lockdep_proc.c

// SPDX-License-Identifier: GPL-2.0
/*
 * kernel/lockdep_proc.c
 *
 * Runtime locking correctness validator
 *
 * Started by Ingo Molnar:
 *
 *  Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
 *
 * Code for /proc/lockdep and /proc/lockdep_stats:
 *
 */
#include <linux/export.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/kallsyms.h>
#include <linux/debug_locks.h>
#include <linux/vmalloc.h>
#include <linux/sort.h>
#include <linux/uaccess.h>
#include <asm/div64.h>

#include "lockdep_internals.h"

/*
 * Since iteration of lock_classes is done without holding the lockdep lock,
 * it is not safe to iterate all_lock_classes list directly as the iteration
 * may branch off to free_lock_classes or the zapped list. Iteration is done
 * directly on the lock_classes array by checking the lock_classes_in_use
 * bitmap and max_lock_class_idx.
 */
#define iterate_lock_classes(idx, class)				\
	for (idx = 0, class = lock_classes; idx <= max_lock_class_idx;	\
	     idx++, class++)

static void *l_next(struct seq_file *m, void *v, loff_t *pos)
{
	struct lock_class *class = v;

	++class;
	*pos = class - lock_classes;
	return (*pos > max_lock_class_idx) ? NULL : class;
}

static void *l_start(struct seq_file *m, loff_t *pos)
{
	unsigned long idx = *pos;

	if (idx > max_lock_class_idx)
		return NULL;
	return lock_classes + idx;
}

static void l_stop(struct seq_file *m, void *v)
{
}

static void print_name(struct seq_file *m, struct lock_class *class)
{
	char str[KSYM_NAME_LEN];
	const char *name = class->name;

	if (!name) {
		name = __get_key_name(class->key, str);
		seq_printf(m, "%s", name);
	} else{
		seq_printf(m, "%s", name);
		if (class->name_version > 1)
			seq_printf(m, "#%d", class->name_version);
		if (class->subclass)
			seq_printf(m, "/%d", class->subclass);
	}
}

static int l_show(struct seq_file *m, void *v)
{
	struct lock_class *class = v;
	struct lock_list *entry;
	char usage[LOCK_USAGE_CHARS];
	int idx = class - lock_classes;

	if (v == lock_classes)
		seq_printf(m, "all lock classes:\n");

	if (!test_bit(idx, lock_classes_in_use))
		return 0;

	seq_printf(m, "%p", class->key);
#ifdef CONFIG_DEBUG_LOCKDEP
	seq_printf(m, " OPS:%8ld", debug_class_ops_read(class));
#endif
	if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
		seq_printf(m, " FD:%5ld", lockdep_count_forward_deps(class));
		seq_printf(m, " BD:%5ld", lockdep_count_backward_deps(class));

		get_usage_chars(class, usage);
		seq_printf(m, " %s", usage);
	}

	seq_printf(m, ": ");
	print_name(m, class);
	seq_puts(m, "\n");

	if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
		list_for_each_entry(entry, &class->locks_after, entry) {
			if (entry->distance == 1) {
				seq_printf(m, " -> [%p] ", entry->class->key);
				print_name(m, entry->class);
				seq_puts(m, "\n");
			}
		}
		seq_puts(m, "\n");
	}

	return 0;
}

static const struct seq_operations lockdep_ops = {
	.start	= l_start,
	.next	= l_next,
	.stop	= l_stop,
	.show	= l_show,
};

#ifdef CONFIG_PROVE_LOCKING
static void *lc_start(struct seq_file *m, loff_t *pos)
{
	if (*pos < 0)
		return NULL;

	if (*pos == 0)
		return SEQ_START_TOKEN;

	return lock_chains + (*pos - 1);
}

static void *lc_next(struct seq_file *m, void *v, loff_t *pos)
{
	*pos = lockdep_next_lockchain(*pos - 1) + 1;
	return lc_start(m, pos);
}

static void lc_stop(struct seq_file *m, void *v)
{
}

static int lc_show(struct seq_file *m, void *v)
{
	struct lock_chain *chain = v;
	struct lock_class *class;
	int i;
	static const char * const irq_strs[] = {
		[0]			     = "0",
		[LOCK_CHAIN_HARDIRQ_CONTEXT] = "hardirq",
		[LOCK_CHAIN_SOFTIRQ_CONTEXT] = "softirq",
		[LOCK_CHAIN_SOFTIRQ_CONTEXT|
		 LOCK_CHAIN_HARDIRQ_CONTEXT] = "hardirq|softirq",
	};

	if (v == SEQ_START_TOKEN) {
		if (!nr_free_chain_hlocks)
			seq_printf(m, "(buggered) ");
		seq_printf(m, "all lock chains:\n");
		return 0;
	}

	seq_printf(m, "irq_context: %s\n", irq_strs[chain->irq_context]);

	for (i = 0; i < chain->depth; i++) {
		class = lock_chain_get_class(chain, i);
		if (!class->key)
			continue;

		seq_printf(m, "[%p] ", class->key);
		print_name(m, class);
		seq_puts(m, "\n");
	}
	seq_puts(m, "\n");

	return 0;
}

static const struct seq_operations lockdep_chains_ops = {
	.start	= lc_start,
	.next	= lc_next,
	.stop	= lc_stop,
	.show	= lc_show,
};
#endif /* CONFIG_PROVE_LOCKING */

static void lockdep_stats_debug_show(struct seq_file *m)
{
#ifdef CONFIG_DEBUG_LOCKDEP
	unsigned long long hi1 = debug_atomic_read(hardirqs_on_events),
			   hi2 = debug_atomic_read(hardirqs_off_events),
			   hr1 = debug_atomic_read(redundant_hardirqs_on),
			   hr2 = debug_atomic_read(redundant_hardirqs_off),
			   si1 = debug_atomic_read(softirqs_on_events),
			   si2 = debug_atomic_read(softirqs_off_events),
			   sr1 = debug_atomic_read(redundant_softirqs_on),
			   sr2 = debug_atomic_read(redundant_softirqs_off);

	seq_printf(m, " chain lookup misses:           %11llu\n",
		debug_atomic_read(chain_lookup_misses));
	seq_printf(m, " chain lookup hits:             %11llu\n",
		debug_atomic_read(chain_lookup_hits));
	seq_printf(m, " cyclic checks:                 %11llu\n",
		debug_atomic_read(nr_cyclic_checks));
	seq_printf(m, " redundant checks:              %11llu\n",
		debug_atomic_read(nr_redundant_checks));
	seq_printf(m, " redundant links:               %11llu\n",
		debug_atomic_read(nr_redundant));
	seq_printf(m, " find-mask forwards checks:     %11llu\n",
		debug_atomic_read(nr_find_usage_forwards_checks));
	seq_printf(m, " find-mask backwards checks:    %11llu\n",
		debug_atomic_read(nr_find_usage_backwards_checks));

	seq_printf(m, " hardirq on events:             %11llu\n", hi1);
	seq_printf(m, " hardirq off events:            %11llu\n", hi2);
	seq_printf(m, " redundant hardirq ons:         %11llu\n", hr1);
	seq_printf(m, " redundant hardirq offs:        %11llu\n", hr2);
	seq_printf(m, " softirq on events:             %11llu\n", si1);
	seq_printf(m, " softirq off events:            %11llu\n", si2);
	seq_printf(m, " redundant softirq ons:         %11llu\n", sr1);
	seq_printf(m, " redundant softirq offs:        %11llu\n", sr2);
#endif
}

static int lockdep_stats_show(struct seq_file *m, void *v)
{
	unsigned long nr_unused = 0, nr_uncategorized = 0,
		      nr_irq_safe = 0, nr_irq_unsafe = 0,
		      nr_softirq_safe = 0, nr_softirq_unsafe = 0,
		      nr_hardirq_safe = 0, nr_hardirq_unsafe = 0,
		      nr_irq_read_safe = 0, nr_irq_read_unsafe = 0,
		      nr_softirq_read_safe = 0, nr_softirq_read_unsafe = 0,
		      nr_hardirq_read_safe = 0, nr_hardirq_read_unsafe = 0,
		      sum_forward_deps = 0;

#ifdef CONFIG_PROVE_LOCKING
	struct lock_class *class;
	unsigned long idx;

	iterate_lock_classes(idx, class) {
		if (!test_bit(idx, lock_classes_in_use))
			continue;

		if (class->usage_mask == 0)
			nr_unused++;
		if (class->usage_mask == LOCKF_USED)
			nr_uncategorized++;
		if (class->usage_mask & LOCKF_USED_IN_IRQ)
			nr_irq_safe++;
		if (class->usage_mask & LOCKF_ENABLED_IRQ)
			nr_irq_unsafe++;
		if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ)
			nr_softirq_safe++;
		if (class->usage_mask & LOCKF_ENABLED_SOFTIRQ)
			nr_softirq_unsafe++;
		if (class->usage_mask & LOCKF_USED_IN_HARDIRQ)
			nr_hardirq_safe++;
		if (class->usage_mask & LOCKF_ENABLED_HARDIRQ)
			nr_hardirq_unsafe++;
		if (class->usage_mask & LOCKF_USED_IN_IRQ_READ)
			nr_irq_read_safe++;
		if (class->usage_mask & LOCKF_ENABLED_IRQ_READ)
			nr_irq_read_unsafe++;
		if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ_READ)
			nr_softirq_read_safe++;
		if (class->usage_mask & LOCKF_ENABLED_SOFTIRQ_READ)
			nr_softirq_read_unsafe++;
		if (class->usage_mask & LOCKF_USED_IN_HARDIRQ_READ)
			nr_hardirq_read_safe++;
		if (class->usage_mask & LOCKF_ENABLED_HARDIRQ_READ)
			nr_hardirq_read_unsafe++;

		sum_forward_deps += lockdep_count_forward_deps(class);
	}

#ifdef CONFIG_DEBUG_LOCKDEP
	DEBUG_LOCKS_WARN_ON(debug_atomic_read(nr_unused_locks) != nr_unused);
#endif

#endif
	seq_printf(m, " lock-classes:                  %11lu [max: %lu]\n",
			nr_lock_classes, MAX_LOCKDEP_KEYS);
	seq_printf(m, " direct dependencies:           %11lu [max: %lu]\n",
			nr_list_entries, MAX_LOCKDEP_ENTRIES);
	seq_printf(m, " indirect dependencies:         %11lu\n",
			sum_forward_deps);

	/*
	 * Total number of dependencies:
	 *
	 * All irq-safe locks may nest inside irq-unsafe locks,
	 * plus all the other known dependencies:
	 */
	seq_printf(m, " all direct dependencies:       %11lu\n",
			nr_irq_unsafe * nr_irq_safe +
			nr_hardirq_unsafe * nr_hardirq_safe +
			nr_list_entries);

#ifdef CONFIG_PROVE_LOCKING
	seq_printf(m, " dependency chains:             %11lu [max: %lu]\n",
			lock_chain_count(), MAX_LOCKDEP_CHAINS);
	seq_printf(m, " dependency chain hlocks used:  %11lu [max: %lu]\n",
			MAX_LOCKDEP_CHAIN_HLOCKS -
			(nr_free_chain_hlocks + nr_lost_chain_hlocks),
			MAX_LOCKDEP_CHAIN_HLOCKS);
	seq_printf(m, " dependency chain hlocks lost:  %11u\n",
			nr_lost_chain_hlocks);
#endif

#ifdef CONFIG_TRACE_IRQFLAGS
	seq_printf(m, " in-hardirq chains:             %11u\n",
			nr_hardirq_chains);
	seq_printf(m, " in-softirq chains:             %11u\n",
			nr_softirq_chains);
#endif
	seq_printf(m, " in-process chains:             %11u\n",
			nr_process_chains);
	seq_printf(m, " stack-trace entries:           %11lu [max: %lu]\n",
			nr_stack_trace_entries, MAX_STACK_TRACE_ENTRIES);
#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
	seq_printf(m, " number of stack traces:        %11llu\n",
		   lockdep_stack_trace_count());
	seq_printf(m, " number of stack hash chains:   %11llu\n",
		   lockdep_stack_hash_count());
#endif
	seq_printf(m, " combined max dependencies:     %11u\n",
			(nr_hardirq_chains + 1) *
			(nr_softirq_chains + 1) *
			(nr_process_chains + 1)
	);
	seq_printf(m, " hardirq-safe locks:            %11lu\n",
			nr_hardirq_safe);
	seq_printf(m, " hardirq-unsafe locks:          %11lu\n",
			nr_hardirq_unsafe);
	seq_printf(m, " softirq-safe locks:            %11lu\n",
			nr_softirq_safe);
	seq_printf(m, " softirq-unsafe locks:          %11lu\n",
			nr_softirq_unsafe);
	seq_printf(m, " irq-safe locks:                %11lu\n",
			nr_irq_safe);
	seq_printf(m, " irq-unsafe locks:              %11lu\n",
			nr_irq_unsafe);

	seq_printf(m, " hardirq-read-safe locks:       %11lu\n",
			nr_hardirq_read_safe);
	seq_printf(m, " hardirq-read-unsafe locks:     %11lu\n",
			nr_hardirq_read_unsafe);
	seq_printf(m, " softirq-read-safe locks:       %11lu\n",
			nr_softirq_read_safe);
	seq_printf(m, " softirq-read-unsafe locks:     %11lu\n",
			nr_softirq_read_unsafe);
	seq_printf(m, " irq-read-safe locks:           %11lu\n",
			nr_irq_read_safe);
	seq_printf(m, " irq-read-unsafe locks:         %11lu\n",
			nr_irq_read_unsafe);

	seq_printf(m, " uncategorized locks:           %11lu\n",
			nr_uncategorized);
	seq_printf(m, " unused locks:                  %11lu\n",
			nr_unused);
	seq_printf(m, " max locking depth:             %11u\n",
			max_lockdep_depth);
#ifdef CONFIG_PROVE_LOCKING
	seq_printf(m, " max bfs queue depth:           %11u\n",
			max_bfs_queue_depth);
#endif
	seq_printf(m, " max lock class index:          %11lu\n",
			max_lock_class_idx);
	lockdep_stats_debug_show(m);
	seq_printf(m, " debug_locks:                   %11u\n",
			debug_locks);

	/*
	 * Zapped classes and lockdep data buffers reuse statistics.
	 */
	seq_puts(m, "\n");
	seq_printf(m, " zapped classes:                %11lu\n",
			nr_zapped_classes);
#ifdef CONFIG_PROVE_LOCKING
	seq_printf(m, " zapped lock chains:            %11lu\n",
			nr_zapped_lock_chains);
	seq_printf(m, " large chain blocks:            %11u\n",
			nr_large_chain_blocks);
#endif
	return 0;
}

#ifdef CONFIG_LOCK_STAT

struct lock_stat_data {
	struct lock_class *class;
	struct lock_class_stats stats;
};

struct lock_stat_seq {
	struct lock_stat_data *iter_end;
	struct lock_stat_data stats[MAX_LOCKDEP_KEYS];
};

/*
 * sort on absolute number of contentions
 */
static int lock_stat_cmp(const void *l, const void *r)
{
	const struct lock_stat_data *dl = l, *dr = r;
	unsigned long nl, nr;

	nl = dl->stats.read_waittime.nr + dl->stats.write_waittime.nr;
	nr = dr->stats.read_waittime.nr + dr->stats.write_waittime.nr;

	return nr - nl;
}

static void seq_line(struct seq_file *m, char c, int offset, int length)
{
	int i;

	for (i = 0; i < offset; i++)
		seq_puts(m, " ");
	for (i = 0; i < length; i++)
		seq_printf(m, "%c", c);
	seq_puts(m, "\n");
}

static void snprint_time(char *buf, size_t bufsiz, s64 nr)
{
	s64 div;
	s32 rem;

	nr += 5; /* for display rounding */
	div = div_s64_rem(nr, 1000, &rem);
	snprintf(buf, bufsiz, "%lld.%02d", (long long)div, (int)rem/10);
}

static void seq_time(struct seq_file *m, s64 time)
{
	char num[15];

	snprint_time(num, sizeof(num), time);
	seq_printf(m, " %14s", num);
}

static void seq_lock_time(struct seq_file *m, struct lock_time *lt)
{
	seq_printf(m, "%14lu", lt->nr);
	seq_time(m, lt->min);
	seq_time(m, lt->max);
	seq_time(m, lt->total);
	seq_time(m, lt->nr ? div64_u64(lt->total, lt->nr) : 0);
}

static void seq_stats(struct seq_file *m, struct lock_stat_data *data)
{
	const struct lockdep_subclass_key *ckey;
	struct lock_class_stats *stats;
	struct lock_class *class;
	const char *cname;
	int i, namelen;
	char name[39];

	class = data->class;
	stats = &data->stats;

	namelen = 38;
	if (class->name_version > 1)
		namelen -= 2; /* XXX truncates versions > 9 */
	if (class->subclass)
		namelen -= 2;

	rcu_read_lock_sched();
	cname = rcu_dereference_sched(class->name);
	ckey  = rcu_dereference_sched(class->key);

	if (!cname && !ckey) {
		rcu_read_unlock_sched();
		return;

	} else if (!cname) {
		char str[KSYM_NAME_LEN];
		const char *key_name;

		key_name = __get_key_name(ckey, str);
		snprintf(name, namelen, "%s", key_name);
	} else {
		snprintf(name, namelen, "%s", cname);
	}
	rcu_read_unlock_sched();

	namelen = strlen(name);
	if (class->name_version > 1) {
		snprintf(name+namelen, 3, "#%d", class->name_version);
		namelen += 2;
	}
	if (class->subclass) {
		snprintf(name+namelen, 3, "/%d", class->subclass);
		namelen += 2;
	}

	if (stats->write_holdtime.nr) {
		if (stats->read_holdtime.nr)
			seq_printf(m, "%38s-W:", name);
		else
			seq_printf(m, "%40s:", name);

		seq_printf(m, "%14lu ", stats->bounces[bounce_contended_write]);
		seq_lock_time(m, &stats->write_waittime);
		seq_printf(m, " %14lu ", stats->bounces[bounce_acquired_write]);
		seq_lock_time(m, &stats->write_holdtime);
		seq_puts(m, "\n");
	}

	if (stats->read_holdtime.nr) {
		seq_printf(m, "%38s-R:", name);
		seq_printf(m, "%14lu ", stats->bounces[bounce_contended_read]);
		seq_lock_time(m, &stats->read_waittime);
		seq_printf(m, " %14lu ", stats->bounces[bounce_acquired_read]);
		seq_lock_time(m, &stats->read_holdtime);
		seq_puts(m, "\n");
	}

	if (stats->read_waittime.nr + stats->write_waittime.nr == 0)
		return;

	if (stats->read_holdtime.nr)
		namelen += 2;

	for (i = 0; i < LOCKSTAT_POINTS; i++) {
		char ip[32];

		if (class->contention_point[i] == 0)
			break;

		if (!i)
			seq_line(m, '-', 40-namelen, namelen);

		snprintf(ip, sizeof(ip), "[<%p>]",
				(void *)class->contention_point[i]);
		seq_printf(m, "%40s %14lu %29s %pS\n",
			   name, stats->contention_point[i],
			   ip, (void *)class->contention_point[i]);
	}
	for (i = 0; i < LOCKSTAT_POINTS; i++) {
		char ip[32];

		if (class->contending_point[i] == 0)
			break;

		if (!i)
			seq_line(m, '-', 40-namelen, namelen);

		snprintf(ip, sizeof(ip), "[<%p>]",
				(void *)class->contending_point[i]);
		seq_printf(m, "%40s %14lu %29s %pS\n",
			   name, stats->contending_point[i],
			   ip, (void *)class->contending_point[i]);
	}
	if (i) {
		seq_puts(m, "\n");
		seq_line(m, '.', 0, 40 + 1 + 12 * (14 + 1));
		seq_puts(m, "\n");
	}
}

static void seq_header(struct seq_file *m)
{
	seq_puts(m, "lock_stat version 0.4\n");

	if (unlikely(!debug_locks))
		seq_printf(m, "*WARNING* lock debugging disabled!! - possibly due to a lockdep warning\n");

	seq_line(m, '-', 0, 40 + 1 + 12 * (14 + 1));
	seq_printf(m, "%40s %14s %14s %14s %14s %14s %14s %14s %14s %14s %14s "
			"%14s %14s\n",
			"class name",
			"con-bounces",
			"contentions",
			"waittime-min",
			"waittime-max",
			"waittime-total",
			"waittime-avg",
			"acq-bounces",
			"acquisitions",
			"holdtime-min",
			"holdtime-max",
			"holdtime-total",
			"holdtime-avg");
	seq_line(m, '-', 0, 40 + 1 + 12 * (14 + 1));
	seq_printf(m, "\n");
}

static void *ls_start(struct seq_file *m, loff_t *pos)
{
	struct lock_stat_seq *data = m->private;
	struct lock_stat_data *iter;

	if (*pos == 0)
		return SEQ_START_TOKEN;

	iter = data->stats + (*pos - 1);
	if (iter >= data->iter_end)
		iter = NULL;

	return iter;
}

static void *ls_next(struct seq_file *m, void *v, loff_t *pos)
{
	(*pos)++;
	return ls_start(m, pos);
}

static void ls_stop(struct seq_file *m, void *v)
{
}

static int ls_show(struct seq_file *m, void *v)
{
	if (v == SEQ_START_TOKEN)
		seq_header(m);
	else
		seq_stats(m, v);

	return 0;
}

static const struct seq_operations lockstat_ops = {
	.start	= ls_start,
	.next	= ls_next,
	.stop	= ls_stop,
	.show	= ls_show,
};

static int lock_stat_open(struct inode *inode, struct file *file)
{
	int res;
	struct lock_class *class;
	struct lock_stat_seq *data = vmalloc(sizeof(struct lock_stat_seq));

	if (!data)
		return -ENOMEM;

	res = seq_open(file, &lockstat_ops);
	if (!res) {
		struct lock_stat_data *iter = data->stats;
		struct seq_file *m = file->private_data;
		unsigned long idx;

		iterate_lock_classes(idx, class) {
			if (!test_bit(idx, lock_classes_in_use))
				continue;
			iter->class = class;
			iter->stats = lock_stats(class);
			iter++;
		}

		data->iter_end = iter;

		sort(data->stats, data->iter_end - data->stats,
				sizeof(struct lock_stat_data),
				lock_stat_cmp, NULL);

		m->private = data;
	} else
		vfree(data);

	return res;
}

static ssize_t lock_stat_write(struct file *file, const char __user *buf,
			       size_t count, loff_t *ppos)
{
	struct lock_class *class;
	unsigned long idx;
	char c;

	if (count) {
		if (get_user(c, buf))
			return -EFAULT;

		if (c != '0')
			return count;

		iterate_lock_classes(idx, class) {
			if (!test_bit(idx, lock_classes_in_use))
				continue;
			clear_lock_stats(class);
		}
	}
	return count;
}

static int lock_stat_release(struct inode *inode, struct file *file)
{
	struct seq_file *seq = file->private_data;

	vfree(seq->private);
	return seq_release(inode, file);
}

static const struct proc_ops lock_stat_proc_ops = {
	.proc_open	= lock_stat_open,
	.proc_write	= lock_stat_write,
	.proc_read	= seq_read,
	.proc_lseek	= seq_lseek,
	.proc_release	= lock_stat_release,
};
#endif /* CONFIG_LOCK_STAT */

static int __init lockdep_proc_init(void)
{
	proc_create_seq("lockdep", S_IRUSR, NULL, &lockdep_ops);
#ifdef CONFIG_PROVE_LOCKING
	proc_create_seq("lockdep_chains", S_IRUSR, NULL, &lockdep_chains_ops);
#endif
	proc_create_single("lockdep_stats", S_IRUSR, NULL, lockdep_stats_show);
#ifdef CONFIG_LOCK_STAT
	proc_create("lock_stat", S_IRUSR | S_IWUSR, NULL, &lock_stat_proc_ops);
#endif

	return 0;
}

__initcall(lockdep_proc_init);