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/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 */
  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)
  44                printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure\n");
  45        if (attr->verbose > 1)
  46                dump_stack();
  47}
  48
  49#define atomic_dec_not_zero(v)          atomic_add_unless((v), -1, 0)
  50
  51static bool fail_task(struct fault_attr *attr, struct task_struct *task)
  52{
  53        return !in_interrupt() && task->make_it_fail;
  54}
  55
  56#define MAX_STACK_TRACE_DEPTH 32
  57
  58#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
  59
  60static bool fail_stacktrace(struct fault_attr *attr)
  61{
  62        struct stack_trace trace;
  63        int depth = attr->stacktrace_depth;
  64        unsigned long entries[MAX_STACK_TRACE_DEPTH];
  65        int n;
  66        bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
  67
  68        if (depth == 0)
  69                return found;
  70
  71        trace.nr_entries = 0;
  72        trace.entries = entries;
  73        trace.max_entries = depth;
  74        trace.skip = 1;
  75
  76        save_stack_trace(&trace);
  77        for (n = 0; n < trace.nr_entries; n++) {
  78                if (attr->reject_start <= entries[n] &&
  79                               entries[n] < attr->reject_end)
  80                        return false;
  81                if (attr->require_start <= entries[n] &&
  82                               entries[n] < attr->require_end)
  83                        found = true;
  84        }
  85        return found;
  86}
  87
  88#else
  89
  90static inline bool fail_stacktrace(struct fault_attr *attr)
  91{
  92        return true;
  93}
  94
  95#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
  96
  97/*
  98 * This code is stolen from failmalloc-1.0
  99 * http://www.nongnu.org/failmalloc/
 100 */
 101
 102bool should_fail(struct fault_attr *attr, ssize_t size)
 103{
 104        if (attr->task_filter && !fail_task(attr, current))
 105                return false;
 106
 107        if (atomic_read(&attr->times) == 0)
 108                return false;
 109
 110        if (atomic_read(&attr->space) > size) {
 111                atomic_sub(size, &attr->space);
 112                return false;
 113        }
 114
 115        if (attr->interval > 1) {
 116                attr->count++;
 117                if (attr->count % attr->interval)
 118                        return false;
 119        }
 120
 121        if (attr->probability <= random32() % 100)
 122                return false;
 123
 124        if (!fail_stacktrace(attr))
 125                return false;
 126
 127        fail_dump(attr);
 128
 129        if (atomic_read(&attr->times) != -1)
 130                atomic_dec_not_zero(&attr->times);
 131
 132        return true;
 133}
 134EXPORT_SYMBOL_GPL(should_fail);
 135
 136#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 137
 138static int debugfs_ul_set(void *data, u64 val)
 139{
 140        *(unsigned long *)data = val;
 141        return 0;
 142}
 143
 144static int debugfs_ul_get(void *data, u64 *val)
 145{
 146        *val = *(unsigned long *)data;
 147        return 0;
 148}
 149
 150DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
 151
 152static struct dentry *debugfs_create_ul(const char *name, umode_t mode,
 153                                struct dentry *parent, unsigned long *value)
 154{
 155        return debugfs_create_file(name, mode, parent, value, &fops_ul);
 156}
 157
 158#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 159
 160static int debugfs_stacktrace_depth_set(void *data, u64 val)
 161{
 162        *(unsigned long *)data =
 163                min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
 164
 165        return 0;
 166}
 167
 168DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
 169                        debugfs_stacktrace_depth_set, "%llu\n");
 170
 171static struct dentry *debugfs_create_stacktrace_depth(
 172        const char *name, umode_t mode,
 173        struct dentry *parent, unsigned long *value)
 174{
 175        return debugfs_create_file(name, mode, parent, value,
 176                                   &fops_stacktrace_depth);
 177}
 178
 179#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 180
 181static int debugfs_atomic_t_set(void *data, u64 val)
 182{
 183        atomic_set((atomic_t *)data, val);
 184        return 0;
 185}
 186
 187static int debugfs_atomic_t_get(void *data, u64 *val)
 188{
 189        *val = atomic_read((atomic_t *)data);
 190        return 0;
 191}
 192
 193DEFINE_SIMPLE_ATTRIBUTE(fops_atomic_t, debugfs_atomic_t_get,
 194                        debugfs_atomic_t_set, "%lld\n");
 195
 196static struct dentry *debugfs_create_atomic_t(const char *name, umode_t mode,
 197                                struct dentry *parent, atomic_t *value)
 198{
 199        return debugfs_create_file(name, mode, parent, value, &fops_atomic_t);
 200}
 201
 202struct 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 (!dir)
 210                return ERR_PTR(-ENOMEM);
 211
 212        if (!debugfs_create_ul("probability", mode, dir, &attr->probability))
 213                goto fail;
 214        if (!debugfs_create_ul("interval", mode, dir, &attr->interval))
 215                goto fail;
 216        if (!debugfs_create_atomic_t("times", mode, dir, &attr->times))
 217                goto fail;
 218        if (!debugfs_create_atomic_t("space", mode, dir, &attr->space))
 219                goto fail;
 220        if (!debugfs_create_ul("verbose", mode, dir, &attr->verbose))
 221                goto fail;
 222        if (!debugfs_create_bool("task-filter", mode, dir, &attr->task_filter))
 223                goto fail;
 224
 225#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 226
 227        if (!debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
 228                                &attr->stacktrace_depth))
 229                goto fail;
 230        if (!debugfs_create_ul("require-start", mode, dir,
 231                                &attr->require_start))
 232                goto fail;
 233        if (!debugfs_create_ul("require-end", mode, dir, &attr->require_end))
 234                goto fail;
 235        if (!debugfs_create_ul("reject-start", mode, dir, &attr->reject_start))
 236                goto fail;
 237        if (!debugfs_create_ul("reject-end", mode, dir, &attr->reject_end))
 238                goto fail;
 239
 240#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 241
 242        return dir;
 243fail:
 244        debugfs_remove_recursive(dir);
 245
 246        return ERR_PTR(-ENOMEM);
 247}
 248EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
 249
 250#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
 251