1#include <linux/kernel.h>
2#include <linux/init.h>
3#include <linux/random.h>
4#include <linux/sched.h>
5#include <linux/stat.h>
6#include <linux/types.h>
7#include <linux/fs.h>
8#include <linux/export.h>
9#include <linux/interrupt.h>
10#include <linux/stacktrace.h>
11#include <linux/fault-inject.h>
12
13/*
14 * setup_fault_attr() is a helper function for various __setup handlers, so it
15 * returns 0 on error, because that is what __setup handlers do.
16 */
17int setup_fault_attr(struct fault_attr *attr, char *str)
18{
19 unsigned long probability;
20 unsigned long interval;
21 int times;
22 int space;
23
24 /* "<interval>,<probability>,<space>,<times>" */
25 if (sscanf(str, "%lu,%lu,%d,%d",
26 &interval, &probability, &space, &times) < 4) {
27 printk(KERN_WARNING
28 "FAULT_INJECTION: failed to parse arguments\n");
29 return 0;
30 }
31
32 attr->probability = probability;
33 attr->interval = interval;
34 atomic_set(&attr->times, times);
35 atomic_set(&attr->space, space);
36
37 return 1;
38}
39EXPORT_SYMBOL_GPL(setup_fault_attr);
40
41static void fail_dump(struct fault_attr *attr)
42{
43 if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
44 printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
45 "name %pd, interval %lu, probability %lu, "
46 "space %d, times %d\n", attr->dname,
47 attr->interval, attr->probability,
48 atomic_read(&attr->space),
49 atomic_read(&attr->times));
50 if (attr->verbose > 1)
51 dump_stack();
52 }
53}
54
55#define atomic_dec_not_zero(v) atomic_add_unless((v), -1, 0)
56
57static bool fail_task(struct fault_attr *attr, struct task_struct *task)
58{
59 return in_task() && task->make_it_fail;
60}
61
62#define MAX_STACK_TRACE_DEPTH 32
63
64#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
65
66static bool fail_stacktrace(struct fault_attr *attr)
67{
68 struct stack_trace trace;
69 int depth = attr->stacktrace_depth;
70 unsigned long entries[MAX_STACK_TRACE_DEPTH];
71 int n;
72 bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
73
74 if (depth == 0)
75 return found;
76
77 trace.nr_entries = 0;
78 trace.entries = entries;
79 trace.max_entries = depth;
80 trace.skip = 1;
81
82 save_stack_trace(&trace);
83 for (n = 0; n < trace.nr_entries; n++) {
84 if (attr->reject_start <= entries[n] &&
85 entries[n] < attr->reject_end)
86 return false;
87 if (attr->require_start <= entries[n] &&
88 entries[n] < attr->require_end)
89 found = true;
90 }
91 return found;
92}
93
94#else
95
96static inline bool fail_stacktrace(struct fault_attr *attr)
97{
98 return true;
99}
100
101#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
102
103/*
104 * This code is stolen from failmalloc-1.0
105 * http://www.nongnu.org/failmalloc/
106 */
107
108bool should_fail(struct fault_attr *attr, ssize_t size)
109{
110 if (in_task()) {
111 unsigned int fail_nth = READ_ONCE(current->fail_nth);
112
113 if (fail_nth) {
114 if (!WRITE_ONCE(current->fail_nth, fail_nth - 1))
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
148fail:
149 fail_dump(attr);
150
151 if (atomic_read(&attr->times) != -1)
152 atomic_dec_not_zero(&attr->times);
153
154 return true;
155}
156EXPORT_SYMBOL_GPL(should_fail);
157
158#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
159
160static int debugfs_ul_set(void *data, u64 val)
161{
162 *(unsigned long *)data = val;
163 return 0;
164}
165
166static int debugfs_ul_get(void *data, u64 *val)
167{
168 *val = *(unsigned long *)data;
169 return 0;
170}
171
172DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
173
174static struct dentry *debugfs_create_ul(const char *name, umode_t mode,
175 struct dentry *parent, unsigned long *value)
176{
177 return debugfs_create_file(name, mode, parent, value, &fops_ul);
178}
179
180#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
181
182static 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
190DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
191 debugfs_stacktrace_depth_set, "%llu\n");
192
193static struct dentry *debugfs_create_stacktrace_depth(
194 const char *name, umode_t mode,
195 struct dentry *parent, unsigned long *value)
196{
197 return debugfs_create_file(name, mode, parent, value,
198 &fops_stacktrace_depth);
199}
200
201#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
202
203struct dentry *fault_create_debugfs_attr(const char *name,
204 struct dentry *parent, struct fault_attr *attr)
205{
206 umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
207 struct dentry *dir;
208
209 dir = debugfs_create_dir(name, parent);
210 if (!dir)
211 return ERR_PTR(-ENOMEM);
212
213 if (!debugfs_create_ul("probability", mode, dir, &attr->probability))
214 goto fail;
215 if (!debugfs_create_ul("interval", mode, dir, &attr->interval))
216 goto fail;
217 if (!debugfs_create_atomic_t("times", mode, dir, &attr->times))
218 goto fail;
219 if (!debugfs_create_atomic_t("space", mode, dir, &attr->space))
220 goto fail;
221 if (!debugfs_create_ul("verbose", mode, dir, &attr->verbose))
222 goto fail;
223 if (!debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
224 &attr->ratelimit_state.interval))
225 goto fail;
226 if (!debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
227 &attr->ratelimit_state.burst))
228 goto fail;
229 if (!debugfs_create_bool("task-filter", mode, dir, &attr->task_filter))
230 goto fail;
231
232#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
233
234 if (!debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
235 &attr->stacktrace_depth))
236 goto fail;
237 if (!debugfs_create_ul("require-start", mode, dir,
238 &attr->require_start))
239 goto fail;
240 if (!debugfs_create_ul("require-end", mode, dir, &attr->require_end))
241 goto fail;
242 if (!debugfs_create_ul("reject-start", mode, dir, &attr->reject_start))
243 goto fail;
244 if (!debugfs_create_ul("reject-end", mode, dir, &attr->reject_end))
245 goto fail;
246
247#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
248
249 attr->dname = dget(dir);
250 return dir;
251fail:
252 debugfs_remove_recursive(dir);
253
254 return ERR_PTR(-ENOMEM);
255}
256EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
257
258#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
259