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604ff0dc | 1 | menu "printk and dmesg options" |
1da177e4 LT |
2 | |
3 | config PRINTK_TIME | |
4 | bool "Show timing information on printks" | |
d3b8b6e5 | 5 | depends on PRINTK |
1da177e4 | 6 | help |
649e6ee3 KS |
7 | Selecting this option causes time stamps of the printk() |
8 | messages to be added to the output of the syslog() system | |
9 | call and at the console. | |
10 | ||
11 | The timestamp is always recorded internally, and exported | |
12 | to /dev/kmsg. This flag just specifies if the timestamp should | |
13 | be included, not that the timestamp is recorded. | |
14 | ||
15 | The behavior is also controlled by the kernel command line | |
8c27ceff | 16 | parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst |
1da177e4 | 17 | |
a8cfdc68 OJ |
18 | config CONSOLE_LOGLEVEL_DEFAULT |
19 | int "Default console loglevel (1-15)" | |
20 | range 1 15 | |
21 | default "7" | |
22 | help | |
23 | Default loglevel to determine what will be printed on the console. | |
24 | ||
25 | Setting a default here is equivalent to passing in loglevel=<x> in | |
26 | the kernel bootargs. loglevel=<x> continues to override whatever | |
27 | value is specified here as well. | |
28 | ||
50f4d9bd | 29 | Note: This does not affect the log level of un-prefixed printk() |
a8cfdc68 OJ |
30 | usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT |
31 | option. | |
32 | ||
42a9dc0b | 33 | config MESSAGE_LOGLEVEL_DEFAULT |
5af5bcb8 MSB |
34 | int "Default message log level (1-7)" |
35 | range 1 7 | |
36 | default "4" | |
37 | help | |
38 | Default log level for printk statements with no specified priority. | |
39 | ||
40 | This was hard-coded to KERN_WARNING since at least 2.6.10 but folks | |
41 | that are auditing their logs closely may want to set it to a lower | |
42 | priority. | |
43 | ||
a8cfdc68 OJ |
44 | Note: This does not affect what message level gets printed on the console |
45 | by default. To change that, use loglevel=<x> in the kernel bootargs, | |
46 | or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value. | |
47 | ||
604ff0dc DH |
48 | config BOOT_PRINTK_DELAY |
49 | bool "Delay each boot printk message by N milliseconds" | |
50 | depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY | |
51 | help | |
52 | This build option allows you to read kernel boot messages | |
53 | by inserting a short delay after each one. The delay is | |
54 | specified in milliseconds on the kernel command line, | |
55 | using "boot_delay=N". | |
56 | ||
57 | It is likely that you would also need to use "lpj=M" to preset | |
58 | the "loops per jiffie" value. | |
59 | See a previous boot log for the "lpj" value to use for your | |
60 | system, and then set "lpj=M" before setting "boot_delay=N". | |
61 | NOTE: Using this option may adversely affect SMP systems. | |
62 | I.e., processors other than the first one may not boot up. | |
63 | BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect | |
64 | what it believes to be lockup conditions. | |
65 | ||
66 | config DYNAMIC_DEBUG | |
67 | bool "Enable dynamic printk() support" | |
68 | default n | |
69 | depends on PRINTK | |
70 | depends on DEBUG_FS | |
71 | help | |
72 | ||
73 | Compiles debug level messages into the kernel, which would not | |
74 | otherwise be available at runtime. These messages can then be | |
75 | enabled/disabled based on various levels of scope - per source file, | |
76 | function, module, format string, and line number. This mechanism | |
77 | implicitly compiles in all pr_debug() and dev_dbg() calls, which | |
78 | enlarges the kernel text size by about 2%. | |
79 | ||
80 | If a source file is compiled with DEBUG flag set, any | |
81 | pr_debug() calls in it are enabled by default, but can be | |
82 | disabled at runtime as below. Note that DEBUG flag is | |
83 | turned on by many CONFIG_*DEBUG* options. | |
84 | ||
85 | Usage: | |
86 | ||
87 | Dynamic debugging is controlled via the 'dynamic_debug/control' file, | |
88 | which is contained in the 'debugfs' filesystem. Thus, the debugfs | |
89 | filesystem must first be mounted before making use of this feature. | |
90 | We refer the control file as: <debugfs>/dynamic_debug/control. This | |
91 | file contains a list of the debug statements that can be enabled. The | |
92 | format for each line of the file is: | |
93 | ||
94 | filename:lineno [module]function flags format | |
95 | ||
96 | filename : source file of the debug statement | |
97 | lineno : line number of the debug statement | |
98 | module : module that contains the debug statement | |
99 | function : function that contains the debug statement | |
100 | flags : '=p' means the line is turned 'on' for printing | |
101 | format : the format used for the debug statement | |
102 | ||
103 | From a live system: | |
104 | ||
105 | nullarbor:~ # cat <debugfs>/dynamic_debug/control | |
106 | # filename:lineno [module]function flags format | |
107 | fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" | |
108 | fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" | |
109 | fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" | |
110 | ||
111 | Example usage: | |
112 | ||
113 | // enable the message at line 1603 of file svcsock.c | |
114 | nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > | |
115 | <debugfs>/dynamic_debug/control | |
116 | ||
117 | // enable all the messages in file svcsock.c | |
118 | nullarbor:~ # echo -n 'file svcsock.c +p' > | |
119 | <debugfs>/dynamic_debug/control | |
120 | ||
121 | // enable all the messages in the NFS server module | |
122 | nullarbor:~ # echo -n 'module nfsd +p' > | |
123 | <debugfs>/dynamic_debug/control | |
124 | ||
125 | // enable all 12 messages in the function svc_process() | |
126 | nullarbor:~ # echo -n 'func svc_process +p' > | |
127 | <debugfs>/dynamic_debug/control | |
128 | ||
129 | // disable all 12 messages in the function svc_process() | |
130 | nullarbor:~ # echo -n 'func svc_process -p' > | |
131 | <debugfs>/dynamic_debug/control | |
132 | ||
f8998c22 HH |
133 | See Documentation/admin-guide/dynamic-debug-howto.rst for additional |
134 | information. | |
604ff0dc DH |
135 | |
136 | endmenu # "printk and dmesg options" | |
137 | ||
6dfc0665 DH |
138 | menu "Compile-time checks and compiler options" |
139 | ||
140 | config DEBUG_INFO | |
141 | bool "Compile the kernel with debug info" | |
12b13835 | 142 | depends on DEBUG_KERNEL && !COMPILE_TEST |
6dfc0665 DH |
143 | help |
144 | If you say Y here the resulting kernel image will include | |
145 | debugging info resulting in a larger kernel image. | |
146 | This adds debug symbols to the kernel and modules (gcc -g), and | |
147 | is needed if you intend to use kernel crashdump or binary object | |
148 | tools like crash, kgdb, LKCD, gdb, etc on the kernel. | |
149 | Say Y here only if you plan to debug the kernel. | |
150 | ||
151 | If unsure, say N. | |
152 | ||
153 | config DEBUG_INFO_REDUCED | |
154 | bool "Reduce debugging information" | |
155 | depends on DEBUG_INFO | |
156 | help | |
157 | If you say Y here gcc is instructed to generate less debugging | |
158 | information for structure types. This means that tools that | |
159 | need full debugging information (like kgdb or systemtap) won't | |
160 | be happy. But if you merely need debugging information to | |
161 | resolve line numbers there is no loss. Advantage is that | |
162 | build directory object sizes shrink dramatically over a full | |
163 | DEBUG_INFO build and compile times are reduced too. | |
164 | Only works with newer gcc versions. | |
165 | ||
866ced95 AK |
166 | config DEBUG_INFO_SPLIT |
167 | bool "Produce split debuginfo in .dwo files" | |
da0510c4 | 168 | depends on DEBUG_INFO && !FRV |
866ced95 AK |
169 | help |
170 | Generate debug info into separate .dwo files. This significantly | |
171 | reduces the build directory size for builds with DEBUG_INFO, | |
172 | because it stores the information only once on disk in .dwo | |
173 | files instead of multiple times in object files and executables. | |
174 | In addition the debug information is also compressed. | |
175 | ||
176 | Requires recent gcc (4.7+) and recent gdb/binutils. | |
177 | Any tool that packages or reads debug information would need | |
178 | to know about the .dwo files and include them. | |
179 | Incompatible with older versions of ccache. | |
180 | ||
bfaf2dd3 AK |
181 | config DEBUG_INFO_DWARF4 |
182 | bool "Generate dwarf4 debuginfo" | |
183 | depends on DEBUG_INFO | |
184 | help | |
185 | Generate dwarf4 debug info. This requires recent versions | |
186 | of gcc and gdb. It makes the debug information larger. | |
187 | But it significantly improves the success of resolving | |
188 | variables in gdb on optimized code. | |
189 | ||
3ee7b3fa JK |
190 | config GDB_SCRIPTS |
191 | bool "Provide GDB scripts for kernel debugging" | |
192 | depends on DEBUG_INFO | |
193 | help | |
194 | This creates the required links to GDB helper scripts in the | |
195 | build directory. If you load vmlinux into gdb, the helper | |
196 | scripts will be automatically imported by gdb as well, and | |
197 | additional functions are available to analyze a Linux kernel | |
700199b0 AP |
198 | instance. See Documentation/dev-tools/gdb-kernel-debugging.rst |
199 | for further details. | |
3ee7b3fa | 200 | |
de488443 JG |
201 | config ENABLE_WARN_DEPRECATED |
202 | bool "Enable __deprecated logic" | |
203 | default y | |
204 | help | |
205 | Enable the __deprecated logic in the kernel build. | |
206 | Disable this to suppress the "warning: 'foo' is deprecated | |
207 | (declared at kernel/power/somefile.c:1234)" messages. | |
208 | ||
cebc04ba AM |
209 | config ENABLE_MUST_CHECK |
210 | bool "Enable __must_check logic" | |
211 | default y | |
212 | help | |
213 | Enable the __must_check logic in the kernel build. Disable this to | |
214 | suppress the "warning: ignoring return value of 'foo', declared with | |
215 | attribute warn_unused_result" messages. | |
1da177e4 | 216 | |
35bb5b1e AK |
217 | config FRAME_WARN |
218 | int "Warn for stack frames larger than (needs gcc 4.4)" | |
219 | range 0 8192 | |
3f181b4d | 220 | default 0 if KASAN |
0e07f663 | 221 | default 2048 if GCC_PLUGIN_LATENT_ENTROPY |
432654df HD |
222 | default 1280 if (!64BIT && PARISC) |
223 | default 1024 if (!64BIT && !PARISC) | |
35bb5b1e AK |
224 | default 2048 if 64BIT |
225 | help | |
226 | Tell gcc to warn at build time for stack frames larger than this. | |
227 | Setting this too low will cause a lot of warnings. | |
228 | Setting it to 0 disables the warning. | |
229 | Requires gcc 4.4 | |
230 | ||
99657c78 RD |
231 | config STRIP_ASM_SYMS |
232 | bool "Strip assembler-generated symbols during link" | |
233 | default n | |
234 | help | |
235 | Strip internal assembler-generated symbols during a link (symbols | |
236 | that look like '.Lxxx') so they don't pollute the output of | |
237 | get_wchan() and suchlike. | |
238 | ||
1873e870 AK |
239 | config READABLE_ASM |
240 | bool "Generate readable assembler code" | |
241 | depends on DEBUG_KERNEL | |
242 | help | |
243 | Disable some compiler optimizations that tend to generate human unreadable | |
244 | assembler output. This may make the kernel slightly slower, but it helps | |
245 | to keep kernel developers who have to stare a lot at assembler listings | |
246 | sane. | |
247 | ||
f71d20e9 AV |
248 | config UNUSED_SYMBOLS |
249 | bool "Enable unused/obsolete exported symbols" | |
250 | default y if X86 | |
251 | help | |
252 | Unused but exported symbols make the kernel needlessly bigger. For | |
253 | that reason most of these unused exports will soon be removed. This | |
254 | option is provided temporarily to provide a transition period in case | |
255 | some external kernel module needs one of these symbols anyway. If you | |
256 | encounter such a case in your module, consider if you are actually | |
257 | using the right API. (rationale: since nobody in the kernel is using | |
258 | this in a module, there is a pretty good chance it's actually the | |
259 | wrong interface to use). If you really need the symbol, please send a | |
260 | mail to the linux kernel mailing list mentioning the symbol and why | |
261 | you really need it, and what the merge plan to the mainline kernel for | |
262 | your module is. | |
263 | ||
48c96a36 JK |
264 | config PAGE_OWNER |
265 | bool "Track page owner" | |
266 | depends on DEBUG_KERNEL && STACKTRACE_SUPPORT | |
267 | select DEBUG_FS | |
268 | select STACKTRACE | |
f2ca0b55 | 269 | select STACKDEPOT |
48c96a36 JK |
270 | select PAGE_EXTENSION |
271 | help | |
272 | This keeps track of what call chain is the owner of a page, may | |
273 | help to find bare alloc_page(s) leaks. Even if you include this | |
274 | feature on your build, it is disabled in default. You should pass | |
275 | "page_owner=on" to boot parameter in order to enable it. Eats | |
276 | a fair amount of memory if enabled. See tools/vm/page_owner_sort.c | |
277 | for user-space helper. | |
278 | ||
279 | If unsure, say N. | |
280 | ||
bf4735a4 DM |
281 | config DEBUG_FS |
282 | bool "Debug Filesystem" | |
bf4735a4 DM |
283 | help |
284 | debugfs is a virtual file system that kernel developers use to put | |
285 | debugging files into. Enable this option to be able to read and | |
286 | write to these files. | |
287 | ||
ff543332 | 288 | For detailed documentation on the debugfs API, see |
e1b4fc7a | 289 | Documentation/filesystems/. |
ff543332 | 290 | |
bf4735a4 DM |
291 | If unsure, say N. |
292 | ||
293 | config HEADERS_CHECK | |
294 | bool "Run 'make headers_check' when building vmlinux" | |
295 | depends on !UML | |
296 | help | |
297 | This option will extract the user-visible kernel headers whenever | |
298 | building the kernel, and will run basic sanity checks on them to | |
299 | ensure that exported files do not attempt to include files which | |
300 | were not exported, etc. | |
301 | ||
302 | If you're making modifications to header files which are | |
303 | relevant for userspace, say 'Y', and check the headers | |
304 | exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in | |
305 | your build tree), to make sure they're suitable. | |
306 | ||
91341d4b SR |
307 | config DEBUG_SECTION_MISMATCH |
308 | bool "Enable full Section mismatch analysis" | |
91341d4b SR |
309 | help |
310 | The section mismatch analysis checks if there are illegal | |
311 | references from one section to another section. | |
e809ab01 MW |
312 | During linktime or runtime, some sections are dropped; |
313 | any use of code/data previously in these sections would | |
91341d4b | 314 | most likely result in an oops. |
e809ab01 | 315 | In the code, functions and variables are annotated with |
0db0628d | 316 | __init,, etc. (see the full list in include/linux/init.h), |
d6fbfa4f | 317 | which results in the code/data being placed in specific sections. |
e809ab01 MW |
318 | The section mismatch analysis is always performed after a full |
319 | kernel build, and enabling this option causes the following | |
320 | additional steps to occur: | |
321 | - Add the option -fno-inline-functions-called-once to gcc commands. | |
322 | When inlining a function annotated with __init in a non-init | |
323 | function, we would lose the section information and thus | |
91341d4b | 324 | the analysis would not catch the illegal reference. |
e809ab01 MW |
325 | This option tells gcc to inline less (but it does result in |
326 | a larger kernel). | |
327 | - Run the section mismatch analysis for each module/built-in.o file. | |
328 | When we run the section mismatch analysis on vmlinux.o, we | |
67797b92 | 329 | lose valuable information about where the mismatch was |
91341d4b SR |
330 | introduced. |
331 | Running the analysis for each module/built-in.o file | |
e809ab01 MW |
332 | tells where the mismatch happens much closer to the |
333 | source. The drawback is that the same mismatch is | |
334 | reported at least twice. | |
335 | - Enable verbose reporting from modpost in order to help resolve | |
336 | the section mismatches that are reported. | |
91341d4b | 337 | |
47490ec1 NB |
338 | config SECTION_MISMATCH_WARN_ONLY |
339 | bool "Make section mismatch errors non-fatal" | |
340 | default y | |
341 | help | |
342 | If you say N here, the build process will fail if there are any | |
343 | section mismatch, instead of just throwing warnings. | |
344 | ||
345 | If unsure, say Y. | |
346 | ||
6dfc0665 DH |
347 | # |
348 | # Select this config option from the architecture Kconfig, if it | |
349 | # is preferred to always offer frame pointers as a config | |
350 | # option on the architecture (regardless of KERNEL_DEBUG): | |
351 | # | |
352 | config ARCH_WANT_FRAME_POINTERS | |
353 | bool | |
f346f4b3 | 354 | help |
f346f4b3 | 355 | |
6dfc0665 DH |
356 | config FRAME_POINTER |
357 | bool "Compile the kernel with frame pointers" | |
358 | depends on DEBUG_KERNEL && \ | |
359 | (CRIS || M68K || FRV || UML || \ | |
695c1208 | 360 | SUPERH || BLACKFIN || MN10300 || METAG) || \ |
6dfc0665 DH |
361 | ARCH_WANT_FRAME_POINTERS |
362 | default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS | |
a304e1b8 | 363 | help |
6dfc0665 DH |
364 | If you say Y here the resulting kernel image will be slightly |
365 | larger and slower, but it gives very useful debugging information | |
366 | in case of kernel bugs. (precise oopses/stacktraces/warnings) | |
a304e1b8 | 367 | |
b9ab5ebb JP |
368 | config STACK_VALIDATION |
369 | bool "Compile-time stack metadata validation" | |
370 | depends on HAVE_STACK_VALIDATION | |
371 | default n | |
372 | help | |
373 | Add compile-time checks to validate stack metadata, including frame | |
374 | pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure | |
375 | that runtime stack traces are more reliable. | |
376 | ||
ee9f8fce | 377 | This is also a prerequisite for generation of ORC unwind data, which |
11af8474 | 378 | is needed for CONFIG_UNWINDER_ORC. |
ee9f8fce | 379 | |
b9ab5ebb JP |
380 | For more information, see |
381 | tools/objtool/Documentation/stack-validation.txt. | |
382 | ||
6dfc0665 DH |
383 | config DEBUG_FORCE_WEAK_PER_CPU |
384 | bool "Force weak per-cpu definitions" | |
385 | depends on DEBUG_KERNEL | |
8446f1d3 | 386 | help |
6dfc0665 DH |
387 | s390 and alpha require percpu variables in modules to be |
388 | defined weak to work around addressing range issue which | |
389 | puts the following two restrictions on percpu variable | |
390 | definitions. | |
8446f1d3 | 391 | |
6dfc0665 DH |
392 | 1. percpu symbols must be unique whether static or not |
393 | 2. percpu variables can't be defined inside a function | |
8446f1d3 | 394 | |
6dfc0665 DH |
395 | To ensure that generic code follows the above rules, this |
396 | option forces all percpu variables to be defined as weak. | |
5f329089 | 397 | |
6dfc0665 | 398 | endmenu # "Compiler options" |
8446f1d3 | 399 | |
6dfc0665 DH |
400 | config MAGIC_SYSRQ |
401 | bool "Magic SysRq key" | |
402 | depends on !UML | |
403 | help | |
404 | If you say Y here, you will have some control over the system even | |
405 | if the system crashes for example during kernel debugging (e.g., you | |
406 | will be able to flush the buffer cache to disk, reboot the system | |
407 | immediately or dump some status information). This is accomplished | |
408 | by pressing various keys while holding SysRq (Alt+PrintScreen). It | |
409 | also works on a serial console (on PC hardware at least), if you | |
410 | send a BREAK and then within 5 seconds a command keypress. The | |
f8998c22 HH |
411 | keys are documented in <file:Documentation/admin-guide/sysrq.rst>. |
412 | Don't say Y unless you really know what this hack does. | |
8446f1d3 | 413 | |
8eaede49 BH |
414 | config MAGIC_SYSRQ_DEFAULT_ENABLE |
415 | hex "Enable magic SysRq key functions by default" | |
416 | depends on MAGIC_SYSRQ | |
417 | default 0x1 | |
418 | help | |
419 | Specifies which SysRq key functions are enabled by default. | |
420 | This may be set to 1 or 0 to enable or disable them all, or | |
f8998c22 | 421 | to a bitmask as described in Documentation/admin-guide/sysrq.rst. |
8eaede49 | 422 | |
732dbf3a FF |
423 | config MAGIC_SYSRQ_SERIAL |
424 | bool "Enable magic SysRq key over serial" | |
425 | depends on MAGIC_SYSRQ | |
426 | default y | |
427 | help | |
428 | Many embedded boards have a disconnected TTL level serial which can | |
429 | generate some garbage that can lead to spurious false sysrq detects. | |
430 | This option allows you to decide whether you want to enable the | |
431 | magic SysRq key. | |
432 | ||
f346f4b3 AB |
433 | config DEBUG_KERNEL |
434 | bool "Kernel debugging" | |
fef2c9bc | 435 | help |
f346f4b3 AB |
436 | Say Y here if you are developing drivers or trying to debug and |
437 | identify kernel problems. | |
fef2c9bc | 438 | |
0610c8a8 | 439 | menu "Memory Debugging" |
fef2c9bc | 440 | |
0610c8a8 | 441 | source mm/Kconfig.debug |
fef2c9bc | 442 | |
0610c8a8 DH |
443 | config DEBUG_OBJECTS |
444 | bool "Debug object operations" | |
445 | depends on DEBUG_KERNEL | |
9c44bc03 | 446 | help |
0610c8a8 DH |
447 | If you say Y here, additional code will be inserted into the |
448 | kernel to track the life time of various objects and validate | |
449 | the operations on those objects. | |
9c44bc03 | 450 | |
0610c8a8 DH |
451 | config DEBUG_OBJECTS_SELFTEST |
452 | bool "Debug objects selftest" | |
453 | depends on DEBUG_OBJECTS | |
454 | help | |
455 | This enables the selftest of the object debug code. | |
9c44bc03 | 456 | |
0610c8a8 DH |
457 | config DEBUG_OBJECTS_FREE |
458 | bool "Debug objects in freed memory" | |
459 | depends on DEBUG_OBJECTS | |
460 | help | |
461 | This enables checks whether a k/v free operation frees an area | |
462 | which contains an object which has not been deactivated | |
463 | properly. This can make kmalloc/kfree-intensive workloads | |
464 | much slower. | |
3ac7fe5a | 465 | |
c6f3a97f TG |
466 | config DEBUG_OBJECTS_TIMERS |
467 | bool "Debug timer objects" | |
468 | depends on DEBUG_OBJECTS | |
469 | help | |
470 | If you say Y here, additional code will be inserted into the | |
471 | timer routines to track the life time of timer objects and | |
472 | validate the timer operations. | |
473 | ||
dc186ad7 TG |
474 | config DEBUG_OBJECTS_WORK |
475 | bool "Debug work objects" | |
476 | depends on DEBUG_OBJECTS | |
477 | help | |
478 | If you say Y here, additional code will be inserted into the | |
479 | work queue routines to track the life time of work objects and | |
480 | validate the work operations. | |
481 | ||
551d55a9 MD |
482 | config DEBUG_OBJECTS_RCU_HEAD |
483 | bool "Debug RCU callbacks objects" | |
fc2ecf7e | 484 | depends on DEBUG_OBJECTS |
551d55a9 MD |
485 | help |
486 | Enable this to turn on debugging of RCU list heads (call_rcu() usage). | |
487 | ||
e2852ae8 TH |
488 | config DEBUG_OBJECTS_PERCPU_COUNTER |
489 | bool "Debug percpu counter objects" | |
490 | depends on DEBUG_OBJECTS | |
491 | help | |
492 | If you say Y here, additional code will be inserted into the | |
493 | percpu counter routines to track the life time of percpu counter | |
494 | objects and validate the percpu counter operations. | |
495 | ||
3ae70205 IM |
496 | config DEBUG_OBJECTS_ENABLE_DEFAULT |
497 | int "debug_objects bootup default value (0-1)" | |
498 | range 0 1 | |
499 | default "1" | |
500 | depends on DEBUG_OBJECTS | |
501 | help | |
502 | Debug objects boot parameter default value | |
503 | ||
1da177e4 | 504 | config DEBUG_SLAB |
4a2f0acf | 505 | bool "Debug slab memory allocations" |
4675ff05 | 506 | depends on DEBUG_KERNEL && SLAB |
1da177e4 LT |
507 | help |
508 | Say Y here to have the kernel do limited verification on memory | |
509 | allocation as well as poisoning memory on free to catch use of freed | |
510 | memory. This can make kmalloc/kfree-intensive workloads much slower. | |
511 | ||
871751e2 AV |
512 | config DEBUG_SLAB_LEAK |
513 | bool "Memory leak debugging" | |
514 | depends on DEBUG_SLAB | |
515 | ||
f0630fff CL |
516 | config SLUB_DEBUG_ON |
517 | bool "SLUB debugging on by default" | |
4675ff05 | 518 | depends on SLUB && SLUB_DEBUG |
f0630fff CL |
519 | default n |
520 | help | |
521 | Boot with debugging on by default. SLUB boots by default with | |
522 | the runtime debug capabilities switched off. Enabling this is | |
523 | equivalent to specifying the "slub_debug" parameter on boot. | |
524 | There is no support for more fine grained debug control like | |
525 | possible with slub_debug=xxx. SLUB debugging may be switched | |
526 | off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying | |
527 | "slub_debug=-". | |
528 | ||
8ff12cfc CL |
529 | config SLUB_STATS |
530 | default n | |
531 | bool "Enable SLUB performance statistics" | |
ab4d5ed5 | 532 | depends on SLUB && SYSFS |
8ff12cfc CL |
533 | help |
534 | SLUB statistics are useful to debug SLUBs allocation behavior in | |
535 | order find ways to optimize the allocator. This should never be | |
536 | enabled for production use since keeping statistics slows down | |
537 | the allocator by a few percentage points. The slabinfo command | |
538 | supports the determination of the most active slabs to figure | |
539 | out which slabs are relevant to a particular load. | |
540 | Try running: slabinfo -DA | |
541 | ||
b69ec42b CM |
542 | config HAVE_DEBUG_KMEMLEAK |
543 | bool | |
544 | ||
3bba00d7 CM |
545 | config DEBUG_KMEMLEAK |
546 | bool "Kernel memory leak detector" | |
525c1f92 | 547 | depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK |
79e0d9bd | 548 | select DEBUG_FS |
3bba00d7 CM |
549 | select STACKTRACE if STACKTRACE_SUPPORT |
550 | select KALLSYMS | |
b60e26a2 | 551 | select CRC32 |
3bba00d7 CM |
552 | help |
553 | Say Y here if you want to enable the memory leak | |
554 | detector. The memory allocation/freeing is traced in a way | |
555 | similar to the Boehm's conservative garbage collector, the | |
556 | difference being that the orphan objects are not freed but | |
557 | only shown in /sys/kernel/debug/kmemleak. Enabling this | |
558 | feature will introduce an overhead to memory | |
700199b0 | 559 | allocations. See Documentation/dev-tools/kmemleak.rst for more |
3bba00d7 CM |
560 | details. |
561 | ||
0610c8a8 DH |
562 | Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances |
563 | of finding leaks due to the slab objects poisoning. | |
564 | ||
565 | In order to access the kmemleak file, debugfs needs to be | |
566 | mounted (usually at /sys/kernel/debug). | |
567 | ||
568 | config DEBUG_KMEMLEAK_EARLY_LOG_SIZE | |
569 | int "Maximum kmemleak early log entries" | |
570 | depends on DEBUG_KMEMLEAK | |
571 | range 200 40000 | |
572 | default 400 | |
573 | help | |
574 | Kmemleak must track all the memory allocations to avoid | |
575 | reporting false positives. Since memory may be allocated or | |
576 | freed before kmemleak is initialised, an early log buffer is | |
577 | used to store these actions. If kmemleak reports "early log | |
578 | buffer exceeded", please increase this value. | |
579 | ||
580 | config DEBUG_KMEMLEAK_TEST | |
581 | tristate "Simple test for the kernel memory leak detector" | |
582 | depends on DEBUG_KMEMLEAK && m | |
583 | help | |
584 | This option enables a module that explicitly leaks memory. | |
585 | ||
586 | If unsure, say N. | |
587 | ||
588 | config DEBUG_KMEMLEAK_DEFAULT_OFF | |
589 | bool "Default kmemleak to off" | |
590 | depends on DEBUG_KMEMLEAK | |
591 | help | |
592 | Say Y here to disable kmemleak by default. It can then be enabled | |
593 | on the command line via kmemleak=on. | |
594 | ||
595 | config DEBUG_STACK_USAGE | |
596 | bool "Stack utilization instrumentation" | |
6c31da34 | 597 | depends on DEBUG_KERNEL && !IA64 |
0610c8a8 DH |
598 | help |
599 | Enables the display of the minimum amount of free stack which each | |
600 | task has ever had available in the sysrq-T and sysrq-P debug output. | |
601 | ||
602 | This option will slow down process creation somewhat. | |
603 | ||
604 | config DEBUG_VM | |
605 | bool "Debug VM" | |
606 | depends on DEBUG_KERNEL | |
607 | help | |
608 | Enable this to turn on extended checks in the virtual-memory system | |
609 | that may impact performance. | |
610 | ||
611 | If unsure, say N. | |
612 | ||
4f115147 DB |
613 | config DEBUG_VM_VMACACHE |
614 | bool "Debug VMA caching" | |
615 | depends on DEBUG_VM | |
616 | help | |
617 | Enable this to turn on VMA caching debug information. Doing so | |
618 | can cause significant overhead, so only enable it in non-production | |
619 | environments. | |
620 | ||
621 | If unsure, say N. | |
622 | ||
0610c8a8 DH |
623 | config DEBUG_VM_RB |
624 | bool "Debug VM red-black trees" | |
625 | depends on DEBUG_VM | |
626 | help | |
a663dad6 | 627 | Enable VM red-black tree debugging information and extra validations. |
0610c8a8 DH |
628 | |
629 | If unsure, say N. | |
630 | ||
95ad9755 KS |
631 | config DEBUG_VM_PGFLAGS |
632 | bool "Debug page-flags operations" | |
633 | depends on DEBUG_VM | |
634 | help | |
635 | Enables extra validation on page flags operations. | |
636 | ||
637 | If unsure, say N. | |
638 | ||
fa5b6ec9 LA |
639 | config ARCH_HAS_DEBUG_VIRTUAL |
640 | bool | |
641 | ||
0610c8a8 DH |
642 | config DEBUG_VIRTUAL |
643 | bool "Debug VM translations" | |
fa5b6ec9 | 644 | depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL |
0610c8a8 DH |
645 | help |
646 | Enable some costly sanity checks in virtual to page code. This can | |
647 | catch mistakes with virt_to_page() and friends. | |
648 | ||
649 | If unsure, say N. | |
650 | ||
651 | config DEBUG_NOMMU_REGIONS | |
652 | bool "Debug the global anon/private NOMMU mapping region tree" | |
653 | depends on DEBUG_KERNEL && !MMU | |
654 | help | |
655 | This option causes the global tree of anonymous and private mapping | |
656 | regions to be regularly checked for invalid topology. | |
657 | ||
658 | config DEBUG_MEMORY_INIT | |
659 | bool "Debug memory initialisation" if EXPERT | |
660 | default !EXPERT | |
661 | help | |
662 | Enable this for additional checks during memory initialisation. | |
663 | The sanity checks verify aspects of the VM such as the memory model | |
664 | and other information provided by the architecture. Verbose | |
665 | information will be printed at KERN_DEBUG loglevel depending | |
666 | on the mminit_loglevel= command-line option. | |
667 | ||
668 | If unsure, say Y | |
669 | ||
670 | config MEMORY_NOTIFIER_ERROR_INJECT | |
671 | tristate "Memory hotplug notifier error injection module" | |
672 | depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION | |
673 | help | |
674 | This option provides the ability to inject artificial errors to | |
675 | memory hotplug notifier chain callbacks. It is controlled through | |
676 | debugfs interface under /sys/kernel/debug/notifier-error-inject/memory | |
677 | ||
678 | If the notifier call chain should be failed with some events | |
679 | notified, write the error code to "actions/<notifier event>/error". | |
680 | ||
681 | Example: Inject memory hotplug offline error (-12 == -ENOMEM) | |
682 | ||
683 | # cd /sys/kernel/debug/notifier-error-inject/memory | |
684 | # echo -12 > actions/MEM_GOING_OFFLINE/error | |
685 | # echo offline > /sys/devices/system/memory/memoryXXX/state | |
686 | bash: echo: write error: Cannot allocate memory | |
687 | ||
688 | To compile this code as a module, choose M here: the module will | |
689 | be called memory-notifier-error-inject. | |
690 | ||
691 | If unsure, say N. | |
692 | ||
693 | config DEBUG_PER_CPU_MAPS | |
694 | bool "Debug access to per_cpu maps" | |
695 | depends on DEBUG_KERNEL | |
696 | depends on SMP | |
697 | help | |
698 | Say Y to verify that the per_cpu map being accessed has | |
699 | been set up. This adds a fair amount of code to kernel memory | |
700 | and decreases performance. | |
701 | ||
702 | Say N if unsure. | |
703 | ||
704 | config DEBUG_HIGHMEM | |
705 | bool "Highmem debugging" | |
706 | depends on DEBUG_KERNEL && HIGHMEM | |
707 | help | |
b1357c9f GU |
708 | This option enables additional error checking for high memory |
709 | systems. Disable for production systems. | |
0610c8a8 DH |
710 | |
711 | config HAVE_DEBUG_STACKOVERFLOW | |
712 | bool | |
713 | ||
714 | config DEBUG_STACKOVERFLOW | |
715 | bool "Check for stack overflows" | |
716 | depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW | |
717 | ---help--- | |
718 | Say Y here if you want to check for overflows of kernel, IRQ | |
edb0ec07 | 719 | and exception stacks (if your architecture uses them). This |
0610c8a8 DH |
720 | option will show detailed messages if free stack space drops |
721 | below a certain limit. | |
722 | ||
723 | These kinds of bugs usually occur when call-chains in the | |
724 | kernel get too deep, especially when interrupts are | |
725 | involved. | |
726 | ||
727 | Use this in cases where you see apparently random memory | |
728 | corruption, especially if it appears in 'struct thread_info' | |
729 | ||
730 | If in doubt, say "N". | |
731 | ||
0b24becc AR |
732 | source "lib/Kconfig.kasan" |
733 | ||
0610c8a8 DH |
734 | endmenu # "Memory Debugging" |
735 | ||
5c9a8750 DV |
736 | config ARCH_HAS_KCOV |
737 | bool | |
738 | help | |
739 | KCOV does not have any arch-specific code, but currently it is enabled | |
740 | only for x86_64. KCOV requires testing on other archs, and most likely | |
741 | disabling of instrumentation for some early boot code. | |
742 | ||
743 | config KCOV | |
744 | bool "Code coverage for fuzzing" | |
745 | depends on ARCH_HAS_KCOV | |
746 | select DEBUG_FS | |
a519167e KC |
747 | select GCC_PLUGINS if !COMPILE_TEST |
748 | select GCC_PLUGIN_SANCOV if !COMPILE_TEST | |
5c9a8750 DV |
749 | help |
750 | KCOV exposes kernel code coverage information in a form suitable | |
751 | for coverage-guided fuzzing (randomized testing). | |
752 | ||
753 | If RANDOMIZE_BASE is enabled, PC values will not be stable across | |
754 | different machines and across reboots. If you need stable PC values, | |
755 | disable RANDOMIZE_BASE. | |
756 | ||
700199b0 | 757 | For more details, see Documentation/dev-tools/kcov.rst. |
5c9a8750 | 758 | |
d677a4d6 VC |
759 | config KCOV_ENABLE_COMPARISONS |
760 | bool "Enable comparison operands collection by KCOV" | |
761 | depends on KCOV | |
762 | default n | |
763 | help | |
764 | KCOV also exposes operands of every comparison in the instrumented | |
765 | code along with operand sizes and PCs of the comparison instructions. | |
766 | These operands can be used by fuzzing engines to improve the quality | |
767 | of fuzzing coverage. | |
768 | ||
a4691dea VN |
769 | config KCOV_INSTRUMENT_ALL |
770 | bool "Instrument all code by default" | |
771 | depends on KCOV | |
772 | default y if KCOV | |
773 | help | |
774 | If you are doing generic system call fuzzing (like e.g. syzkaller), | |
775 | then you will want to instrument the whole kernel and you should | |
776 | say y here. If you are doing more targeted fuzzing (like e.g. | |
777 | filesystem fuzzing with AFL) then you will want to enable coverage | |
778 | for more specific subsets of files, and should say n here. | |
779 | ||
a304e1b8 DW |
780 | config DEBUG_SHIRQ |
781 | bool "Debug shared IRQ handlers" | |
0244ad00 | 782 | depends on DEBUG_KERNEL |
a304e1b8 DW |
783 | help |
784 | Enable this to generate a spurious interrupt as soon as a shared | |
785 | interrupt handler is registered, and just before one is deregistered. | |
786 | Drivers ought to be able to handle interrupts coming in at those | |
787 | points; some don't and need to be caught. | |
788 | ||
92aef8fb DH |
789 | menu "Debug Lockups and Hangs" |
790 | ||
58687acb | 791 | config LOCKUP_DETECTOR |
05a4a952 NP |
792 | bool |
793 | ||
794 | config SOFTLOCKUP_DETECTOR | |
795 | bool "Detect Soft Lockups" | |
dea20a3f | 796 | depends on DEBUG_KERNEL && !S390 |
05a4a952 | 797 | select LOCKUP_DETECTOR |
8446f1d3 | 798 | help |
58687acb | 799 | Say Y here to enable the kernel to act as a watchdog to detect |
05a4a952 | 800 | soft lockups. |
58687acb DZ |
801 | |
802 | Softlockups are bugs that cause the kernel to loop in kernel | |
5f329089 | 803 | mode for more than 20 seconds, without giving other tasks a |
58687acb DZ |
804 | chance to run. The current stack trace is displayed upon |
805 | detection and the system will stay locked up. | |
8446f1d3 | 806 | |
05a4a952 NP |
807 | config HARDLOCKUP_DETECTOR_PERF |
808 | bool | |
809 | select SOFTLOCKUP_DETECTOR | |
810 | ||
7edaeb68 TG |
811 | # |
812 | # Enables a timestamp based low pass filter to compensate for perf based | |
813 | # hard lockup detection which runs too fast due to turbo modes. | |
814 | # | |
815 | config HARDLOCKUP_CHECK_TIMESTAMP | |
816 | bool | |
817 | ||
05a4a952 NP |
818 | # |
819 | # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard | |
820 | # lockup detector rather than the perf based detector. | |
821 | # | |
822 | config HARDLOCKUP_DETECTOR | |
823 | bool "Detect Hard Lockups" | |
824 | depends on DEBUG_KERNEL && !S390 | |
825 | depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH | |
826 | select LOCKUP_DETECTOR | |
827 | select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF | |
828 | select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH | |
829 | help | |
830 | Say Y here to enable the kernel to act as a watchdog to detect | |
831 | hard lockups. | |
832 | ||
58687acb | 833 | Hardlockups are bugs that cause the CPU to loop in kernel mode |
5f329089 | 834 | for more than 10 seconds, without letting other interrupts have a |
58687acb DZ |
835 | chance to run. The current stack trace is displayed upon detection |
836 | and the system will stay locked up. | |
8446f1d3 | 837 | |
fef2c9bc DZ |
838 | config BOOTPARAM_HARDLOCKUP_PANIC |
839 | bool "Panic (Reboot) On Hard Lockups" | |
8f1f66ed | 840 | depends on HARDLOCKUP_DETECTOR |
fef2c9bc DZ |
841 | help |
842 | Say Y here to enable the kernel to panic on "hard lockups", | |
843 | which are bugs that cause the kernel to loop in kernel | |
5f329089 FLVC |
844 | mode with interrupts disabled for more than 10 seconds (configurable |
845 | using the watchdog_thresh sysctl). | |
fef2c9bc DZ |
846 | |
847 | Say N if unsure. | |
848 | ||
849 | config BOOTPARAM_HARDLOCKUP_PANIC_VALUE | |
850 | int | |
8f1f66ed | 851 | depends on HARDLOCKUP_DETECTOR |
fef2c9bc DZ |
852 | range 0 1 |
853 | default 0 if !BOOTPARAM_HARDLOCKUP_PANIC | |
854 | default 1 if BOOTPARAM_HARDLOCKUP_PANIC | |
855 | ||
9c44bc03 IM |
856 | config BOOTPARAM_SOFTLOCKUP_PANIC |
857 | bool "Panic (Reboot) On Soft Lockups" | |
05a4a952 | 858 | depends on SOFTLOCKUP_DETECTOR |
9c44bc03 IM |
859 | help |
860 | Say Y here to enable the kernel to panic on "soft lockups", | |
861 | which are bugs that cause the kernel to loop in kernel | |
5f329089 FLVC |
862 | mode for more than 20 seconds (configurable using the watchdog_thresh |
863 | sysctl), without giving other tasks a chance to run. | |
9c44bc03 IM |
864 | |
865 | The panic can be used in combination with panic_timeout, | |
866 | to cause the system to reboot automatically after a | |
867 | lockup has been detected. This feature is useful for | |
868 | high-availability systems that have uptime guarantees and | |
869 | where a lockup must be resolved ASAP. | |
870 | ||
871 | Say N if unsure. | |
872 | ||
873 | config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE | |
874 | int | |
05a4a952 | 875 | depends on SOFTLOCKUP_DETECTOR |
9c44bc03 IM |
876 | range 0 1 |
877 | default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC | |
878 | default 1 if BOOTPARAM_SOFTLOCKUP_PANIC | |
879 | ||
e162b39a MSB |
880 | config DETECT_HUNG_TASK |
881 | bool "Detect Hung Tasks" | |
882 | depends on DEBUG_KERNEL | |
05a4a952 | 883 | default SOFTLOCKUP_DETECTOR |
e162b39a | 884 | help |
0610c8a8 DH |
885 | Say Y here to enable the kernel to detect "hung tasks", |
886 | which are bugs that cause the task to be stuck in | |
96b03ab8 | 887 | uninterruptible "D" state indefinitely. |
1da177e4 | 888 | |
0610c8a8 DH |
889 | When a hung task is detected, the kernel will print the |
890 | current stack trace (which you should report), but the | |
891 | task will stay in uninterruptible state. If lockdep is | |
892 | enabled then all held locks will also be reported. This | |
893 | feature has negligible overhead. | |
871751e2 | 894 | |
0610c8a8 DH |
895 | config DEFAULT_HUNG_TASK_TIMEOUT |
896 | int "Default timeout for hung task detection (in seconds)" | |
897 | depends on DETECT_HUNG_TASK | |
898 | default 120 | |
f0630fff | 899 | help |
0610c8a8 DH |
900 | This option controls the default timeout (in seconds) used |
901 | to determine when a task has become non-responsive and should | |
902 | be considered hung. | |
f0630fff | 903 | |
0610c8a8 DH |
904 | It can be adjusted at runtime via the kernel.hung_task_timeout_secs |
905 | sysctl or by writing a value to | |
906 | /proc/sys/kernel/hung_task_timeout_secs. | |
8ff12cfc | 907 | |
0610c8a8 DH |
908 | A timeout of 0 disables the check. The default is two minutes. |
909 | Keeping the default should be fine in most cases. | |
b69ec42b | 910 | |
0610c8a8 DH |
911 | config BOOTPARAM_HUNG_TASK_PANIC |
912 | bool "Panic (Reboot) On Hung Tasks" | |
913 | depends on DETECT_HUNG_TASK | |
3bba00d7 | 914 | help |
0610c8a8 DH |
915 | Say Y here to enable the kernel to panic on "hung tasks", |
916 | which are bugs that cause the kernel to leave a task stuck | |
917 | in uninterruptible "D" state. | |
3bba00d7 | 918 | |
0610c8a8 DH |
919 | The panic can be used in combination with panic_timeout, |
920 | to cause the system to reboot automatically after a | |
921 | hung task has been detected. This feature is useful for | |
922 | high-availability systems that have uptime guarantees and | |
923 | where a hung tasks must be resolved ASAP. | |
bf96d1e3 | 924 | |
0610c8a8 | 925 | Say N if unsure. |
bf96d1e3 | 926 | |
0610c8a8 DH |
927 | config BOOTPARAM_HUNG_TASK_PANIC_VALUE |
928 | int | |
929 | depends on DETECT_HUNG_TASK | |
930 | range 0 1 | |
931 | default 0 if !BOOTPARAM_HUNG_TASK_PANIC | |
932 | default 1 if BOOTPARAM_HUNG_TASK_PANIC | |
3bba00d7 | 933 | |
82607adc TH |
934 | config WQ_WATCHDOG |
935 | bool "Detect Workqueue Stalls" | |
936 | depends on DEBUG_KERNEL | |
937 | help | |
938 | Say Y here to enable stall detection on workqueues. If a | |
939 | worker pool doesn't make forward progress on a pending work | |
940 | item for over a given amount of time, 30s by default, a | |
941 | warning message is printed along with dump of workqueue | |
942 | state. This can be configured through kernel parameter | |
943 | "workqueue.watchdog_thresh" and its sysfs counterpart. | |
944 | ||
92aef8fb DH |
945 | endmenu # "Debug lockups and hangs" |
946 | ||
947 | config PANIC_ON_OOPS | |
948 | bool "Panic on Oops" | |
a9d9058a | 949 | help |
92aef8fb DH |
950 | Say Y here to enable the kernel to panic when it oopses. This |
951 | has the same effect as setting oops=panic on the kernel command | |
952 | line. | |
a9d9058a | 953 | |
92aef8fb DH |
954 | This feature is useful to ensure that the kernel does not do |
955 | anything erroneous after an oops which could result in data | |
956 | corruption or other issues. | |
957 | ||
958 | Say N if unsure. | |
959 | ||
960 | config PANIC_ON_OOPS_VALUE | |
961 | int | |
962 | range 0 1 | |
963 | default 0 if !PANIC_ON_OOPS | |
964 | default 1 if PANIC_ON_OOPS | |
965 | ||
5800dc3c JB |
966 | config PANIC_TIMEOUT |
967 | int "panic timeout" | |
968 | default 0 | |
969 | help | |
970 | Set the timeout value (in seconds) until a reboot occurs when the | |
971 | the kernel panics. If n = 0, then we wait forever. A timeout | |
972 | value n > 0 will wait n seconds before rebooting, while a timeout | |
973 | value n < 0 will reboot immediately. | |
974 | ||
0610c8a8 DH |
975 | config SCHED_DEBUG |
976 | bool "Collect scheduler debugging info" | |
977 | depends on DEBUG_KERNEL && PROC_FS | |
978 | default y | |
0822ee4a | 979 | help |
0610c8a8 DH |
980 | If you say Y here, the /proc/sched_debug file will be provided |
981 | that can help debug the scheduler. The runtime overhead of this | |
982 | option is minimal. | |
0822ee4a | 983 | |
f6db8347 NR |
984 | config SCHED_INFO |
985 | bool | |
986 | default n | |
987 | ||
0610c8a8 DH |
988 | config SCHEDSTATS |
989 | bool "Collect scheduler statistics" | |
990 | depends on DEBUG_KERNEL && PROC_FS | |
f6db8347 | 991 | select SCHED_INFO |
0610c8a8 DH |
992 | help |
993 | If you say Y here, additional code will be inserted into the | |
994 | scheduler and related routines to collect statistics about | |
995 | scheduler behavior and provide them in /proc/schedstat. These | |
996 | stats may be useful for both tuning and debugging the scheduler | |
997 | If you aren't debugging the scheduler or trying to tune a specific | |
998 | application, you can say N to avoid the very slight overhead | |
999 | this adds. | |
0822ee4a | 1000 | |
0d9e2632 AT |
1001 | config SCHED_STACK_END_CHECK |
1002 | bool "Detect stack corruption on calls to schedule()" | |
1003 | depends on DEBUG_KERNEL | |
1004 | default n | |
1005 | help | |
1006 | This option checks for a stack overrun on calls to schedule(). | |
1007 | If the stack end location is found to be over written always panic as | |
1008 | the content of the corrupted region can no longer be trusted. | |
1009 | This is to ensure no erroneous behaviour occurs which could result in | |
1010 | data corruption or a sporadic crash at a later stage once the region | |
1011 | is examined. The runtime overhead introduced is minimal. | |
1012 | ||
3c17ad19 JS |
1013 | config DEBUG_TIMEKEEPING |
1014 | bool "Enable extra timekeeping sanity checking" | |
1015 | help | |
1016 | This option will enable additional timekeeping sanity checks | |
1017 | which may be helpful when diagnosing issues where timekeeping | |
1018 | problems are suspected. | |
1019 | ||
1020 | This may include checks in the timekeeping hotpaths, so this | |
1021 | option may have a (very small) performance impact to some | |
1022 | workloads. | |
1023 | ||
1024 | If unsure, say N. | |
1025 | ||
1da177e4 LT |
1026 | config DEBUG_PREEMPT |
1027 | bool "Debug preemptible kernel" | |
01deab98 | 1028 | depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT |
1da177e4 LT |
1029 | default y |
1030 | help | |
1031 | If you say Y here then the kernel will use a debug variant of the | |
1032 | commonly used smp_processor_id() function and will print warnings | |
1033 | if kernel code uses it in a preemption-unsafe way. Also, the kernel | |
1034 | will detect preemption count underflows. | |
1035 | ||
9eade16b DH |
1036 | menu "Lock Debugging (spinlocks, mutexes, etc...)" |
1037 | ||
e7eebaf6 IM |
1038 | config DEBUG_RT_MUTEXES |
1039 | bool "RT Mutex debugging, deadlock detection" | |
e7eebaf6 IM |
1040 | depends on DEBUG_KERNEL && RT_MUTEXES |
1041 | help | |
1042 | This allows rt mutex semantics violations and rt mutex related | |
1043 | deadlocks (lockups) to be detected and reported automatically. | |
1044 | ||
1da177e4 | 1045 | config DEBUG_SPINLOCK |
4d9f34ad | 1046 | bool "Spinlock and rw-lock debugging: basic checks" |
1da177e4 | 1047 | depends on DEBUG_KERNEL |
e335e3eb | 1048 | select UNINLINE_SPIN_UNLOCK |
1da177e4 LT |
1049 | help |
1050 | Say Y here and build SMP to catch missing spinlock initialization | |
1051 | and certain other kinds of spinlock errors commonly made. This is | |
1052 | best used in conjunction with the NMI watchdog so that spinlock | |
1053 | deadlocks are also debuggable. | |
1054 | ||
4d9f34ad IM |
1055 | config DEBUG_MUTEXES |
1056 | bool "Mutex debugging: basic checks" | |
1057 | depends on DEBUG_KERNEL | |
1058 | help | |
1059 | This feature allows mutex semantics violations to be detected and | |
1060 | reported. | |
1061 | ||
23010027 DV |
1062 | config DEBUG_WW_MUTEX_SLOWPATH |
1063 | bool "Wait/wound mutex debugging: Slowpath testing" | |
1064 | depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT | |
1065 | select DEBUG_LOCK_ALLOC | |
1066 | select DEBUG_SPINLOCK | |
1067 | select DEBUG_MUTEXES | |
1068 | help | |
1069 | This feature enables slowpath testing for w/w mutex users by | |
1070 | injecting additional -EDEADLK wound/backoff cases. Together with | |
1071 | the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this | |
1072 | will test all possible w/w mutex interface abuse with the | |
1073 | exception of simply not acquiring all the required locks. | |
4d692373 RC |
1074 | Note that this feature can introduce significant overhead, so |
1075 | it really should not be enabled in a production or distro kernel, | |
1076 | even a debug kernel. If you are a driver writer, enable it. If | |
1077 | you are a distro, do not. | |
23010027 | 1078 | |
4d9f34ad IM |
1079 | config DEBUG_LOCK_ALLOC |
1080 | bool "Lock debugging: detect incorrect freeing of live locks" | |
517e7aa5 | 1081 | depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT |
4d9f34ad IM |
1082 | select DEBUG_SPINLOCK |
1083 | select DEBUG_MUTEXES | |
f5694788 | 1084 | select DEBUG_RT_MUTEXES if RT_MUTEXES |
4d9f34ad IM |
1085 | select LOCKDEP |
1086 | help | |
1087 | This feature will check whether any held lock (spinlock, rwlock, | |
1088 | mutex or rwsem) is incorrectly freed by the kernel, via any of the | |
1089 | memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), | |
1090 | vfree(), etc.), whether a live lock is incorrectly reinitialized via | |
1091 | spin_lock_init()/mutex_init()/etc., or whether there is any lock | |
1092 | held during task exit. | |
1093 | ||
1094 | config PROVE_LOCKING | |
1095 | bool "Lock debugging: prove locking correctness" | |
517e7aa5 | 1096 | depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT |
4d9f34ad IM |
1097 | select LOCKDEP |
1098 | select DEBUG_SPINLOCK | |
1099 | select DEBUG_MUTEXES | |
f5694788 | 1100 | select DEBUG_RT_MUTEXES if RT_MUTEXES |
4d9f34ad | 1101 | select DEBUG_LOCK_ALLOC |
46b93b74 | 1102 | select TRACE_IRQFLAGS |
4d9f34ad IM |
1103 | default n |
1104 | help | |
1105 | This feature enables the kernel to prove that all locking | |
1106 | that occurs in the kernel runtime is mathematically | |
1107 | correct: that under no circumstance could an arbitrary (and | |
1108 | not yet triggered) combination of observed locking | |
1109 | sequences (on an arbitrary number of CPUs, running an | |
1110 | arbitrary number of tasks and interrupt contexts) cause a | |
1111 | deadlock. | |
1112 | ||
1113 | In short, this feature enables the kernel to report locking | |
1114 | related deadlocks before they actually occur. | |
1115 | ||
1116 | The proof does not depend on how hard and complex a | |
1117 | deadlock scenario would be to trigger: how many | |
1118 | participant CPUs, tasks and irq-contexts would be needed | |
1119 | for it to trigger. The proof also does not depend on | |
1120 | timing: if a race and a resulting deadlock is possible | |
1121 | theoretically (no matter how unlikely the race scenario | |
1122 | is), it will be proven so and will immediately be | |
1123 | reported by the kernel (once the event is observed that | |
1124 | makes the deadlock theoretically possible). | |
1125 | ||
1126 | If a deadlock is impossible (i.e. the locking rules, as | |
1127 | observed by the kernel, are mathematically correct), the | |
1128 | kernel reports nothing. | |
1129 | ||
1130 | NOTE: this feature can also be enabled for rwlocks, mutexes | |
1131 | and rwsems - in which case all dependencies between these | |
1132 | different locking variants are observed and mapped too, and | |
1133 | the proof of observed correctness is also maintained for an | |
1134 | arbitrary combination of these separate locking variants. | |
1135 | ||
214e0aed | 1136 | For more details, see Documentation/locking/lockdep-design.txt. |
4d9f34ad IM |
1137 | |
1138 | config LOCKDEP | |
1139 | bool | |
517e7aa5 | 1140 | depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT |
4d9f34ad | 1141 | select STACKTRACE |
a34a766f | 1142 | select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE && !X86 |
4d9f34ad IM |
1143 | select KALLSYMS |
1144 | select KALLSYMS_ALL | |
1145 | ||
395102db DJ |
1146 | config LOCKDEP_SMALL |
1147 | bool | |
1148 | ||
f20786ff | 1149 | config LOCK_STAT |
fdfb870f | 1150 | bool "Lock usage statistics" |
f20786ff PZ |
1151 | depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT |
1152 | select LOCKDEP | |
1153 | select DEBUG_SPINLOCK | |
1154 | select DEBUG_MUTEXES | |
f5694788 | 1155 | select DEBUG_RT_MUTEXES if RT_MUTEXES |
f20786ff PZ |
1156 | select DEBUG_LOCK_ALLOC |
1157 | default n | |
1158 | help | |
1159 | This feature enables tracking lock contention points | |
1160 | ||
214e0aed | 1161 | For more details, see Documentation/locking/lockstat.txt |
a560aa48 | 1162 | |
dd8b1cf6 FW |
1163 | This also enables lock events required by "perf lock", |
1164 | subcommand of perf. | |
1165 | If you want to use "perf lock", you also need to turn on | |
1166 | CONFIG_EVENT_TRACING. | |
84c6f88f HM |
1167 | |
1168 | CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. | |
dd8b1cf6 | 1169 | (CONFIG_LOCKDEP defines "acquire" and "release" events.) |
84c6f88f | 1170 | |
4d9f34ad IM |
1171 | config DEBUG_LOCKDEP |
1172 | bool "Lock dependency engine debugging" | |
517e7aa5 | 1173 | depends on DEBUG_KERNEL && LOCKDEP |
4d9f34ad IM |
1174 | help |
1175 | If you say Y here, the lock dependency engine will do | |
1176 | additional runtime checks to debug itself, at the price | |
1177 | of more runtime overhead. | |
1178 | ||
d902db1e FW |
1179 | config DEBUG_ATOMIC_SLEEP |
1180 | bool "Sleep inside atomic section checking" | |
e8f7c70f | 1181 | select PREEMPT_COUNT |
1da177e4 LT |
1182 | depends on DEBUG_KERNEL |
1183 | help | |
1184 | If you say Y here, various routines which may sleep will become very | |
d902db1e FW |
1185 | noisy if they are called inside atomic sections: when a spinlock is |
1186 | held, inside an rcu read side critical section, inside preempt disabled | |
1187 | sections, inside an interrupt, etc... | |
1da177e4 | 1188 | |
cae2ed9a IM |
1189 | config DEBUG_LOCKING_API_SELFTESTS |
1190 | bool "Locking API boot-time self-tests" | |
1191 | depends on DEBUG_KERNEL | |
1192 | help | |
1193 | Say Y here if you want the kernel to run a short self-test during | |
1194 | bootup. The self-test checks whether common types of locking bugs | |
1195 | are detected by debugging mechanisms or not. (if you disable | |
1196 | lock debugging then those bugs wont be detected of course.) | |
1197 | The following locking APIs are covered: spinlocks, rwlocks, | |
1198 | mutexes and rwsems. | |
1199 | ||
0af3fe1e PM |
1200 | config LOCK_TORTURE_TEST |
1201 | tristate "torture tests for locking" | |
1202 | depends on DEBUG_KERNEL | |
1203 | select TORTURE_TEST | |
1204 | default n | |
1205 | help | |
1206 | This option provides a kernel module that runs torture tests | |
1207 | on kernel locking primitives. The kernel module may be built | |
1208 | after the fact on the running kernel to be tested, if desired. | |
1209 | ||
1210 | Say Y here if you want kernel locking-primitive torture tests | |
1211 | to be built into the kernel. | |
1212 | Say M if you want these torture tests to build as a module. | |
1213 | Say N if you are unsure. | |
1214 | ||
f2a5fec1 CW |
1215 | config WW_MUTEX_SELFTEST |
1216 | tristate "Wait/wound mutex selftests" | |
1217 | help | |
1218 | This option provides a kernel module that runs tests on the | |
1219 | on the struct ww_mutex locking API. | |
1220 | ||
1221 | It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction | |
1222 | with this test harness. | |
1223 | ||
1224 | Say M if you want these self tests to build as a module. | |
1225 | Say N if you are unsure. | |
1226 | ||
9eade16b | 1227 | endmenu # lock debugging |
8637c099 | 1228 | |
9eade16b DH |
1229 | config TRACE_IRQFLAGS |
1230 | bool | |
5ca43f6c | 1231 | help |
9eade16b DH |
1232 | Enables hooks to interrupt enabling and disabling for |
1233 | either tracing or lock debugging. | |
5ca43f6c | 1234 | |
8637c099 | 1235 | config STACKTRACE |
0c38e1fe | 1236 | bool "Stack backtrace support" |
8637c099 | 1237 | depends on STACKTRACE_SUPPORT |
0c38e1fe DJ |
1238 | help |
1239 | This option causes the kernel to create a /proc/pid/stack for | |
1240 | every process, showing its current stack trace. | |
1241 | It is also used by various kernel debugging features that require | |
1242 | stack trace generation. | |
5ca43f6c | 1243 | |
eecabf56 TT |
1244 | config WARN_ALL_UNSEEDED_RANDOM |
1245 | bool "Warn for all uses of unseeded randomness" | |
1246 | default n | |
d06bfd19 JD |
1247 | help |
1248 | Some parts of the kernel contain bugs relating to their use of | |
1249 | cryptographically secure random numbers before it's actually possible | |
1250 | to generate those numbers securely. This setting ensures that these | |
1251 | flaws don't go unnoticed, by enabling a message, should this ever | |
1252 | occur. This will allow people with obscure setups to know when things | |
1253 | are going wrong, so that they might contact developers about fixing | |
1254 | it. | |
1255 | ||
eecabf56 TT |
1256 | Unfortunately, on some models of some architectures getting |
1257 | a fully seeded CRNG is extremely difficult, and so this can | |
1258 | result in dmesg getting spammed for a surprisingly long | |
1259 | time. This is really bad from a security perspective, and | |
1260 | so architecture maintainers really need to do what they can | |
1261 | to get the CRNG seeded sooner after the system is booted. | |
1262 | However, since users can not do anything actionble to | |
1263 | address this, by default the kernel will issue only a single | |
1264 | warning for the first use of unseeded randomness. | |
1265 | ||
1266 | Say Y here if you want to receive warnings for all uses of | |
1267 | unseeded randomness. This will be of use primarily for | |
1268 | those developers interersted in improving the security of | |
1269 | Linux kernels running on their architecture (or | |
1270 | subarchitecture). | |
d06bfd19 | 1271 | |
1da177e4 LT |
1272 | config DEBUG_KOBJECT |
1273 | bool "kobject debugging" | |
1274 | depends on DEBUG_KERNEL | |
1275 | help | |
1276 | If you say Y here, some extra kobject debugging messages will be sent | |
1277 | to the syslog. | |
1278 | ||
c817a67e RK |
1279 | config DEBUG_KOBJECT_RELEASE |
1280 | bool "kobject release debugging" | |
2a999aa0 | 1281 | depends on DEBUG_OBJECTS_TIMERS |
c817a67e RK |
1282 | help |
1283 | kobjects are reference counted objects. This means that their | |
1284 | last reference count put is not predictable, and the kobject can | |
1285 | live on past the point at which a driver decides to drop it's | |
1286 | initial reference to the kobject gained on allocation. An | |
1287 | example of this would be a struct device which has just been | |
1288 | unregistered. | |
1289 | ||
1290 | However, some buggy drivers assume that after such an operation, | |
1291 | the memory backing the kobject can be immediately freed. This | |
1292 | goes completely against the principles of a refcounted object. | |
1293 | ||
1294 | If you say Y here, the kernel will delay the release of kobjects | |
1295 | on the last reference count to improve the visibility of this | |
1296 | kind of kobject release bug. | |
1297 | ||
9b2a60c4 CM |
1298 | config HAVE_DEBUG_BUGVERBOSE |
1299 | bool | |
1300 | ||
1da177e4 | 1301 | config DEBUG_BUGVERBOSE |
6a108a14 | 1302 | bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT |
9b2a60c4 | 1303 | depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) |
8420e7ef | 1304 | default y |
1da177e4 LT |
1305 | help |
1306 | Say Y here to make BUG() panics output the file name and line number | |
1307 | of the BUG call as well as the EIP and oops trace. This aids | |
1308 | debugging but costs about 70-100K of memory. | |
1309 | ||
199a9afc DJ |
1310 | config DEBUG_LIST |
1311 | bool "Debug linked list manipulation" | |
4520bcb2 | 1312 | depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION |
199a9afc DJ |
1313 | help |
1314 | Enable this to turn on extended checks in the linked-list | |
1315 | walking routines. | |
1316 | ||
1317 | If unsure, say N. | |
1318 | ||
b8cfff68 DS |
1319 | config DEBUG_PI_LIST |
1320 | bool "Debug priority linked list manipulation" | |
1321 | depends on DEBUG_KERNEL | |
1322 | help | |
1323 | Enable this to turn on extended checks in the priority-ordered | |
1324 | linked-list (plist) walking routines. This checks the entire | |
1325 | list multiple times during each manipulation. | |
1326 | ||
1327 | If unsure, say N. | |
1328 | ||
d6ec0842 JA |
1329 | config DEBUG_SG |
1330 | bool "Debug SG table operations" | |
1331 | depends on DEBUG_KERNEL | |
1332 | help | |
1333 | Enable this to turn on checks on scatter-gather tables. This can | |
1334 | help find problems with drivers that do not properly initialize | |
1335 | their sg tables. | |
1336 | ||
1337 | If unsure, say N. | |
1338 | ||
1b2439db AV |
1339 | config DEBUG_NOTIFIERS |
1340 | bool "Debug notifier call chains" | |
1341 | depends on DEBUG_KERNEL | |
1342 | help | |
1343 | Enable this to turn on sanity checking for notifier call chains. | |
1344 | This is most useful for kernel developers to make sure that | |
1345 | modules properly unregister themselves from notifier chains. | |
1346 | This is a relatively cheap check but if you care about maximum | |
1347 | performance, say N. | |
1348 | ||
e0e81739 DH |
1349 | config DEBUG_CREDENTIALS |
1350 | bool "Debug credential management" | |
1351 | depends on DEBUG_KERNEL | |
1352 | help | |
1353 | Enable this to turn on some debug checking for credential | |
1354 | management. The additional code keeps track of the number of | |
1355 | pointers from task_structs to any given cred struct, and checks to | |
1356 | see that this number never exceeds the usage count of the cred | |
1357 | struct. | |
1358 | ||
1359 | Furthermore, if SELinux is enabled, this also checks that the | |
1360 | security pointer in the cred struct is never seen to be invalid. | |
1361 | ||
1362 | If unsure, say N. | |
1363 | ||
43a0a2a7 | 1364 | source "kernel/rcu/Kconfig.debug" |
2f03e3ca | 1365 | |
f303fccb TH |
1366 | config DEBUG_WQ_FORCE_RR_CPU |
1367 | bool "Force round-robin CPU selection for unbound work items" | |
1368 | depends on DEBUG_KERNEL | |
1369 | default n | |
1370 | help | |
1371 | Workqueue used to implicitly guarantee that work items queued | |
1372 | without explicit CPU specified are put on the local CPU. This | |
1373 | guarantee is no longer true and while local CPU is still | |
1374 | preferred work items may be put on foreign CPUs. Kernel | |
1375 | parameter "workqueue.debug_force_rr_cpu" is added to force | |
1376 | round-robin CPU selection to flush out usages which depend on the | |
1377 | now broken guarantee. This config option enables the debug | |
1378 | feature by default. When enabled, memory and cache locality will | |
1379 | be impacted. | |
1380 | ||
870d6656 TH |
1381 | config DEBUG_BLOCK_EXT_DEVT |
1382 | bool "Force extended block device numbers and spread them" | |
1383 | depends on DEBUG_KERNEL | |
1384 | depends on BLOCK | |
759f8ca3 | 1385 | default n |
870d6656 | 1386 | help |
0e11e342 TH |
1387 | BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON |
1388 | SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT | |
1389 | YOU ARE DOING. Distros, please enable this and fix whatever | |
1390 | is broken. | |
1391 | ||
870d6656 TH |
1392 | Conventionally, block device numbers are allocated from |
1393 | predetermined contiguous area. However, extended block area | |
1394 | may introduce non-contiguous block device numbers. This | |
1395 | option forces most block device numbers to be allocated from | |
1396 | the extended space and spreads them to discover kernel or | |
1397 | userland code paths which assume predetermined contiguous | |
1398 | device number allocation. | |
1399 | ||
55dc7db7 TH |
1400 | Note that turning on this debug option shuffles all the |
1401 | device numbers for all IDE and SCSI devices including libata | |
1402 | ones, so root partition specified using device number | |
1403 | directly (via rdev or root=MAJ:MIN) won't work anymore. | |
1404 | Textual device names (root=/dev/sdXn) will continue to work. | |
1405 | ||
870d6656 TH |
1406 | Say N if you are unsure. |
1407 | ||
757c989b TG |
1408 | config CPU_HOTPLUG_STATE_CONTROL |
1409 | bool "Enable CPU hotplug state control" | |
1410 | depends on DEBUG_KERNEL | |
1411 | depends on HOTPLUG_CPU | |
1412 | default n | |
1413 | help | |
1414 | Allows to write steps between "offline" and "online" to the CPUs | |
1415 | sysfs target file so states can be stepped granular. This is a debug | |
1416 | option for now as the hotplug machinery cannot be stopped and | |
1417 | restarted at arbitrary points yet. | |
1418 | ||
1419 | Say N if your are unsure. | |
1420 | ||
8d438288 AM |
1421 | config NOTIFIER_ERROR_INJECTION |
1422 | tristate "Notifier error injection" | |
1423 | depends on DEBUG_KERNEL | |
1424 | select DEBUG_FS | |
1425 | help | |
e41e85cc | 1426 | This option provides the ability to inject artificial errors to |
8d438288 AM |
1427 | specified notifier chain callbacks. It is useful to test the error |
1428 | handling of notifier call chain failures. | |
1429 | ||
1430 | Say N if unsure. | |
1431 | ||
048b9c35 AM |
1432 | config PM_NOTIFIER_ERROR_INJECT |
1433 | tristate "PM notifier error injection module" | |
1434 | depends on PM && NOTIFIER_ERROR_INJECTION | |
1435 | default m if PM_DEBUG | |
1436 | help | |
e41e85cc | 1437 | This option provides the ability to inject artificial errors to |
048b9c35 AM |
1438 | PM notifier chain callbacks. It is controlled through debugfs |
1439 | interface /sys/kernel/debug/notifier-error-inject/pm | |
1440 | ||
1441 | If the notifier call chain should be failed with some events | |
1442 | notified, write the error code to "actions/<notifier event>/error". | |
1443 | ||
1444 | Example: Inject PM suspend error (-12 = -ENOMEM) | |
1445 | ||
1446 | # cd /sys/kernel/debug/notifier-error-inject/pm/ | |
1447 | # echo -12 > actions/PM_SUSPEND_PREPARE/error | |
1448 | # echo mem > /sys/power/state | |
1449 | bash: echo: write error: Cannot allocate memory | |
1450 | ||
1451 | To compile this code as a module, choose M here: the module will | |
1452 | be called pm-notifier-error-inject. | |
1453 | ||
1454 | If unsure, say N. | |
1455 | ||
d526e85f BH |
1456 | config OF_RECONFIG_NOTIFIER_ERROR_INJECT |
1457 | tristate "OF reconfig notifier error injection module" | |
1458 | depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION | |
08dfb4dd | 1459 | help |
e41e85cc | 1460 | This option provides the ability to inject artificial errors to |
d526e85f | 1461 | OF reconfig notifier chain callbacks. It is controlled |
08dfb4dd | 1462 | through debugfs interface under |
d526e85f | 1463 | /sys/kernel/debug/notifier-error-inject/OF-reconfig/ |
08dfb4dd AM |
1464 | |
1465 | If the notifier call chain should be failed with some events | |
1466 | notified, write the error code to "actions/<notifier event>/error". | |
1467 | ||
1468 | To compile this code as a module, choose M here: the module will | |
e12a95f4 | 1469 | be called of-reconfig-notifier-error-inject. |
08dfb4dd AM |
1470 | |
1471 | If unsure, say N. | |
1472 | ||
02fff96a NA |
1473 | config NETDEV_NOTIFIER_ERROR_INJECT |
1474 | tristate "Netdev notifier error injection module" | |
1475 | depends on NET && NOTIFIER_ERROR_INJECTION | |
1476 | help | |
1477 | This option provides the ability to inject artificial errors to | |
1478 | netdevice notifier chain callbacks. It is controlled through debugfs | |
1479 | interface /sys/kernel/debug/notifier-error-inject/netdev | |
1480 | ||
1481 | If the notifier call chain should be failed with some events | |
1482 | notified, write the error code to "actions/<notifier event>/error". | |
1483 | ||
1484 | Example: Inject netdevice mtu change error (-22 = -EINVAL) | |
1485 | ||
1486 | # cd /sys/kernel/debug/notifier-error-inject/netdev | |
1487 | # echo -22 > actions/NETDEV_CHANGEMTU/error | |
1488 | # ip link set eth0 mtu 1024 | |
1489 | RTNETLINK answers: Invalid argument | |
1490 | ||
1491 | To compile this code as a module, choose M here: the module will | |
1492 | be called netdev-notifier-error-inject. | |
1493 | ||
1494 | If unsure, say N. | |
1495 | ||
6ff1cb35 | 1496 | config FAULT_INJECTION |
1ab8509a AM |
1497 | bool "Fault-injection framework" |
1498 | depends on DEBUG_KERNEL | |
329409ae AM |
1499 | help |
1500 | Provide fault-injection framework. | |
1501 | For more details, see Documentation/fault-injection/. | |
6ff1cb35 | 1502 | |
8a8b6502 | 1503 | config FAILSLAB |
1ab8509a AM |
1504 | bool "Fault-injection capability for kmalloc" |
1505 | depends on FAULT_INJECTION | |
773ff60e | 1506 | depends on SLAB || SLUB |
8a8b6502 | 1507 | help |
1ab8509a | 1508 | Provide fault-injection capability for kmalloc. |
8a8b6502 | 1509 | |
933e312e AM |
1510 | config FAIL_PAGE_ALLOC |
1511 | bool "Fault-injection capabilitiy for alloc_pages()" | |
1ab8509a | 1512 | depends on FAULT_INJECTION |
933e312e | 1513 | help |
1ab8509a | 1514 | Provide fault-injection capability for alloc_pages(). |
933e312e | 1515 | |
c17bb495 | 1516 | config FAIL_MAKE_REQUEST |
86327d19 | 1517 | bool "Fault-injection capability for disk IO" |
581d4e28 | 1518 | depends on FAULT_INJECTION && BLOCK |
c17bb495 | 1519 | help |
1ab8509a | 1520 | Provide fault-injection capability for disk IO. |
c17bb495 | 1521 | |
581d4e28 | 1522 | config FAIL_IO_TIMEOUT |
f4d01439 | 1523 | bool "Fault-injection capability for faking disk interrupts" |
581d4e28 JA |
1524 | depends on FAULT_INJECTION && BLOCK |
1525 | help | |
1526 | Provide fault-injection capability on end IO handling. This | |
1527 | will make the block layer "forget" an interrupt as configured, | |
1528 | thus exercising the error handling. | |
1529 | ||
1530 | Only works with drivers that use the generic timeout handling, | |
1531 | for others it wont do anything. | |
1532 | ||
1b676f70 PF |
1533 | config FAIL_MMC_REQUEST |
1534 | bool "Fault-injection capability for MMC IO" | |
28ff4fda | 1535 | depends on FAULT_INJECTION_DEBUG_FS && MMC |
1b676f70 PF |
1536 | help |
1537 | Provide fault-injection capability for MMC IO. | |
1538 | This will make the mmc core return data errors. This is | |
1539 | useful to test the error handling in the mmc block device | |
1540 | and to test how the mmc host driver handles retries from | |
1541 | the block device. | |
1542 | ||
ab51fbab DB |
1543 | config FAIL_FUTEX |
1544 | bool "Fault-injection capability for futexes" | |
1545 | select DEBUG_FS | |
1546 | depends on FAULT_INJECTION && FUTEX | |
1547 | help | |
1548 | Provide fault-injection capability for futexes. | |
1549 | ||
6ff1cb35 AM |
1550 | config FAULT_INJECTION_DEBUG_FS |
1551 | bool "Debugfs entries for fault-injection capabilities" | |
1ab8509a | 1552 | depends on FAULT_INJECTION && SYSFS && DEBUG_FS |
6ff1cb35 | 1553 | help |
1ab8509a | 1554 | Enable configuration of fault-injection capabilities via debugfs. |
1df49008 AM |
1555 | |
1556 | config FAULT_INJECTION_STACKTRACE_FILTER | |
1557 | bool "stacktrace filter for fault-injection capabilities" | |
1558 | depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT | |
6d690dca | 1559 | depends on !X86_64 |
1df49008 | 1560 | select STACKTRACE |
a34a766f | 1561 | select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE && !X86 |
1df49008 AM |
1562 | help |
1563 | Provide stacktrace filter for fault-injection capabilities | |
267c4025 | 1564 | |
9745512c AV |
1565 | config LATENCYTOP |
1566 | bool "Latency measuring infrastructure" | |
625fdcaa RD |
1567 | depends on DEBUG_KERNEL |
1568 | depends on STACKTRACE_SUPPORT | |
1569 | depends on PROC_FS | |
a34a766f | 1570 | select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !X86 |
9745512c AV |
1571 | select KALLSYMS |
1572 | select KALLSYMS_ALL | |
1573 | select STACKTRACE | |
1574 | select SCHEDSTATS | |
1575 | select SCHED_DEBUG | |
9745512c AV |
1576 | help |
1577 | Enable this option if you want to use the LatencyTOP tool | |
1578 | to find out which userspace is blocking on what kernel operations. | |
1579 | ||
16444a8a ACM |
1580 | source kernel/trace/Kconfig |
1581 | ||
cc3fa840 RD |
1582 | config PROVIDE_OHCI1394_DMA_INIT |
1583 | bool "Remote debugging over FireWire early on boot" | |
1584 | depends on PCI && X86 | |
1585 | help | |
1586 | If you want to debug problems which hang or crash the kernel early | |
1587 | on boot and the crashing machine has a FireWire port, you can use | |
1588 | this feature to remotely access the memory of the crashed machine | |
1589 | over FireWire. This employs remote DMA as part of the OHCI1394 | |
1590 | specification which is now the standard for FireWire controllers. | |
1591 | ||
1592 | With remote DMA, you can monitor the printk buffer remotely using | |
1593 | firescope and access all memory below 4GB using fireproxy from gdb. | |
1594 | Even controlling a kernel debugger is possible using remote DMA. | |
1595 | ||
1596 | Usage: | |
1597 | ||
1598 | If ohci1394_dma=early is used as boot parameter, it will initialize | |
1599 | all OHCI1394 controllers which are found in the PCI config space. | |
1600 | ||
1601 | As all changes to the FireWire bus such as enabling and disabling | |
1602 | devices cause a bus reset and thereby disable remote DMA for all | |
1603 | devices, be sure to have the cable plugged and FireWire enabled on | |
1604 | the debugging host before booting the debug target for debugging. | |
1605 | ||
1606 | This code (~1k) is freed after boot. By then, the firewire stack | |
1607 | in charge of the OHCI-1394 controllers should be used instead. | |
1608 | ||
1609 | See Documentation/debugging-via-ohci1394.txt for more information. | |
1610 | ||
1611 | config DMA_API_DEBUG | |
1612 | bool "Enable debugging of DMA-API usage" | |
1613 | depends on HAVE_DMA_API_DEBUG | |
1614 | help | |
1615 | Enable this option to debug the use of the DMA API by device drivers. | |
1616 | With this option you will be able to detect common bugs in device | |
1617 | drivers like double-freeing of DMA mappings or freeing mappings that | |
1618 | were never allocated. | |
1619 | ||
1620 | This also attempts to catch cases where a page owned by DMA is | |
1621 | accessed by the cpu in a way that could cause data corruption. For | |
1622 | example, this enables cow_user_page() to check that the source page is | |
1623 | not undergoing DMA. | |
1624 | ||
1625 | This option causes a performance degradation. Use only if you want to | |
1626 | debug device drivers and dma interactions. | |
1627 | ||
1628 | If unsure, say N. | |
1629 | ||
881c5149 DH |
1630 | menu "Runtime Testing" |
1631 | ||
1632 | config LKDTM | |
1633 | tristate "Linux Kernel Dump Test Tool Module" | |
1634 | depends on DEBUG_FS | |
1635 | depends on BLOCK | |
1636 | default n | |
1637 | help | |
1638 | This module enables testing of the different dumping mechanisms by | |
1639 | inducing system failures at predefined crash points. | |
1640 | If you don't need it: say N | |
1641 | Choose M here to compile this code as a module. The module will be | |
1642 | called lkdtm. | |
1643 | ||
1644 | Documentation on how to use the module can be found in | |
1645 | Documentation/fault-injection/provoke-crashes.txt | |
1646 | ||
1647 | config TEST_LIST_SORT | |
e327fd7c GU |
1648 | tristate "Linked list sorting test" |
1649 | depends on DEBUG_KERNEL || m | |
881c5149 DH |
1650 | help |
1651 | Enable this to turn on 'list_sort()' function test. This test is | |
e327fd7c GU |
1652 | executed only once during system boot (so affects only boot time), |
1653 | or at module load time. | |
881c5149 DH |
1654 | |
1655 | If unsure, say N. | |
1656 | ||
c5adae95 | 1657 | config TEST_SORT |
5c4e6798 GU |
1658 | tristate "Array-based sort test" |
1659 | depends on DEBUG_KERNEL || m | |
c5adae95 | 1660 | help |
5c4e6798 GU |
1661 | This option enables the self-test function of 'sort()' at boot, |
1662 | or at module load time. | |
c5adae95 KF |
1663 | |
1664 | If unsure, say N. | |
1665 | ||
881c5149 DH |
1666 | config KPROBES_SANITY_TEST |
1667 | bool "Kprobes sanity tests" | |
1668 | depends on DEBUG_KERNEL | |
1669 | depends on KPROBES | |
1670 | default n | |
1671 | help | |
1672 | This option provides for testing basic kprobes functionality on | |
1673 | boot. A sample kprobe, jprobe and kretprobe are inserted and | |
1674 | verified for functionality. | |
1675 | ||
1676 | Say N if you are unsure. | |
1677 | ||
1678 | config BACKTRACE_SELF_TEST | |
1679 | tristate "Self test for the backtrace code" | |
1680 | depends on DEBUG_KERNEL | |
1681 | default n | |
1682 | help | |
1683 | This option provides a kernel module that can be used to test | |
1684 | the kernel stack backtrace code. This option is not useful | |
1685 | for distributions or general kernels, but only for kernel | |
1686 | developers working on architecture code. | |
1687 | ||
1688 | Note that if you want to also test saved backtraces, you will | |
1689 | have to enable STACKTRACE as well. | |
1690 | ||
1691 | Say N if you are unsure. | |
1692 | ||
910a742d ML |
1693 | config RBTREE_TEST |
1694 | tristate "Red-Black tree test" | |
7c993e11 | 1695 | depends on DEBUG_KERNEL |
910a742d ML |
1696 | help |
1697 | A benchmark measuring the performance of the rbtree library. | |
1698 | Also includes rbtree invariant checks. | |
1699 | ||
fff3fd8a ML |
1700 | config INTERVAL_TREE_TEST |
1701 | tristate "Interval tree test" | |
0f789b67 | 1702 | depends on DEBUG_KERNEL |
a88cc108 | 1703 | select INTERVAL_TREE |
fff3fd8a ML |
1704 | help |
1705 | A benchmark measuring the performance of the interval tree library | |
1706 | ||
623fd807 GT |
1707 | config PERCPU_TEST |
1708 | tristate "Per cpu operations test" | |
1709 | depends on m && DEBUG_KERNEL | |
1710 | help | |
1711 | Enable this option to build test module which validates per-cpu | |
1712 | operations. | |
1713 | ||
1714 | If unsure, say N. | |
1715 | ||
881c5149 | 1716 | config ATOMIC64_SELFTEST |
55ded955 | 1717 | tristate "Perform an atomic64_t self-test" |
881c5149 | 1718 | help |
55ded955 GU |
1719 | Enable this option to test the atomic64_t functions at boot or |
1720 | at module load time. | |
881c5149 DH |
1721 | |
1722 | If unsure, say N. | |
1723 | ||
1724 | config ASYNC_RAID6_TEST | |
1725 | tristate "Self test for hardware accelerated raid6 recovery" | |
1726 | depends on ASYNC_RAID6_RECOV | |
1727 | select ASYNC_MEMCPY | |
1728 | ---help--- | |
1729 | This is a one-shot self test that permutes through the | |
1730 | recovery of all the possible two disk failure scenarios for a | |
1731 | N-disk array. Recovery is performed with the asynchronous | |
1732 | raid6 recovery routines, and will optionally use an offload | |
1733 | engine if one is available. | |
1734 | ||
1735 | If unsure, say N. | |
1736 | ||
64d1d77a AS |
1737 | config TEST_HEXDUMP |
1738 | tristate "Test functions located in the hexdump module at runtime" | |
1739 | ||
881c5149 DH |
1740 | config TEST_STRING_HELPERS |
1741 | tristate "Test functions located in the string_helpers module at runtime" | |
1742 | ||
1743 | config TEST_KSTRTOX | |
1744 | tristate "Test kstrto*() family of functions at runtime" | |
1745 | ||
707cc728 RV |
1746 | config TEST_PRINTF |
1747 | tristate "Test printf() family of functions at runtime" | |
1748 | ||
5fd003f5 DD |
1749 | config TEST_BITMAP |
1750 | tristate "Test bitmap_*() family of functions at runtime" | |
1751 | default n | |
1752 | help | |
1753 | Enable this option to test the bitmap functions at boot. | |
1754 | ||
1755 | If unsure, say N. | |
1756 | ||
cfaff0e5 AS |
1757 | config TEST_UUID |
1758 | tristate "Test functions located in the uuid module at runtime" | |
1759 | ||
7e1e7763 | 1760 | config TEST_RHASHTABLE |
9d6dbe1b | 1761 | tristate "Perform selftest on resizable hash table" |
7e1e7763 TG |
1762 | default n |
1763 | help | |
1764 | Enable this option to test the rhashtable functions at boot. | |
1765 | ||
1766 | If unsure, say N. | |
1767 | ||
468a9428 GS |
1768 | config TEST_HASH |
1769 | tristate "Perform selftest on hash functions" | |
1770 | default n | |
1771 | help | |
2c956a60 JD |
1772 | Enable this option to test the kernel's integer (<linux/hash.h>), |
1773 | string (<linux/stringhash.h>), and siphash (<linux/siphash.h>) | |
1774 | hash functions on boot (or module load). | |
468a9428 GS |
1775 | |
1776 | This is intended to help people writing architecture-specific | |
1777 | optimized versions. If unsure, say N. | |
1778 | ||
44091d29 JP |
1779 | config TEST_PARMAN |
1780 | tristate "Perform selftest on priority array manager" | |
1781 | default n | |
1782 | depends on PARMAN | |
1783 | help | |
1784 | Enable this option to test priority array manager on boot | |
1785 | (or module load). | |
1786 | ||
1787 | If unsure, say N. | |
1788 | ||
8a6f0b47 | 1789 | config TEST_LKM |
93e9ef83 KC |
1790 | tristate "Test module loading with 'hello world' module" |
1791 | default n | |
1792 | depends on m | |
1793 | help | |
1794 | This builds the "test_module" module that emits "Hello, world" | |
1795 | on printk when loaded. It is designed to be used for basic | |
1796 | evaluation of the module loading subsystem (for example when | |
1797 | validating module verification). It lacks any extra dependencies, | |
1798 | and will not normally be loaded by the system unless explicitly | |
1799 | requested by name. | |
1800 | ||
1801 | If unsure, say N. | |
1802 | ||
3e2a4c18 KC |
1803 | config TEST_USER_COPY |
1804 | tristate "Test user/kernel boundary protections" | |
1805 | default n | |
1806 | depends on m | |
1807 | help | |
1808 | This builds the "test_user_copy" module that runs sanity checks | |
1809 | on the copy_to/from_user infrastructure, making sure basic | |
1810 | user/kernel boundary testing is working. If it fails to load, | |
1811 | a regression has been detected in the user/kernel memory boundary | |
1812 | protections. | |
1813 | ||
1814 | If unsure, say N. | |
1815 | ||
64a8946b AS |
1816 | config TEST_BPF |
1817 | tristate "Test BPF filter functionality" | |
1818 | default n | |
98920ba6 | 1819 | depends on m && NET |
64a8946b AS |
1820 | help |
1821 | This builds the "test_bpf" module that runs various test vectors | |
1822 | against the BPF interpreter or BPF JIT compiler depending on the | |
1823 | current setting. This is in particular useful for BPF JIT compiler | |
1824 | development, but also to run regression tests against changes in | |
3c731eba AS |
1825 | the interpreter code. It also enables test stubs for eBPF maps and |
1826 | verifier used by user space verifier testsuite. | |
64a8946b AS |
1827 | |
1828 | If unsure, say N. | |
1829 | ||
4441fca0 YN |
1830 | config TEST_FIND_BIT |
1831 | tristate "Test find_bit functions" | |
1832 | default n | |
1833 | help | |
1834 | This builds the "test_find_bit" module that measure find_*_bit() | |
1835 | functions performance. | |
1836 | ||
1837 | If unsure, say N. | |
1838 | ||
0a8adf58 KC |
1839 | config TEST_FIRMWARE |
1840 | tristate "Test firmware loading via userspace interface" | |
1841 | default n | |
1842 | depends on FW_LOADER | |
1843 | help | |
1844 | This builds the "test_firmware" module that creates a userspace | |
1845 | interface for testing firmware loading. This can be used to | |
1846 | control the triggering of firmware loading without needing an | |
1847 | actual firmware-using device. The contents can be rechecked by | |
1848 | userspace. | |
1849 | ||
1850 | If unsure, say N. | |
1851 | ||
9308f2f9 LR |
1852 | config TEST_SYSCTL |
1853 | tristate "sysctl test driver" | |
1854 | default n | |
1855 | depends on PROC_SYSCTL | |
1856 | help | |
1857 | This builds the "test_sysctl" module. This driver enables to test the | |
1858 | proc sysctl interfaces available to drivers safely without affecting | |
1859 | production knobs which might alter system functionality. | |
1860 | ||
1861 | If unsure, say N. | |
1862 | ||
e704f93a DR |
1863 | config TEST_UDELAY |
1864 | tristate "udelay test driver" | |
1865 | default n | |
1866 | help | |
1867 | This builds the "udelay_test" module that helps to make sure | |
1868 | that udelay() is working properly. | |
1869 | ||
1870 | If unsure, say N. | |
1871 | ||
2bf9e0ab IM |
1872 | config TEST_STATIC_KEYS |
1873 | tristate "Test static keys" | |
579e1acb JB |
1874 | default n |
1875 | depends on m | |
1876 | help | |
2bf9e0ab | 1877 | Test the static key interfaces. |
579e1acb JB |
1878 | |
1879 | If unsure, say N. | |
1880 | ||
d9c6a72d LR |
1881 | config TEST_KMOD |
1882 | tristate "kmod stress tester" | |
1883 | default n | |
1884 | depends on m | |
1885 | depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS | |
1886 | depends on NETDEVICES && NET_CORE && INET # for TUN | |
1887 | select TEST_LKM | |
1888 | select XFS_FS | |
1889 | select TUN | |
1890 | select BTRFS_FS | |
1891 | help | |
1892 | Test the kernel's module loading mechanism: kmod. kmod implements | |
1893 | support to load modules using the Linux kernel's usermode helper. | |
1894 | This test provides a series of tests against kmod. | |
1895 | ||
1896 | Although technically you can either build test_kmod as a module or | |
1897 | into the kernel we disallow building it into the kernel since | |
1898 | it stress tests request_module() and this will very likely cause | |
1899 | some issues by taking over precious threads available from other | |
1900 | module load requests, ultimately this could be fatal. | |
1901 | ||
1902 | To run tests run: | |
1903 | ||
1904 | tools/testing/selftests/kmod/kmod.sh --help | |
1905 | ||
1906 | If unsure, say N. | |
1907 | ||
e4dace36 FF |
1908 | config TEST_DEBUG_VIRTUAL |
1909 | tristate "Test CONFIG_DEBUG_VIRTUAL feature" | |
1910 | depends on DEBUG_VIRTUAL | |
1911 | help | |
1912 | Test the kernel's ability to detect incorrect calls to | |
1913 | virt_to_phys() done against the non-linear part of the | |
1914 | kernel's virtual address map. | |
1915 | ||
1916 | If unsure, say N. | |
1917 | ||
cc3fa840 RD |
1918 | endmenu # runtime tests |
1919 | ||
1920 | config MEMTEST | |
1921 | bool "Memtest" | |
1922 | depends on HAVE_MEMBLOCK | |
1923 | ---help--- | |
1924 | This option adds a kernel parameter 'memtest', which allows memtest | |
1925 | to be set. | |
1926 | memtest=0, mean disabled; -- default | |
1927 | memtest=1, mean do 1 test pattern; | |
1928 | ... | |
1929 | memtest=17, mean do 17 test patterns. | |
1930 | If you are unsure how to answer this question, answer N. | |
1931 | ||
1932 | config BUG_ON_DATA_CORRUPTION | |
1933 | bool "Trigger a BUG when data corruption is detected" | |
1934 | select DEBUG_LIST | |
1935 | help | |
1936 | Select this option if the kernel should BUG when it encounters | |
1937 | data corruption in kernel memory structures when they get checked | |
1938 | for validity. | |
1939 | ||
1940 | If unsure, say N. | |
e4dace36 | 1941 | |
267c4025 | 1942 | source "samples/Kconfig" |
dc7d5527 JW |
1943 | |
1944 | source "lib/Kconfig.kgdb" | |
0a4af3b0 | 1945 | |
c6d30853 AR |
1946 | source "lib/Kconfig.ubsan" |
1947 | ||
21266be9 DW |
1948 | config ARCH_HAS_DEVMEM_IS_ALLOWED |
1949 | bool | |
1950 | ||
1951 | config STRICT_DEVMEM | |
1952 | bool "Filter access to /dev/mem" | |
6b2a65c7 | 1953 | depends on MMU && DEVMEM |
21266be9 DW |
1954 | depends on ARCH_HAS_DEVMEM_IS_ALLOWED |
1955 | default y if TILE || PPC | |
1956 | ---help--- | |
1957 | If this option is disabled, you allow userspace (root) access to all | |
1958 | of memory, including kernel and userspace memory. Accidental | |
1959 | access to this is obviously disastrous, but specific access can | |
1960 | be used by people debugging the kernel. Note that with PAT support | |
1961 | enabled, even in this case there are restrictions on /dev/mem | |
1962 | use due to the cache aliasing requirements. | |
1963 | ||
90a545e9 DW |
1964 | If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem |
1965 | file only allows userspace access to PCI space and the BIOS code and | |
1966 | data regions. This is sufficient for dosemu and X and all common | |
1967 | users of /dev/mem. | |
1968 | ||
1969 | If in doubt, say Y. | |
1970 | ||
1971 | config IO_STRICT_DEVMEM | |
1972 | bool "Filter I/O access to /dev/mem" | |
1973 | depends on STRICT_DEVMEM | |
90a545e9 DW |
1974 | ---help--- |
1975 | If this option is disabled, you allow userspace (root) access to all | |
1976 | io-memory regardless of whether a driver is actively using that | |
1977 | range. Accidental access to this is obviously disastrous, but | |
1978 | specific access can be used by people debugging kernel drivers. | |
1979 | ||
21266be9 | 1980 | If this option is switched on, the /dev/mem file only allows |
90a545e9 DW |
1981 | userspace access to *idle* io-memory ranges (see /proc/iomem) This |
1982 | may break traditional users of /dev/mem (dosemu, legacy X, etc...) | |
1983 | if the driver using a given range cannot be disabled. | |
21266be9 DW |
1984 | |
1985 | If in doubt, say Y. |