drm/i915: Allow i915_pc8_status debug info on BDW
[sfrench/cifs-2.6.git] / lib / fault-inject.c
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  */
17 int 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 EXPORT_SYMBOL_GPL(setup_fault_attr);
40
41 static void fail_dump(struct fault_attr *attr)
42 {
43         if (attr->verbose > 0)
44                 printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure\n");
45         if (attr->verbose > 1)
46                 dump_stack();
47 }
48
49 #define atomic_dec_not_zero(v)          atomic_add_unless((v), -1, 0)
50
51 static bool fail_task(struct fault_attr *attr, struct task_struct *task)
52 {
53         return !in_interrupt() && task->make_it_fail;
54 }
55
56 #define MAX_STACK_TRACE_DEPTH 32
57
58 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
59
60 static bool fail_stacktrace(struct fault_attr *attr)
61 {
62         struct stack_trace trace;
63         int depth = attr->stacktrace_depth;
64         unsigned long entries[MAX_STACK_TRACE_DEPTH];
65         int n;
66         bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
67
68         if (depth == 0)
69                 return found;
70
71         trace.nr_entries = 0;
72         trace.entries = entries;
73         trace.max_entries = depth;
74         trace.skip = 1;
75
76         save_stack_trace(&trace);
77         for (n = 0; n < trace.nr_entries; n++) {
78                 if (attr->reject_start <= entries[n] &&
79                                entries[n] < attr->reject_end)
80                         return false;
81                 if (attr->require_start <= entries[n] &&
82                                entries[n] < attr->require_end)
83                         found = true;
84         }
85         return found;
86 }
87
88 #else
89
90 static inline bool fail_stacktrace(struct fault_attr *attr)
91 {
92         return true;
93 }
94
95 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
96
97 /*
98  * This code is stolen from failmalloc-1.0
99  * http://www.nongnu.org/failmalloc/
100  */
101
102 bool should_fail(struct fault_attr *attr, ssize_t size)
103 {
104         /* No need to check any other properties if the probability is 0 */
105         if (attr->probability == 0)
106                 return false;
107
108         if (attr->task_filter && !fail_task(attr, current))
109                 return false;
110
111         if (atomic_read(&attr->times) == 0)
112                 return false;
113
114         if (atomic_read(&attr->space) > size) {
115                 atomic_sub(size, &attr->space);
116                 return false;
117         }
118
119         if (attr->interval > 1) {
120                 attr->count++;
121                 if (attr->count % attr->interval)
122                         return false;
123         }
124
125         if (attr->probability <= prandom_u32() % 100)
126                 return false;
127
128         if (!fail_stacktrace(attr))
129                 return false;
130
131         fail_dump(attr);
132
133         if (atomic_read(&attr->times) != -1)
134                 atomic_dec_not_zero(&attr->times);
135
136         return true;
137 }
138 EXPORT_SYMBOL_GPL(should_fail);
139
140 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
141
142 static int debugfs_ul_set(void *data, u64 val)
143 {
144         *(unsigned long *)data = val;
145         return 0;
146 }
147
148 static int debugfs_ul_get(void *data, u64 *val)
149 {
150         *val = *(unsigned long *)data;
151         return 0;
152 }
153
154 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
155
156 static struct dentry *debugfs_create_ul(const char *name, umode_t mode,
157                                 struct dentry *parent, unsigned long *value)
158 {
159         return debugfs_create_file(name, mode, parent, value, &fops_ul);
160 }
161
162 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
163
164 static int debugfs_stacktrace_depth_set(void *data, u64 val)
165 {
166         *(unsigned long *)data =
167                 min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
168
169         return 0;
170 }
171
172 DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
173                         debugfs_stacktrace_depth_set, "%llu\n");
174
175 static struct dentry *debugfs_create_stacktrace_depth(
176         const char *name, umode_t mode,
177         struct dentry *parent, unsigned long *value)
178 {
179         return debugfs_create_file(name, mode, parent, value,
180                                    &fops_stacktrace_depth);
181 }
182
183 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
184
185 struct dentry *fault_create_debugfs_attr(const char *name,
186                         struct dentry *parent, struct fault_attr *attr)
187 {
188         umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
189         struct dentry *dir;
190
191         dir = debugfs_create_dir(name, parent);
192         if (!dir)
193                 return ERR_PTR(-ENOMEM);
194
195         if (!debugfs_create_ul("probability", mode, dir, &attr->probability))
196                 goto fail;
197         if (!debugfs_create_ul("interval", mode, dir, &attr->interval))
198                 goto fail;
199         if (!debugfs_create_atomic_t("times", mode, dir, &attr->times))
200                 goto fail;
201         if (!debugfs_create_atomic_t("space", mode, dir, &attr->space))
202                 goto fail;
203         if (!debugfs_create_ul("verbose", mode, dir, &attr->verbose))
204                 goto fail;
205         if (!debugfs_create_bool("task-filter", mode, dir, &attr->task_filter))
206                 goto fail;
207
208 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
209
210         if (!debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
211                                 &attr->stacktrace_depth))
212                 goto fail;
213         if (!debugfs_create_ul("require-start", mode, dir,
214                                 &attr->require_start))
215                 goto fail;
216         if (!debugfs_create_ul("require-end", mode, dir, &attr->require_end))
217                 goto fail;
218         if (!debugfs_create_ul("reject-start", mode, dir, &attr->reject_start))
219                 goto fail;
220         if (!debugfs_create_ul("reject-end", mode, dir, &attr->reject_end))
221                 goto fail;
222
223 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
224
225         return dir;
226 fail:
227         debugfs_remove_recursive(dir);
228
229         return ERR_PTR(-ENOMEM);
230 }
231 EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
232
233 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */