xref: /openbmc/linux/lib/fault-inject.c (revision 9c1f8594)
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/module.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  */
17 int __init 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 }
39 
40 static void fail_dump(struct fault_attr *attr)
41 {
42 	if (attr->verbose > 0)
43 		printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure\n");
44 	if (attr->verbose > 1)
45 		dump_stack();
46 }
47 
48 #define atomic_dec_not_zero(v)		atomic_add_unless((v), -1, 0)
49 
50 static bool fail_task(struct fault_attr *attr, struct task_struct *task)
51 {
52 	return !in_interrupt() && task->make_it_fail;
53 }
54 
55 #define MAX_STACK_TRACE_DEPTH 32
56 
57 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
58 
59 static bool fail_stacktrace(struct fault_attr *attr)
60 {
61 	struct stack_trace trace;
62 	int depth = attr->stacktrace_depth;
63 	unsigned long entries[MAX_STACK_TRACE_DEPTH];
64 	int n;
65 	bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
66 
67 	if (depth == 0)
68 		return found;
69 
70 	trace.nr_entries = 0;
71 	trace.entries = entries;
72 	trace.max_entries = depth;
73 	trace.skip = 1;
74 
75 	save_stack_trace(&trace);
76 	for (n = 0; n < trace.nr_entries; n++) {
77 		if (attr->reject_start <= entries[n] &&
78 			       entries[n] < attr->reject_end)
79 			return false;
80 		if (attr->require_start <= entries[n] &&
81 			       entries[n] < attr->require_end)
82 			found = true;
83 	}
84 	return found;
85 }
86 
87 #else
88 
89 static inline bool fail_stacktrace(struct fault_attr *attr)
90 {
91 	return true;
92 }
93 
94 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
95 
96 /*
97  * This code is stolen from failmalloc-1.0
98  * http://www.nongnu.org/failmalloc/
99  */
100 
101 bool should_fail(struct fault_attr *attr, ssize_t size)
102 {
103 	if (attr->task_filter && !fail_task(attr, current))
104 		return false;
105 
106 	if (atomic_read(&attr->times) == 0)
107 		return false;
108 
109 	if (atomic_read(&attr->space) > size) {
110 		atomic_sub(size, &attr->space);
111 		return false;
112 	}
113 
114 	if (attr->interval > 1) {
115 		attr->count++;
116 		if (attr->count % attr->interval)
117 			return false;
118 	}
119 
120 	if (attr->probability <= random32() % 100)
121 		return false;
122 
123 	if (!fail_stacktrace(attr))
124 		return false;
125 
126 	fail_dump(attr);
127 
128 	if (atomic_read(&attr->times) != -1)
129 		atomic_dec_not_zero(&attr->times);
130 
131 	return true;
132 }
133 
134 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
135 
136 static int debugfs_ul_set(void *data, u64 val)
137 {
138 	*(unsigned long *)data = val;
139 	return 0;
140 }
141 
142 static int debugfs_ul_get(void *data, u64 *val)
143 {
144 	*val = *(unsigned long *)data;
145 	return 0;
146 }
147 
148 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
149 
150 static struct dentry *debugfs_create_ul(const char *name, mode_t mode,
151 				struct dentry *parent, unsigned long *value)
152 {
153 	return debugfs_create_file(name, mode, parent, value, &fops_ul);
154 }
155 
156 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
157 
158 static int debugfs_stacktrace_depth_set(void *data, u64 val)
159 {
160 	*(unsigned long *)data =
161 		min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
162 
163 	return 0;
164 }
165 
166 DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
167 			debugfs_stacktrace_depth_set, "%llu\n");
168 
169 static struct dentry *debugfs_create_stacktrace_depth(
170 	const char *name, mode_t mode,
171 	struct dentry *parent, unsigned long *value)
172 {
173 	return debugfs_create_file(name, mode, parent, value,
174 				   &fops_stacktrace_depth);
175 }
176 
177 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
178 
179 static int debugfs_atomic_t_set(void *data, u64 val)
180 {
181 	atomic_set((atomic_t *)data, val);
182 	return 0;
183 }
184 
185 static int debugfs_atomic_t_get(void *data, u64 *val)
186 {
187 	*val = atomic_read((atomic_t *)data);
188 	return 0;
189 }
190 
191 DEFINE_SIMPLE_ATTRIBUTE(fops_atomic_t, debugfs_atomic_t_get,
192 			debugfs_atomic_t_set, "%lld\n");
193 
194 static struct dentry *debugfs_create_atomic_t(const char *name, mode_t mode,
195 				struct dentry *parent, atomic_t *value)
196 {
197 	return debugfs_create_file(name, mode, parent, value, &fops_atomic_t);
198 }
199 
200 struct dentry *fault_create_debugfs_attr(const char *name,
201 			struct dentry *parent, struct fault_attr *attr)
202 {
203 	mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
204 	struct dentry *dir;
205 
206 	dir = debugfs_create_dir(name, parent);
207 	if (!dir)
208 		return ERR_PTR(-ENOMEM);
209 
210 	if (!debugfs_create_ul("probability", mode, dir, &attr->probability))
211 		goto fail;
212 	if (!debugfs_create_ul("interval", mode, dir, &attr->interval))
213 		goto fail;
214 	if (!debugfs_create_atomic_t("times", mode, dir, &attr->times))
215 		goto fail;
216 	if (!debugfs_create_atomic_t("space", mode, dir, &attr->space))
217 		goto fail;
218 	if (!debugfs_create_ul("verbose", mode, dir, &attr->verbose))
219 		goto fail;
220 	if (!debugfs_create_bool("task-filter", mode, dir, &attr->task_filter))
221 		goto fail;
222 
223 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
224 
225 	if (!debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
226 				&attr->stacktrace_depth))
227 		goto fail;
228 	if (!debugfs_create_ul("require-start", mode, dir,
229 				&attr->require_start))
230 		goto fail;
231 	if (!debugfs_create_ul("require-end", mode, dir, &attr->require_end))
232 		goto fail;
233 	if (!debugfs_create_ul("reject-start", mode, dir, &attr->reject_start))
234 		goto fail;
235 	if (!debugfs_create_ul("reject-end", mode, dir, &attr->reject_end))
236 		goto fail;
237 
238 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
239 
240 	return dir;
241 fail:
242 	debugfs_remove_recursive(dir);
243 
244 	return ERR_PTR(-ENOMEM);
245 }
246 
247 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
248