Root/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 */
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)
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
51static 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
60static 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
90static 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
102bool 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}
138EXPORT_SYMBOL_GPL(should_fail);
139
140#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
141
142static int debugfs_ul_set(void *data, u64 val)
143{
144    *(unsigned long *)data = val;
145    return 0;
146}
147
148static int debugfs_ul_get(void *data, u64 *val)
149{
150    *val = *(unsigned long *)data;
151    return 0;
152}
153
154DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
155
156static 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
164static 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
172DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
173            debugfs_stacktrace_depth_set, "%llu\n");
174
175static 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
185struct 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;
226fail:
227    debugfs_remove_recursive(dir);
228
229    return ERR_PTR(-ENOMEM);
230}
231EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
232
233#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
234

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