lib/fault-inject.c

   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  */
  18 int 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, &times) < 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 }
  40 EXPORT_SYMBOL_GPL(setup_fault_attr);
  41
  42 static 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
  58 static 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
  67 static 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
  91 static 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
 103 bool 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
 151 fail:
 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
 161 bool should_fail(struct fault_attr *attr, ssize_t size)
 162 {
 163         return should_fail_ex(attr, size, 0);
 164 }
 165 EXPORT_SYMBOL_GPL(should_fail);
 166
 167 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 168
 169 static int debugfs_ul_set(void *data, u64 val)
 170 {
 171         *(unsigned long *)data = val;
 172         return 0;
 173 }
 174
 175 static int debugfs_ul_get(void *data, u64 *val)
 176 {
 177         *val = *(unsigned long *)data;
 178         return 0;
 179 }
 180
 181 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
 182
 183 static 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
 191 static 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
 199 DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
 200                         debugfs_stacktrace_depth_set, "%llu\n");
 201
 202 static 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
 211 struct 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 }
 244 EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
 245
 246 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */