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/fault-inject.h>
  10
  11 /*
  12  * setup_fault_attr() is a helper function for various __setup handlers, so it
  13  * returns 0 on error, because that is what __setup handlers do.
  14  */
  15 int __init setup_fault_attr(struct fault_attr *attr, char *str)
  16 {
  17         unsigned long probability;
  18         unsigned long interval;
  19         int times;
  20         int space;
  21
  22         /* "<interval>,<probability>,<space>,<times>" */
  23         if (sscanf(str, "%lu,%lu,%d,%d",
  24                         &interval, &probability, &space, &times) < 4) {
  25                 printk(KERN_WARNING
  26                         "FAULT_INJECTION: failed to parse arguments\n");
  27                 return 0;
  28         }
  29
  30         attr->probability = probability;
  31         attr->interval = interval;
  32         atomic_set(&attr->times, times);
  33         atomic_set(&attr->space, space);
  34
  35         return 1;
  36 }
  37
  38 static void fail_dump(struct fault_attr *attr)
  39 {
  40         if (attr->verbose > 0)
  41                 printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure\n");
  42         if (attr->verbose > 1)
  43                 dump_stack();
  44 }
  45
  46 #define atomic_dec_not_zero(v)          atomic_add_unless((v), -1, 0)
  47
  48 static int fail_task(struct fault_attr *attr, struct task_struct *task)
  49 {
  50         return !in_interrupt() && task->make_it_fail;
  51 }
  52
  53 /*
  54  * This code is stolen from failmalloc-1.0
  55  * http://www.nongnu.org/failmalloc/
  56  */
  57
  58 int should_fail(struct fault_attr *attr, ssize_t size)
  59 {
  60         if (attr->task_filter && !fail_task(attr, current))
  61                 return 0;
  62
  63         if (atomic_read(&attr->times) == 0)
  64                 return 0;
  65
  66         if (atomic_read(&attr->space) > size) {
  67                 atomic_sub(size, &attr->space);
  68                 return 0;
  69         }
  70
  71         if (attr->interval > 1) {
  72                 attr->count++;
  73                 if (attr->count % attr->interval)
  74                         return 0;
  75         }
  76
  77         if (attr->probability > random32() % 100)
  78                 goto fail;
  79
  80         return 0;
  81
  82 fail:
  83         fail_dump(attr);
  84
  85         if (atomic_read(&attr->times) != -1)
  86                 atomic_dec_not_zero(&attr->times);
  87
  88         return 1;
  89 }
  90
  91 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
  92
  93 static void debugfs_ul_set(void *data, u64 val)
  94 {
  95         *(unsigned long *)data = val;
  96 }
  97
  98 static u64 debugfs_ul_get(void *data)
  99 {
 100         return *(unsigned long *)data;
 101 }
 102
 103 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
 104
 105 static struct dentry *debugfs_create_ul(const char *name, mode_t mode,
 106                                 struct dentry *parent, unsigned long *value)
 107 {
 108         return debugfs_create_file(name, mode, parent, value, &fops_ul);
 109 }
 110
 111 static void debugfs_atomic_t_set(void *data, u64 val)
 112 {
 113         atomic_set((atomic_t *)data, val);
 114 }
 115
 116 static u64 debugfs_atomic_t_get(void *data)
 117 {
 118         return atomic_read((atomic_t *)data);
 119 }
 120
 121 DEFINE_SIMPLE_ATTRIBUTE(fops_atomic_t, debugfs_atomic_t_get,
 122                         debugfs_atomic_t_set, "%lld\n");
 123
 124 static struct dentry *debugfs_create_atomic_t(const char *name, mode_t mode,
 125                                 struct dentry *parent, atomic_t *value)
 126 {
 127         return debugfs_create_file(name, mode, parent, value, &fops_atomic_t);
 128 }
 129
 130 void cleanup_fault_attr_dentries(struct fault_attr *attr)
 131 {
 132         debugfs_remove(attr->dentries.probability_file);
 133         attr->dentries.probability_file = NULL;
 134
 135         debugfs_remove(attr->dentries.interval_file);
 136         attr->dentries.interval_file = NULL;
 137
 138         debugfs_remove(attr->dentries.times_file);
 139         attr->dentries.times_file = NULL;
 140
 141         debugfs_remove(attr->dentries.space_file);
 142         attr->dentries.space_file = NULL;
 143
 144         debugfs_remove(attr->dentries.verbose_file);
 145         attr->dentries.verbose_file = NULL;
 146
 147         debugfs_remove(attr->dentries.task_filter_file);
 148         attr->dentries.task_filter_file = NULL;
 149
 150         if (attr->dentries.dir)
 151                 WARN_ON(!simple_empty(attr->dentries.dir));
 152
 153         debugfs_remove(attr->dentries.dir);
 154         attr->dentries.dir = NULL;
 155 }
 156
 157 int init_fault_attr_dentries(struct fault_attr *attr, const char *name)
 158 {
 159         mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
 160         struct dentry *dir;
 161
 162         memset(&attr->dentries, 0, sizeof(attr->dentries));
 163
 164         dir = debugfs_create_dir(name, NULL);
 165         if (!dir)
 166                 goto fail;
 167         attr->dentries.dir = dir;
 168
 169         attr->dentries.probability_file =
 170                 debugfs_create_ul("probability", mode, dir, &attr->probability);
 171
 172         attr->dentries.interval_file =
 173                 debugfs_create_ul("interval", mode, dir, &attr->interval);
 174
 175         attr->dentries.times_file =
 176                 debugfs_create_atomic_t("times", mode, dir, &attr->times);
 177
 178         attr->dentries.space_file =
 179                 debugfs_create_atomic_t("space", mode, dir, &attr->space);
 180
 181         attr->dentries.verbose_file =
 182                 debugfs_create_ul("verbose", mode, dir, &attr->verbose);
 183
 184         attr->dentries.task_filter_file = debugfs_create_bool("task-filter",
 185                                                 mode, dir, &attr->task_filter);
 186
 187         if (!attr->dentries.probability_file || !attr->dentries.interval_file
 188             || !attr->dentries.times_file || !attr->dentries.space_file
 189             || !attr->dentries.verbose_file || !attr->dentries.task_filter_file)
 190                 goto fail;
 191
 192         return 0;
 193 fail:
 194         cleanup_fault_attr_dentries(attr);
 195         return -ENOMEM;
 196 }
 197
 198 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */