lib/fault-inject.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <linux/kernel.h>
   3 #include <linux/init.h>
   4 #include <linux/random.h>
   5 #include <linux/sched.h>
   6 #include <linux/stat.h>
   7 #include <linux/types.h>
   8 #include <linux/fs.h>
   9 #include <linux/export.h>
  10 #include <linux/interrupt.h>
  11 #include <linux/stacktrace.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 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 EXPORT_SYMBOL_GPL(setup_fault_attr);
  41
  42 static void fail_dump(struct fault_attr *attr)
  43 {
  44         if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
  45                 printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
  46                        "name %pd, interval %lu, probability %lu, "
  47                        "space %d, times %d\n", attr->dname,
  48                        attr->interval, attr->probability,
  49                        atomic_read(&attr->space),
  50                        atomic_read(&attr->times));
  51                 if (attr->verbose > 1)
  52                         dump_stack();
  53         }
  54 }
  55
  56 #define atomic_dec_not_zero(v)          atomic_add_unless((v), -1, 0)
  57
  58 static bool fail_task(struct fault_attr *attr, struct task_struct *task)
  59 {
  60         return in_task() && task->make_it_fail;
  61 }
  62
  63 #define MAX_STACK_TRACE_DEPTH 32
  64
  65 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
  66
  67 static bool fail_stacktrace(struct fault_attr *attr)
  68 {
  69         int depth = attr->stacktrace_depth;
  70         unsigned long entries[MAX_STACK_TRACE_DEPTH];
  71         int n, nr_entries;
  72         bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
  73
  74         if (depth == 0)
  75                 return found;
  76
  77         nr_entries = stack_trace_save(entries, depth, 1);
  78         for (n = 0; n < nr_entries; n++) {
  79                 if (attr->reject_start <= entries[n] &&
  80                                entries[n] < attr->reject_end)
  81                         return false;
  82                 if (attr->require_start <= entries[n] &&
  83                                entries[n] < attr->require_end)
  84                         found = true;
  85         }
  86         return found;
  87 }
  88
  89 #else
  90
  91 static inline bool fail_stacktrace(struct fault_attr *attr)
  92 {
  93         return true;
  94 }
  95
  96 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
  97
  98 /*
  99  * This code is stolen from failmalloc-1.0
 100  * http://www.nongnu.org/failmalloc/
 101  */
 102
 103 bool should_fail(struct fault_attr *attr, ssize_t size)
 104 {
 105         if (in_task()) {
 106                 unsigned int fail_nth = READ_ONCE(current->fail_nth);
 107
 108                 if (fail_nth) {
 109                         if (!WRITE_ONCE(current->fail_nth, fail_nth - 1))
 110                                 goto fail;
 111
 112                         return false;
 113                 }
 114         }
 115
 116         /* No need to check any other properties if the probability is 0 */
 117         if (attr->probability == 0)
 118                 return false;
 119
 120         if (attr->task_filter && !fail_task(attr, current))
 121                 return false;
 122
 123         if (atomic_read(&attr->times) == 0)
 124                 return false;
 125
 126         if (atomic_read(&attr->space) > size) {
 127                 atomic_sub(size, &attr->space);
 128                 return false;
 129         }
 130
 131         if (attr->interval > 1) {
 132                 attr->count++;
 133                 if (attr->count % attr->interval)
 134                         return false;
 135         }
 136
 137         if (attr->probability <= prandom_u32() % 100)
 138                 return false;
 139
 140         if (!fail_stacktrace(attr))
 141                 return false;
 142
 143 fail:
 144         fail_dump(attr);
 145
 146         if (atomic_read(&attr->times) != -1)
 147                 atomic_dec_not_zero(&attr->times);
 148
 149         return true;
 150 }
 151 EXPORT_SYMBOL_GPL(should_fail);
 152
 153 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 154
 155 static int debugfs_ul_set(void *data, u64 val)
 156 {
 157         *(unsigned long *)data = val;
 158         return 0;
 159 }
 160
 161 static int debugfs_ul_get(void *data, u64 *val)
 162 {
 163         *val = *(unsigned long *)data;
 164         return 0;
 165 }
 166
 167 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
 168
 169 static struct dentry *debugfs_create_ul(const char *name, umode_t mode,
 170                                 struct dentry *parent, unsigned long *value)
 171 {
 172         return debugfs_create_file(name, mode, parent, value, &fops_ul);
 173 }
 174
 175 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 176
 177 static int debugfs_stacktrace_depth_set(void *data, u64 val)
 178 {
 179         *(unsigned long *)data =
 180                 min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
 181
 182         return 0;
 183 }
 184
 185 DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
 186                         debugfs_stacktrace_depth_set, "%llu\n");
 187
 188 static struct dentry *debugfs_create_stacktrace_depth(
 189         const char *name, umode_t mode,
 190         struct dentry *parent, unsigned long *value)
 191 {
 192         return debugfs_create_file(name, mode, parent, value,
 193                                    &fops_stacktrace_depth);
 194 }
 195
 196 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 197
 198 struct dentry *fault_create_debugfs_attr(const char *name,
 199                         struct dentry *parent, struct fault_attr *attr)
 200 {
 201         umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
 202         struct dentry *dir;
 203
 204         dir = debugfs_create_dir(name, parent);
 205         if (!dir)
 206                 return ERR_PTR(-ENOMEM);
 207
 208         if (!debugfs_create_ul("probability", mode, dir, &attr->probability))
 209                 goto fail;
 210         if (!debugfs_create_ul("interval", mode, dir, &attr->interval))
 211                 goto fail;
 212         if (!debugfs_create_atomic_t("times", mode, dir, &attr->times))
 213                 goto fail;
 214         if (!debugfs_create_atomic_t("space", mode, dir, &attr->space))
 215                 goto fail;
 216         if (!debugfs_create_ul("verbose", mode, dir, &attr->verbose))
 217                 goto fail;
 218         if (!debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
 219                                 &attr->ratelimit_state.interval))
 220                 goto fail;
 221         if (!debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
 222                                 &attr->ratelimit_state.burst))
 223                 goto fail;
 224         if (!debugfs_create_bool("task-filter", mode, dir, &attr->task_filter))
 225                 goto fail;
 226
 227 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 228
 229         if (!debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
 230                                 &attr->stacktrace_depth))
 231                 goto fail;
 232         if (!debugfs_create_ul("require-start", mode, dir,
 233                                 &attr->require_start))
 234                 goto fail;
 235         if (!debugfs_create_ul("require-end", mode, dir, &attr->require_end))
 236                 goto fail;
 237         if (!debugfs_create_ul("reject-start", mode, dir, &attr->reject_start))
 238                 goto fail;
 239         if (!debugfs_create_ul("reject-end", mode, dir, &attr->reject_end))
 240                 goto fail;
 241
 242 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 243
 244         attr->dname = dget(dir);
 245         return dir;
 246 fail:
 247         debugfs_remove_recursive(dir);
 248
 249         return ERR_PTR(-ENOMEM);
 250 }
 251 EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
 252
 253 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */