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                         fail_nth--;
 110                         WRITE_ONCE(current->fail_nth, fail_nth);
 111                         if (!fail_nth)
 112                                 goto fail;
 113
 114                         return false;
 115                 }
 116         }
 117
 118         /* No need to check any other properties if the probability is 0 */
 119         if (attr->probability == 0)
 120                 return false;
 121
 122         if (attr->task_filter && !fail_task(attr, current))
 123                 return false;
 124
 125         if (atomic_read(&attr->times) == 0)
 126                 return false;
 127
 128         if (atomic_read(&attr->space) > size) {
 129                 atomic_sub(size, &attr->space);
 130                 return false;
 131         }
 132
 133         if (attr->interval > 1) {
 134                 attr->count++;
 135                 if (attr->count % attr->interval)
 136                         return false;
 137         }
 138
 139         if (attr->probability <= prandom_u32() % 100)
 140                 return false;
 141
 142         if (!fail_stacktrace(attr))
 143                 return false;
 144
 145 fail:
 146         fail_dump(attr);
 147
 148         if (atomic_read(&attr->times) != -1)
 149                 atomic_dec_not_zero(&attr->times);
 150
 151         return true;
 152 }
 153 EXPORT_SYMBOL_GPL(should_fail);
 154
 155 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 156
 157 static int debugfs_ul_set(void *data, u64 val)
 158 {
 159         *(unsigned long *)data = val;
 160         return 0;
 161 }
 162
 163 static int debugfs_ul_get(void *data, u64 *val)
 164 {
 165         *val = *(unsigned long *)data;
 166         return 0;
 167 }
 168
 169 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
 170
 171 static void debugfs_create_ul(const char *name, umode_t mode,
 172                               struct dentry *parent, unsigned long *value)
 173 {
 174         debugfs_create_file(name, mode, parent, value, &fops_ul);
 175 }
 176
 177 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 178
 179 static int debugfs_stacktrace_depth_set(void *data, u64 val)
 180 {
 181         *(unsigned long *)data =
 182                 min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
 183
 184         return 0;
 185 }
 186
 187 DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
 188                         debugfs_stacktrace_depth_set, "%llu\n");
 189
 190 static void debugfs_create_stacktrace_depth(const char *name, umode_t mode,
 191                                             struct dentry *parent,
 192                                             unsigned long *value)
 193 {
 194         debugfs_create_file(name, mode, parent, value, &fops_stacktrace_depth);
 195 }
 196
 197 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 198
 199 struct dentry *fault_create_debugfs_attr(const char *name,
 200                         struct dentry *parent, struct fault_attr *attr)
 201 {
 202         umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
 203         struct dentry *dir;
 204
 205         dir = debugfs_create_dir(name, parent);
 206         if (IS_ERR(dir))
 207                 return dir;
 208
 209         debugfs_create_ul("probability", mode, dir, &attr->probability);
 210         debugfs_create_ul("interval", mode, dir, &attr->interval);
 211         debugfs_create_atomic_t("times", mode, dir, &attr->times);
 212         debugfs_create_atomic_t("space", mode, dir, &attr->space);
 213         debugfs_create_ul("verbose", mode, dir, &attr->verbose);
 214         debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
 215                            &attr->ratelimit_state.interval);
 216         debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
 217                            &attr->ratelimit_state.burst);
 218         debugfs_create_bool("task-filter", mode, dir, &attr->task_filter);
 219
 220 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 221         debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
 222                                         &attr->stacktrace_depth);
 223         debugfs_create_ul("require-start", mode, dir, &attr->require_start);
 224         debugfs_create_ul("require-end", mode, dir, &attr->require_end);
 225         debugfs_create_ul("reject-start", mode, dir, &attr->reject_start);
 226         debugfs_create_ul("reject-end", mode, dir, &attr->reject_end);
 227 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 228
 229         attr->dname = dget(dir);
 230         return dir;
 231 }
 232 EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
 233
 234 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */