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->no_warn)
45 return;
46
47 if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
48 printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
49 "name %pd, interval %lu, probability %lu, "
50 "space %d, times %d\n", attr->dname,
51 attr->interval, attr->probability,
52 atomic_read(&attr->space),
53 atomic_read(&attr->times));
54 if (attr->verbose > 1)
55 dump_stack();
56 }
57 }
58
59 #define atomic_dec_not_zero(v) atomic_add_unless((v), -1, 0)
60
fail_task(struct fault_attr * attr,struct task_struct * task)61 static bool fail_task(struct fault_attr *attr, struct task_struct *task)
62 {
63 return in_task() && task->make_it_fail;
64 }
65
66 #define MAX_STACK_TRACE_DEPTH 32
67
68 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
69
fail_stacktrace(struct fault_attr * attr)70 static bool fail_stacktrace(struct fault_attr *attr)
71 {
72 int depth = attr->stacktrace_depth;
73 unsigned long entries[MAX_STACK_TRACE_DEPTH];
74 int n, nr_entries;
75 bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
76
77 if (depth == 0)
78 return found;
79
80 nr_entries = stack_trace_save(entries, depth, 1);
81 for (n = 0; n < nr_entries; n++) {
82 if (attr->reject_start <= entries[n] &&
83 entries[n] < attr->reject_end)
84 return false;
85 if (attr->require_start <= entries[n] &&
86 entries[n] < attr->require_end)
87 found = true;
88 }
89 return found;
90 }
91
92 #else
93
fail_stacktrace(struct fault_attr * attr)94 static inline bool fail_stacktrace(struct fault_attr *attr)
95 {
96 return true;
97 }
98
99 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
100
101 /*
102 * This code is stolen from failmalloc-1.0
103 * http://www.nongnu.org/failmalloc/
104 */
105
should_fail(struct fault_attr * attr,ssize_t size)106 bool should_fail(struct fault_attr *attr, ssize_t size)
107 {
108 if (in_task()) {
109 unsigned int fail_nth = READ_ONCE(current->fail_nth);
110
111 if (fail_nth) {
112 fail_nth--;
113 WRITE_ONCE(current->fail_nth, fail_nth);
114 if (!fail_nth)
115 goto fail;
116
117 return false;
118 }
119 }
120
121 /* No need to check any other properties if the probability is 0 */
122 if (attr->probability == 0)
123 return false;
124
125 if (attr->task_filter && !fail_task(attr, current))
126 return false;
127
128 if (atomic_read(&attr->times) == 0)
129 return false;
130
131 if (atomic_read(&attr->space) > size) {
132 atomic_sub(size, &attr->space);
133 return false;
134 }
135
136 if (attr->interval > 1) {
137 attr->count++;
138 if (attr->count % attr->interval)
139 return false;
140 }
141
142 if (attr->probability <= prandom_u32() % 100)
143 return false;
144
145 if (!fail_stacktrace(attr))
146 return false;
147
148 fail:
149 fail_dump(attr);
150
151 if (atomic_read(&attr->times) != -1)
152 atomic_dec_not_zero(&attr->times);
153
154 return true;
155 }
156 EXPORT_SYMBOL_GPL(should_fail);
157
158 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
159
debugfs_ul_set(void * data,u64 val)160 static int debugfs_ul_set(void *data, u64 val)
161 {
162 *(unsigned long *)data = val;
163 return 0;
164 }
165
debugfs_ul_get(void * data,u64 * val)166 static int debugfs_ul_get(void *data, u64 *val)
167 {
168 *val = *(unsigned long *)data;
169 return 0;
170 }
171
172 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
173
debugfs_create_ul(const char * name,umode_t mode,struct dentry * parent,unsigned long * value)174 static void debugfs_create_ul(const char *name, umode_t mode,
175 struct dentry *parent, unsigned long *value)
176 {
177 debugfs_create_file(name, mode, parent, value, &fops_ul);
178 }
179
180 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
181
debugfs_stacktrace_depth_set(void * data,u64 val)182 static int debugfs_stacktrace_depth_set(void *data, u64 val)
183 {
184 *(unsigned long *)data =
185 min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
186
187 return 0;
188 }
189
190 DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
191 debugfs_stacktrace_depth_set, "%llu\n");
192
debugfs_create_stacktrace_depth(const char * name,umode_t mode,struct dentry * parent,unsigned long * value)193 static void debugfs_create_stacktrace_depth(const char *name, umode_t mode,
194 struct dentry *parent,
195 unsigned long *value)
196 {
197 debugfs_create_file(name, mode, parent, value, &fops_stacktrace_depth);
198 }
199
200 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
201
fault_create_debugfs_attr(const char * name,struct dentry * parent,struct fault_attr * attr)202 struct dentry *fault_create_debugfs_attr(const char *name,
203 struct dentry *parent, struct fault_attr *attr)
204 {
205 umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
206 struct dentry *dir;
207
208 dir = debugfs_create_dir(name, parent);
209 if (IS_ERR(dir))
210 return dir;
211
212 debugfs_create_ul("probability", mode, dir, &attr->probability);
213 debugfs_create_ul("interval", mode, dir, &attr->interval);
214 debugfs_create_atomic_t("times", mode, dir, &attr->times);
215 debugfs_create_atomic_t("space", mode, dir, &attr->space);
216 debugfs_create_ul("verbose", mode, dir, &attr->verbose);
217 debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
218 &attr->ratelimit_state.interval);
219 debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
220 &attr->ratelimit_state.burst);
221 debugfs_create_bool("task-filter", mode, dir, &attr->task_filter);
222
223 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
224 debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
225 &attr->stacktrace_depth);
226 debugfs_create_ul("require-start", mode, dir, &attr->require_start);
227 debugfs_create_ul("require-end", mode, dir, &attr->require_end);
228 debugfs_create_ul("reject-start", mode, dir, &attr->reject_start);
229 debugfs_create_ul("reject-end", mode, dir, &attr->reject_end);
230 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
231
232 attr->dname = dget(dir);
233 return dir;
234 }
235 EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
236
237 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
238