Commit | Line | Data |
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10ffebbe | 1 | =========================================== |
de1ba09b AM |
2 | Fault injection capabilities infrastructure |
3 | =========================================== | |
4 | ||
1892ce4c | 5 | See also drivers/md/md-faulty.c and "every_nth" module option for scsi_debug. |
de1ba09b AM |
6 | |
7 | ||
8 | Available fault injection capabilities | |
9 | -------------------------------------- | |
10 | ||
10ffebbe | 11 | - failslab |
de1ba09b AM |
12 | |
13 | injects slab allocation failures. (kmalloc(), kmem_cache_alloc(), ...) | |
14 | ||
10ffebbe | 15 | - fail_page_alloc |
de1ba09b AM |
16 | |
17 | injects page allocation failures. (alloc_pages(), get_free_pages(), ...) | |
18 | ||
2c739ced AL |
19 | - fail_usercopy |
20 | ||
21 | injects failures in user memory access functions. (copy_from_user(), get_user(), ...) | |
22 | ||
10ffebbe | 23 | - fail_futex |
ab51fbab DB |
24 | |
25 | injects futex deadlock and uaddr fault errors. | |
26 | ||
400edd8c CL |
27 | - fail_sunrpc |
28 | ||
29 | injects kernel RPC client and server failures. | |
30 | ||
10ffebbe | 31 | - fail_make_request |
de1ba09b | 32 | |
5d0ffa2b | 33 | injects disk IO errors on devices permitted by setting |
de1ba09b | 34 | /sys/block/<device>/make-it-fail or |
ed00aabd | 35 | /sys/block/<device>/<partition>/make-it-fail. (submit_bio_noacct()) |
de1ba09b | 36 | |
10ffebbe | 37 | - fail_mmc_request |
1e4cb22b PF |
38 | |
39 | injects MMC data errors on devices permitted by setting | |
40 | debugfs entries under /sys/kernel/debug/mmc0/fail_mmc_request | |
41 | ||
10ffebbe | 42 | - fail_function |
4b1a29a7 MH |
43 | |
44 | injects error return on specific functions, which are marked by | |
45 | ALLOW_ERROR_INJECTION() macro, by setting debugfs entries | |
46 | under /sys/kernel/debug/fail_function. No boot option supported. | |
47 | ||
10ffebbe | 48 | - NVMe fault injection |
cf4182f3 TT |
49 | |
50 | inject NVMe status code and retry flag on devices permitted by setting | |
51 | debugfs entries under /sys/kernel/debug/nvme*/fault_inject. The default | |
52 | status code is NVME_SC_INVALID_OPCODE with no retry. The status code and | |
53 | retry flag can be set via the debugfs. | |
54 | ||
55 | ||
de1ba09b AM |
56 | Configure fault-injection capabilities behavior |
57 | ----------------------------------------------- | |
58 | ||
10ffebbe MCC |
59 | debugfs entries |
60 | ^^^^^^^^^^^^^^^ | |
de1ba09b AM |
61 | |
62 | fault-inject-debugfs kernel module provides some debugfs entries for runtime | |
63 | configuration of fault-injection capabilities. | |
64 | ||
156f5a78 | 65 | - /sys/kernel/debug/fail*/probability: |
de1ba09b AM |
66 | |
67 | likelihood of failure injection, in percent. | |
10ffebbe | 68 | |
de1ba09b AM |
69 | Format: <percent> |
70 | ||
5d0ffa2b DM |
71 | Note that one-failure-per-hundred is a very high error rate |
72 | for some testcases. Consider setting probability=100 and configure | |
156f5a78 | 73 | /sys/kernel/debug/fail*/interval for such testcases. |
de1ba09b | 74 | |
156f5a78 | 75 | - /sys/kernel/debug/fail*/interval: |
de1ba09b AM |
76 | |
77 | specifies the interval between failures, for calls to | |
78 | should_fail() that pass all the other tests. | |
79 | ||
80 | Note that if you enable this, by setting interval>1, you will | |
81 | probably want to set probability=100. | |
82 | ||
156f5a78 | 83 | - /sys/kernel/debug/fail*/times: |
de1ba09b | 84 | |
00574752 | 85 | specifies how many times failures may happen at most. A value of -1 |
d472cf79 | 86 | means "no limit". |
de1ba09b | 87 | |
156f5a78 | 88 | - /sys/kernel/debug/fail*/space: |
de1ba09b AM |
89 | |
90 | specifies an initial resource "budget", decremented by "size" | |
91 | on each call to should_fail(,size). Failure injection is | |
92 | suppressed until "space" reaches zero. | |
93 | ||
156f5a78 | 94 | - /sys/kernel/debug/fail*/verbose |
de1ba09b AM |
95 | |
96 | Format: { 0 | 1 | 2 } | |
10ffebbe | 97 | |
5d0ffa2b DM |
98 | specifies the verbosity of the messages when failure is |
99 | injected. '0' means no messages; '1' will print only a single | |
100 | log line per failure; '2' will print a call trace too -- useful | |
101 | to debug the problems revealed by fault injection. | |
de1ba09b | 102 | |
156f5a78 | 103 | - /sys/kernel/debug/fail*/task-filter: |
de1ba09b | 104 | |
5d0ffa2b | 105 | Format: { 'Y' | 'N' } |
10ffebbe | 106 | |
5d0ffa2b | 107 | A value of 'N' disables filtering by process (default). |
de1ba09b AM |
108 | Any positive value limits failures to only processes indicated by |
109 | /proc/<pid>/make-it-fail==1. | |
110 | ||
10ffebbe MCC |
111 | - /sys/kernel/debug/fail*/require-start, |
112 | /sys/kernel/debug/fail*/require-end, | |
113 | /sys/kernel/debug/fail*/reject-start, | |
114 | /sys/kernel/debug/fail*/reject-end: | |
de1ba09b AM |
115 | |
116 | specifies the range of virtual addresses tested during | |
117 | stacktrace walking. Failure is injected only if some caller | |
329409ae AM |
118 | in the walked stacktrace lies within the required range, and |
119 | none lies within the rejected range. | |
120 | Default required range is [0,ULONG_MAX) (whole of virtual address space). | |
121 | Default rejected range is [0,0). | |
de1ba09b | 122 | |
156f5a78 | 123 | - /sys/kernel/debug/fail*/stacktrace-depth: |
de1ba09b AM |
124 | |
125 | specifies the maximum stacktrace depth walked during search | |
5d0ffa2b DM |
126 | for a caller within [require-start,require-end) OR |
127 | [reject-start,reject-end). | |
de1ba09b | 128 | |
156f5a78 | 129 | - /sys/kernel/debug/fail_page_alloc/ignore-gfp-highmem: |
de1ba09b | 130 | |
5d0ffa2b | 131 | Format: { 'Y' | 'N' } |
10ffebbe | 132 | |
bad3fbb2 DY |
133 | default is 'Y', setting it to 'N' will also inject failures into |
134 | highmem/user allocations (__GFP_HIGHMEM allocations). | |
de1ba09b | 135 | |
156f5a78 GL |
136 | - /sys/kernel/debug/failslab/ignore-gfp-wait: |
137 | - /sys/kernel/debug/fail_page_alloc/ignore-gfp-wait: | |
de1ba09b | 138 | |
5d0ffa2b | 139 | Format: { 'Y' | 'N' } |
10ffebbe | 140 | |
bad3fbb2 DY |
141 | default is 'Y', setting it to 'N' will also inject failures |
142 | into allocations that can sleep (__GFP_DIRECT_RECLAIM allocations). | |
de1ba09b | 143 | |
156f5a78 | 144 | - /sys/kernel/debug/fail_page_alloc/min-order: |
54114994 AM |
145 | |
146 | specifies the minimum page allocation order to be injected | |
147 | failures. | |
148 | ||
ab51fbab DB |
149 | - /sys/kernel/debug/fail_futex/ignore-private: |
150 | ||
151 | Format: { 'Y' | 'N' } | |
10ffebbe | 152 | |
ab51fbab DB |
153 | default is 'N', setting it to 'Y' will disable failure injections |
154 | when dealing with private (address space) futexes. | |
155 | ||
400edd8c CL |
156 | - /sys/kernel/debug/fail_sunrpc/ignore-client-disconnect: |
157 | ||
158 | Format: { 'Y' | 'N' } | |
159 | ||
160 | default is 'N', setting it to 'Y' will disable disconnect | |
161 | injection on the RPC client. | |
162 | ||
163 | - /sys/kernel/debug/fail_sunrpc/ignore-server-disconnect: | |
164 | ||
165 | Format: { 'Y' | 'N' } | |
166 | ||
167 | default is 'N', setting it to 'Y' will disable disconnect | |
168 | injection on the RPC server. | |
169 | ||
36f2ef2d CL |
170 | - /sys/kernel/debug/fail_sunrpc/ignore-cache-wait: |
171 | ||
172 | Format: { 'Y' | 'N' } | |
173 | ||
174 | default is 'N', setting it to 'Y' will disable cache wait | |
175 | injection on the RPC server. | |
176 | ||
4b1a29a7 MH |
177 | - /sys/kernel/debug/fail_function/inject: |
178 | ||
179 | Format: { 'function-name' | '!function-name' | '' } | |
10ffebbe | 180 | |
4b1a29a7 MH |
181 | specifies the target function of error injection by name. |
182 | If the function name leads '!' prefix, given function is | |
183 | removed from injection list. If nothing specified ('') | |
184 | injection list is cleared. | |
185 | ||
186 | - /sys/kernel/debug/fail_function/injectable: | |
187 | ||
188 | (read only) shows error injectable functions and what type of | |
189 | error values can be specified. The error type will be one of | |
190 | below; | |
191 | - NULL: retval must be 0. | |
192 | - ERRNO: retval must be -1 to -MAX_ERRNO (-4096). | |
193 | - ERR_NULL: retval must be 0 or -1 to -MAX_ERRNO (-4096). | |
194 | ||
00574752 | 195 | - /sys/kernel/debug/fail_function/<function-name>/retval: |
4b1a29a7 | 196 | |
00574752 WS |
197 | specifies the "error" return value to inject to the given function. |
198 | This will be created when the user specifies a new injection entry. | |
199 | Note that this file only accepts unsigned values. So, if you want to | |
200 | use a negative errno, you better use 'printf' instead of 'echo', e.g.: | |
201 | $ printf %#x -12 > retval | |
4b1a29a7 | 202 | |
10ffebbe MCC |
203 | Boot option |
204 | ^^^^^^^^^^^ | |
de1ba09b AM |
205 | |
206 | In order to inject faults while debugfs is not available (early boot time), | |
10ffebbe | 207 | use the boot option:: |
de1ba09b AM |
208 | |
209 | failslab= | |
210 | fail_page_alloc= | |
2c739ced | 211 | fail_usercopy= |
1e4cb22b | 212 | fail_make_request= |
ab51fbab | 213 | fail_futex= |
199e3f4b | 214 | mmc_core.fail_request=<interval>,<probability>,<space>,<times> |
de1ba09b | 215 | |
10ffebbe MCC |
216 | proc entries |
217 | ^^^^^^^^^^^^ | |
e41d5818 | 218 | |
10ffebbe MCC |
219 | - /proc/<pid>/fail-nth, |
220 | /proc/self/task/<tid>/fail-nth: | |
e41d5818 | 221 | |
9049f2f6 | 222 | Write to this file of integer N makes N-th call in the task fail. |
bfc74093 AM |
223 | Read from this file returns a integer value. A value of '0' indicates |
224 | that the fault setup with a previous write to this file was injected. | |
225 | A positive integer N indicates that the fault wasn't yet injected. | |
e41d5818 DV |
226 | Note that this file enables all types of faults (slab, futex, etc). |
227 | This setting takes precedence over all other generic debugfs settings | |
228 | like probability, interval, times, etc. But per-capability settings | |
229 | (e.g. fail_futex/ignore-private) take precedence over it. | |
230 | ||
231 | This feature is intended for systematic testing of faults in a single | |
232 | system call. See an example below. | |
233 | ||
bef7ec4e MHG |
234 | |
235 | Error Injectable Functions | |
236 | -------------------------- | |
237 | ||
238 | This part is for the kenrel developers considering to add a function to | |
239 | ALLOW_ERROR_INJECTION() macro. | |
240 | ||
241 | Requirements for the Error Injectable Functions | |
242 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
243 | ||
244 | Since the function-level error injection forcibly changes the code path | |
245 | and returns an error even if the input and conditions are proper, this can | |
246 | cause unexpected kernel crash if you allow error injection on the function | |
247 | which is NOT error injectable. Thus, you (and reviewers) must ensure; | |
248 | ||
249 | - The function returns an error code if it fails, and the callers must check | |
250 | it correctly (need to recover from it). | |
251 | ||
252 | - The function does not execute any code which can change any state before | |
253 | the first error return. The state includes global or local, or input | |
254 | variable. For example, clear output address storage (e.g. `*ret = NULL`), | |
255 | increments/decrements counter, set a flag, preempt/irq disable or get | |
256 | a lock (if those are recovered before returning error, that will be OK.) | |
257 | ||
258 | The first requirement is important, and it will result in that the release | |
259 | (free objects) functions are usually harder to inject errors than allocate | |
260 | functions. If errors of such release functions are not correctly handled | |
261 | it will cause a memory leak easily (the caller will confuse that the object | |
262 | has been released or corrupted.) | |
263 | ||
264 | The second one is for the caller which expects the function should always | |
265 | does something. Thus if the function error injection skips whole of the | |
266 | function, the expectation is betrayed and causes an unexpected error. | |
267 | ||
268 | Type of the Error Injectable Functions | |
269 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
270 | ||
271 | Each error injectable functions will have the error type specified by the | |
272 | ALLOW_ERROR_INJECTION() macro. You have to choose it carefully if you add | |
273 | a new error injectable function. If the wrong error type is chosen, the | |
274 | kernel may crash because it may not be able to handle the error. | |
275 | There are 4 types of errors defined in include/asm-generic/error-injection.h | |
276 | ||
277 | EI_ETYPE_NULL | |
278 | This function will return `NULL` if it fails. e.g. return an allocateed | |
279 | object address. | |
280 | ||
281 | EI_ETYPE_ERRNO | |
282 | This function will return an `-errno` error code if it fails. e.g. return | |
283 | -EINVAL if the input is wrong. This will include the functions which will | |
284 | return an address which encodes `-errno` by ERR_PTR() macro. | |
285 | ||
286 | EI_ETYPE_ERRNO_NULL | |
287 | This function will return an `-errno` or `NULL` if it fails. If the caller | |
288 | of this function checks the return value with IS_ERR_OR_NULL() macro, this | |
289 | type will be appropriate. | |
290 | ||
291 | EI_ETYPE_TRUE | |
292 | This function will return `true` (non-zero positive value) if it fails. | |
293 | ||
294 | If you specifies a wrong type, for example, EI_TYPE_ERRNO for the function | |
295 | which returns an allocated object, it may cause a problem because the returned | |
296 | value is not an object address and the caller can not access to the address. | |
297 | ||
298 | ||
de1ba09b AM |
299 | How to add new fault injection capability |
300 | ----------------------------------------- | |
301 | ||
10ffebbe | 302 | - #include <linux/fault-inject.h> |
de1ba09b | 303 | |
10ffebbe | 304 | - define the fault attributes |
de1ba09b | 305 | |
2d87948a | 306 | DECLARE_FAULT_ATTR(name); |
de1ba09b AM |
307 | |
308 | Please see the definition of struct fault_attr in fault-inject.h | |
309 | for details. | |
310 | ||
10ffebbe | 311 | - provide a way to configure fault attributes |
de1ba09b AM |
312 | |
313 | - boot option | |
314 | ||
315 | If you need to enable the fault injection capability from boot time, you can | |
5d0ffa2b | 316 | provide boot option to configure it. There is a helper function for it: |
de1ba09b | 317 | |
5d0ffa2b | 318 | setup_fault_attr(attr, str); |
de1ba09b AM |
319 | |
320 | - debugfs entries | |
321 | ||
2c739ced | 322 | failslab, fail_page_alloc, fail_usercopy, and fail_make_request use this way. |
5d0ffa2b | 323 | Helper functions: |
de1ba09b | 324 | |
dd48c085 | 325 | fault_create_debugfs_attr(name, parent, attr); |
de1ba09b AM |
326 | |
327 | - module parameters | |
328 | ||
329 | If the scope of the fault injection capability is limited to a | |
330 | single kernel module, it is better to provide module parameters to | |
331 | configure the fault attributes. | |
332 | ||
10ffebbe | 333 | - add a hook to insert failures |
de1ba09b | 334 | |
10ffebbe | 335 | Upon should_fail() returning true, client code should inject a failure: |
de1ba09b | 336 | |
5d0ffa2b | 337 | should_fail(attr, size); |
de1ba09b AM |
338 | |
339 | Application Examples | |
340 | -------------------- | |
341 | ||
10ffebbe | 342 | - Inject slab allocation failures into module init/exit code:: |
de1ba09b | 343 | |
10ffebbe | 344 | #!/bin/bash |
de1ba09b | 345 | |
10ffebbe MCC |
346 | FAILTYPE=failslab |
347 | echo Y > /sys/kernel/debug/$FAILTYPE/task-filter | |
348 | echo 10 > /sys/kernel/debug/$FAILTYPE/probability | |
349 | echo 100 > /sys/kernel/debug/$FAILTYPE/interval | |
d472cf79 | 350 | echo -1 > /sys/kernel/debug/$FAILTYPE/times |
10ffebbe MCC |
351 | echo 0 > /sys/kernel/debug/$FAILTYPE/space |
352 | echo 2 > /sys/kernel/debug/$FAILTYPE/verbose | |
bad3fbb2 | 353 | echo Y > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait |
de1ba09b | 354 | |
10ffebbe MCC |
355 | faulty_system() |
356 | { | |
18584870 | 357 | bash -c "echo 1 > /proc/self/make-it-fail && exec $*" |
10ffebbe | 358 | } |
de1ba09b | 359 | |
10ffebbe MCC |
360 | if [ $# -eq 0 ] |
361 | then | |
18584870 AM |
362 | echo "Usage: $0 modulename [ modulename ... ]" |
363 | exit 1 | |
10ffebbe | 364 | fi |
18584870 | 365 | |
10ffebbe MCC |
366 | for m in $* |
367 | do | |
18584870 AM |
368 | echo inserting $m... |
369 | faulty_system modprobe $m | |
de1ba09b | 370 | |
18584870 AM |
371 | echo removing $m... |
372 | faulty_system modprobe -r $m | |
10ffebbe | 373 | done |
de1ba09b AM |
374 | |
375 | ------------------------------------------------------------------------------ | |
376 | ||
10ffebbe | 377 | - Inject page allocation failures only for a specific module:: |
de1ba09b | 378 | |
10ffebbe | 379 | #!/bin/bash |
de1ba09b | 380 | |
10ffebbe MCC |
381 | FAILTYPE=fail_page_alloc |
382 | module=$1 | |
de1ba09b | 383 | |
10ffebbe MCC |
384 | if [ -z $module ] |
385 | then | |
18584870 AM |
386 | echo "Usage: $0 <modulename>" |
387 | exit 1 | |
10ffebbe | 388 | fi |
de1ba09b | 389 | |
10ffebbe | 390 | modprobe $module |
de1ba09b | 391 | |
10ffebbe MCC |
392 | if [ ! -d /sys/module/$module/sections ] |
393 | then | |
18584870 AM |
394 | echo Module $module is not loaded |
395 | exit 1 | |
10ffebbe | 396 | fi |
18584870 | 397 | |
10ffebbe MCC |
398 | cat /sys/module/$module/sections/.text > /sys/kernel/debug/$FAILTYPE/require-start |
399 | cat /sys/module/$module/sections/.data > /sys/kernel/debug/$FAILTYPE/require-end | |
18584870 | 400 | |
10ffebbe MCC |
401 | echo N > /sys/kernel/debug/$FAILTYPE/task-filter |
402 | echo 10 > /sys/kernel/debug/$FAILTYPE/probability | |
403 | echo 100 > /sys/kernel/debug/$FAILTYPE/interval | |
d472cf79 | 404 | echo -1 > /sys/kernel/debug/$FAILTYPE/times |
10ffebbe MCC |
405 | echo 0 > /sys/kernel/debug/$FAILTYPE/space |
406 | echo 2 > /sys/kernel/debug/$FAILTYPE/verbose | |
bad3fbb2 DY |
407 | echo Y > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait |
408 | echo Y > /sys/kernel/debug/$FAILTYPE/ignore-gfp-highmem | |
10ffebbe | 409 | echo 10 > /sys/kernel/debug/$FAILTYPE/stacktrace-depth |
18584870 | 410 | |
10ffebbe | 411 | trap "echo 0 > /sys/kernel/debug/$FAILTYPE/probability" SIGINT SIGTERM EXIT |
18584870 | 412 | |
10ffebbe MCC |
413 | echo "Injecting errors into the module $module... (interrupt to stop)" |
414 | sleep 1000000 | |
de1ba09b | 415 | |
4b1a29a7 MH |
416 | ------------------------------------------------------------------------------ |
417 | ||
10ffebbe MCC |
418 | - Inject open_ctree error while btrfs mount:: |
419 | ||
420 | #!/bin/bash | |
421 | ||
422 | rm -f testfile.img | |
423 | dd if=/dev/zero of=testfile.img bs=1M seek=1000 count=1 | |
424 | DEVICE=$(losetup --show -f testfile.img) | |
425 | mkfs.btrfs -f $DEVICE | |
426 | mkdir -p tmpmnt | |
427 | ||
428 | FAILTYPE=fail_function | |
429 | FAILFUNC=open_ctree | |
430 | echo $FAILFUNC > /sys/kernel/debug/$FAILTYPE/inject | |
00574752 | 431 | printf %#x -12 > /sys/kernel/debug/$FAILTYPE/$FAILFUNC/retval |
10ffebbe MCC |
432 | echo N > /sys/kernel/debug/$FAILTYPE/task-filter |
433 | echo 100 > /sys/kernel/debug/$FAILTYPE/probability | |
434 | echo 0 > /sys/kernel/debug/$FAILTYPE/interval | |
d472cf79 | 435 | echo -1 > /sys/kernel/debug/$FAILTYPE/times |
10ffebbe MCC |
436 | echo 0 > /sys/kernel/debug/$FAILTYPE/space |
437 | echo 1 > /sys/kernel/debug/$FAILTYPE/verbose | |
438 | ||
439 | mount -t btrfs $DEVICE tmpmnt | |
440 | if [ $? -ne 0 ] | |
441 | then | |
4b1a29a7 | 442 | echo "SUCCESS!" |
10ffebbe | 443 | else |
4b1a29a7 MH |
444 | echo "FAILED!" |
445 | umount tmpmnt | |
10ffebbe | 446 | fi |
4b1a29a7 | 447 | |
10ffebbe | 448 | echo > /sys/kernel/debug/$FAILTYPE/inject |
4b1a29a7 | 449 | |
10ffebbe MCC |
450 | rmdir tmpmnt |
451 | losetup -d $DEVICE | |
452 | rm testfile.img | |
4b1a29a7 MH |
453 | |
454 | ||
c24aa64d AM |
455 | Tool to run command with failslab or fail_page_alloc |
456 | ---------------------------------------------------- | |
457 | In order to make it easier to accomplish the tasks mentioned above, we can use | |
458 | tools/testing/fault-injection/failcmd.sh. Please run a command | |
459 | "./tools/testing/fault-injection/failcmd.sh --help" for more information and | |
460 | see the following examples. | |
461 | ||
462 | Examples: | |
463 | ||
464 | Run a command "make -C tools/testing/selftests/ run_tests" with injecting slab | |
10ffebbe | 465 | allocation failure:: |
c24aa64d AM |
466 | |
467 | # ./tools/testing/fault-injection/failcmd.sh \ | |
468 | -- make -C tools/testing/selftests/ run_tests | |
469 | ||
470 | Same as above except to specify 100 times failures at most instead of one time | |
10ffebbe | 471 | at most by default:: |
c24aa64d AM |
472 | |
473 | # ./tools/testing/fault-injection/failcmd.sh --times=100 \ | |
474 | -- make -C tools/testing/selftests/ run_tests | |
475 | ||
476 | Same as above except to inject page allocation failure instead of slab | |
10ffebbe | 477 | allocation failure:: |
c24aa64d AM |
478 | |
479 | # env FAILCMD_TYPE=fail_page_alloc \ | |
480 | ./tools/testing/fault-injection/failcmd.sh --times=100 \ | |
10ffebbe | 481 | -- make -C tools/testing/selftests/ run_tests |
e41d5818 DV |
482 | |
483 | Systematic faults using fail-nth | |
484 | --------------------------------- | |
485 | ||
486 | The following code systematically faults 0-th, 1-st, 2-nd and so on | |
10ffebbe MCC |
487 | capabilities in the socketpair() system call:: |
488 | ||
489 | #include <sys/types.h> | |
490 | #include <sys/stat.h> | |
491 | #include <sys/socket.h> | |
492 | #include <sys/syscall.h> | |
493 | #include <fcntl.h> | |
494 | #include <unistd.h> | |
495 | #include <string.h> | |
496 | #include <stdlib.h> | |
497 | #include <stdio.h> | |
498 | #include <errno.h> | |
499 | ||
500 | int main() | |
501 | { | |
e41d5818 DV |
502 | int i, err, res, fail_nth, fds[2]; |
503 | char buf[128]; | |
504 | ||
505 | system("echo N > /sys/kernel/debug/failslab/ignore-gfp-wait"); | |
506 | sprintf(buf, "/proc/self/task/%ld/fail-nth", syscall(SYS_gettid)); | |
507 | fail_nth = open(buf, O_RDWR); | |
9049f2f6 | 508 | for (i = 1;; i++) { |
e41d5818 DV |
509 | sprintf(buf, "%d", i); |
510 | write(fail_nth, buf, strlen(buf)); | |
511 | res = socketpair(AF_LOCAL, SOCK_STREAM, 0, fds); | |
512 | err = errno; | |
bfc74093 | 513 | pread(fail_nth, buf, sizeof(buf), 0); |
e41d5818 DV |
514 | if (res == 0) { |
515 | close(fds[0]); | |
516 | close(fds[1]); | |
517 | } | |
bfc74093 AM |
518 | printf("%d-th fault %c: res=%d/%d\n", i, atoi(buf) ? 'N' : 'Y', |
519 | res, err); | |
520 | if (atoi(buf)) | |
e41d5818 DV |
521 | break; |
522 | } | |
523 | return 0; | |
10ffebbe MCC |
524 | } |
525 | ||
526 | An example output:: | |
527 | ||
528 | 1-th fault Y: res=-1/23 | |
529 | 2-th fault Y: res=-1/23 | |
530 | 3-th fault Y: res=-1/12 | |
531 | 4-th fault Y: res=-1/12 | |
532 | 5-th fault Y: res=-1/23 | |
533 | 6-th fault Y: res=-1/23 | |
534 | 7-th fault Y: res=-1/23 | |
535 | 8-th fault Y: res=-1/12 | |
536 | 9-th fault Y: res=-1/12 | |
537 | 10-th fault Y: res=-1/12 | |
538 | 11-th fault Y: res=-1/12 | |
539 | 12-th fault Y: res=-1/12 | |
540 | 13-th fault Y: res=-1/12 | |
541 | 14-th fault Y: res=-1/12 | |
542 | 15-th fault Y: res=-1/12 | |
543 | 16-th fault N: res=0/12 |