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) {
 114                         if (!WRITE_ONCE(current->fail_nth, fail_nth - 1))
 115                                 goto fail;
 116
 117                         return false;
 118                 }
 119         }
 120
 121         /* No need to check any other properties if the probability is 0 */
 122         if (attr->probability == 0)
 123                 return false;
 124
 125         if (attr->task_filter && !fail_task(attr, current))
 126                 return false;
 127
 128         if (atomic_read(&attr->times) == 0)
 129                 return false;
 130
 131         if (atomic_read(&attr->space) > size) {
 132                 atomic_sub(size, &attr->space);
 133                 return false;
 134         }
 135
 136         if (attr->interval > 1) {
 137                 attr->count++;
 138                 if (attr->count % attr->interval)
 139                         return false;
 140         }
 141
 142         if (attr->probability <= prandom_u32() % 100)
 143                 return false;
 144
 145         if (!fail_stacktrace(attr))
 146                 return false;
 147
 148 fail:
 149         fail_dump(attr);
 150
 151         if (atomic_read(&attr->times) != -1)
 152                 atomic_dec_not_zero(&attr->times);
 153
 154         return true;
 155 }
 156 EXPORT_SYMBOL_GPL(should_fail);
 157
 158 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 159
 160 static int debugfs_ul_set(void *data, u64 val)
 161 {
 162         *(unsigned long *)data = val;
 163         return 0;
 164 }
 165
 166 static int debugfs_ul_get(void *data, u64 *val)
 167 {
 168         *val = *(unsigned long *)data;
 169         return 0;
 170 }
 171
 172 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
 173
 174 static struct dentry *debugfs_create_ul(const char *name, umode_t mode,
 175                                 struct dentry *parent, unsigned long *value)
 176 {
 177         return debugfs_create_file(name, mode, parent, value, &fops_ul);
 178 }
 179
 180 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 181
 182 static int debugfs_stacktrace_depth_set(void *data, u64 val)
 183 {
 184         *(unsigned long *)data =
 185                 min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
 186
 187         return 0;
 188 }
 189
 190 DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
 191                         debugfs_stacktrace_depth_set, "%llu\n");
 192
 193 static struct dentry *debugfs_create_stacktrace_depth(
 194         const char *name, umode_t mode,
 195         struct dentry *parent, unsigned long *value)
 196 {
 197         return debugfs_create_file(name, mode, parent, value,
 198                                    &fops_stacktrace_depth);
 199 }
 200
 201 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 202
 203 struct dentry *fault_create_debugfs_attr(const char *name,
 204                         struct dentry *parent, struct fault_attr *attr)
 205 {
 206         umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
 207         struct dentry *dir;
 208
 209         dir = debugfs_create_dir(name, parent);
 210         if (!dir)
 211                 return ERR_PTR(-ENOMEM);
 212
 213         if (!debugfs_create_ul("probability", mode, dir, &attr->probability))
 214                 goto fail;
 215         if (!debugfs_create_ul("interval", mode, dir, &attr->interval))
 216                 goto fail;
 217         if (!debugfs_create_atomic_t("times", mode, dir, &attr->times))
 218                 goto fail;
 219         if (!debugfs_create_atomic_t("space", mode, dir, &attr->space))
 220                 goto fail;
 221         if (!debugfs_create_ul("verbose", mode, dir, &attr->verbose))
 222                 goto fail;
 223         if (!debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
 224                                 &attr->ratelimit_state.interval))
 225                 goto fail;
 226         if (!debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
 227                                 &attr->ratelimit_state.burst))
 228                 goto fail;
 229         if (!debugfs_create_bool("task-filter", mode, dir, &attr->task_filter))
 230                 goto fail;
 231
 232 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 233
 234         if (!debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
 235                                 &attr->stacktrace_depth))
 236                 goto fail;
 237         if (!debugfs_create_ul("require-start", mode, dir,
 238                                 &attr->require_start))
 239                 goto fail;
 240         if (!debugfs_create_ul("require-end", mode, dir, &attr->require_end))
 241                 goto fail;
 242         if (!debugfs_create_ul("reject-start", mode, dir, &attr->reject_start))
 243                 goto fail;
 244         if (!debugfs_create_ul("reject-end", mode, dir, &attr->reject_end))
 245                 goto fail;
 246
 247 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 248
 249         attr->dname = dget(dir);
 250         return dir;
 251 fail:
 252         debugfs_remove_recursive(dir);
 253
 254         return ERR_PTR(-ENOMEM);
 255 }
 256 EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
 257
 258 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */