1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/kernel.h>
3 #include <linux/init.h>
4 #include <linux/random.h>
5 #include <linux/sched.h>
6 #include <linux/stat.h>
7 #include <linux/types.h>
8 #include <linux/fs.h>
9 #include <linux/export.h>
10 #include <linux/interrupt.h>
11 #include <linux/stacktrace.h>
12 #include <linux/fault-inject.h>
13
14 /*
15 * setup_fault_attr() is a helper function for various __setup handlers, so it
16 * returns 0 on error, because that is what __setup handlers do.
17 */
setup_fault_attr(struct fault_attr * attr,char * str)18 int setup_fault_attr(struct fault_attr *attr, char *str)
19 {
20 unsigned long probability;
21 unsigned long interval;
22 int times;
23 int space;
24
25 /* "<interval>,<probability>,<space>,<times>" */
26 if (sscanf(str, "%lu,%lu,%d,%d",
27 &interval, &probability, &space, ×) < 4) {
28 printk(KERN_WARNING
29 "FAULT_INJECTION: failed to parse arguments\n");
30 return 0;
31 }
32
33 attr->probability = probability;
34 attr->interval = interval;
35 atomic_set(&attr->times, times);
36 atomic_set(&attr->space, space);
37
38 return 1;
39 }
40 EXPORT_SYMBOL_GPL(setup_fault_attr);
41
fail_dump(struct fault_attr * attr)42 static void fail_dump(struct fault_attr *attr)
43 {
44 if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
45 printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
46 "name %pd, interval %lu, probability %lu, "
47 "space %d, times %d\n", attr->dname,
48 attr->interval, attr->probability,
49 atomic_read(&attr->space),
50 atomic_read(&attr->times));
51 if (attr->verbose > 1)
52 dump_stack();
53 }
54 }
55
56 #define atomic_dec_not_zero(v) atomic_add_unless((v), -1, 0)
57
fail_task(struct fault_attr * attr,struct task_struct * task)58 static bool fail_task(struct fault_attr *attr, struct task_struct *task)
59 {
60 return in_task() && task->make_it_fail;
61 }
62
63 #define MAX_STACK_TRACE_DEPTH 32
64
65 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
66
fail_stacktrace(struct fault_attr * attr)67 static bool fail_stacktrace(struct fault_attr *attr)
68 {
69 int depth = attr->stacktrace_depth;
70 unsigned long entries[MAX_STACK_TRACE_DEPTH];
71 int n, nr_entries;
72 bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
73
74 if (depth == 0)
75 return found;
76
77 nr_entries = stack_trace_save(entries, depth, 1);
78 for (n = 0; n < nr_entries; n++) {
79 if (attr->reject_start <= entries[n] &&
80 entries[n] < attr->reject_end)
81 return false;
82 if (attr->require_start <= entries[n] &&
83 entries[n] < attr->require_end)
84 found = true;
85 }
86 return found;
87 }
88
89 #else
90
fail_stacktrace(struct fault_attr * attr)91 static inline bool fail_stacktrace(struct fault_attr *attr)
92 {
93 return true;
94 }
95
96 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
97
98 /*
99 * This code is stolen from failmalloc-1.0
100 * http://www.nongnu.org/failmalloc/
101 */
102
should_fail_ex(struct fault_attr * attr,ssize_t size,int flags)103 bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags)
104 {
105 if (in_task()) {
106 unsigned int fail_nth = READ_ONCE(current->fail_nth);
107
108 if (fail_nth) {
109 fail_nth--;
110 WRITE_ONCE(current->fail_nth, fail_nth);
111 if (!fail_nth)
112 goto fail;
113
114 return false;
115 }
116 }
117
118 /* No need to check any other properties if the probability is 0 */
119 if (attr->probability == 0)
120 return false;
121
122 if (attr->task_filter && !fail_task(attr, current))
123 return false;
124
125 if (atomic_read(&attr->times) == 0)
126 return false;
127
128 if (atomic_read(&attr->space) > size) {
129 atomic_sub(size, &attr->space);
130 return false;
131 }
132
133 if (attr->interval > 1) {
134 attr->count++;
135 if (attr->count % attr->interval)
136 return false;
137 }
138
139 if (attr->probability <= prandom_u32_max(100))
140 return false;
141
142 if (!fail_stacktrace(attr))
143 return false;
144
145 fail:
146 if (!(flags & FAULT_NOWARN))
147 fail_dump(attr);
148
149 if (atomic_read(&attr->times) != -1)
150 atomic_dec_not_zero(&attr->times);
151
152 return true;
153 }
154
should_fail(struct fault_attr * attr,ssize_t size)155 bool should_fail(struct fault_attr *attr, ssize_t size)
156 {
157 return should_fail_ex(attr, size, 0);
158 }
159 EXPORT_SYMBOL_GPL(should_fail);
160
161 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
162
debugfs_ul_set(void * data,u64 val)163 static int debugfs_ul_set(void *data, u64 val)
164 {
165 *(unsigned long *)data = val;
166 return 0;
167 }
168
debugfs_ul_get(void * data,u64 * val)169 static int debugfs_ul_get(void *data, u64 *val)
170 {
171 *val = *(unsigned long *)data;
172 return 0;
173 }
174
175 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
176
debugfs_create_ul(const char * name,umode_t mode,struct dentry * parent,unsigned long * value)177 static void debugfs_create_ul(const char *name, umode_t mode,
178 struct dentry *parent, unsigned long *value)
179 {
180 debugfs_create_file(name, mode, parent, value, &fops_ul);
181 }
182
183 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
184
debugfs_stacktrace_depth_set(void * data,u64 val)185 static int debugfs_stacktrace_depth_set(void *data, u64 val)
186 {
187 *(unsigned long *)data =
188 min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
189
190 return 0;
191 }
192
193 DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
194 debugfs_stacktrace_depth_set, "%llu\n");
195
debugfs_create_stacktrace_depth(const char * name,umode_t mode,struct dentry * parent,unsigned long * value)196 static void debugfs_create_stacktrace_depth(const char *name, umode_t mode,
197 struct dentry *parent,
198 unsigned long *value)
199 {
200 debugfs_create_file(name, mode, parent, value, &fops_stacktrace_depth);
201 }
202
203 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
204
fault_create_debugfs_attr(const char * name,struct dentry * parent,struct fault_attr * attr)205 struct dentry *fault_create_debugfs_attr(const char *name,
206 struct dentry *parent, struct fault_attr *attr)
207 {
208 umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
209 struct dentry *dir;
210
211 dir = debugfs_create_dir(name, parent);
212 if (IS_ERR(dir))
213 return dir;
214
215 debugfs_create_ul("probability", mode, dir, &attr->probability);
216 debugfs_create_ul("interval", mode, dir, &attr->interval);
217 debugfs_create_atomic_t("times", mode, dir, &attr->times);
218 debugfs_create_atomic_t("space", mode, dir, &attr->space);
219 debugfs_create_ul("verbose", mode, dir, &attr->verbose);
220 debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
221 &attr->ratelimit_state.interval);
222 debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
223 &attr->ratelimit_state.burst);
224 debugfs_create_bool("task-filter", mode, dir, &attr->task_filter);
225
226 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
227 debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
228 &attr->stacktrace_depth);
229 debugfs_create_ul("require-start", mode, dir, &attr->require_start);
230 debugfs_create_ul("require-end", mode, dir, &attr->require_end);
231 debugfs_create_ul("reject-start", mode, dir, &attr->reject_start);
232 debugfs_create_ul("reject-end", mode, dir, &attr->reject_end);
233 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
234
235 attr->dname = dget(dir);
236 return dir;
237 }
238 EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
239
240 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
241
