linux/lib/fault-inject.c
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   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 */
  17int 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}
  39EXPORT_SYMBOL_GPL(setup_fault_attr);
  40
  41static void fail_dump(struct fault_attr *attr)
  42{
  43        if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
  44                printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
  45                       "name %pd, interval %lu, probability %lu, "
  46                       "space %d, times %d\n", attr->dname,
  47                       attr->probability, attr->interval,
  48                       atomic_read(&attr->space),
  49                       atomic_read(&attr->times));
  50                if (attr->verbose > 1)
  51                        dump_stack();
  52        }
  53}
  54
  55#define atomic_dec_not_zero(v)          atomic_add_unless((v), -1, 0)
  56
  57static bool fail_task(struct fault_attr *attr, struct task_struct *task)
  58{
  59        return !in_interrupt() && task->make_it_fail;
  60}
  61
  62#define MAX_STACK_TRACE_DEPTH 32
  63
  64#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
  65
  66static bool fail_stacktrace(struct fault_attr *attr)
  67{
  68        struct stack_trace trace;
  69        int depth = attr->stacktrace_depth;
  70        unsigned long entries[MAX_STACK_TRACE_DEPTH];
  71        int n;
  72        bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
  73
  74        if (depth == 0)
  75                return found;
  76
  77        trace.nr_entries = 0;
  78        trace.entries = entries;
  79        trace.max_entries = depth;
  80        trace.skip = 1;
  81
  82        save_stack_trace(&trace);
  83        for (n = 0; n < trace.nr_entries; n++) {
  84                if (attr->reject_start <= entries[n] &&
  85                               entries[n] < attr->reject_end)
  86                        return false;
  87                if (attr->require_start <= entries[n] &&
  88                               entries[n] < attr->require_end)
  89                        found = true;
  90        }
  91        return found;
  92}
  93
  94#else
  95
  96static inline bool fail_stacktrace(struct fault_attr *attr)
  97{
  98        return true;
  99}
 100
 101#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 102
 103/*
 104 * This code is stolen from failmalloc-1.0
 105 * http://www.nongnu.org/failmalloc/
 106 */
 107
 108bool should_fail(struct fault_attr *attr, ssize_t size)
 109{
 110        /* No need to check any other properties if the probability is 0 */
 111        if (attr->probability == 0)
 112                return false;
 113
 114        if (attr->task_filter && !fail_task(attr, current))
 115                return false;
 116
 117        if (atomic_read(&attr->times) == 0)
 118                return false;
 119
 120        if (atomic_read(&attr->space) > size) {
 121                atomic_sub(size, &attr->space);
 122                return false;
 123        }
 124
 125        if (attr->interval > 1) {
 126                attr->count++;
 127                if (attr->count % attr->interval)
 128                        return false;
 129        }
 130
 131        if (attr->probability <= prandom_u32() % 100)
 132                return false;
 133
 134        if (!fail_stacktrace(attr))
 135                return false;
 136
 137        fail_dump(attr);
 138
 139        if (atomic_read(&attr->times) != -1)
 140                atomic_dec_not_zero(&attr->times);
 141
 142        return true;
 143}
 144EXPORT_SYMBOL_GPL(should_fail);
 145
 146#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 147
 148static int debugfs_ul_set(void *data, u64 val)
 149{
 150        *(unsigned long *)data = val;
 151        return 0;
 152}
 153
 154static int debugfs_ul_get(void *data, u64 *val)
 155{
 156        *val = *(unsigned long *)data;
 157        return 0;
 158}
 159
 160DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
 161
 162static struct dentry *debugfs_create_ul(const char *name, umode_t mode,
 163                                struct dentry *parent, unsigned long *value)
 164{
 165        return debugfs_create_file(name, mode, parent, value, &fops_ul);
 166}
 167
 168#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 169
 170static int debugfs_stacktrace_depth_set(void *data, u64 val)
 171{
 172        *(unsigned long *)data =
 173                min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
 174
 175        return 0;
 176}
 177
 178DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
 179                        debugfs_stacktrace_depth_set, "%llu\n");
 180
 181static struct dentry *debugfs_create_stacktrace_depth(
 182        const char *name, umode_t mode,
 183        struct dentry *parent, unsigned long *value)
 184{
 185        return debugfs_create_file(name, mode, parent, value,
 186                                   &fops_stacktrace_depth);
 187}
 188
 189#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 190
 191struct dentry *fault_create_debugfs_attr(const char *name,
 192                        struct dentry *parent, struct fault_attr *attr)
 193{
 194        umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
 195        struct dentry *dir;
 196
 197        dir = debugfs_create_dir(name, parent);
 198        if (!dir)
 199                return ERR_PTR(-ENOMEM);
 200
 201        if (!debugfs_create_ul("probability", mode, dir, &attr->probability))
 202                goto fail;
 203        if (!debugfs_create_ul("interval", mode, dir, &attr->interval))
 204                goto fail;
 205        if (!debugfs_create_atomic_t("times", mode, dir, &attr->times))
 206                goto fail;
 207        if (!debugfs_create_atomic_t("space", mode, dir, &attr->space))
 208                goto fail;
 209        if (!debugfs_create_ul("verbose", mode, dir, &attr->verbose))
 210                goto fail;
 211        if (!debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
 212                                &attr->ratelimit_state.interval))
 213                goto fail;
 214        if (!debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
 215                                &attr->ratelimit_state.burst))
 216                goto fail;
 217        if (!debugfs_create_bool("task-filter", mode, dir, &attr->task_filter))
 218                goto fail;
 219
 220#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 221
 222        if (!debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
 223                                &attr->stacktrace_depth))
 224                goto fail;
 225        if (!debugfs_create_ul("require-start", mode, dir,
 226                                &attr->require_start))
 227                goto fail;
 228        if (!debugfs_create_ul("require-end", mode, dir, &attr->require_end))
 229                goto fail;
 230        if (!debugfs_create_ul("reject-start", mode, dir, &attr->reject_start))
 231                goto fail;
 232        if (!debugfs_create_ul("reject-end", mode, dir, &attr->reject_end))
 233                goto fail;
 234
 235#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 236
 237        attr->dname = dget(dir);
 238        return dir;
 239fail:
 240        debugfs_remove_recursive(dir);
 241
 242        return ERR_PTR(-ENOMEM);
 243}
 244EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
 245
 246#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
 247