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_interrupt() && 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	/* No need to check any other properties if the probability is 0 */
111	if (attr->probability == 0)
112		return false;
113
114	if (attr->task_filter && !fail_task(attr, current))
115		return false;
116
117	if (atomic_read(&attr->times) == 0)
118		return false;
119
120	if (atomic_read(&attr->space) > size) {
121		atomic_sub(size, &attr->space);
122		return false;
123	}
124
125	if (attr->interval > 1) {
126		attr->count++;
127		if (attr->count % attr->interval)
128			return false;
129	}
130
131	if (attr->probability <= prandom_u32() % 100)
132		return false;
133
134	if (!fail_stacktrace(attr))
135		return false;
136
137	fail_dump(attr);
138
139	if (atomic_read(&attr->times) != -1)
140		atomic_dec_not_zero(&attr->times);
141
142	return true;
143}
144EXPORT_SYMBOL_GPL(should_fail);
145
146#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
147
148static int debugfs_ul_set(void *data, u64 val)
149{
150	*(unsigned long *)data = val;
151	return 0;
152}
153
154static int debugfs_ul_get(void *data, u64 *val)
155{
156	*val = *(unsigned long *)data;
157	return 0;
158}
159
160DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
161
162static struct dentry *debugfs_create_ul(const char *name, umode_t mode,
163				struct dentry *parent, unsigned long *value)
164{
165	return debugfs_create_file(name, mode, parent, value, &fops_ul);
166}
167
168#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
169
170static int debugfs_stacktrace_depth_set(void *data, u64 val)
171{
172	*(unsigned long *)data =
173		min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
174
175	return 0;
176}
177
178DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
179			debugfs_stacktrace_depth_set, "%llu\n");
180
181static struct dentry *debugfs_create_stacktrace_depth(
182	const char *name, umode_t mode,
183	struct dentry *parent, unsigned long *value)
184{
185	return debugfs_create_file(name, mode, parent, value,
186				   &fops_stacktrace_depth);
187}
188
189#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
190
191struct dentry *fault_create_debugfs_attr(const char *name,
192			struct dentry *parent, struct fault_attr *attr)
193{
194	umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
195	struct dentry *dir;
196
197	dir = debugfs_create_dir(name, parent);
198	if (!dir)
199		return ERR_PTR(-ENOMEM);
200
201	if (!debugfs_create_ul("probability", mode, dir, &attr->probability))
202		goto fail;
203	if (!debugfs_create_ul("interval", mode, dir, &attr->interval))
204		goto fail;
205	if (!debugfs_create_atomic_t("times", mode, dir, &attr->times))
206		goto fail;
207	if (!debugfs_create_atomic_t("space", mode, dir, &attr->space))
208		goto fail;
209	if (!debugfs_create_ul("verbose", mode, dir, &attr->verbose))
210		goto fail;
211	if (!debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
212				&attr->ratelimit_state.interval))
213		goto fail;
214	if (!debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
215				&attr->ratelimit_state.burst))
216		goto fail;
217	if (!debugfs_create_bool("task-filter", mode, dir, &attr->task_filter))
218		goto fail;
219
220#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
221
222	if (!debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
223				&attr->stacktrace_depth))
224		goto fail;
225	if (!debugfs_create_ul("require-start", mode, dir,
226				&attr->require_start))
227		goto fail;
228	if (!debugfs_create_ul("require-end", mode, dir, &attr->require_end))
229		goto fail;
230	if (!debugfs_create_ul("reject-start", mode, dir, &attr->reject_start))
231		goto fail;
232	if (!debugfs_create_ul("reject-end", mode, dir, &attr->reject_end))
233		goto fail;
234
235#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
236
237	attr->dname = dget(dir);
238	return dir;
239fail:
240	debugfs_remove_recursive(dir);
241
242	return ERR_PTR(-ENOMEM);
243}
244EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
245
246#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
247