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)
  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 bool fail_task(struct fault_attr *attr, struct task_struct *task)
  52 {
  53         return !in_interrupt() && task->make_it_fail;
  54 }
  55
  56 #define MAX_STACK_TRACE_DEPTH 32
  57
  58 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
  59
  60 static bool fail_stacktrace(struct fault_attr *attr)
  61 {
  62         struct stack_trace trace;
  63         int depth = attr->stacktrace_depth;
  64         unsigned long entries[MAX_STACK_TRACE_DEPTH];
  65         int n;
  66         bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
  67
  68         if (depth == 0)
  69                 return found;
  70
  71         trace.nr_entries = 0;
  72         trace.entries = entries;
  73         trace.max_entries = depth;
  74         trace.skip = 1;
  75
  76         save_stack_trace(&trace);
  77         for (n = 0; n < trace.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         /* No need to check any other properties if the probability is 0 */
 105         if (attr->probability == 0)
 106                 return false;
 107
 108         if (attr->task_filter && !fail_task(attr, current))
 109                 return false;
 110
 111         if (atomic_read(&attr->times) == 0)
 112                 return false;
 113
 114         if (atomic_read(&attr->space) > size) {
 115                 atomic_sub(size, &attr->space);
 116                 return false;
 117         }
 118
 119         if (attr->interval > 1) {
 120                 attr->count++;
 121                 if (attr->count % attr->interval)
 122                         return false;
 123         }
 124
 125         if (attr->probability <= prandom_u32() % 100)
 126                 return false;
 127
 128         if (!fail_stacktrace(attr))
 129                 return false;
 130
 131         fail_dump(attr);
 132
 133         if (atomic_read(&attr->times) != -1)
 134                 atomic_dec_not_zero(&attr->times);
 135
 136         return true;
 137 }
 138 EXPORT_SYMBOL_GPL(should_fail);
 139
 140 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 141
 142 static int debugfs_ul_set(void *data, u64 val)
 143 {
 144         *(unsigned long *)data = val;
 145         return 0;
 146 }
 147
 148 static int debugfs_ul_get(void *data, u64 *val)
 149 {
 150         *val = *(unsigned long *)data;
 151         return 0;
 152 }
 153
 154 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
 155
 156 static struct dentry *debugfs_create_ul(const char *name, umode_t mode,
 157                                 struct dentry *parent, unsigned long *value)
 158 {
 159         return debugfs_create_file(name, mode, parent, value, &fops_ul);
 160 }
 161
 162 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 163
 164 static int debugfs_stacktrace_depth_set(void *data, u64 val)
 165 {
 166         *(unsigned long *)data =
 167                 min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
 168
 169         return 0;
 170 }
 171
 172 DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
 173                         debugfs_stacktrace_depth_set, "%llu\n");
 174
 175 static struct dentry *debugfs_create_stacktrace_depth(
 176         const char *name, umode_t mode,
 177         struct dentry *parent, unsigned long *value)
 178 {
 179         return debugfs_create_file(name, mode, parent, value,
 180                                    &fops_stacktrace_depth);
 181 }
 182
 183 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 184
 185 struct dentry *fault_create_debugfs_attr(const char *name,
 186                         struct dentry *parent, struct fault_attr *attr)
 187 {
 188         umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
 189         struct dentry *dir;
 190
 191         dir = debugfs_create_dir(name, parent);
 192         if (!dir)
 193                 return ERR_PTR(-ENOMEM);
 194
 195         if (!debugfs_create_ul("probability", mode, dir, &attr->probability))
 196                 goto fail;
 197         if (!debugfs_create_ul("interval", mode, dir, &attr->interval))
 198                 goto fail;
 199         if (!debugfs_create_atomic_t("times", mode, dir, &attr->times))
 200                 goto fail;
 201         if (!debugfs_create_atomic_t("space", mode, dir, &attr->space))
 202                 goto fail;
 203         if (!debugfs_create_ul("verbose", mode, dir, &attr->verbose))
 204                 goto fail;
 205         if (!debugfs_create_bool("task-filter", mode, dir, &attr->task_filter))
 206                 goto fail;
 207
 208 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 209
 210         if (!debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
 211                                 &attr->stacktrace_depth))
 212                 goto fail;
 213         if (!debugfs_create_ul("require-start", mode, dir,
 214                                 &attr->require_start))
 215                 goto fail;
 216         if (!debugfs_create_ul("require-end", mode, dir, &attr->require_end))
 217                 goto fail;
 218         if (!debugfs_create_ul("reject-start", mode, dir, &attr->reject_start))
 219                 goto fail;
 220         if (!debugfs_create_ul("reject-end", mode, dir, &attr->reject_end))
 221                 goto fail;
 222
 223 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 224
 225         return dir;
 226 fail:
 227         debugfs_remove_recursive(dir);
 228
 229         return ERR_PTR(-ENOMEM);
 230 }
 231 EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
 232
 233 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */