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1 | Fault injection capabilities infrastructure |
2 | =========================================== | |
3 | ||
4 | See also drivers/md/faulty.c and "every_nth" module option for scsi_debug. | |
5 | ||
6 | ||
7 | Available fault injection capabilities | |
8 | -------------------------------------- | |
9 | ||
10 | o failslab | |
11 | ||
12 | injects slab allocation failures. (kmalloc(), kmem_cache_alloc(), ...) | |
13 | ||
14 | o fail_page_alloc | |
15 | ||
16 | injects page allocation failures. (alloc_pages(), get_free_pages(), ...) | |
17 | ||
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18 | o fail_futex |
19 | ||
20 | injects futex deadlock and uaddr fault errors. | |
21 | ||
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22 | o fail_make_request |
23 | ||
5d0ffa2b | 24 | injects disk IO errors on devices permitted by setting |
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25 | /sys/block/<device>/make-it-fail or |
26 | /sys/block/<device>/<partition>/make-it-fail. (generic_make_request()) | |
27 | ||
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28 | o fail_mmc_request |
29 | ||
30 | injects MMC data errors on devices permitted by setting | |
31 | debugfs entries under /sys/kernel/debug/mmc0/fail_mmc_request | |
32 | ||
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33 | Configure fault-injection capabilities behavior |
34 | ----------------------------------------------- | |
35 | ||
36 | o debugfs entries | |
37 | ||
38 | fault-inject-debugfs kernel module provides some debugfs entries for runtime | |
39 | configuration of fault-injection capabilities. | |
40 | ||
156f5a78 | 41 | - /sys/kernel/debug/fail*/probability: |
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42 | |
43 | likelihood of failure injection, in percent. | |
44 | Format: <percent> | |
45 | ||
5d0ffa2b DM |
46 | Note that one-failure-per-hundred is a very high error rate |
47 | for some testcases. Consider setting probability=100 and configure | |
156f5a78 | 48 | /sys/kernel/debug/fail*/interval for such testcases. |
de1ba09b | 49 | |
156f5a78 | 50 | - /sys/kernel/debug/fail*/interval: |
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51 | |
52 | specifies the interval between failures, for calls to | |
53 | should_fail() that pass all the other tests. | |
54 | ||
55 | Note that if you enable this, by setting interval>1, you will | |
56 | probably want to set probability=100. | |
57 | ||
156f5a78 | 58 | - /sys/kernel/debug/fail*/times: |
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59 | |
60 | specifies how many times failures may happen at most. | |
61 | A value of -1 means "no limit". | |
62 | ||
156f5a78 | 63 | - /sys/kernel/debug/fail*/space: |
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64 | |
65 | specifies an initial resource "budget", decremented by "size" | |
66 | on each call to should_fail(,size). Failure injection is | |
67 | suppressed until "space" reaches zero. | |
68 | ||
156f5a78 | 69 | - /sys/kernel/debug/fail*/verbose |
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70 | |
71 | Format: { 0 | 1 | 2 } | |
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72 | specifies the verbosity of the messages when failure is |
73 | injected. '0' means no messages; '1' will print only a single | |
74 | log line per failure; '2' will print a call trace too -- useful | |
75 | to debug the problems revealed by fault injection. | |
de1ba09b | 76 | |
156f5a78 | 77 | - /sys/kernel/debug/fail*/task-filter: |
de1ba09b | 78 | |
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79 | Format: { 'Y' | 'N' } |
80 | A value of 'N' disables filtering by process (default). | |
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81 | Any positive value limits failures to only processes indicated by |
82 | /proc/<pid>/make-it-fail==1. | |
83 | ||
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84 | - /sys/kernel/debug/fail*/require-start: |
85 | - /sys/kernel/debug/fail*/require-end: | |
86 | - /sys/kernel/debug/fail*/reject-start: | |
87 | - /sys/kernel/debug/fail*/reject-end: | |
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88 | |
89 | specifies the range of virtual addresses tested during | |
90 | stacktrace walking. Failure is injected only if some caller | |
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91 | in the walked stacktrace lies within the required range, and |
92 | none lies within the rejected range. | |
93 | Default required range is [0,ULONG_MAX) (whole of virtual address space). | |
94 | Default rejected range is [0,0). | |
de1ba09b | 95 | |
156f5a78 | 96 | - /sys/kernel/debug/fail*/stacktrace-depth: |
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97 | |
98 | specifies the maximum stacktrace depth walked during search | |
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99 | for a caller within [require-start,require-end) OR |
100 | [reject-start,reject-end). | |
de1ba09b | 101 | |
156f5a78 | 102 | - /sys/kernel/debug/fail_page_alloc/ignore-gfp-highmem: |
de1ba09b | 103 | |
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104 | Format: { 'Y' | 'N' } |
105 | default is 'N', setting it to 'Y' won't inject failures into | |
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106 | highmem/user allocations. |
107 | ||
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108 | - /sys/kernel/debug/failslab/ignore-gfp-wait: |
109 | - /sys/kernel/debug/fail_page_alloc/ignore-gfp-wait: | |
de1ba09b | 110 | |
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111 | Format: { 'Y' | 'N' } |
112 | default is 'N', setting it to 'Y' will inject failures | |
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113 | only into non-sleep allocations (GFP_ATOMIC allocations). |
114 | ||
156f5a78 | 115 | - /sys/kernel/debug/fail_page_alloc/min-order: |
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116 | |
117 | specifies the minimum page allocation order to be injected | |
118 | failures. | |
119 | ||
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120 | - /sys/kernel/debug/fail_futex/ignore-private: |
121 | ||
122 | Format: { 'Y' | 'N' } | |
123 | default is 'N', setting it to 'Y' will disable failure injections | |
124 | when dealing with private (address space) futexes. | |
125 | ||
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126 | o Boot option |
127 | ||
128 | In order to inject faults while debugfs is not available (early boot time), | |
129 | use the boot option: | |
130 | ||
131 | failslab= | |
132 | fail_page_alloc= | |
1e4cb22b | 133 | fail_make_request= |
ab51fbab | 134 | fail_futex= |
199e3f4b | 135 | mmc_core.fail_request=<interval>,<probability>,<space>,<times> |
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136 | |
137 | How to add new fault injection capability | |
138 | ----------------------------------------- | |
139 | ||
140 | o #include <linux/fault-inject.h> | |
141 | ||
142 | o define the fault attributes | |
143 | ||
144 | DECLARE_FAULT_INJECTION(name); | |
145 | ||
146 | Please see the definition of struct fault_attr in fault-inject.h | |
147 | for details. | |
148 | ||
5d0ffa2b | 149 | o provide a way to configure fault attributes |
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150 | |
151 | - boot option | |
152 | ||
153 | If you need to enable the fault injection capability from boot time, you can | |
5d0ffa2b | 154 | provide boot option to configure it. There is a helper function for it: |
de1ba09b | 155 | |
5d0ffa2b | 156 | setup_fault_attr(attr, str); |
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157 | |
158 | - debugfs entries | |
159 | ||
160 | failslab, fail_page_alloc, and fail_make_request use this way. | |
5d0ffa2b | 161 | Helper functions: |
de1ba09b | 162 | |
dd48c085 | 163 | fault_create_debugfs_attr(name, parent, attr); |
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164 | |
165 | - module parameters | |
166 | ||
167 | If the scope of the fault injection capability is limited to a | |
168 | single kernel module, it is better to provide module parameters to | |
169 | configure the fault attributes. | |
170 | ||
171 | o add a hook to insert failures | |
172 | ||
5d0ffa2b | 173 | Upon should_fail() returning true, client code should inject a failure. |
de1ba09b | 174 | |
5d0ffa2b | 175 | should_fail(attr, size); |
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176 | |
177 | Application Examples | |
178 | -------------------- | |
179 | ||
18584870 | 180 | o Inject slab allocation failures into module init/exit code |
de1ba09b | 181 | |
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182 | #!/bin/bash |
183 | ||
18584870 | 184 | FAILTYPE=failslab |
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185 | echo Y > /sys/kernel/debug/$FAILTYPE/task-filter |
186 | echo 10 > /sys/kernel/debug/$FAILTYPE/probability | |
187 | echo 100 > /sys/kernel/debug/$FAILTYPE/interval | |
188 | echo -1 > /sys/kernel/debug/$FAILTYPE/times | |
189 | echo 0 > /sys/kernel/debug/$FAILTYPE/space | |
190 | echo 2 > /sys/kernel/debug/$FAILTYPE/verbose | |
191 | echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait | |
de1ba09b | 192 | |
18584870 | 193 | faulty_system() |
de1ba09b | 194 | { |
18584870 | 195 | bash -c "echo 1 > /proc/self/make-it-fail && exec $*" |
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196 | } |
197 | ||
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198 | if [ $# -eq 0 ] |
199 | then | |
200 | echo "Usage: $0 modulename [ modulename ... ]" | |
201 | exit 1 | |
202 | fi | |
203 | ||
204 | for m in $* | |
205 | do | |
206 | echo inserting $m... | |
207 | faulty_system modprobe $m | |
de1ba09b | 208 | |
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209 | echo removing $m... |
210 | faulty_system modprobe -r $m | |
211 | done | |
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212 | |
213 | ------------------------------------------------------------------------------ | |
214 | ||
18584870 | 215 | o Inject page allocation failures only for a specific module |
de1ba09b | 216 | |
de1ba09b AM |
217 | #!/bin/bash |
218 | ||
18584870 AM |
219 | FAILTYPE=fail_page_alloc |
220 | module=$1 | |
de1ba09b | 221 | |
18584870 AM |
222 | if [ -z $module ] |
223 | then | |
224 | echo "Usage: $0 <modulename>" | |
225 | exit 1 | |
226 | fi | |
de1ba09b | 227 | |
18584870 | 228 | modprobe $module |
de1ba09b | 229 | |
18584870 AM |
230 | if [ ! -d /sys/module/$module/sections ] |
231 | then | |
232 | echo Module $module is not loaded | |
233 | exit 1 | |
234 | fi | |
235 | ||
156f5a78 GL |
236 | cat /sys/module/$module/sections/.text > /sys/kernel/debug/$FAILTYPE/require-start |
237 | cat /sys/module/$module/sections/.data > /sys/kernel/debug/$FAILTYPE/require-end | |
18584870 | 238 | |
156f5a78 GL |
239 | echo N > /sys/kernel/debug/$FAILTYPE/task-filter |
240 | echo 10 > /sys/kernel/debug/$FAILTYPE/probability | |
241 | echo 100 > /sys/kernel/debug/$FAILTYPE/interval | |
242 | echo -1 > /sys/kernel/debug/$FAILTYPE/times | |
243 | echo 0 > /sys/kernel/debug/$FAILTYPE/space | |
244 | echo 2 > /sys/kernel/debug/$FAILTYPE/verbose | |
245 | echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait | |
246 | echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-highmem | |
247 | echo 10 > /sys/kernel/debug/$FAILTYPE/stacktrace-depth | |
18584870 | 248 | |
156f5a78 | 249 | trap "echo 0 > /sys/kernel/debug/$FAILTYPE/probability" SIGINT SIGTERM EXIT |
18584870 AM |
250 | |
251 | echo "Injecting errors into the module $module... (interrupt to stop)" | |
252 | sleep 1000000 | |
de1ba09b | 253 | |
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254 | Tool to run command with failslab or fail_page_alloc |
255 | ---------------------------------------------------- | |
256 | In order to make it easier to accomplish the tasks mentioned above, we can use | |
257 | tools/testing/fault-injection/failcmd.sh. Please run a command | |
258 | "./tools/testing/fault-injection/failcmd.sh --help" for more information and | |
259 | see the following examples. | |
260 | ||
261 | Examples: | |
262 | ||
263 | Run a command "make -C tools/testing/selftests/ run_tests" with injecting slab | |
264 | allocation failure. | |
265 | ||
266 | # ./tools/testing/fault-injection/failcmd.sh \ | |
267 | -- make -C tools/testing/selftests/ run_tests | |
268 | ||
269 | Same as above except to specify 100 times failures at most instead of one time | |
270 | at most by default. | |
271 | ||
272 | # ./tools/testing/fault-injection/failcmd.sh --times=100 \ | |
273 | -- make -C tools/testing/selftests/ run_tests | |
274 | ||
275 | Same as above except to inject page allocation failure instead of slab | |
276 | allocation failure. | |
277 | ||
278 | # env FAILCMD_TYPE=fail_page_alloc \ | |
279 | ./tools/testing/fault-injection/failcmd.sh --times=100 \ | |
280 | -- make -C tools/testing/selftests/ run_tests |