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