// SPDX-License-Identifier: GPL-2.0 #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" /* * Statistics counters. */static atomic_long_t counters[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); static const char *counter_to_name(enum kcsan_counter_id id){	switch (id) {	case KCSAN_COUNTER_USED_WATCHPOINTS:		return "used_watchpoints";	case KCSAN_COUNTER_SETUP_WATCHPOINTS:		return "setup_watchpoints";	case KCSAN_COUNTER_DATA_RACES:			return "data_races";	case KCSAN_COUNTER_ASSERT_FAILURES:		return "assert_failures";	case KCSAN_COUNTER_NO_CAPACITY:			return "no_capacity";	case KCSAN_COUNTER_REPORT_RACES:		return "report_races";	case KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN:	return "races_unknown_origin";	case KCSAN_COUNTER_UNENCODABLE_ACCESSES:	return "unencodable_accesses";	case KCSAN_COUNTER_ENCODING_FALSE_POSITIVES:	return "encoding_false_positives";	case KCSAN_COUNTER_COUNT:		BUG();	}	return NULL;} void kcsan_counter_inc(enum kcsan_counter_id id){	atomic_long_inc(&counters[id]);} void kcsan_counter_dec(enum kcsan_counter_id id){	atomic_long_dec(&counters[id]);} /* * 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("KCSAN: %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("KCSAN: %s end   | cycles: %llu\n", __func__, cycles); 	WRITE_ONCE(kcsan_enabled, was_enabled);	/* restore context */	current->kcsan_ctx = ctx_save;} /* * Simple test to create conflicting accesses. Write 'test=<iters>' to KCSAN's * debugfs file from multiple tasks to generate real conflicts and show reports. */static long test_dummy;static long test_flags;static long test_scoped;static noinline void test_thread(unsigned long iters){	const long CHANGE_BITS = 0xff00ff00ff00ff00L;	const struct kcsan_ctx ctx_save = current->kcsan_ctx;	cycles_t cycles; 	/* We may have been called from an atomic region; reset context. */	memset(&current->kcsan_ctx, 0, sizeof(current->kcsan_ctx)); 	pr_info("KCSAN: %s begin | iters: %lu\n", __func__, iters);	pr_info("test_dummy@%px, test_flags@%px, test_scoped@%px,\n",		&test_dummy, &test_flags, &test_scoped); 	cycles = get_cycles();	while (iters--) {		/* These all should generate reports. */		__kcsan_check_read(&test_dummy, sizeof(test_dummy));		ASSERT_EXCLUSIVE_WRITER(test_dummy);		ASSERT_EXCLUSIVE_ACCESS(test_dummy); 		ASSERT_EXCLUSIVE_BITS(test_flags, ~CHANGE_BITS); /* no report */		__kcsan_check_read(&test_flags, sizeof(test_flags)); /* no report */ 		ASSERT_EXCLUSIVE_BITS(test_flags, CHANGE_BITS); /* report */		__kcsan_check_read(&test_flags, sizeof(test_flags)); /* no report */ 		/* not actually instrumented */		WRITE_ONCE(test_dummy, iters);  /* to observe value-change */		__kcsan_check_write(&test_dummy, sizeof(test_dummy)); 		test_flags ^= CHANGE_BITS; /* generate value-change */		__kcsan_check_write(&test_flags, sizeof(test_flags)); 		BUG_ON(current->kcsan_ctx.scoped_accesses.prev);		{			/* Should generate reports anywhere in this block. */			ASSERT_EXCLUSIVE_WRITER_SCOPED(test_scoped);			ASSERT_EXCLUSIVE_ACCESS_SCOPED(test_scoped);			BUG_ON(!current->kcsan_ctx.scoped_accesses.prev);			/* Unrelated accesses. */			__kcsan_check_access(&cycles, sizeof(cycles), 0);			__kcsan_check_access(&cycles, sizeof(cycles), KCSAN_ACCESS_ATOMIC);		}		BUG_ON(current->kcsan_ctx.scoped_accesses.prev);	}	cycles = get_cycles() - cycles; 	pr_info("KCSAN: %s end   | cycles: %llu\n", __func__, cycles); 	/* 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("KCSAN: 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_to_name(i),			   atomic_long_read(&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_tdebugfs_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 (!strncmp(arg, "microbench=", sizeof("microbench=") - 1)) {		unsigned long iters; 		if (kstrtoul(&arg[sizeof("microbench=") - 1], 0, &iters))			return -EINVAL;		microbenchmark(iters);	} else if (!strncmp(arg, "test=", sizeof("test=") - 1)) {		unsigned long iters; 		if (kstrtoul(&arg[sizeof("test=") - 1], 0, &iters))			return -EINVAL;		test_thread(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);}