// SPDX-License-Identifier: GPL-2.0-only

  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/random.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>
  
  /*
   * 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, &times) < 4) {
  		printk(KERN_WARNING
  			"FAULT_INJECTION: failed to parse arguments
  ");
  		return 0;
  	}
  
  	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.
  "
  		       "name %pd, interval %lu, probability %lu, "
  		       "space %d, times %d
  ", 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)
  		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(struct fault_attr *attr, ssize_t size)

  {

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

  		if (fail_nth) {
  			if (!WRITE_ONCE(current->fail_nth, fail_nth - 1))
  				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 (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 <= prandom_u32() % 100)

  		return false;

  	if (!fail_stacktrace(attr))
  		return false;

  fail:

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

  	return true;

  }

  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
  ");

  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
  ");

  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;
  
  	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_ul("require-start", mode, dir, &attr->require_start);
  	debugfs_create_ul("require-end", mode, dir, &attr->require_end);
  	debugfs_create_ul("reject-start", mode, dir, &attr->reject_start);
  	debugfs_create_ul("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 */