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/module.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 __init 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
  40 static void fail_dump(struct fault_attr *attr)
  41 {
  42         if (attr->verbose > 0)
  43                 printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure\n");
  44         if (attr->verbose > 1)
  45                 dump_stack();
  46 }
  47
  48 #define atomic_dec_not_zero(v)          atomic_add_unless((v), -1, 0)
  49
  50 static bool fail_task(struct fault_attr *attr, struct task_struct *task)
  51 {
  52         return !in_interrupt() && task->make_it_fail;
  53 }
  54
  55 #define MAX_STACK_TRACE_DEPTH 32
  56
  57 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
  58
  59 static bool fail_stacktrace(struct fault_attr *attr)
  60 {
  61         struct stack_trace trace;
  62         int depth = attr->stacktrace_depth;
  63         unsigned long entries[MAX_STACK_TRACE_DEPTH];
  64         int n;
  65         bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
  66
  67         if (depth == 0)
  68                 return found;
  69
  70         trace.nr_entries = 0;
  71         trace.entries = entries;
  72         trace.max_entries = depth;
  73         trace.skip = 1;
  74
  75         save_stack_trace(&trace);
  76         for (n = 0; n < trace.nr_entries; n++) {
  77                 if (attr->reject_start <= entries[n] &&
  78                                entries[n] < attr->reject_end)
  79                         return false;
  80                 if (attr->require_start <= entries[n] &&
  81                                entries[n] < attr->require_end)
  82                         found = true;
  83         }
  84         return found;
  85 }
  86
  87 #else
  88
  89 static inline bool fail_stacktrace(struct fault_attr *attr)
  90 {
  91         return true;
  92 }
  93
  94 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
  95
  96 /*
  97  * This code is stolen from failmalloc-1.0
  98  * http://www.nongnu.org/failmalloc/
  99  */
 100
 101 bool should_fail(struct fault_attr *attr, ssize_t size)
 102 {
 103         if (attr->task_filter && !fail_task(attr, current))
 104                 return false;
 105
 106         if (atomic_read(&attr->times) == 0)
 107                 return false;
 108
 109         if (atomic_read(&attr->space) > size) {
 110                 atomic_sub(size, &attr->space);
 111                 return false;
 112         }
 113
 114         if (attr->interval > 1) {
 115                 attr->count++;
 116                 if (attr->count % attr->interval)
 117                         return false;
 118         }
 119
 120         if (attr->probability <= random32() % 100)
 121                 return false;
 122
 123         if (!fail_stacktrace(attr))
 124                 return false;
 125
 126         fail_dump(attr);
 127
 128         if (atomic_read(&attr->times) != -1)
 129                 atomic_dec_not_zero(&attr->times);
 130
 131         return true;
 132 }
 133
 134 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 135
 136 static int debugfs_ul_set(void *data, u64 val)
 137 {
 138         *(unsigned long *)data = val;
 139         return 0;
 140 }
 141
 142 static int debugfs_ul_get(void *data, u64 *val)
 143 {
 144         *val = *(unsigned long *)data;
 145         return 0;
 146 }
 147
 148 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
 149
 150 static struct dentry *debugfs_create_ul(const char *name, mode_t mode,
 151                                 struct dentry *parent, unsigned long *value)
 152 {
 153         return debugfs_create_file(name, mode, parent, value, &fops_ul);
 154 }
 155
 156 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 157
 158 static int debugfs_stacktrace_depth_set(void *data, u64 val)
 159 {
 160         *(unsigned long *)data =
 161                 min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
 162
 163         return 0;
 164 }
 165
 166 DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
 167                         debugfs_stacktrace_depth_set, "%llu\n");
 168
 169 static struct dentry *debugfs_create_stacktrace_depth(
 170         const char *name, mode_t mode,
 171         struct dentry *parent, unsigned long *value)
 172 {
 173         return debugfs_create_file(name, mode, parent, value,
 174                                    &fops_stacktrace_depth);
 175 }
 176
 177 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 178
 179 static int debugfs_atomic_t_set(void *data, u64 val)
 180 {
 181         atomic_set((atomic_t *)data, val);
 182         return 0;
 183 }
 184
 185 static int debugfs_atomic_t_get(void *data, u64 *val)
 186 {
 187         *val = atomic_read((atomic_t *)data);
 188         return 0;
 189 }
 190
 191 DEFINE_SIMPLE_ATTRIBUTE(fops_atomic_t, debugfs_atomic_t_get,
 192                         debugfs_atomic_t_set, "%lld\n");
 193
 194 static struct dentry *debugfs_create_atomic_t(const char *name, mode_t mode,
 195                                 struct dentry *parent, atomic_t *value)
 196 {
 197         return debugfs_create_file(name, mode, parent, value, &fops_atomic_t);
 198 }
 199
 200 struct dentry *fault_create_debugfs_attr(const char *name,
 201                         struct dentry *parent, struct fault_attr *attr)
 202 {
 203         mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
 204         struct dentry *dir;
 205
 206         dir = debugfs_create_dir(name, parent);
 207         if (!dir)
 208                 return ERR_PTR(-ENOMEM);
 209
 210         if (!debugfs_create_ul("probability", mode, dir, &attr->probability))
 211                 goto fail;
 212         if (!debugfs_create_ul("interval", mode, dir, &attr->interval))
 213                 goto fail;
 214         if (!debugfs_create_atomic_t("times", mode, dir, &attr->times))
 215                 goto fail;
 216         if (!debugfs_create_atomic_t("space", mode, dir, &attr->space))
 217                 goto fail;
 218         if (!debugfs_create_ul("verbose", mode, dir, &attr->verbose))
 219                 goto fail;
 220         if (!debugfs_create_bool("task-filter", mode, dir, &attr->task_filter))
 221                 goto fail;
 222
 223 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 224
 225         if (!debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
 226                                 &attr->stacktrace_depth))
 227                 goto fail;
 228         if (!debugfs_create_ul("require-start", mode, dir,
 229                                 &attr->require_start))
 230                 goto fail;
 231         if (!debugfs_create_ul("require-end", mode, dir, &attr->require_end))
 232                 goto fail;
 233         if (!debugfs_create_ul("reject-start", mode, dir, &attr->reject_start))
 234                 goto fail;
 235         if (!debugfs_create_ul("reject-end", mode, dir, &attr->reject_end))
 236                 goto fail;
 237
 238 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 239
 240         return dir;
 241 fail:
 242         debugfs_remove_recursive(dir);
 243
 244         return ERR_PTR(-ENOMEM);
 245 }
 246
 247 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */