Quelle fault-inject.c Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/prandom.h>
#include <linux/debugfs.h>
#include <linux/sched.h>
#include <linux/stat.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/export.h>
#include <linux/interrupt.h>
#include <linux/stacktrace.h>
#include <linux/fault-inject.h>

/*
* The should_fail() functions use prandom instead of the normal Linux RNG
* since they don't need cryptographically secure random numbers.
*/
static DEFINE_PER_CPU(struct rnd_state, fault_rnd_state);

static u32 fault_prandom_u32_below_100(void)
{
struct rnd_state *state;
u32 res;

state = &get_cpu_var(fault_rnd_state);
res = prandom_u32_state(state);
put_cpu_var(fault_rnd_state);

return res % 100;
}

/*
* setup_fault_attr() is a helper function for various __setup handlers, so it
* returns 0 on error, because that is what __setup handlers do.
*/
int setup_fault_attr(struct fault_attr *attr, char *str)
{
unsigned long probability;
unsigned long interval;
int times;
int space;

/* "<interval>,<probability>,<space>,<times>" */
if (sscanf(str, "%lu,%lu,%d,%d",
   &interval, &probability, &space, ×) < 4) {
  printk(KERN_WARNING
   "FAULT_INJECTION: failed to parse arguments\n");
  return 0;
}

prandom_init_once(&fault_rnd_state);

attr->probability = probability;
attr->interval = interval;
atomic_set(&attr->times, times);
atomic_set(&attr->space, space);

return 1;
}
EXPORT_SYMBOL_GPL(setup_fault_attr);

static void fail_dump(struct fault_attr *attr)
{
if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
  printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
         "name %pd, interval %lu, probability %lu, "
         "space %d, times %d\n", attr->dname,
         attr->interval, attr->probability,
         atomic_read(&attr->space),
         atomic_read(&attr->times));
  if (attr->verbose > 1)
   dump_stack();
}
}

#define atomic_dec_not_zero(v)  atomic_add_unless((v), -1, 0)

static bool fail_task(struct fault_attr *attr, struct task_struct *task)
{
return in_task() && task->make_it_fail;
}

#define MAX_STACK_TRACE_DEPTH 32

#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER

static bool fail_stacktrace(struct fault_attr *attr)
{
int depth = attr->stacktrace_depth;
unsigned long entries[MAX_STACK_TRACE_DEPTH];
int n, nr_entries;
bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);

if (depth == 0 || (found && !attr->reject_start && !attr->reject_end))
  return found;

nr_entries = stack_trace_save(entries, depth, 1);
for (n = 0; n < nr_entries; n++) {
  if (attr->reject_start <= entries[n] &&
          entries[n] < attr->reject_end)
   return false;
  if (attr->require_start <= entries[n] &&
          entries[n] < attr->require_end)
   found = true;
}
return found;
}

#else

static inline bool fail_stacktrace(struct fault_attr *attr)
{
return true;
}

#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */

/*
* This code is stolen from failmalloc-1.0
* http://www.nongnu.org/failmalloc/
*/

bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags)
{
bool stack_checked = false;

if (in_task()) {
  unsigned int fail_nth = READ_ONCE(current->fail_nth);

  if (fail_nth) {
   if (!fail_stacktrace(attr))
    return false;

   stack_checked = true;
   fail_nth--;
   WRITE_ONCE(current->fail_nth, fail_nth);
   if (!fail_nth)
    goto fail;

   return false;
  }
}

/* No need to check any other properties if the probability is 0 */
if (attr->probability == 0)
  return false;

if (attr->task_filter && !fail_task(attr, current))
  return false;

if (atomic_read(&attr->times) == 0)
  return false;

if (!stack_checked && !fail_stacktrace(attr))
  return false;

if (atomic_read(&attr->space) > size) {
  atomic_sub(size, &attr->space);
  return false;
}

if (attr->interval > 1) {
  attr->count++;
  if (attr->count % attr->interval)
   return false;
}

if (attr->probability <= fault_prandom_u32_below_100())
  return false;

fail:
if (!(flags & FAULT_NOWARN))
  fail_dump(attr);

if (atomic_read(&attr->times) != -1)
  atomic_dec_not_zero(&attr->times);

return true;
}

bool should_fail(struct fault_attr *attr, ssize_t size)
{
return should_fail_ex(attr, size, 0);
}
EXPORT_SYMBOL_GPL(should_fail);

#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS

static int debugfs_ul_set(void *data, u64 val)
{
*(unsigned long *)data = val;
return 0;
}

static int debugfs_ul_get(void *data, u64 *val)
{
*val = *(unsigned long *)data;
return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");

static void debugfs_create_ul(const char *name, umode_t mode,
         struct dentry *parent, unsigned long *value)
{
debugfs_create_file(name, mode, parent, value, &fops_ul);
}

#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER

static int debugfs_stacktrace_depth_set(void *data, u64 val)
{
*(unsigned long *)data =
  min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);

return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
   debugfs_stacktrace_depth_set, "%llu\n");

static void debugfs_create_stacktrace_depth(const char *name, umode_t mode,
         struct dentry *parent,
         unsigned long *value)
{
debugfs_create_file(name, mode, parent, value, &fops_stacktrace_depth);
}

#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */

struct dentry *fault_create_debugfs_attr(const char *name,
   struct dentry *parent, struct fault_attr *attr)
{
umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
struct dentry *dir;

dir = debugfs_create_dir(name, parent);
if (IS_ERR(dir))
  return dir;

prandom_init_once(&fault_rnd_state);

debugfs_create_ul("probability", mode, dir, &attr->probability);
debugfs_create_ul("interval", mode, dir, &attr->interval);
debugfs_create_atomic_t("times", mode, dir, &attr->times);
debugfs_create_atomic_t("space", mode, dir, &attr->space);
debugfs_create_ul("verbose", mode, dir, &attr->verbose);
debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
      &attr->ratelimit_state.interval);
debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
      &attr->ratelimit_state.burst);
debugfs_create_bool("task-filter", mode, dir, &attr->task_filter);

#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
     &attr->stacktrace_depth);
debugfs_create_xul("require-start", mode, dir, &attr->require_start);
debugfs_create_xul("require-end", mode, dir, &attr->require_end);
debugfs_create_xul("reject-start", mode, dir, &attr->reject_start);
debugfs_create_xul("reject-end", mode, dir, &attr->reject_end);
#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */

attr->dname = dget(dir);
return dir;
}
EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);

#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */

#ifdef CONFIG_FAULT_INJECTION_CONFIGFS

/* These configfs attribute utilities are copied from drivers/block/null_blk/main.c */

static ssize_t fault_uint_attr_show(unsigned int val, char *page)
{
return snprintf(page, PAGE_SIZE, "%u\n", val);
}

static ssize_t fault_ulong_attr_show(unsigned long val, char *page)
{
return snprintf(page, PAGE_SIZE, "%lu\n", val);
}

static ssize_t fault_bool_attr_show(bool val, char *page)
{
return snprintf(page, PAGE_SIZE, "%u\n", val);
}

static ssize_t fault_atomic_t_attr_show(atomic_t val, char *page)
{
return snprintf(page, PAGE_SIZE, "%d\n", atomic_read(&val));
}

static ssize_t fault_uint_attr_store(unsigned int *val, const char *page, size_t count)
{
unsigned int tmp;
int result;

result = kstrtouint(page, 0, &tmp);
if (result < 0)
  return result;

*val = tmp;
return count;
}

static ssize_t fault_ulong_attr_store(unsigned long *val, const char *page, size_t count)
{
int result;
unsigned long tmp;

result = kstrtoul(page, 0, &tmp);
if (result < 0)
  return result;

*val = tmp;
return count;
}

static ssize_t fault_bool_attr_store(bool *val, const char *page, size_t count)
{
bool tmp;
int result;

result = kstrtobool(page, &tmp);
if (result < 0)
  return result;

*val = tmp;
return count;
}

static ssize_t fault_atomic_t_attr_store(atomic_t *val, const char *page, size_t count)
{
int tmp;
int result;

result = kstrtoint(page, 0, &tmp);
if (result < 0)
  return result;

atomic_set(val, tmp);
return count;
}

#define CONFIGFS_ATTR_NAMED(_pfx, _name, _attr_name) \
static struct configfs_attribute _pfx##attr_##_name = { \
.ca_name = _attr_name,   \
.ca_mode = 0644,    \
.ca_owner = THIS_MODULE,   \
.show  = _pfx##_name##_show,  \
.store  = _pfx##_name##_store,  \
}

static struct fault_config *to_fault_config(struct config_item *item)
{
return container_of(to_config_group(item), struct fault_config, group);
}

#define FAULT_CONFIGFS_ATTR_NAMED(NAME, ATTR_NAME, MEMBER, TYPE)    \
static ssize_t fault_##NAME##_show(struct config_item *item, char *page)   \
{            \
return fault_##TYPE##_attr_show(to_fault_config(item)->attr.MEMBER, page);  \
}            \
static ssize_t fault_##NAME##_store(struct config_item *item, const char *page, size_t count) \
{            \
struct fault_config *config = to_fault_config(item);     \
return fault_##TYPE##_attr_store(&config->attr.MEMBER, page, count);   \
}            \
CONFIGFS_ATTR_NAMED(fault_, NAME, ATTR_NAME)

#define FAULT_CONFIGFS_ATTR(NAME, TYPE) \
FAULT_CONFIGFS_ATTR_NAMED(NAME, __stringify(NAME), NAME, TYPE)

FAULT_CONFIGFS_ATTR(probability, ulong);
FAULT_CONFIGFS_ATTR(interval, ulong);
FAULT_CONFIGFS_ATTR(times, atomic_t);
FAULT_CONFIGFS_ATTR(space, atomic_t);
FAULT_CONFIGFS_ATTR(verbose, ulong);
FAULT_CONFIGFS_ATTR_NAMED(ratelimit_interval, "verbose_ratelimit_interval_ms",
  ratelimit_state.interval, uint);
FAULT_CONFIGFS_ATTR_NAMED(ratelimit_burst, "verbose_ratelimit_burst",
  ratelimit_state.burst, uint);
FAULT_CONFIGFS_ATTR_NAMED(task_filter, "task-filter", task_filter, bool);

#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER

static ssize_t fault_stacktrace_depth_show(struct config_item *item, char *page)
{
return fault_ulong_attr_show(to_fault_config(item)->attr.stacktrace_depth, page);
}

static ssize_t fault_stacktrace_depth_store(struct config_item *item, const char *page,
  size_t count)
{
int result;
unsigned long tmp;

result = kstrtoul(page, 0, &tmp);
if (result < 0)
  return result;

to_fault_config(item)->attr.stacktrace_depth =
  min_t(unsigned long, tmp, MAX_STACK_TRACE_DEPTH);

return count;
}

CONFIGFS_ATTR_NAMED(fault_, stacktrace_depth, "stacktrace-depth");

static ssize_t fault_xul_attr_show(unsigned long val, char *page)
{
return snprintf(page, PAGE_SIZE,
   sizeof(val) == sizeof(u32) ? "0x%08lx\n" : "0x%016lx\n", val);
}

static ssize_t fault_xul_attr_store(unsigned long *val, const char *page, size_t count)
{
return fault_ulong_attr_store(val, page, count);
}

FAULT_CONFIGFS_ATTR_NAMED(require_start, "require-start", require_start, xul);
FAULT_CONFIGFS_ATTR_NAMED(require_end, "require-end", require_end, xul);
FAULT_CONFIGFS_ATTR_NAMED(reject_start, "reject-start", reject_start, xul);
FAULT_CONFIGFS_ATTR_NAMED(reject_end, "reject-end", reject_end, xul);

#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */

static struct configfs_attribute *fault_config_attrs[] = {
&fault_attr_probability,
&fault_attr_interval,
&fault_attr_times,
&fault_attr_space,
&fault_attr_verbose,
&fault_attr_ratelimit_interval,
&fault_attr_ratelimit_burst,
&fault_attr_task_filter,
#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
&fault_attr_stacktrace_depth,
&fault_attr_require_start,
&fault_attr_require_end,
&fault_attr_reject_start,
&fault_attr_reject_end,
#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
NULL,
};

static const struct config_item_type fault_config_type = {
.ct_attrs = fault_config_attrs,
.ct_owner = THIS_MODULE,
};

void fault_config_init(struct fault_config *config, const char *name)
{
prandom_init_once(&fault_rnd_state);

config_group_init_type_name(&config->group, name, &fault_config_type);
}
EXPORT_SYMBOL_GPL(fault_config_init);

#endif /* CONFIG_FAULT_INJECTION_CONFIGFS */

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