// SPDX-License-Identifier: GPL-2.0

  #define pr_fmt(fmt) "kcsan: " fmt

  #include <linux/atomic.h>
  #include <linux/bsearch.h>
  #include <linux/bug.h>
  #include <linux/debugfs.h>
  #include <linux/init.h>
  #include <linux/kallsyms.h>

  #include <linux/sched.h>

  #include <linux/seq_file.h>
  #include <linux/slab.h>
  #include <linux/sort.h>
  #include <linux/string.h>
  #include <linux/uaccess.h>
  
  #include "kcsan.h"

  atomic_long_t kcsan_counters[KCSAN_COUNTER_COUNT];

  static const char *const counter_names[] = {
  	[KCSAN_COUNTER_USED_WATCHPOINTS]		= "used_watchpoints",
  	[KCSAN_COUNTER_SETUP_WATCHPOINTS]		= "setup_watchpoints",
  	[KCSAN_COUNTER_DATA_RACES]			= "data_races",
  	[KCSAN_COUNTER_ASSERT_FAILURES]			= "assert_failures",
  	[KCSAN_COUNTER_NO_CAPACITY]			= "no_capacity",
  	[KCSAN_COUNTER_REPORT_RACES]			= "report_races",
  	[KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN]		= "races_unknown_origin",
  	[KCSAN_COUNTER_UNENCODABLE_ACCESSES]		= "unencodable_accesses",
  	[KCSAN_COUNTER_ENCODING_FALSE_POSITIVES]	= "encoding_false_positives",
  };
  static_assert(ARRAY_SIZE(counter_names) == KCSAN_COUNTER_COUNT);

  
  /*
   * Addresses for filtering functions from reporting. This list can be used as a
   * whitelist or blacklist.
   */
  static struct {

  	unsigned long	*addrs;		/* array of addresses */
  	size_t		size;		/* current size */
  	int		used;		/* number of elements used */
  	bool		sorted;		/* if elements are sorted */
  	bool		whitelist;	/* if list is a blacklist or whitelist */

  } report_filterlist = {

  	.addrs		= NULL,
  	.size		= 8,		/* small initial size */
  	.used		= 0,
  	.sorted		= false,
  	.whitelist	= false,	/* default is blacklist */

  };
  static DEFINE_SPINLOCK(report_filterlist_lock);

  /*
   * The microbenchmark allows benchmarking KCSAN core runtime only. To run
   * multiple threads, pipe 'microbench=<iters>' from multiple tasks into the

   * debugfs file. This will not generate any conflicts, and tests fast-path only.

   */

  static noinline void microbenchmark(unsigned long iters)

  {

  	const struct kcsan_ctx ctx_save = current->kcsan_ctx;
  	const bool was_enabled = READ_ONCE(kcsan_enabled);

  	cycles_t cycles;

  	/* We may have been called from an atomic region; reset context. */
  	memset(&current->kcsan_ctx, 0, sizeof(current->kcsan_ctx));
  	/*
  	 * Disable to benchmark fast-path for all accesses, and (expected
  	 * negligible) call into slow-path, but never set up watchpoints.
  	 */
  	WRITE_ONCE(kcsan_enabled, false);

  	pr_info("%s begin | iters: %lu
  ", __func__, iters);

  
  	cycles = get_cycles();
  	while (iters--) {

  		unsigned long addr = iters & ((PAGE_SIZE << 8) - 1);
  		int type = !(iters & 0x7f) ? KCSAN_ACCESS_ATOMIC :
  				(!(iters & 0xf) ? KCSAN_ACCESS_WRITE : 0);
  		__kcsan_check_access((void *)addr, sizeof(long), type);

  	}
  	cycles = get_cycles() - cycles;

  	pr_info("%s end   | cycles: %llu
  ", __func__, cycles);

  
  	WRITE_ONCE(kcsan_enabled, was_enabled);
  	/* restore context */
  	current->kcsan_ctx = ctx_save;

  }
  
  static int cmp_filterlist_addrs(const void *rhs, const void *lhs)
  {
  	const unsigned long a = *(const unsigned long *)rhs;
  	const unsigned long b = *(const unsigned long *)lhs;
  
  	return a < b ? -1 : a == b ? 0 : 1;
  }
  
  bool kcsan_skip_report_debugfs(unsigned long func_addr)
  {
  	unsigned long symbolsize, offset;
  	unsigned long flags;
  	bool ret = false;
  
  	if (!kallsyms_lookup_size_offset(func_addr, &symbolsize, &offset))
  		return false;

  	func_addr -= offset; /* Get function start */

  
  	spin_lock_irqsave(&report_filterlist_lock, flags);
  	if (report_filterlist.used == 0)
  		goto out;
  
  	/* Sort array if it is unsorted, and then do a binary search. */
  	if (!report_filterlist.sorted) {
  		sort(report_filterlist.addrs, report_filterlist.used,
  		     sizeof(unsigned long), cmp_filterlist_addrs, NULL);
  		report_filterlist.sorted = true;
  	}
  	ret = !!bsearch(&func_addr, report_filterlist.addrs,
  			report_filterlist.used, sizeof(unsigned long),
  			cmp_filterlist_addrs);
  	if (report_filterlist.whitelist)
  		ret = !ret;
  
  out:
  	spin_unlock_irqrestore(&report_filterlist_lock, flags);
  	return ret;
  }
  
  static void set_report_filterlist_whitelist(bool whitelist)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&report_filterlist_lock, flags);
  	report_filterlist.whitelist = whitelist;
  	spin_unlock_irqrestore(&report_filterlist_lock, flags);
  }
  
  /* Returns 0 on success, error-code otherwise. */
  static ssize_t insert_report_filterlist(const char *func)
  {
  	unsigned long flags;
  	unsigned long addr = kallsyms_lookup_name(func);
  	ssize_t ret = 0;
  
  	if (!addr) {

  		pr_err("could not find function: '%s'
  ", func);

  		return -ENOENT;
  	}
  
  	spin_lock_irqsave(&report_filterlist_lock, flags);
  
  	if (report_filterlist.addrs == NULL) {
  		/* initial allocation */
  		report_filterlist.addrs =
  			kmalloc_array(report_filterlist.size,

  				      sizeof(unsigned long), GFP_ATOMIC);

  		if (report_filterlist.addrs == NULL) {
  			ret = -ENOMEM;
  			goto out;
  		}
  	} else if (report_filterlist.used == report_filterlist.size) {
  		/* resize filterlist */
  		size_t new_size = report_filterlist.size * 2;
  		unsigned long *new_addrs =
  			krealloc(report_filterlist.addrs,

  				 new_size * sizeof(unsigned long), GFP_ATOMIC);

  
  		if (new_addrs == NULL) {
  			/* leave filterlist itself untouched */
  			ret = -ENOMEM;
  			goto out;
  		}
  
  		report_filterlist.size = new_size;
  		report_filterlist.addrs = new_addrs;
  	}
  
  	/* Note: deduplicating should be done in userspace. */
  	report_filterlist.addrs[report_filterlist.used++] =
  		kallsyms_lookup_name(func);
  	report_filterlist.sorted = false;
  
  out:
  	spin_unlock_irqrestore(&report_filterlist_lock, flags);

  	return ret;
  }
  
  static int show_info(struct seq_file *file, void *v)
  {
  	int i;
  	unsigned long flags;
  
  	/* show stats */
  	seq_printf(file, "enabled: %i
  ", READ_ONCE(kcsan_enabled));

  	for (i = 0; i < KCSAN_COUNTER_COUNT; ++i) {
  		seq_printf(file, "%s: %ld
  ", counter_names[i],
  			   atomic_long_read(&kcsan_counters[i]));
  	}

  
  	/* show filter functions, and filter type */
  	spin_lock_irqsave(&report_filterlist_lock, flags);
  	seq_printf(file, "
  %s functions: %s
  ",
  		   report_filterlist.whitelist ? "whitelisted" : "blacklisted",
  		   report_filterlist.used == 0 ? "none" : "");
  	for (i = 0; i < report_filterlist.used; ++i)
  		seq_printf(file, " %ps
  ", (void *)report_filterlist.addrs[i]);
  	spin_unlock_irqrestore(&report_filterlist_lock, flags);
  
  	return 0;
  }
  
  static int debugfs_open(struct inode *inode, struct file *file)
  {
  	return single_open(file, show_info, NULL);
  }

  static ssize_t
  debugfs_write(struct file *file, const char __user *buf, size_t count, loff_t *off)

  {
  	char kbuf[KSYM_NAME_LEN];
  	char *arg;
  	int read_len = count < (sizeof(kbuf) - 1) ? count : (sizeof(kbuf) - 1);
  
  	if (copy_from_user(kbuf, buf, read_len))
  		return -EFAULT;
  	kbuf[read_len] = '\0';
  	arg = strstrip(kbuf);
  
  	if (!strcmp(arg, "on")) {
  		WRITE_ONCE(kcsan_enabled, true);
  	} else if (!strcmp(arg, "off")) {
  		WRITE_ONCE(kcsan_enabled, false);

  	} else if (str_has_prefix(arg, "microbench=")) {

  		unsigned long iters;

  		if (kstrtoul(&arg[strlen("microbench=")], 0, &iters))

  			return -EINVAL;
  		microbenchmark(iters);
  	} else if (!strcmp(arg, "whitelist")) {
  		set_report_filterlist_whitelist(true);
  	} else if (!strcmp(arg, "blacklist")) {
  		set_report_filterlist_whitelist(false);
  	} else if (arg[0] == '!') {
  		ssize_t ret = insert_report_filterlist(&arg[1]);
  
  		if (ret < 0)
  			return ret;
  	} else {
  		return -EINVAL;
  	}
  
  	return count;
  }

  static const struct file_operations debugfs_ops =
  {
  	.read	 = seq_read,
  	.open	 = debugfs_open,
  	.write	 = debugfs_write,
  	.release = single_release
  };

  
  void __init kcsan_debugfs_init(void)
  {
  	debugfs_create_file("kcsan", 0644, NULL, NULL, &debugfs_ops);
  }