10-30 15:03:19 -080068
Michael Witten88f7a642012-04-02 00:46:58 +000069 bzip2 -dc linux-3.X.tar.bz2 | tar xvf -
Hormsb39f72f2005-10-30 15:03:19 -080070
Michael Witten5b4285f2012-04-01 22:27:30 +000071 Replace "X" with the version number of the latest kernel.
Linus Torvalds1da177e2005-04-16 15:20:36 -070072
73 Do NOT use the /usr/src/linux area! This area has a (usually
74 incomplete) set of kernel headers that are used by the library header
75 files. They should match the library, and not get messed up by
76 whatever the kernel-du-jour happens to be.
77
Jesper Juhl0466dcb2011-07-01 12:46:56 +020078 - You can also upgrade between 3.x releases by patching. Patches are
Håkon Løvdal2b422382006-03-20 20:32:04 +010079 distributed in the traditional gzip and the newer bzip2 format. To
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 install by patching, get all the newer patch files, enter the
Michael Witten5b4285f2012-04-01 22:27:30 +000081 top level directory of the kernel source (linux-3.X) and execute:
Linus Torvalds1da177e2005-04-16 15:20:36 -070082
Jesper Juhl0466dcb2011-07-01 12:46:56 +020083 gzip -cd ../patch-3.x.gz | patch -p1
Linus Torvalds1da177e2005-04-16 15:20:36 -070084
85 or
Michael Witten88f7a642012-04-02 00:46:58 +000086
Jesper Juhl0466dcb2011-07-01 12:46:56 +020087 bzip2 -dc ../patch-3.x.bz2 | patch -p1
Linus Torvalds1da177e2005-04-16 15:20:36 -070088
Michael Witten5b4285f2012-04-01 22:27:30 +000089 Replace "x" for all versions bigger than the version "X" of your current
90 source tree, _in_order_, and you should be ok. You may want to remove
91 the backup files (some-file-name~ or some-file-name.orig), and make sure
92 that there are no failed patches (some-file-name# or some-file-name.rej).
Michael Wittena20e3a72012-04-03 19:20:02 +000093 If there are, either you or I have made a mistake.
Linus Torvalds1da177e2005-04-16 15:20:36 -070094
Jesper Juhl0466dcb2011-07-01 12:46:56 +020095 Unlike patches for the 3.x kernels, patches for the 3.x.y kernels
Jesper Juhl6ad44222005-11-13 16:07:44 -080096 (also known as the -stable kernels) are not incremental but instead apply
Jesper Juhl0466dcb2011-07-01 12:46:56 +020097 directly to the base 3.x kernel. Please read
Jesper Juhl6ad44222005-11-13 16:07:44 -080098 Documentation/applying-patches.txt for more information.
99
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100 Alternatively, the script patch-kernel can be used to automate this
101 process. It determines the current kernel version and applies any
102 patches found.
103
104 linux/scripts/patch-kernel linux
105
106 The first argument in the command above is the location of the
107 kernel source. Patches are applied from the current directory, but
108 an alternative directory can be specified as the second argument.
109
Kurt Wall896e5512005-07-27 11:45:20 -0700110 - If you are upgrading between releases using the stable series patches
Jesper Juhl0466dcb2011-07-01 12:46:56 +0200111 (for example, patch-3.x.y), note that these "dot-releases" are
112 not incremental and must be applied to the 3.x base tree. For
113 example, if your base kernel is 3.0 and you want to apply the
114 3.0.3 patch, you do not and indeed must not first apply the
115 3.0.1 and 3.0.2 patches. Similarly, if you are running kernel
116 version 3.0.2 and want to jump to 3.0.3, you must first
117 reverse the 3.0.2 patch (that is, patch -R) _before_ applying
118 the 3.0.3 patch.
Jesper Juhl620034c2006-12-07 00:45:58 +0100119 You can read more on this in Documentation/applying-patches.txt
Kurt Wall896e5512005-07-27 11:45:20 -0700120
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121 - Make sure you have no stale .o files and dependencies lying around:
122
123 cd linux
124 make mrproper
125
126 You should now have the sources correctly installed.
127
128SOFTWARE REQUIREMENTS
129
Jesper Juhl0466dcb2011-07-01 12:46:56 +0200130 Compiling and running the 3.x kernels requires up-to-date
Linus Torvalds1da177e2005-04-16 15:20:36 -0700131 versions of various software packages. Consult
132 Documentation/Changes for the minimum version numbers required
133 and how to get updates for these packages. Beware that using
134 excessively old versions of these packages can cause indirect
135 errors that are very difficult to track down, so don't assume that
136 you can just update packages when obvious problems arise during
137 build or operation.
138
139BUILD directory for the kernel:
140
Michael Wittena6144bb2012-04-02 00:31:33 +0000141 When compiling the kernel, all output files will per default be
Linus Torvalds1da177e2005-04-16 15:20:36 -0700142 stored together with the kernel source code.
143 Using the option "make O=output/dir" allow you to specify an alternate
144 place for the output files (including .config).
145 Example:
Michael Witten88f7a642012-04-02 00:46:58 +0000146
Michael Witten5b4285f2012-04-01 22:27:30 +0000147 kernel source code: /usr/src/linux-3.X
Linus Torvalds1da177e2005-04-16 15:20:36 -0700148 build directory: /home/name/build/kernel
149
Michael Wittena6144bb2012-04-02 00:31:33 +0000150 To configure and build the kernel, use:
Michael Witten88f7a642012-04-02 00:46:58 +0000151
152 cd /usr/src/linux-3.X
153 make O=/home/name/build/kernel menuconfig
154 make O=/home/name/build/kernel
155 sudo make O=/home/name/build/kernel modules_install install
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156
Michael Wittena6144bb2012-04-02 00:31:33 +0000157 Please note: If the 'O=output/dir' option is used, then it must be
Linus Torvalds1da177e2005-04-16 15:20:36 -0700158 used for all invocations of make.
159
160CONFIGURING the kernel:
161
162 Do not skip this step even if you are only upgrading one minor
163 version. New configuration options are added in each release, and
164 odd problems will turn up if the configuration files are not set up
165 as expected. If you want to carry your existing configuration to a
166 new version with minimal work, use "make oldconfig", which will
167 only ask you for the answers to new questions.
168
Michael Witten6d127602012-04-02 00:33:02 +0000169 - Alternative configuration commands are:
Michael Witten88f7a642012-04-02 00:46:58 +0000170
Jesper Juhl620034c2006-12-07 00:45:58 +0100171 "make config" Plain text interface.
Michael Witten88f7a642012-04-02 00:46:58 +0000172
Linus Torvalds1da177e2005-04-16 15:20:36 -0700173 "make menuconfig" Text based color menus, radiolists & dialogs.
Michael Witten88f7a642012-04-02 00:46:58 +0000174
Andrea Gelminib3235fe2010-10-01 14:15:35 -0700175 "make nconfig" Enhanced text based color menus.
Michael Witten88f7a642012-04-02 00:46:58 +0000176
Linus Torvalds1da177e2005-04-16 15:20:36 -0700177 "make xconfig" X windows (Qt) based configuration tool.
Michael Witten88f7a642012-04-02 00:46:58 +0000178
Linus Torvalds1da177e2005-04-16 15:20:36 -0700179 "make gconfig" X windows (Gtk) based configuration tool.
Michael Witten88f7a642012-04-02 00:46:58 +0000180
Linus Torvalds1da177e2005-04-16 15:20:36 -0700181 "make oldconfig" Default all questions based on the contents of
Randy Dunlap9dfb5632006-04-18 22:21:53 -0700182 your existing ./.config file and asking about
183 new config symbols.
Michael Witten88f7a642012-04-02 00:46:58 +0000184
Paolo 'Blaisorblade' Giarrussof875a1a2005-09-21 09:55:37 -0700185 "make silentoldconfig"
186 Like above, but avoids cluttering the screen
Randy Dunlape3fc4cc2005-09-22 21:44:07 -0700187 with questions already answered.
Markus Heidelberg590a5852009-05-18 01:36:46 +0200188 Additionally updates the dependencies.
Michael Witten88f7a642012-04-02 00:46:58 +0000189
Randy Dunlap9dfb5632006-04-18 22:21:53 -0700190 "make defconfig" Create a ./.config file by using the default
Patrick Ringlb2d89932009-06-12 13:58:36 +0200191 symbol values from either arch/$ARCH/defconfig
192 or arch/$ARCH/configs/${PLATFORM}_defconfig,
193 depending on the architecture.
Michael Witten88f7a642012-04-02 00:46:58 +0000194
Patrick Ringlb2d89932009-06-12 13:58:36 +0200195 "make ${PLATFORM}_defconfig"
Michael Witten88f7a642012-04-02 00:46:58 +0000196 Create a ./.config file by using the default
197 symbol values from
198 arch/$ARCH/configs/${PLATFORM}_defconfig.
199 Use "make help" to get a list of all available
200 platforms of your architecture.
201
Randy Dunlap9dfb5632006-04-18 22:21:53 -0700202 "make allyesconfig"
203 Create a ./.config file by setting symbol
204 values to 'y' as much as possible.
Michael Witten88f7a642012-04-02 00:46:58 +0000205
Randy Dunlap9dfb5632006-04-18 22:21:53 -0700206 "make allmodconfig"
207 Create a ./.config file by setting symbol
208 values to 'm' as much as possible.
Michael Witten88f7a642012-04-02 00:46:58 +0000209
Randy Dunlap9dfb5632006-04-18 22:21:53 -0700210 "make allnoconfig" Create a ./.config file by setting symbol
211 values to 'n' as much as possible.
Michael Witten88f7a642012-04-02 00:46:58 +0000212
Randy Dunlap9dfb5632006-04-18 22:21:53 -0700213 "make randconfig" Create a ./.config file by setting symbol
214 values to random values.
215
Randy Dunlap2af238e2008-02-29 14:21:53 -0800216 You can find more information on using the Linux kernel config tools
Li Zefanad444682009-02-20 15:38:43 -0800217 in Documentation/kbuild/kconfig.txt.
Randy Dunlap2af238e2008-02-29 14:21:53 -0800218
Linus Torvalds1da177e2005-04-16 15:20:36 -0700219 NOTES on "make config":
Michael Witten88f7a642012-04-02 00:46:58 +0000220
Linus Torvalds1da177e2005-04-16 15:20:36 -0700221 - having unnecessary drivers will make the kernel bigger, and can
222 under some circumstances lead to problems: probing for a
223 nonexistent controller card may confuse your other controllers
Michael Witten88f7a642012-04-02 00:46:58 +0000224
Linus Torvalds1da177e2005-04-16 15:20:36 -0700225 - compiling the kernel with "Processor type" set higher than 386
226 will result in a kernel that does NOT work on a 386. The
227 kernel will detect this on bootup, and give up.
Michael Witten88f7a642012-04-02 00:46:58 +0000228
Linus Torvalds1da177e2005-04-16 15:20:36 -0700229 - A kernel with math-emulation compiled in will still use the
230 coprocessor if one is present: the math emulation will just
231 never get used in that case. The kernel will be slightly larger,
232 but will work on different machines regardless of whether they
233 have a math coprocessor or not.
Michael Witten88f7a642012-04-02 00:46:58 +0000234
Linus Torvalds1da177e2005-04-16 15:20:36 -0700235 - the "kernel hacking" configuration details usually result in a
236 bigger or slower kernel (or both), and can even make the kernel
237 less stable by configuring some routines to actively try to
238 break bad code to find kernel problems (kmalloc()). Thus you
239 should probably answer 'n' to the questions for
240 "development", "experimental", or "debugging" features.
241
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242COMPILING the kernel:
243
Andrew Mortona1365642006-01-08 01:04:09 -0800244 - Make sure you have at least gcc 3.2 available.
245 For more information, refer to Documentation/Changes.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700246
247 Please note that you can still run a.out user programs with this kernel.
248
249 - Do a "make" to create a compressed kernel image. It is also
250 possible to do "make install" if you have lilo installed to suit the
251 kernel makefiles, but you may want to check your particular lilo setup first.
252
Michael Wittena6144bb2012-04-02 00:31:33 +0000253 To do the actual install, you have to be root, but none of the normal
Linus Torvalds1da177e2005-04-16 15:20:36 -0700254 build should require that. Don't take the name of root in vain.
255
256 - If you configured any of the parts of the kernel as `modules', you
257 will also have to do "make modules_install".
258
Randy Dunlap2af238e2008-02-29 14:21:53 -0800259 - Verbose kernel compile/build output:
260
Michael Wittena6144bb2012-04-02 00:31:33 +0000261 Normally, the kernel build system runs in a fairly quiet mode (but not
Randy Dunlap2af238e2008-02-29 14:21:53 -0800262 totally silent). However, sometimes you or other kernel developers need
263 to see compile, link, or other commands exactly as they are executed.
264 For this, use "verbose" build mode. This is done by inserting
265 "V=1" in the "make" command. E.g.:
266
267 make V=1 all
268
269 To have the build system also tell the reason for the rebuild of each
270 target, use "V=2". The default is "V=0".
271
Linus Torvalds1da177e2005-04-16 15:20:36 -0700272 - Keep a backup kernel handy in case something goes wrong. This is
273 especially true for the development releases, since each new release
274 contains new code which has not been debugged. Make sure you keep a
275 backup of the modules corresponding to that kernel, as well. If you
276 are installing a new kernel with the same version number as your
277 working kernel, make a backup of your modules directory before you
278 do a "make modules_install".
Michael Witten88f7a642012-04-02 00:46:58 +0000279
Randy Dunlape3fc4cc2005-09-22 21:44:07 -0700280 Alternatively, before compiling, use the kernel config option
281 "LOCALVERSION" to append a unique suffix to the regular kernel version.
282 LOCALVERSION can be set in the "General Setup" menu.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700283
284 - In order to boot your new kernel, you'll need to copy the kernel
285 image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
286 to the place where your regular bootable kernel is found.
287
288 - Booting a kernel directly from a floppy without the assistance of a
289 bootloader such as LILO, is no longer supported.
290
Michael Wittena6144bb2012-04-02 00:31:33 +0000291 If you boot Linux from the hard drive, chances are you use LILO, which
Linus Torvalds1da177e2005-04-16 15:20:36 -0700292 uses the kernel image as specified in the file /etc/lilo.conf. The
293 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
294 /boot/bzImage. To use the new kernel, save a copy of the old image
295 and copy the new image over the old one. Then, you MUST RERUN LILO
296 to update the loading map!! If you don't, you won't be able to boot
297 the new kernel image.
298
299 Reinstalling LILO is usually a matter of running /sbin/lilo.
300 You may wish to edit /etc/lilo.conf to specify an entry for your
301 old kernel image (say, /vmlinux.old) in case the new one does not
302 work. See the LILO docs for more information.
303
304 After reinstalling LILO, you should be all set. Shutdown the system,
305 reboot, and enjoy!
306
307 If you ever need to change the default root device, video mode,
308 ramdisk size, etc. in the kernel image, use the 'rdev' program (or
309 alternatively the LILO boot options when appropriate). No need to
310 recompile the kernel to change these parameters.
311
312 - Reboot with the new kernel and enjoy.
313
314IF SOMETHING GOES WRONG:
315
316 - If you have problems that seem to be due to kernel bugs, please check
317 the file MAINTAINERS to see if there is a particular person associated
318 with the part of the kernel that you are having trouble with. If there
319 isn't anyone listed there, then the second best thing is to mail
Linus Torvalds99ddcc72007-01-23 14:22:35 -0800320 them to me (torvalds@linux-foundation.org), and possibly to any other
321 relevant mailing-list or to the newsgroup.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700322
323 - In all bug-reports, *please* tell what kernel you are talking about,
324 how to duplicate the problem, and what your setup is (use your common
325 sense). If the problem is new, tell me so, and if the problem is
326 old, please try to tell me when you first noticed it.
327
328 - If the bug results in a message like
329
330 unable to handle kernel paging request at address C0000010
331 Oops: 0002
332 EIP: 0010:XXXXXXXX
333 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
334 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
335 ds: xxxx es: xxxx fs: xxxx gs: xxxx
336 Pid: xx, process nr: xx
337 xx xx xx xx xx xx xx xx xx xx
338
339 or similar kernel debugging information on your screen or in your
340 system log, please duplicate it *exactly*. The dump may look
341 incomprehensible to you, but it does contain information that may
342 help debugging the problem. The text above the dump is also
343 important: it tells something about why the kernel dumped code (in
Michael Wittena6144bb2012-04-02 00:31:33 +0000344 the above example, it's due to a bad kernel pointer). More information
Linus Torvalds1da177e2005-04-16 15:20:36 -0700345 on making sense of the dump is in Documentation/oops-tracing.txt
346
347 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
348 as is, otherwise you will have to use the "ksymoops" program to make
Jesper Juhl620034c2006-12-07 00:45:58 +0100349 sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
350 This utility can be downloaded from
351 ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .
Michael Witten6d127602012-04-02 00:33:02 +0000352 Alternatively, you can do the dump lookup by hand:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700353
354 - In debugging dumps like the above, it helps enormously if you can
355 look up what the EIP value means. The hex value as such doesn't help
356 me or anybody else very much: it will depend on your particular
357 kernel setup. What you should do is take the hex value from the EIP
358 line (ignore the "0010:"), and look it up in the kernel namelist to
359 see which kernel function contains the offending address.
360
361 To find out the kernel function name, you'll need to find the system
362 binary associated with the kernel that exhibited the symptom. This is
363 the file 'linux/vmlinux'. To extract the namelist and match it against
364 the EIP from the kernel crash, do:
365
366 nm vmlinux | sort | less
367
368 This will give you a list of kernel addresses sorted in ascending
369 order, from which it is simple to find the function that contains the
370 offending address. Note that the address given by the kernel
371 debugging messages will not necessarily match exactly with the
372 function addresses (in fact, that is very unlikely), so you can't
373 just 'grep' the list: the list will, however, give you the starting
374 point of each kernel function, so by looking for the function that
375 has a starting address lower than the one you are searching for but
376 is followed by a function with a higher address you will find the one
377 you want. In fact, it may be a good idea to include a bit of
378 "context" in your problem report, giving a few lines around the
379 interesting one.
380
381 If you for some reason cannot do the above (you have a pre-compiled
382 kernel image or similar), telling me as much about your setup as
Jesper Juhl620034c2006-12-07 00:45:58 +0100383 possible will help. Please read the REPORTING-BUGS document for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384
Michael Witten6d127602012-04-02 00:33:02 +0000385 - Alternatively, you can use gdb on a running kernel. (read-only; i.e. you
Linus Torvalds1da177e2005-04-16 15:20:36 -0700386 cannot change values or set break points.) To do this, first compile the
387 kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
388 clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
389
390 After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
391 You can now use all the usual gdb commands. The command to look up the
392 point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
393 with the EIP value.)
394
395 gdb'ing a non-running kernel currently fails because gdb (wrongly)
396 disregards the starting offset for which the kernel is compiled.
397