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         struct stack_trace trace;
  69         int depth = attr->stacktrace_depth;
  70         unsigned long entries[MAX_STACK_TRACE_DEPTH];
  71         int n;
  72         bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
  73
  74         if (depth == 0)
  75                 return found;
  76
  77         trace.nr_entries = 0;
  78         trace.entries = entries;
  79         trace.max_entries = depth;
  80         trace.skip = 1;
  81
  82         save_stack_trace(&trace);
  83         for (n = 0; n < trace.nr_entries; n++) {
  84                 if (attr->reject_start <= entries[n] &&
  85                                entries[n] < attr->reject_end)
  86                         return false;
  87                 if (attr->require_start <= entries[n] &&
  88                                entries[n] < attr->require_end)
  89                         found = true;
  90         }
  91         return found;
  92 }
  93
  94 #else
  95
  96 static inline bool fail_stacktrace(struct fault_attr *attr)
  97 {
  98         return true;
  99 }
 100
 101 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 102
 103 /*
 104  * This code is stolen from failmalloc-1.0
 105  * http://www.nongnu.org/failmalloc/
 106  */
 107
 108 bool should_fail(struct fault_attr *attr, ssize_t size)
 109 {
 110         if (in_task()) {
 111                 unsigned int fail_nth = READ_ONCE(current->fail_nth);
 112
 113                 if (fail_nth && !WRITE_ONCE(current->fail_nth, fail_nth - 1))
 114                         goto fail;
 115
 116                 return false;
 117         }
 118
 119         /* No need to check any other properties if the probability is 0 */
 120         if (attr->probability == 0)
 121                 return false;
 122
 123         if (attr->task_filter && !fail_task(attr, current))
 124                 return false;
 125
 126         if (atomic_read(&attr->times) == 0)
 127                 return false;
 128
 129         if (atomic_read(&attr->space) > size) {
 130                 atomic_sub(size, &attr->space);
 131                 return false;
 132         }
 133
 134         if (attr->interval > 1) {
 135                 attr->count++;
 136                 if (attr->count % attr->interval)
 137                         return false;
 138         }
 139
 140         if (attr->probability <= prandom_u32() % 100)
 141                 return false;
 142
 143         if (!fail_stacktrace(attr))
 144                 return false;
 145
 146 fail:
 147         fail_dump(attr);
 148
 149         if (atomic_read(&attr->times) != -1)
 150                 atomic_dec_not_zero(&attr->times);
 151
 152         return true;
 153 }
 154 EXPORT_SYMBOL_GPL(should_fail);
 155
 156 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 157
 158 static int debugfs_ul_set(void *data, u64 val)
 159 {
 160         *(unsigned long *)data = val;
 161         return 0;
 162 }
 163
 164 static int debugfs_ul_get(void *data, u64 *val)
 165 {
 166         *val = *(unsigned long *)data;
 167         return 0;
 168 }
 169
 170 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
 171
 172 static struct dentry *debugfs_create_ul(const char *name, umode_t mode,
 173                                 struct dentry *parent, unsigned long *value)
 174 {
 175         return debugfs_create_file(name, mode, parent, value, &fops_ul);
 176 }
 177
 178 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 179
 180 static int debugfs_stacktrace_depth_set(void *data, u64 val)
 181 {
 182         *(unsigned long *)data =
 183                 min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
 184
 185         return 0;
 186 }
 187
 188 DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
 189                         debugfs_stacktrace_depth_set, "%llu\n");
 190
 191 static struct dentry *debugfs_create_stacktrace_depth(
 192         const char *name, umode_t mode,
 193         struct dentry *parent, unsigned long *value)
 194 {
 195         return debugfs_create_file(name, mode, parent, value,
 196                                    &fops_stacktrace_depth);
 197 }
 198
 199 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 200
 201 struct dentry *fault_create_debugfs_attr(const char *name,
 202                         struct dentry *parent, struct fault_attr *attr)
 203 {
 204         umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
 205         struct dentry *dir;
 206
 207         dir = debugfs_create_dir(name, parent);
 208         if (!dir)
 209                 return ERR_PTR(-ENOMEM);
 210
 211         if (!debugfs_create_ul("probability", mode, dir, &attr->probability))
 212                 goto fail;
 213         if (!debugfs_create_ul("interval", mode, dir, &attr->interval))
 214                 goto fail;
 215         if (!debugfs_create_atomic_t("times", mode, dir, &attr->times))
 216                 goto fail;
 217         if (!debugfs_create_atomic_t("space", mode, dir, &attr->space))
 218                 goto fail;
 219         if (!debugfs_create_ul("verbose", mode, dir, &attr->verbose))
 220                 goto fail;
 221         if (!debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
 222                                 &attr->ratelimit_state.interval))
 223                 goto fail;
 224         if (!debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
 225                                 &attr->ratelimit_state.burst))
 226                 goto fail;
 227         if (!debugfs_create_bool("task-filter", mode, dir, &attr->task_filter))
 228                 goto fail;
 229
 230 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 231
 232         if (!debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
 233                                 &attr->stacktrace_depth))
 234                 goto fail;
 235         if (!debugfs_create_ul("require-start", mode, dir,
 236                                 &attr->require_start))
 237                 goto fail;
 238         if (!debugfs_create_ul("require-end", mode, dir, &attr->require_end))
 239                 goto fail;
 240         if (!debugfs_create_ul("reject-start", mode, dir, &attr->reject_start))
 241                 goto fail;
 242         if (!debugfs_create_ul("reject-end", mode, dir, &attr->reject_end))
 243                 goto fail;
 244
 245 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 246
 247         attr->dname = dget(dir);
 248         return dir;
 249 fail:
 250         debugfs_remove_recursive(dir);
 251
 252         return ERR_PTR(-ENOMEM);
 253 }
 254 EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
 255
 256 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */