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 && __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
  57 static bool fail_task(struct fault_attr *attr, struct task_struct *task)
  58 {
  59         return in_task() && task->make_it_fail;
  60 }
  61
  62 #define MAX_STACK_TRACE_DEPTH 32
  63
  64 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
  65
  66 static bool fail_stacktrace(struct fault_attr *attr)
  67 {
  68         int depth = attr->stacktrace_depth;
  69         unsigned long entries[MAX_STACK_TRACE_DEPTH];
  70         int n, nr_entries;
  71         bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
  72
  73         if (depth == 0)
  74                 return found;
  75
  76         nr_entries = stack_trace_save(entries, depth, 1);
  77         for (n = 0; n < 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         if (in_task()) {
 105                 unsigned int fail_nth = READ_ONCE(current->fail_nth);
 106
 107                 if (fail_nth) {
 108                         if (!WRITE_ONCE(current->fail_nth, fail_nth - 1))
 109                                 goto fail;
 110
 111                         return false;
 112                 }
 113         }
 114
 115         /* No need to check any other properties if the probability is 0 */
 116         if (attr->probability == 0)
 117                 return false;
 118
 119         if (attr->task_filter && !fail_task(attr, current))
 120                 return false;
 121
 122         if (atomic_read(&attr->times) == 0)
 123                 return false;
 124
 125         if (atomic_read(&attr->space) > size) {
 126                 atomic_sub(size, &attr->space);
 127                 return false;
 128         }
 129
 130         if (attr->interval > 1) {
 131                 attr->count++;
 132                 if (attr->count % attr->interval)
 133                         return false;
 134         }
 135
 136         if (attr->probability <= prandom_u32() % 100)
 137                 return false;
 138
 139         if (!fail_stacktrace(attr))
 140                 return false;
 141
 142 fail:
 143         fail_dump(attr);
 144
 145         if (atomic_read(&attr->times) != -1)
 146                 atomic_dec_not_zero(&attr->times);
 147
 148         return true;
 149 }
 150 EXPORT_SYMBOL_GPL(should_fail);
 151
 152 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 153
 154 static int debugfs_ul_set(void *data, u64 val)
 155 {
 156         *(unsigned long *)data = val;
 157         return 0;
 158 }
 159
 160 static int debugfs_ul_get(void *data, u64 *val)
 161 {
 162         *val = *(unsigned long *)data;
 163         return 0;
 164 }
 165
 166 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
 167
 168 static struct dentry *debugfs_create_ul(const char *name, umode_t mode,
 169                                 struct dentry *parent, unsigned long *value)
 170 {
 171         return debugfs_create_file(name, mode, parent, value, &fops_ul);
 172 }
 173
 174 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 175
 176 static int debugfs_stacktrace_depth_set(void *data, u64 val)
 177 {
 178         *(unsigned long *)data =
 179                 min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
 180
 181         return 0;
 182 }
 183
 184 DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
 185                         debugfs_stacktrace_depth_set, "%llu\n");
 186
 187 static struct dentry *debugfs_create_stacktrace_depth(
 188         const char *name, umode_t mode,
 189         struct dentry *parent, unsigned long *value)
 190 {
 191         return debugfs_create_file(name, mode, parent, value,
 192                                    &fops_stacktrace_depth);
 193 }
 194
 195 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 196
 197 struct dentry *fault_create_debugfs_attr(const char *name,
 198                         struct dentry *parent, struct fault_attr *attr)
 199 {
 200         umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
 201         struct dentry *dir;
 202
 203         dir = debugfs_create_dir(name, parent);
 204         if (!dir)
 205                 return ERR_PTR(-ENOMEM);
 206
 207         if (!debugfs_create_ul("probability", mode, dir, &attr->probability))
 208                 goto fail;
 209         if (!debugfs_create_ul("interval", mode, dir, &attr->interval))
 210                 goto fail;
 211         if (!debugfs_create_atomic_t("times", mode, dir, &attr->times))
 212                 goto fail;
 213         if (!debugfs_create_atomic_t("space", mode, dir, &attr->space))
 214                 goto fail;
 215         if (!debugfs_create_ul("verbose", mode, dir, &attr->verbose))
 216                 goto fail;
 217         if (!debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
 218                                 &attr->ratelimit_state.interval))
 219                 goto fail;
 220         if (!debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
 221                                 &attr->ratelimit_state.burst))
 222                 goto fail;
 223         if (!debugfs_create_bool("task-filter", mode, dir, &attr->task_filter))
 224                 goto fail;
 225
 226 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 227
 228         if (!debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
 229                                 &attr->stacktrace_depth))
 230                 goto fail;
 231         if (!debugfs_create_ul("require-start", mode, dir,
 232                                 &attr->require_start))
 233                 goto fail;
 234         if (!debugfs_create_ul("require-end", mode, dir, &attr->require_end))
 235                 goto fail;
 236         if (!debugfs_create_ul("reject-start", mode, dir, &attr->reject_start))
 237                 goto fail;
 238         if (!debugfs_create_ul("reject-end", mode, dir, &attr->reject_end))
 239                 goto fail;
 240
 241 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 242
 243         attr->dname = dget(dir);
 244         return dir;
 245 fail:
 246         debugfs_remove_recursive(dir);
 247
 248         return ERR_PTR(-ENOMEM);
 249 }
 250 EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
 251
 252 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */