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 __init 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}
  39
  40static void fail_dump(struct fault_attr *attr)
  41{
  42        if (attr->verbose > 0)
  43                printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure\n");
  44        if (attr->verbose > 1)
  45                dump_stack();
  46}
  47
  48#define atomic_dec_not_zero(v)          atomic_add_unless((v), -1, 0)
  49
  50static bool fail_task(struct fault_attr *attr, struct task_struct *task)
  51{
  52        return !in_interrupt() && task->make_it_fail;
  53}
  54
  55#define MAX_STACK_TRACE_DEPTH 32
  56
  57#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
  58
  59static bool fail_stacktrace(struct fault_attr *attr)
  60{
  61        struct stack_trace trace;
  62        int depth = attr->stacktrace_depth;
  63        unsigned long entries[MAX_STACK_TRACE_DEPTH];
  64        int n;
  65        bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
  66
  67        if (depth == 0)
  68                return found;
  69
  70        trace.nr_entries = 0;
  71        trace.entries = entries;
  72        trace.max_entries = depth;
  73        trace.skip = 1;
  74
  75        save_stack_trace(&trace);
  76        for (n = 0; n < trace.nr_entries; n++) {
  77                if (attr->reject_start <= entries[n] &&
  78                               entries[n] < attr->reject_end)
  79                        return false;
  80                if (attr->require_start <= entries[n] &&
  81                               entries[n] < attr->require_end)
  82                        found = true;
  83        }
  84        return found;
  85}
  86
  87#else
  88
  89static inline bool fail_stacktrace(struct fault_attr *attr)
  90{
  91        return true;
  92}
  93
  94#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
  95
  96/*
  97 * This code is stolen from failmalloc-1.0
  98 * http://www.nongnu.org/failmalloc/
  99 */
 100
 101bool should_fail(struct fault_attr *attr, ssize_t size)
 102{
 103        if (attr->task_filter && !fail_task(attr, current))
 104                return false;
 105
 106        if (atomic_read(&attr->times) == 0)
 107                return false;
 108
 109        if (atomic_read(&attr->space) > size) {
 110                atomic_sub(size, &attr->space);
 111                return false;
 112        }
 113
 114        if (attr->interval > 1) {
 115                attr->count++;
 116                if (attr->count % attr->interval)
 117                        return false;
 118        }
 119
 120        if (attr->probability <= random32() % 100)
 121                return false;
 122
 123        if (!fail_stacktrace(attr))
 124                return false;
 125
 126        fail_dump(attr);
 127
 128        if (atomic_read(&attr->times) != -1)
 129                atomic_dec_not_zero(&attr->times);
 130
 131        return true;
 132}
 133
 134#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 135
 136static int debugfs_ul_set(void *data, u64 val)
 137{
 138        *(unsigned long *)data = val;
 139        return 0;
 140}
 141
 142static int debugfs_ul_get(void *data, u64 *val)
 143{
 144        *val = *(unsigned long *)data;
 145        return 0;
 146}
 147
 148DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
 149
 150static struct dentry *debugfs_create_ul(const char *name, mode_t mode,
 151                                struct dentry *parent, unsigned long *value)
 152{
 153        return debugfs_create_file(name, mode, parent, value, &fops_ul);
 154}
 155
 156#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 157
 158static int debugfs_stacktrace_depth_set(void *data, u64 val)
 159{
 160        *(unsigned long *)data =
 161                min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
 162
 163        return 0;
 164}
 165
 166DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
 167                        debugfs_stacktrace_depth_set, "%llu\n");
 168
 169static struct dentry *debugfs_create_stacktrace_depth(
 170        const char *name, mode_t mode,
 171        struct dentry *parent, unsigned long *value)
 172{
 173        return debugfs_create_file(name, mode, parent, value,
 174                                   &fops_stacktrace_depth);
 175}
 176
 177#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 178
 179static int debugfs_atomic_t_set(void *data, u64 val)
 180{
 181        atomic_set((atomic_t *)data, val);
 182        return 0;
 183}
 184
 185static int debugfs_atomic_t_get(void *data, u64 *val)
 186{
 187        *val = atomic_read((atomic_t *)data);
 188        return 0;
 189}
 190
 191DEFINE_SIMPLE_ATTRIBUTE(fops_atomic_t, debugfs_atomic_t_get,
 192                        debugfs_atomic_t_set, "%lld\n");
 193
 194static struct dentry *debugfs_create_atomic_t(const char *name, mode_t mode,
 195                                struct dentry *parent, atomic_t *value)
 196{
 197        return debugfs_create_file(name, mode, parent, value, &fops_atomic_t);
 198}
 199
 200struct dentry *fault_create_debugfs_attr(const char *name,
 201                        struct dentry *parent, struct fault_attr *attr)
 202{
 203        mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
 204        struct dentry *dir;
 205
 206        dir = debugfs_create_dir(name, parent);
 207        if (!dir)
 208                return ERR_PTR(-ENOMEM);
 209
 210        if (!debugfs_create_ul("probability", mode, dir, &attr->probability))
 211                goto fail;
 212        if (!debugfs_create_ul("interval", mode, dir, &attr->interval))
 213                goto fail;
 214        if (!debugfs_create_atomic_t("times", mode, dir, &attr->times))
 215                goto fail;
 216        if (!debugfs_create_atomic_t("space", mode, dir, &attr->space))
 217                goto fail;
 218        if (!debugfs_create_ul("verbose", mode, dir, &attr->verbose))
 219                goto fail;
 220        if (!debugfs_create_bool("task-filter", mode, dir, &attr->task_filter))
 221                goto fail;
 222
 223#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
 224
 225        if (!debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
 226                                &attr->stacktrace_depth))
 227                goto fail;
 228        if (!debugfs_create_ul("require-start", mode, dir,
 229                                &attr->require_start))
 230                goto fail;
 231        if (!debugfs_create_ul("require-end", mode, dir, &attr->require_end))
 232                goto fail;
 233        if (!debugfs_create_ul("reject-start", mode, dir, &attr->reject_start))
 234                goto fail;
 235        if (!debugfs_create_ul("reject-end", mode, dir, &attr->reject_end))
 236                goto fail;
 237
 238#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
 239
 240        return dir;
 241fail:
 242        debugfs_remove_recursive(dir);
 243
 244        return ERR_PTR(-ENOMEM);
 245}
 246
 247#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
 248
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