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Michael Witten3773b452012-04-02 01:07:52 +00001 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 Dunlap2af238e42008-02-29 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 Dunlap2af238e42008-02-29 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
Michael Witten3773b452012-04-02 01:07:52 +000065 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 Witten3773b452012-04-02 01:07:52 +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
Michael Witten3773b452012-04-02 01:07:52 +000083 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
Michael Witten3773b452012-04-02 01:07:52 +000087 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
Michael Witten7f65e922012-04-02 00:53:29 +000097 directly to the base 3.x kernel. For example, if your base kernel is 3.0
98 and you want to apply the 3.0.3 patch, you must not first apply the 3.0.1
99 and 3.0.2 patches. Similarly, if you are running kernel version 3.0.2 and
100 want to jump to 3.0.3, you must first reverse the 3.0.2 patch (that is,
101 patch -R) _before_ applying the 3.0.3 patch. You can read more on this in
102 Documentation/applying-patches.txt
Jesper Juhl6ad44222005-11-13 16:07:44 -0800103
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 Alternatively, the script patch-kernel can be used to automate this
105 process. It determines the current kernel version and applies any
106 patches found.
107
Michael Witten3773b452012-04-02 01:07:52 +0000108 linux/scripts/patch-kernel linux
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109
110 The first argument in the command above is the location of the
111 kernel source. Patches are applied from the current directory, but
112 an alternative directory can be specified as the second argument.
113
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114 - Make sure you have no stale .o files and dependencies lying around:
115
Michael Witten3773b452012-04-02 01:07:52 +0000116 cd linux
117 make mrproper
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118
119 You should now have the sources correctly installed.
120
121SOFTWARE REQUIREMENTS
122
Jesper Juhl0466dcb2011-07-01 12:46:56 +0200123 Compiling and running the 3.x kernels requires up-to-date
Linus Torvalds1da177e2005-04-16 15:20:36 -0700124 versions of various software packages. Consult
125 Documentation/Changes for the minimum version numbers required
126 and how to get updates for these packages. Beware that using
127 excessively old versions of these packages can cause indirect
128 errors that are very difficult to track down, so don't assume that
129 you can just update packages when obvious problems arise during
130 build or operation.
131
132BUILD directory for the kernel:
133
Michael Wittena6144bb2012-04-02 00:31:33 +0000134 When compiling the kernel, all output files will per default be
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135 stored together with the kernel source code.
136 Using the option "make O=output/dir" allow you to specify an alternate
137 place for the output files (including .config).
138 Example:
Michael Witten88f7a642012-04-02 00:46:58 +0000139
Michael Witten3773b452012-04-02 01:07:52 +0000140 kernel source code: /usr/src/linux-3.X
141 build directory: /home/name/build/kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -0700142
Michael Wittena6144bb2012-04-02 00:31:33 +0000143 To configure and build the kernel, use:
Michael Witten88f7a642012-04-02 00:46:58 +0000144
145 cd /usr/src/linux-3.X
146 make O=/home/name/build/kernel menuconfig
147 make O=/home/name/build/kernel
148 sudo make O=/home/name/build/kernel modules_install install
Linus Torvalds1da177e2005-04-16 15:20:36 -0700149
Michael Wittena6144bb2012-04-02 00:31:33 +0000150 Please note: If the 'O=output/dir' option is used, then it must be
Linus Torvalds1da177e2005-04-16 15:20:36 -0700151 used for all invocations of make.
152
153CONFIGURING the kernel:
154
155 Do not skip this step even if you are only upgrading one minor
156 version. New configuration options are added in each release, and
157 odd problems will turn up if the configuration files are not set up
158 as expected. If you want to carry your existing configuration to a
159 new version with minimal work, use "make oldconfig", which will
160 only ask you for the answers to new questions.
161
Michael Witten6d127602012-04-02 00:33:02 +0000162 - Alternative configuration commands are:
Michael Witten88f7a642012-04-02 00:46:58 +0000163
Michael Witten3773b452012-04-02 01:07:52 +0000164 "make config" Plain text interface.
Michael Witten88f7a642012-04-02 00:46:58 +0000165
Michael Witten3773b452012-04-02 01:07:52 +0000166 "make menuconfig" Text based color menus, radiolists & dialogs.
Michael Witten88f7a642012-04-02 00:46:58 +0000167
Michael Witten3773b452012-04-02 01:07:52 +0000168 "make nconfig" Enhanced text based color menus.
Michael Witten88f7a642012-04-02 00:46:58 +0000169
Michael Witten3773b452012-04-02 01:07:52 +0000170 "make xconfig" X windows (Qt) based configuration tool.
Michael Witten88f7a642012-04-02 00:46:58 +0000171
Michael Witten3773b452012-04-02 01:07:52 +0000172 "make gconfig" X windows (Gtk) based configuration tool.
Michael Witten88f7a642012-04-02 00:46:58 +0000173
Michael Witten3773b452012-04-02 01:07:52 +0000174 "make oldconfig" Default all questions based on the contents of
175 your existing ./.config file and asking about
176 new config symbols.
Michael Witten88f7a642012-04-02 00:46:58 +0000177
Michael Witten3773b452012-04-02 01:07:52 +0000178 "make silentoldconfig"
179 Like above, but avoids cluttering the screen
180 with questions already answered.
181 Additionally updates the dependencies.
Michael Witten88f7a642012-04-02 00:46:58 +0000182
Kees Cookfc0d1b92012-10-24 10:22:43 -0700183 "make olddefconfig"
184 Like above, but sets new symbols to their default
185 values without prompting.
186
Michael Witten3773b452012-04-02 01:07:52 +0000187 "make defconfig" Create a ./.config file by using the default
188 symbol values from either arch/$ARCH/defconfig
189 or arch/$ARCH/configs/${PLATFORM}_defconfig,
190 depending on the architecture.
Michael Witten88f7a642012-04-02 00:46:58 +0000191
Michael Witten3773b452012-04-02 01:07:52 +0000192 "make ${PLATFORM}_defconfig"
193 Create a ./.config file by using the default
194 symbol values from
195 arch/$ARCH/configs/${PLATFORM}_defconfig.
196 Use "make help" to get a list of all available
197 platforms of your architecture.
Michael Witten88f7a642012-04-02 00:46:58 +0000198
Michael Witten3773b452012-04-02 01:07:52 +0000199 "make allyesconfig"
200 Create a ./.config file by setting symbol
201 values to 'y' as much as possible.
Michael Witten88f7a642012-04-02 00:46:58 +0000202
Michael Witten3773b452012-04-02 01:07:52 +0000203 "make allmodconfig"
204 Create a ./.config file by setting symbol
205 values to 'm' as much as possible.
Michael Witten88f7a642012-04-02 00:46:58 +0000206
Michael Witten3773b452012-04-02 01:07:52 +0000207 "make allnoconfig" Create a ./.config file by setting symbol
208 values to 'n' as much as possible.
Michael Witten88f7a642012-04-02 00:46:58 +0000209
Michael Witten3773b452012-04-02 01:07:52 +0000210 "make randconfig" Create a ./.config file by setting symbol
211 values to random values.
Randy Dunlap9dfb5632006-04-18 22:21:53 -0700212
Steven Rostedt80b810b2012-10-05 16:52:50 -0400213 "make localmodconfig" Create a config based on current config and
214 loaded modules (lsmod). Disables any module
215 option that is not needed for the loaded modules.
216
217 To create a localmodconfig for another machine,
218 store the lsmod of that machine into a file
219 and pass it in as a LSMOD parameter.
220
221 target$ lsmod > /tmp/mylsmod
222 target$ scp /tmp/mylsmod host:/tmp
223
224 host$ make LSMOD=/tmp/mylsmod localmodconfig
225
226 The above also works when cross compiling.
227
228 "make localyesconfig" Similar to localmodconfig, except it will convert
229 all module options to built in (=y) options.
230
Randy Dunlap2af238e42008-02-29 14:21:53 -0800231 You can find more information on using the Linux kernel config tools
Li Zefanad444682009-02-20 15:38:43 -0800232 in Documentation/kbuild/kconfig.txt.
Randy Dunlap2af238e42008-02-29 14:21:53 -0800233
Michael Witten3773b452012-04-02 01:07:52 +0000234 - NOTES on "make config":
Michael Witten88f7a642012-04-02 00:46:58 +0000235
Michael Witten3773b452012-04-02 01:07:52 +0000236 - Having unnecessary drivers will make the kernel bigger, and can
237 under some circumstances lead to problems: probing for a
238 nonexistent controller card may confuse your other controllers
Michael Witten88f7a642012-04-02 00:46:58 +0000239
Michael Witten3773b452012-04-02 01:07:52 +0000240 - Compiling the kernel with "Processor type" set higher than 386
241 will result in a kernel that does NOT work on a 386. The
242 kernel will detect this on bootup, and give up.
Michael Witten88f7a642012-04-02 00:46:58 +0000243
Michael Witten3773b452012-04-02 01:07:52 +0000244 - A kernel with math-emulation compiled in will still use the
245 coprocessor if one is present: the math emulation will just
246 never get used in that case. The kernel will be slightly larger,
247 but will work on different machines regardless of whether they
248 have a math coprocessor or not.
Michael Witten88f7a642012-04-02 00:46:58 +0000249
Michael Witten3773b452012-04-02 01:07:52 +0000250 - The "kernel hacking" configuration details usually result in a
251 bigger or slower kernel (or both), and can even make the kernel
252 less stable by configuring some routines to actively try to
253 break bad code to find kernel problems (kmalloc()). Thus you
254 should probably answer 'n' to the questions for "development",
255 "experimental", or "debugging" features.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700256
Linus Torvalds1da177e2005-04-16 15:20:36 -0700257COMPILING the kernel:
258
Andrew Mortona1365642006-01-08 01:04:09 -0800259 - Make sure you have at least gcc 3.2 available.
260 For more information, refer to Documentation/Changes.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700261
262 Please note that you can still run a.out user programs with this kernel.
263
264 - Do a "make" to create a compressed kernel image. It is also
265 possible to do "make install" if you have lilo installed to suit the
266 kernel makefiles, but you may want to check your particular lilo setup first.
267
Michael Wittena6144bb2012-04-02 00:31:33 +0000268 To do the actual install, you have to be root, but none of the normal
Linus Torvalds1da177e2005-04-16 15:20:36 -0700269 build should require that. Don't take the name of root in vain.
270
271 - If you configured any of the parts of the kernel as `modules', you
272 will also have to do "make modules_install".
273
Randy Dunlap2af238e42008-02-29 14:21:53 -0800274 - Verbose kernel compile/build output:
275
Michael Wittena6144bb2012-04-02 00:31:33 +0000276 Normally, the kernel build system runs in a fairly quiet mode (but not
Randy Dunlap2af238e42008-02-29 14:21:53 -0800277 totally silent). However, sometimes you or other kernel developers need
278 to see compile, link, or other commands exactly as they are executed.
279 For this, use "verbose" build mode. This is done by inserting
280 "V=1" in the "make" command. E.g.:
281
Michael Witten3773b452012-04-02 01:07:52 +0000282 make V=1 all
Randy Dunlap2af238e42008-02-29 14:21:53 -0800283
284 To have the build system also tell the reason for the rebuild of each
285 target, use "V=2". The default is "V=0".
286
Linus Torvalds1da177e2005-04-16 15:20:36 -0700287 - Keep a backup kernel handy in case something goes wrong. This is
288 especially true for the development releases, since each new release
289 contains new code which has not been debugged. Make sure you keep a
290 backup of the modules corresponding to that kernel, as well. If you
291 are installing a new kernel with the same version number as your
292 working kernel, make a backup of your modules directory before you
293 do a "make modules_install".
Michael Witten88f7a642012-04-02 00:46:58 +0000294
Randy Dunlape3fc4cc2005-09-22 21:44:07 -0700295 Alternatively, before compiling, use the kernel config option
296 "LOCALVERSION" to append a unique suffix to the regular kernel version.
297 LOCALVERSION can be set in the "General Setup" menu.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700298
299 - In order to boot your new kernel, you'll need to copy the kernel
300 image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
301 to the place where your regular bootable kernel is found.
302
303 - Booting a kernel directly from a floppy without the assistance of a
304 bootloader such as LILO, is no longer supported.
305
Michael Wittena6144bb2012-04-02 00:31:33 +0000306 If you boot Linux from the hard drive, chances are you use LILO, which
Linus Torvalds1da177e2005-04-16 15:20:36 -0700307 uses the kernel image as specified in the file /etc/lilo.conf. The
308 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
309 /boot/bzImage. To use the new kernel, save a copy of the old image
310 and copy the new image over the old one. Then, you MUST RERUN LILO
311 to update the loading map!! If you don't, you won't be able to boot
312 the new kernel image.
313
314 Reinstalling LILO is usually a matter of running /sbin/lilo.
315 You may wish to edit /etc/lilo.conf to specify an entry for your
316 old kernel image (say, /vmlinux.old) in case the new one does not
317 work. See the LILO docs for more information.
318
319 After reinstalling LILO, you should be all set. Shutdown the system,
320 reboot, and enjoy!
321
322 If you ever need to change the default root device, video mode,
323 ramdisk size, etc. in the kernel image, use the 'rdev' program (or
324 alternatively the LILO boot options when appropriate). No need to
325 recompile the kernel to change these parameters.
326
327 - Reboot with the new kernel and enjoy.
328
329IF SOMETHING GOES WRONG:
330
331 - If you have problems that seem to be due to kernel bugs, please check
332 the file MAINTAINERS to see if there is a particular person associated
333 with the part of the kernel that you are having trouble with. If there
334 isn't anyone listed there, then the second best thing is to mail
Linus Torvalds99ddcc72007-01-23 14:22:35 -0800335 them to me (torvalds@linux-foundation.org), and possibly to any other
336 relevant mailing-list or to the newsgroup.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700337
338 - In all bug-reports, *please* tell what kernel you are talking about,
339 how to duplicate the problem, and what your setup is (use your common
340 sense). If the problem is new, tell me so, and if the problem is
341 old, please try to tell me when you first noticed it.
342
343 - If the bug results in a message like
344
Michael Witten3773b452012-04-02 01:07:52 +0000345 unable to handle kernel paging request at address C0000010
346 Oops: 0002
347 EIP: 0010:XXXXXXXX
348 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
349 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
350 ds: xxxx es: xxxx fs: xxxx gs: xxxx
351 Pid: xx, process nr: xx
352 xx xx xx xx xx xx xx xx xx xx
Linus Torvalds1da177e2005-04-16 15:20:36 -0700353
354 or similar kernel debugging information on your screen or in your
355 system log, please duplicate it *exactly*. The dump may look
356 incomprehensible to you, but it does contain information that may
357 help debugging the problem. The text above the dump is also
358 important: it tells something about why the kernel dumped code (in
Michael Wittena6144bb2012-04-02 00:31:33 +0000359 the above example, it's due to a bad kernel pointer). More information
Linus Torvalds1da177e2005-04-16 15:20:36 -0700360 on making sense of the dump is in Documentation/oops-tracing.txt
361
362 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
363 as is, otherwise you will have to use the "ksymoops" program to make
Jesper Juhl620034c2006-12-07 00:45:58 +0100364 sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
365 This utility can be downloaded from
366 ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .
Michael Witten6d127602012-04-02 00:33:02 +0000367 Alternatively, you can do the dump lookup by hand:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700368
369 - In debugging dumps like the above, it helps enormously if you can
370 look up what the EIP value means. The hex value as such doesn't help
371 me or anybody else very much: it will depend on your particular
372 kernel setup. What you should do is take the hex value from the EIP
373 line (ignore the "0010:"), and look it up in the kernel namelist to
374 see which kernel function contains the offending address.
375
376 To find out the kernel function name, you'll need to find the system
377 binary associated with the kernel that exhibited the symptom. This is
378 the file 'linux/vmlinux'. To extract the namelist and match it against
379 the EIP from the kernel crash, do:
380
Michael Witten3773b452012-04-02 01:07:52 +0000381 nm vmlinux | sort | less
Linus Torvalds1da177e2005-04-16 15:20:36 -0700382
383 This will give you a list of kernel addresses sorted in ascending
384 order, from which it is simple to find the function that contains the
385 offending address. Note that the address given by the kernel
386 debugging messages will not necessarily match exactly with the
387 function addresses (in fact, that is very unlikely), so you can't
388 just 'grep' the list: the list will, however, give you the starting
389 point of each kernel function, so by looking for the function that
390 has a starting address lower than the one you are searching for but
391 is followed by a function with a higher address you will find the one
392 you want. In fact, it may be a good idea to include a bit of
393 "context" in your problem report, giving a few lines around the
394 interesting one.
395
396 If you for some reason cannot do the above (you have a pre-compiled
397 kernel image or similar), telling me as much about your setup as
Jesper Juhl620034c2006-12-07 00:45:58 +0100398 possible will help. Please read the REPORTING-BUGS document for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700399
Michael Witten6d127602012-04-02 00:33:02 +0000400 - Alternatively, you can use gdb on a running kernel. (read-only; i.e. you
Linus Torvalds1da177e2005-04-16 15:20:36 -0700401 cannot change values or set break points.) To do this, first compile the
402 kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
403 clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
404
405 After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
406 You can now use all the usual gdb commands. The command to look up the
407 point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
408 with the EIP value.)
409
410 gdb'ing a non-running kernel currently fails because gdb (wrongly)
411 disregards the starting offset for which the kernel is compiled.
412