tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1// SPDX-License-Identifier: GPL-2.0-only
2#include <linux/kernel.h>
3#include <linux/init.h>
4#include <linux/random.h>
5#include <linux/sched.h>
6#include <linux/stat.h>
7#include <linux/types.h>
8#include <linux/fs.h>
9#include <linux/export.h>
10#include <linux/interrupt.h>
11#include <linux/stacktrace.h>
12#include <linux/fault-inject.h>
13
14/*
15 * setup_fault_attr() is a helper function for various __setup handlers, so it
16 * returns 0 on error, because that is what __setup handlers do.
17 */
18int setup_fault_attr(struct fault_attr *attr, char *str)
19{
20 unsigned long probability;
21 unsigned long interval;
22 int times;
23 int space;
24
25 /* "<interval>,<probability>,<space>,<times>" */
26 if (sscanf(str, "%lu,%lu,%d,%d",
27 &interval, &probability, &space, ×) < 4) {
28 printk(KERN_WARNING
29 "FAULT_INJECTION: failed to parse arguments\n");
30 return 0;
31 }
32
33 attr->probability = probability;
34 attr->interval = interval;
35 atomic_set(&attr->times, times);
36 atomic_set(&attr->space, space);
37
38 return 1;
39}
40EXPORT_SYMBOL_GPL(setup_fault_attr);
41
42static void fail_dump(struct fault_attr *attr)
43{
44 if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
45 printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
46 "name %pd, interval %lu, probability %lu, "
47 "space %d, times %d\n", attr->dname,
48 attr->interval, attr->probability,
49 atomic_read(&attr->space),
50 atomic_read(&attr->times));
51 if (attr->verbose > 1)
52 dump_stack();
53 }
54}
55
56#define atomic_dec_not_zero(v) atomic_add_unless((v), -1, 0)
57
58static bool fail_task(struct fault_attr *attr, struct task_struct *task)
59{
60 return in_task() && task->make_it_fail;
61}
62
63#define MAX_STACK_TRACE_DEPTH 32
64
65#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
66
67static bool fail_stacktrace(struct fault_attr *attr)
68{
69 int depth = attr->stacktrace_depth;
70 unsigned long entries[MAX_STACK_TRACE_DEPTH];
71 int n, nr_entries;
72 bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
73
74 if (depth == 0 || (found && !attr->reject_start && !attr->reject_end))
75 return found;
76
77 nr_entries = stack_trace_save(entries, depth, 1);
78 for (n = 0; n < nr_entries; n++) {
79 if (attr->reject_start <= entries[n] &&
80 entries[n] < attr->reject_end)
81 return false;
82 if (attr->require_start <= entries[n] &&
83 entries[n] < attr->require_end)
84 found = true;
85 }
86 return found;
87}
88
89#else
90
91static inline bool fail_stacktrace(struct fault_attr *attr)
92{
93 return true;
94}
95
96#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
97
98/*
99 * This code is stolen from failmalloc-1.0
100 * http://www.nongnu.org/failmalloc/
101 */
102
103bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags)
104{
105 bool stack_checked = false;
106
107 if (in_task()) {
108 unsigned int fail_nth = READ_ONCE(current->fail_nth);
109
110 if (fail_nth) {
111 if (!fail_stacktrace(attr))
112 return false;
113
114 stack_checked = true;
115 fail_nth--;
116 WRITE_ONCE(current->fail_nth, fail_nth);
117 if (!fail_nth)
118 goto fail;
119
120 return false;
121 }
122 }
123
124 /* No need to check any other properties if the probability is 0 */
125 if (attr->probability == 0)
126 return false;
127
128 if (attr->task_filter && !fail_task(attr, current))
129 return false;
130
131 if (atomic_read(&attr->times) == 0)
132 return false;
133
134 if (!stack_checked && !fail_stacktrace(attr))
135 return false;
136
137 if (atomic_read(&attr->space) > size) {
138 atomic_sub(size, &attr->space);
139 return false;
140 }
141
142 if (attr->interval > 1) {
143 attr->count++;
144 if (attr->count % attr->interval)
145 return false;
146 }
147
148 if (attr->probability <= get_random_u32_below(100))
149 return false;
150
151fail:
152 if (!(flags & FAULT_NOWARN))
153 fail_dump(attr);
154
155 if (atomic_read(&attr->times) != -1)
156 atomic_dec_not_zero(&attr->times);
157
158 return true;
159}
160
161bool should_fail(struct fault_attr *attr, ssize_t size)
162{
163 return should_fail_ex(attr, size, 0);
164}
165EXPORT_SYMBOL_GPL(should_fail);
166
167#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
168
169static int debugfs_ul_set(void *data, u64 val)
170{
171 *(unsigned long *)data = val;
172 return 0;
173}
174
175static int debugfs_ul_get(void *data, u64 *val)
176{
177 *val = *(unsigned long *)data;
178 return 0;
179}
180
181DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
182
183static void debugfs_create_ul(const char *name, umode_t mode,
184 struct dentry *parent, unsigned long *value)
185{
186 debugfs_create_file(name, mode, parent, value, &fops_ul);
187}
188
189#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
190
191static int debugfs_stacktrace_depth_set(void *data, u64 val)
192{
193 *(unsigned long *)data =
194 min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
195
196 return 0;
197}
198
199DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
200 debugfs_stacktrace_depth_set, "%llu\n");
201
202static void debugfs_create_stacktrace_depth(const char *name, umode_t mode,
203 struct dentry *parent,
204 unsigned long *value)
205{
206 debugfs_create_file(name, mode, parent, value, &fops_stacktrace_depth);
207}
208
209#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
210
211struct dentry *fault_create_debugfs_attr(const char *name,
212 struct dentry *parent, struct fault_attr *attr)
213{
214 umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
215 struct dentry *dir;
216
217 dir = debugfs_create_dir(name, parent);
218 if (IS_ERR(dir))
219 return dir;
220
221 debugfs_create_ul("probability", mode, dir, &attr->probability);
222 debugfs_create_ul("interval", mode, dir, &attr->interval);
223 debugfs_create_atomic_t("times", mode, dir, &attr->times);
224 debugfs_create_atomic_t("space", mode, dir, &attr->space);
225 debugfs_create_ul("verbose", mode, dir, &attr->verbose);
226 debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
227 &attr->ratelimit_state.interval);
228 debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
229 &attr->ratelimit_state.burst);
230 debugfs_create_bool("task-filter", mode, dir, &attr->task_filter);
231
232#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
233 debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
234 &attr->stacktrace_depth);
235 debugfs_create_xul("require-start", mode, dir, &attr->require_start);
236 debugfs_create_xul("require-end", mode, dir, &attr->require_end);
237 debugfs_create_xul("reject-start", mode, dir, &attr->reject_start);
238 debugfs_create_xul("reject-end", mode, dir, &attr->reject_end);
239#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
240
241 attr->dname = dget(dir);
242 return dir;
243}
244EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
245
246#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */