lib/fault-inject.c

   1 #include <linux/kernel.h>
   2 #include <linux/init.h>
   3 #include <linux/random.h>
   4 #include <linux/stat.h>
   5 #include <linux/types.h>
   6 #include <linux/fs.h>
   7 #include <linux/module.h>
   8 #include <linux/interrupt.h>
   9 #include <linux/unwind.h>
  10 #include <linux/stacktrace.h>
  11 #include <linux/kallsyms.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 __init 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
  41 static void fail_dump(struct fault_attr *attr)
  42 {
  43         if (attr->verbose > 0)
  44                 printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure\n");
  45         if (attr->verbose > 1)
  46                 dump_stack();
  47 }
  48
  49 #define atomic_dec_not_zero(v)          atomic_add_unless((v), -1, 0)
  50
  51 static int fail_task(struct fault_attr *attr, struct task_struct *task)
  52 {
  53         return !in_interrupt() && task->make_it_fail;
  54 }
  55
  56 #ifdef CONFIG_STACK_UNWIND
  57
  58 static asmlinkage int fail_stacktrace_callback(struct unwind_frame_info *info,
  59                                                 void *arg)
  60 {
  61         int depth;
  62         struct fault_attr *attr = arg;
  63         bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
  64
  65         for (depth = 0; depth < attr->stacktrace_depth
  66                         && unwind(info) == 0 && UNW_PC(info); depth++) {
  67                 if (arch_unw_user_mode(info))
  68                         break;
  69                 if (attr->reject_start <= UNW_PC(info) &&
  70                                UNW_PC(info) < attr->reject_end)
  71                         return 0;
  72                 if (attr->require_start <= UNW_PC(info) &&
  73                                UNW_PC(info) < attr->require_end)
  74                         found = 1;
  75         }
  76         return found;
  77 }
  78
  79 static int fail_stacktrace(struct fault_attr *attr)
  80 {
  81         struct unwind_frame_info info;
  82
  83         return unwind_init_running(&info, fail_stacktrace_callback, attr);
  84 }
  85
  86 #elif defined(CONFIG_STACKTRACE)
  87
  88 #define MAX_STACK_TRACE_DEPTH 32
  89
  90 static int fail_stacktrace(struct fault_attr *attr)
  91 {
  92         struct stack_trace trace;
  93         int depth = attr->stacktrace_depth;
  94         unsigned long entries[MAX_STACK_TRACE_DEPTH];
  95         int n;
  96         bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
  97
  98         if (depth == 0)
  99                 return found;
 100
 101         trace.nr_entries = 0;
 102         trace.entries = entries;
 103         trace.max_entries = (depth < MAX_STACK_TRACE_DEPTH) ?
 104                                 depth : MAX_STACK_TRACE_DEPTH;
 105         trace.skip = 1;
 106         trace.all_contexts = 0;
 107
 108         save_stack_trace(&trace, NULL);
 109         for (n = 0; n < trace.nr_entries; n++) {
 110                 if (attr->reject_start <= entries[n] &&
 111                                entries[n] < attr->reject_end)
 112                         return 0;
 113                 if (attr->require_start <= entries[n] &&
 114                                entries[n] < attr->require_end)
 115                         found = 1;
 116         }
 117         return found;
 118 }
 119
 120 #else
 121
 122 static inline int fail_stacktrace(struct fault_attr *attr)
 123 {
 124         static int firsttime = 1;
 125
 126         if (firsttime) {
 127                 printk(KERN_WARNING
 128                 "This architecture does not implement save_stack_trace()\n");
 129                 firsttime = 0;
 130         }
 131         return 0;
 132 }
 133
 134 #endif
 135
 136 /*
 137  * This code is stolen from failmalloc-1.0
 138  * http://www.nongnu.org/failmalloc/
 139  */
 140
 141 int should_fail(struct fault_attr *attr, ssize_t size)
 142 {
 143         if (attr->task_filter && !fail_task(attr, current))
 144                 return 0;
 145
 146         if (!fail_stacktrace(attr))
 147                 return 0;
 148
 149         if (atomic_read(&attr->times) == 0)
 150                 return 0;
 151
 152         if (atomic_read(&attr->space) > size) {
 153                 atomic_sub(size, &attr->space);
 154                 return 0;
 155         }
 156
 157         if (attr->interval > 1) {
 158                 attr->count++;
 159                 if (attr->count % attr->interval)
 160                         return 0;
 161         }
 162
 163         if (attr->probability > random32() % 100)
 164                 goto fail;
 165
 166         return 0;
 167
 168 fail:
 169         fail_dump(attr);
 170
 171         if (atomic_read(&attr->times) != -1)
 172                 atomic_dec_not_zero(&attr->times);
 173
 174         return 1;
 175 }
 176
 177 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 178
 179 static void debugfs_ul_set(void *data, u64 val)
 180 {
 181         *(unsigned long *)data = val;
 182 }
 183
 184 static u64 debugfs_ul_get(void *data)
 185 {
 186         return *(unsigned long *)data;
 187 }
 188
 189 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
 190
 191 static struct dentry *debugfs_create_ul(const char *name, mode_t mode,
 192                                 struct dentry *parent, unsigned long *value)
 193 {
 194         return debugfs_create_file(name, mode, parent, value, &fops_ul);
 195 }
 196
 197 static void debugfs_atomic_t_set(void *data, u64 val)
 198 {
 199         atomic_set((atomic_t *)data, val);
 200 }
 201
 202 static u64 debugfs_atomic_t_get(void *data)
 203 {
 204         return atomic_read((atomic_t *)data);
 205 }
 206
 207 DEFINE_SIMPLE_ATTRIBUTE(fops_atomic_t, debugfs_atomic_t_get,
 208                         debugfs_atomic_t_set, "%lld\n");
 209
 210 static struct dentry *debugfs_create_atomic_t(const char *name, mode_t mode,
 211                                 struct dentry *parent, atomic_t *value)
 212 {
 213         return debugfs_create_file(name, mode, parent, value, &fops_atomic_t);
 214 }
 215
 216 void cleanup_fault_attr_dentries(struct fault_attr *attr)
 217 {
 218         debugfs_remove(attr->dentries.probability_file);
 219         attr->dentries.probability_file = NULL;
 220
 221         debugfs_remove(attr->dentries.interval_file);
 222         attr->dentries.interval_file = NULL;
 223
 224         debugfs_remove(attr->dentries.times_file);
 225         attr->dentries.times_file = NULL;
 226
 227         debugfs_remove(attr->dentries.space_file);
 228         attr->dentries.space_file = NULL;
 229
 230         debugfs_remove(attr->dentries.verbose_file);
 231         attr->dentries.verbose_file = NULL;
 232
 233         debugfs_remove(attr->dentries.task_filter_file);
 234         attr->dentries.task_filter_file = NULL;
 235
 236         debugfs_remove(attr->dentries.stacktrace_depth_file);
 237         attr->dentries.stacktrace_depth_file = NULL;
 238
 239         debugfs_remove(attr->dentries.require_start_file);
 240         attr->dentries.require_start_file = NULL;
 241
 242         debugfs_remove(attr->dentries.require_end_file);
 243         attr->dentries.require_end_file = NULL;
 244
 245         debugfs_remove(attr->dentries.reject_start_file);
 246         attr->dentries.reject_start_file = NULL;
 247
 248         debugfs_remove(attr->dentries.reject_end_file);
 249         attr->dentries.reject_end_file = NULL;
 250
 251         if (attr->dentries.dir)
 252                 WARN_ON(!simple_empty(attr->dentries.dir));
 253
 254         debugfs_remove(attr->dentries.dir);
 255         attr->dentries.dir = NULL;
 256 }
 257
 258 int init_fault_attr_dentries(struct fault_attr *attr, const char *name)
 259 {
 260         mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
 261         struct dentry *dir;
 262
 263         memset(&attr->dentries, 0, sizeof(attr->dentries));
 264
 265         dir = debugfs_create_dir(name, NULL);
 266         if (!dir)
 267                 goto fail;
 268         attr->dentries.dir = dir;
 269
 270         attr->dentries.probability_file =
 271                 debugfs_create_ul("probability", mode, dir, &attr->probability);
 272
 273         attr->dentries.interval_file =
 274                 debugfs_create_ul("interval", mode, dir, &attr->interval);
 275
 276         attr->dentries.times_file =
 277                 debugfs_create_atomic_t("times", mode, dir, &attr->times);
 278
 279         attr->dentries.space_file =
 280                 debugfs_create_atomic_t("space", mode, dir, &attr->space);
 281
 282         attr->dentries.verbose_file =
 283                 debugfs_create_ul("verbose", mode, dir, &attr->verbose);
 284
 285         attr->dentries.task_filter_file = debugfs_create_bool("task-filter",
 286                                                 mode, dir, &attr->task_filter);
 287
 288         attr->dentries.stacktrace_depth_file =
 289                 debugfs_create_ul("stacktrace-depth", mode, dir,
 290                                   &attr->stacktrace_depth);
 291
 292         attr->dentries.require_start_file =
 293                 debugfs_create_ul("require-start", mode, dir, &attr->require_start);
 294
 295         attr->dentries.require_end_file =
 296                 debugfs_create_ul("require-end", mode, dir, &attr->require_end);
 297
 298         attr->dentries.reject_start_file =
 299                 debugfs_create_ul("reject-start", mode, dir, &attr->reject_start);
 300
 301         attr->dentries.reject_end_file =
 302                 debugfs_create_ul("reject-end", mode, dir, &attr->reject_end);
 303
 304
 305         if (!attr->dentries.probability_file || !attr->dentries.interval_file
 306             || !attr->dentries.times_file || !attr->dentries.space_file
 307             || !attr->dentries.verbose_file || !attr->dentries.task_filter_file
 308             || !attr->dentries.stacktrace_depth_file
 309             || !attr->dentries.require_start_file
 310             || !attr->dentries.require_end_file
 311             || !attr->dentries.reject_start_file
 312             || !attr->dentries.reject_end_file
 313             )
 314                 goto fail;
 315
 316         return 0;
 317 fail:
 318         cleanup_fault_attr_dentries(attr);
 319         return -ENOMEM;
 320 }
 321
 322 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */