fault-inject.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2#include <linux/kernel.h>
  3#include <linux/init.h>
  4#include <linux/prandom.h>
  5#include <linux/debugfs.h>
  6#include <linux/sched.h>
  7#include <linux/stat.h>
  8#include <linux/types.h>
  9#include <linux/fs.h>
 10#include <linux/export.h>
 11#include <linux/interrupt.h>
 12#include <linux/stacktrace.h>
 13#include <linux/fault-inject.h>
 14
 15/*
 16 * The should_fail() functions use prandom instead of the normal Linux RNG
 17 * since they don't need cryptographically secure random numbers.
 18 */
 19static DEFINE_PER_CPU(struct rnd_state, fault_rnd_state);
 20
 21static u32 fault_prandom_u32_below_100(void)
 22{
 23	struct rnd_state *state;
 24	u32 res;
 25
 26	state = &get_cpu_var(fault_rnd_state);
 27	res = prandom_u32_state(state);
 28	put_cpu_var(fault_rnd_state);
 29
 30	return res % 100;
 31}
 32
 33/*
 34 * setup_fault_attr() is a helper function for various __setup handlers, so it
 35 * returns 0 on error, because that is what __setup handlers do.
 36 */
 37int setup_fault_attr(struct fault_attr *attr, char *str)
 38{
 39	unsigned long probability;
 40	unsigned long interval;
 41	int times;
 42	int space;
 43
 44	/* "<interval>,<probability>,<space>,<times>" */
 45	if (sscanf(str, "%lu,%lu,%d,%d",
 46			&interval, &probability, &space, &times) < 4) {
 47		printk(KERN_WARNING
 48			"FAULT_INJECTION: failed to parse arguments\n");
 49		return 0;
 50	}
 51
 52	prandom_init_once(&fault_rnd_state);
 53
 54	attr->probability = probability;
 55	attr->interval = interval;
 56	atomic_set(&attr->times, times);
 57	atomic_set(&attr->space, space);
 58
 59	return 1;
 60}
 61EXPORT_SYMBOL_GPL(setup_fault_attr);
 62
 63static void fail_dump(struct fault_attr *attr)
 64{
 65	if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
 66		printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
 67		       "name %pd, interval %lu, probability %lu, "
 68		       "space %d, times %d\n", attr->dname,
 69		       attr->interval, attr->probability,
 70		       atomic_read(&attr->space),
 71		       atomic_read(&attr->times));
 72		if (attr->verbose > 1)
 73			dump_stack();
 74	}
 75}
 76
 77#define atomic_dec_not_zero(v)		atomic_add_unless((v), -1, 0)
 78
 79static bool fail_task(struct fault_attr *attr, struct task_struct *task)
 80{
 81	return in_task() && task->make_it_fail;
 82}
 83
 84#define MAX_STACK_TRACE_DEPTH 32
 85
 86#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 87
 88static bool fail_stacktrace(struct fault_attr *attr)
 89{
 90	int depth = attr->stacktrace_depth;
 91	unsigned long entries[MAX_STACK_TRACE_DEPTH];
 92	int n, nr_entries;
 93	bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
 94
 95	if (depth == 0 || (found && !attr->reject_start && !attr->reject_end))
 96		return found;
 97
 98	nr_entries = stack_trace_save(entries, depth, 1);
 99	for (n = 0; n < nr_entries; n++) {
100		if (attr->reject_start <= entries[n] &&
101			       entries[n] < attr->reject_end)
102			return false;
103		if (attr->require_start <= entries[n] &&
104			       entries[n] < attr->require_end)
105			found = true;
106	}
107	return found;
108}
109
110#else
111
112static inline bool fail_stacktrace(struct fault_attr *attr)
113{
114	return true;
115}
116
117#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
118
119/*
120 * This code is stolen from failmalloc-1.0
121 * http://www.nongnu.org/failmalloc/
122 */
123
124bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags)
125{
126	bool stack_checked = false;
127
128	if (in_task()) {
129		unsigned int fail_nth = READ_ONCE(current->fail_nth);
130
131		if (fail_nth) {
132			if (!fail_stacktrace(attr))
133				return false;
134
135			stack_checked = true;
136			fail_nth--;
137			WRITE_ONCE(current->fail_nth, fail_nth);
138			if (!fail_nth)
139				goto fail;
140
141			return false;
142		}
143	}
144
145	/* No need to check any other properties if the probability is 0 */
146	if (attr->probability == 0)
147		return false;
148
149	if (attr->task_filter && !fail_task(attr, current))
150		return false;
151
152	if (atomic_read(&attr->times) == 0)
153		return false;
154
155	if (!stack_checked && !fail_stacktrace(attr))
156		return false;
157
158	if (atomic_read(&attr->space) > size) {
159		atomic_sub(size, &attr->space);
160		return false;
161	}
162
163	if (attr->interval > 1) {
164		attr->count++;
165		if (attr->count % attr->interval)
166			return false;
167	}
168
169	if (attr->probability <= fault_prandom_u32_below_100())
170		return false;
171
172fail:
173	if (!(flags & FAULT_NOWARN))
174		fail_dump(attr);
175
176	if (atomic_read(&attr->times) != -1)
177		atomic_dec_not_zero(&attr->times);
178
179	return true;
180}
181
182bool should_fail(struct fault_attr *attr, ssize_t size)
183{
184	return should_fail_ex(attr, size, 0);
185}
186EXPORT_SYMBOL_GPL(should_fail);
187
188#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
189
190static int debugfs_ul_set(void *data, u64 val)
191{
192	*(unsigned long *)data = val;
193	return 0;
194}
195
196static int debugfs_ul_get(void *data, u64 *val)
197{
198	*val = *(unsigned long *)data;
199	return 0;
200}
201
202DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
203
204static void debugfs_create_ul(const char *name, umode_t mode,
205			      struct dentry *parent, unsigned long *value)
206{
207	debugfs_create_file(name, mode, parent, value, &fops_ul);
208}
209
210#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
211
212static int debugfs_stacktrace_depth_set(void *data, u64 val)
213{
214	*(unsigned long *)data =
215		min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
216
217	return 0;
218}
219
220DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
221			debugfs_stacktrace_depth_set, "%llu\n");
222
223static void debugfs_create_stacktrace_depth(const char *name, umode_t mode,
224					    struct dentry *parent,
225					    unsigned long *value)
226{
227	debugfs_create_file(name, mode, parent, value, &fops_stacktrace_depth);
228}
229
230#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
231
232struct dentry *fault_create_debugfs_attr(const char *name,
233			struct dentry *parent, struct fault_attr *attr)
234{
235	umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
236	struct dentry *dir;
237
238	dir = debugfs_create_dir(name, parent);
239	if (IS_ERR(dir))
240		return dir;
241
242	prandom_init_once(&fault_rnd_state);
243
244	debugfs_create_ul("probability", mode, dir, &attr->probability);
245	debugfs_create_ul("interval", mode, dir, &attr->interval);
246	debugfs_create_atomic_t("times", mode, dir, &attr->times);
247	debugfs_create_atomic_t("space", mode, dir, &attr->space);
248	debugfs_create_ul("verbose", mode, dir, &attr->verbose);
249	debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
250			   &attr->ratelimit_state.interval);
251	debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
252			   &attr->ratelimit_state.burst);
253	debugfs_create_bool("task-filter", mode, dir, &attr->task_filter);
254
255#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
256	debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
257					&attr->stacktrace_depth);
258	debugfs_create_xul("require-start", mode, dir, &attr->require_start);
259	debugfs_create_xul("require-end", mode, dir, &attr->require_end);
260	debugfs_create_xul("reject-start", mode, dir, &attr->reject_start);
261	debugfs_create_xul("reject-end", mode, dir, &attr->reject_end);
262#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
263
264	attr->dname = dget(dir);
265	return dir;
266}
267EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
268
269#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
270
271#ifdef CONFIG_FAULT_INJECTION_CONFIGFS
272
273/* These configfs attribute utilities are copied from drivers/block/null_blk/main.c */
274
275static ssize_t fault_uint_attr_show(unsigned int val, char *page)
276{
277	return snprintf(page, PAGE_SIZE, "%u\n", val);
278}
279
280static ssize_t fault_ulong_attr_show(unsigned long val, char *page)
281{
282	return snprintf(page, PAGE_SIZE, "%lu\n", val);
283}
284
285static ssize_t fault_bool_attr_show(bool val, char *page)
286{
287	return snprintf(page, PAGE_SIZE, "%u\n", val);
288}
289
290static ssize_t fault_atomic_t_attr_show(atomic_t val, char *page)
291{
292	return snprintf(page, PAGE_SIZE, "%d\n", atomic_read(&val));
293}
294
295static ssize_t fault_uint_attr_store(unsigned int *val, const char *page, size_t count)
296{
297	unsigned int tmp;
298	int result;
299
300	result = kstrtouint(page, 0, &tmp);
301	if (result < 0)
302		return result;
303
304	*val = tmp;
305	return count;
306}
307
308static ssize_t fault_ulong_attr_store(unsigned long *val, const char *page, size_t count)
309{
310	int result;
311	unsigned long tmp;
312
313	result = kstrtoul(page, 0, &tmp);
314	if (result < 0)
315		return result;
316
317	*val = tmp;
318	return count;
319}
320
321static ssize_t fault_bool_attr_store(bool *val, const char *page, size_t count)
322{
323	bool tmp;
324	int result;
325
326	result = kstrtobool(page, &tmp);
327	if (result < 0)
328		return result;
329
330	*val = tmp;
331	return count;
332}
333
334static ssize_t fault_atomic_t_attr_store(atomic_t *val, const char *page, size_t count)
335{
336	int tmp;
337	int result;
338
339	result = kstrtoint(page, 0, &tmp);
340	if (result < 0)
341		return result;
342
343	atomic_set(val, tmp);
344	return count;
345}
346
347#define CONFIGFS_ATTR_NAMED(_pfx, _name, _attr_name)	\
348static struct configfs_attribute _pfx##attr_##_name = {	\
349	.ca_name	= _attr_name,			\
350	.ca_mode	= 0644,				\
351	.ca_owner	= THIS_MODULE,			\
352	.show		= _pfx##_name##_show,		\
353	.store		= _pfx##_name##_store,		\
354}
355
356static struct fault_config *to_fault_config(struct config_item *item)
357{
358	return container_of(to_config_group(item), struct fault_config, group);
359}
360
361#define FAULT_CONFIGFS_ATTR_NAMED(NAME, ATTR_NAME, MEMBER, TYPE)				\
362static ssize_t fault_##NAME##_show(struct config_item *item, char *page)			\
363{												\
364	return fault_##TYPE##_attr_show(to_fault_config(item)->attr.MEMBER, page);		\
365}												\
366static ssize_t fault_##NAME##_store(struct config_item *item, const char *page, size_t count)	\
367{												\
368	struct fault_config *config = to_fault_config(item);					\
369	return fault_##TYPE##_attr_store(&config->attr.MEMBER, page, count);			\
370}												\
371CONFIGFS_ATTR_NAMED(fault_, NAME, ATTR_NAME)
372
373#define FAULT_CONFIGFS_ATTR(NAME, TYPE)	\
374	FAULT_CONFIGFS_ATTR_NAMED(NAME, __stringify(NAME), NAME, TYPE)
375
376FAULT_CONFIGFS_ATTR(probability, ulong);
377FAULT_CONFIGFS_ATTR(interval, ulong);
378FAULT_CONFIGFS_ATTR(times, atomic_t);
379FAULT_CONFIGFS_ATTR(space, atomic_t);
380FAULT_CONFIGFS_ATTR(verbose, ulong);
381FAULT_CONFIGFS_ATTR_NAMED(ratelimit_interval, "verbose_ratelimit_interval_ms",
382		ratelimit_state.interval, uint);
383FAULT_CONFIGFS_ATTR_NAMED(ratelimit_burst, "verbose_ratelimit_burst",
384		ratelimit_state.burst, uint);
385FAULT_CONFIGFS_ATTR_NAMED(task_filter, "task-filter", task_filter, bool);
386
387#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
388
389static ssize_t fault_stacktrace_depth_show(struct config_item *item, char *page)
390{
391	return fault_ulong_attr_show(to_fault_config(item)->attr.stacktrace_depth, page);
392}
393
394static ssize_t fault_stacktrace_depth_store(struct config_item *item, const char *page,
395		size_t count)
396{
397	int result;
398	unsigned long tmp;
399
400	result = kstrtoul(page, 0, &tmp);
401	if (result < 0)
402		return result;
403
404	to_fault_config(item)->attr.stacktrace_depth =
405		min_t(unsigned long, tmp, MAX_STACK_TRACE_DEPTH);
406
407	return count;
408}
409
410CONFIGFS_ATTR_NAMED(fault_, stacktrace_depth, "stacktrace-depth");
411
412static ssize_t fault_xul_attr_show(unsigned long val, char *page)
413{
414	return snprintf(page, PAGE_SIZE,
415			sizeof(val) == sizeof(u32) ? "0x%08lx\n" : "0x%016lx\n", val);
416}
417
418static ssize_t fault_xul_attr_store(unsigned long *val, const char *page, size_t count)
419{
420	return fault_ulong_attr_store(val, page, count);
421}
422
423FAULT_CONFIGFS_ATTR_NAMED(require_start, "require-start", require_start, xul);
424FAULT_CONFIGFS_ATTR_NAMED(require_end, "require-end", require_end, xul);
425FAULT_CONFIGFS_ATTR_NAMED(reject_start, "reject-start", reject_start, xul);
426FAULT_CONFIGFS_ATTR_NAMED(reject_end, "reject-end", reject_end, xul);
427
428#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
429
430static struct configfs_attribute *fault_config_attrs[] = {
431	&fault_attr_probability,
432	&fault_attr_interval,
433	&fault_attr_times,
434	&fault_attr_space,
435	&fault_attr_verbose,
436	&fault_attr_ratelimit_interval,
437	&fault_attr_ratelimit_burst,
438	&fault_attr_task_filter,
439#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
440	&fault_attr_stacktrace_depth,
441	&fault_attr_require_start,
442	&fault_attr_require_end,
443	&fault_attr_reject_start,
444	&fault_attr_reject_end,
445#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
446	NULL,
447};
448
449static const struct config_item_type fault_config_type = {
450	.ct_attrs	= fault_config_attrs,
451	.ct_owner	= THIS_MODULE,
452};
453
454void fault_config_init(struct fault_config *config, const char *name)
455{
456	prandom_init_once(&fault_rnd_state);
457
458	config_group_init_type_name(&config->group, name, &fault_config_type);
459}
460EXPORT_SYMBOL_GPL(fault_config_init);
461
462#endif /* CONFIG_FAULT_INJECTION_CONFIGFS */