[linux-block.git] / kernel / kcsan / debugfs.c

// SPDX-License-Identifier: GPL-2.0
/*
 * KCSAN debugfs interface.
 *
 * Copyright (C) 2019, Google LLC.
 */

#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);
	u64 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\n", __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\n", __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'\n", 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\n", READ_ONCE(kcsan_enabled));
	for (i = 0; i < KCSAN_COUNTER_COUNT; ++i) {
		seq_printf(file, "%s: %ld\n", 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, "\n%s functions: %s\n",
		   report_filterlist.whitelist ? "whitelisted" : "blacklisted",
		   report_filterlist.used == 0 ? "none" : "");
	for (i = 0; i < report_filterlist.used; ++i)
		seq_printf(file, " %ps\n", (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
};

static int __init kcsan_debugfs_init(void)
{
	debugfs_create_file("kcsan", 0644, NULL, NULL, &debugfs_ops);
	return 0;
}

late_initcall(kcsan_debugfs_init);
Commit	Line	Data
dfd402a4	1	// SPDX-License-Identifier: GPL-2.0
bd0ccc4a ME	2	/*
	3	* KCSAN debugfs interface.
	4	*
	5	* Copyright (C) 2019, Google LLC.
	6	*/
dfd402a4	7
178a1877 ME	8	#define pr_fmt(fmt) "kcsan: " fmt
178a1877 ME	9
dfd402a4 ME	10	#include <linux/atomic.h>
	11	#include <linux/bsearch.h>
	12	#include <linux/bug.h>
	13	#include <linux/debugfs.h>
	14	#include <linux/init.h>
	15	#include <linux/kallsyms.h>
a3120135	16	#include <linux/sched.h>
dfd402a4 ME	17	#include <linux/seq_file.h>
	18	#include <linux/slab.h>
	19	#include <linux/sort.h>
	20	#include <linux/string.h>
	21	#include <linux/uaccess.h>
	22
	23	#include "kcsan.h"
	24
2e986b81	25	atomic_long_t kcsan_counters[KCSAN_COUNTER_COUNT];
69b2c81b ME	26	static const char *const counter_names[] = {
	27	[KCSAN_COUNTER_USED_WATCHPOINTS] = "used_watchpoints",
	28	[KCSAN_COUNTER_SETUP_WATCHPOINTS] = "setup_watchpoints",
	29	[KCSAN_COUNTER_DATA_RACES] = "data_races",
	30	[KCSAN_COUNTER_ASSERT_FAILURES] = "assert_failures",
	31	[KCSAN_COUNTER_NO_CAPACITY] = "no_capacity",
	32	[KCSAN_COUNTER_REPORT_RACES] = "report_races",
	33	[KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN] = "races_unknown_origin",
	34	[KCSAN_COUNTER_UNENCODABLE_ACCESSES] = "unencodable_accesses",
	35	[KCSAN_COUNTER_ENCODING_FALSE_POSITIVES] = "encoding_false_positives",
	36	};
	37	static_assert(ARRAY_SIZE(counter_names) == KCSAN_COUNTER_COUNT);
dfd402a4 ME	38
	39	/*
	40	* Addresses for filtering functions from reporting. This list can be used as a
	41	* whitelist or blacklist.
	42	*/
	43	static struct {
5cbaefe9 IM	44	unsigned long addrs; / array of addresses */
	45	size_t size; /* current size */
	46	int used; /* number of elements used */
	47	bool sorted; /* if elements are sorted */
	48	bool whitelist; /* if list is a blacklist or whitelist */
dfd402a4	49	} report_filterlist = {
5cbaefe9 IM	50	.addrs = NULL,
	51	.size = 8, /* small initial size */
	52	.used = 0,
	53	.sorted = false,
	54	.whitelist = false, /* default is blacklist */
dfd402a4 ME	55	};
	56	static DEFINE_SPINLOCK(report_filterlist_lock);
	57
dfd402a4 ME	58	/*
	59	* The microbenchmark allows benchmarking KCSAN core runtime only. To run
	60	* multiple threads, pipe 'microbench=<iters>' from multiple tasks into the
a3120135	61	* debugfs file. This will not generate any conflicts, and tests fast-path only.
dfd402a4	62	*/
a3120135	63	static noinline void microbenchmark(unsigned long iters)
dfd402a4	64	{
44656d3d ME	65	const struct kcsan_ctx ctx_save = current->kcsan_ctx;
44656d3d ME	66	const bool was_enabled = READ_ONCE(kcsan_enabled);
09b1b134	67	u64 cycles;
dfd402a4	68
44656d3d ME	69	/* We may have been called from an atomic region; reset context. */
	70	memset(&current->kcsan_ctx, 0, sizeof(current->kcsan_ctx));
	71	/*
	72	* Disable to benchmark fast-path for all accesses, and (expected
	73	* negligible) call into slow-path, but never set up watchpoints.
	74	*/
	75	WRITE_ONCE(kcsan_enabled, false);
	76
178a1877	77	pr_info("%s begin \| iters: %lu\n", __func__, iters);
dfd402a4 ME	78
	79	cycles = get_cycles();
	80	while (iters--) {
44656d3d ME	81	unsigned long addr = iters & ((PAGE_SIZE << 8) - 1);
	82	int type = !(iters & 0x7f) ? KCSAN_ACCESS_ATOMIC :
	83	(!(iters & 0xf) ? KCSAN_ACCESS_WRITE : 0);
	84	__kcsan_check_access((void *)addr, sizeof(long), type);
dfd402a4 ME	85	}
	86	cycles = get_cycles() - cycles;
	87
178a1877	88	pr_info("%s end \| cycles: %llu\n", __func__, cycles);
44656d3d ME	89
	90	WRITE_ONCE(kcsan_enabled, was_enabled);
	91	/* restore context */
	92	current->kcsan_ctx = ctx_save;
dfd402a4 ME	93	}
	94
	95	static int cmp_filterlist_addrs(const void rhs, const void lhs)
	96	{
	97	const unsigned long a = (const unsigned long )rhs;
	98	const unsigned long b = (const unsigned long )lhs;
	99
	100	return a < b ? -1 : a == b ? 0 : 1;
	101	}
	102
	103	bool kcsan_skip_report_debugfs(unsigned long func_addr)
	104	{
	105	unsigned long symbolsize, offset;
	106	unsigned long flags;
	107	bool ret = false;
	108
	109	if (!kallsyms_lookup_size_offset(func_addr, &symbolsize, &offset))
	110	return false;
5cbaefe9	111	func_addr -= offset; /* Get function start */
dfd402a4 ME	112
	113	spin_lock_irqsave(&report_filterlist_lock, flags);
	114	if (report_filterlist.used == 0)
	115	goto out;
	116
	117	/* Sort array if it is unsorted, and then do a binary search. */
	118	if (!report_filterlist.sorted) {
	119	sort(report_filterlist.addrs, report_filterlist.used,
	120	sizeof(unsigned long), cmp_filterlist_addrs, NULL);
	121	report_filterlist.sorted = true;
	122	}
	123	ret = !!bsearch(&func_addr, report_filterlist.addrs,
	124	report_filterlist.used, sizeof(unsigned long),
	125	cmp_filterlist_addrs);
	126	if (report_filterlist.whitelist)
	127	ret = !ret;
	128
	129	out:
	130	spin_unlock_irqrestore(&report_filterlist_lock, flags);
	131	return ret;
	132	}
	133
	134	static void set_report_filterlist_whitelist(bool whitelist)
	135	{
	136	unsigned long flags;
	137
	138	spin_lock_irqsave(&report_filterlist_lock, flags);
	139	report_filterlist.whitelist = whitelist;
	140	spin_unlock_irqrestore(&report_filterlist_lock, flags);
	141	}
	142
	143	/* Returns 0 on success, error-code otherwise. */
	144	static ssize_t insert_report_filterlist(const char *func)
	145	{
	146	unsigned long flags;
	147	unsigned long addr = kallsyms_lookup_name(func);
	148	ssize_t ret = 0;
	149
	150	if (!addr) {
178a1877	151	pr_err("could not find function: '%s'\n", func);
dfd402a4 ME	152	return -ENOENT;
	153	}
	154
	155	spin_lock_irqsave(&report_filterlist_lock, flags);
	156
	157	if (report_filterlist.addrs == NULL) {
	158	/* initial allocation */
	159	report_filterlist.addrs =
	160	kmalloc_array(report_filterlist.size,
52785b6a	161	sizeof(unsigned long), GFP_ATOMIC);
dfd402a4 ME	162	if (report_filterlist.addrs == NULL) {
	163	ret = -ENOMEM;
	164	goto out;
	165	}
	166	} else if (report_filterlist.used == report_filterlist.size) {
	167	/* resize filterlist */
	168	size_t new_size = report_filterlist.size * 2;
	169	unsigned long *new_addrs =
	170	krealloc(report_filterlist.addrs,
52785b6a	171	new_size * sizeof(unsigned long), GFP_ATOMIC);
dfd402a4 ME	172
	173	if (new_addrs == NULL) {
	174	/* leave filterlist itself untouched */
	175	ret = -ENOMEM;
	176	goto out;
	177	}
	178
	179	report_filterlist.size = new_size;
	180	report_filterlist.addrs = new_addrs;
	181	}
	182
	183	/* Note: deduplicating should be done in userspace. */
	184	report_filterlist.addrs[report_filterlist.used++] =
	185	kallsyms_lookup_name(func);
	186	report_filterlist.sorted = false;
	187
	188	out:
	189	spin_unlock_irqrestore(&report_filterlist_lock, flags);
5cbaefe9	190
dfd402a4 ME	191	return ret;
	192	}
	193
	194	static int show_info(struct seq_file file, void v)
	195	{
	196	int i;
	197	unsigned long flags;
	198
	199	/* show stats */
	200	seq_printf(file, "enabled: %i\n", READ_ONCE(kcsan_enabled));
2e986b81 ME	201	for (i = 0; i < KCSAN_COUNTER_COUNT; ++i) {
	202	seq_printf(file, "%s: %ld\n", counter_names[i],
	203	atomic_long_read(&kcsan_counters[i]));
	204	}
dfd402a4 ME	205
	206	/* show filter functions, and filter type */
	207	spin_lock_irqsave(&report_filterlist_lock, flags);
	208	seq_printf(file, "\n%s functions: %s\n",
	209	report_filterlist.whitelist ? "whitelisted" : "blacklisted",
	210	report_filterlist.used == 0 ? "none" : "");
	211	for (i = 0; i < report_filterlist.used; ++i)
	212	seq_printf(file, " %ps\n", (void *)report_filterlist.addrs[i]);
	213	spin_unlock_irqrestore(&report_filterlist_lock, flags);
	214
	215	return 0;
	216	}
	217
	218	static int debugfs_open(struct inode inode, struct file file)
	219	{
	220	return single_open(file, show_info, NULL);
	221	}
	222
5cbaefe9 IM	223	static ssize_t
5cbaefe9 IM	224	debugfs_write(struct file file, const char __user buf, size_t count, loff_t *off)
dfd402a4 ME	225	{
	226	char kbuf[KSYM_NAME_LEN];
	227	char *arg;
	228	int read_len = count < (sizeof(kbuf) - 1) ? count : (sizeof(kbuf) - 1);
	229
	230	if (copy_from_user(kbuf, buf, read_len))
	231	return -EFAULT;
	232	kbuf[read_len] = '\0';
	233	arg = strstrip(kbuf);
	234
	235	if (!strcmp(arg, "on")) {
	236	WRITE_ONCE(kcsan_enabled, true);
	237	} else if (!strcmp(arg, "off")) {
	238	WRITE_ONCE(kcsan_enabled, false);
a4e74fa5	239	} else if (str_has_prefix(arg, "microbench=")) {
dfd402a4 ME	240	unsigned long iters;
dfd402a4 ME	241
a4e74fa5	242	if (kstrtoul(&arg[strlen("microbench=")], 0, &iters))
dfd402a4 ME	243	return -EINVAL;
	244	microbenchmark(iters);
	245	} else if (!strcmp(arg, "whitelist")) {
	246	set_report_filterlist_whitelist(true);
	247	} else if (!strcmp(arg, "blacklist")) {
	248	set_report_filterlist_whitelist(false);
	249	} else if (arg[0] == '!') {
	250	ssize_t ret = insert_report_filterlist(&arg[1]);
	251
	252	if (ret < 0)
	253	return ret;
	254	} else {
	255	return -EINVAL;
	256	}
	257
	258	return count;
	259	}
	260
5cbaefe9 IM	261	static const struct file_operations debugfs_ops =
	262	{
	263	.read = seq_read,
	264	.open = debugfs_open,
	265	.write = debugfs_write,
	266	.release = single_release
	267	};
dfd402a4	268
976aac5f	269	static int __init kcsan_debugfs_init(void)
dfd402a4 ME	270	{
dfd402a4 ME	271	debugfs_create_file("kcsan", 0644, NULL, NULL, &debugfs_ops);
976aac5f	272	return 0;
dfd402a4	273	}
e36299ef ME	274
e36299ef ME	275	late_initcall(kcsan_debugfs_init);