// 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;static DEFINE_RAW_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 */ 	raw_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:	raw_spin_unlock_irqrestore(&report_filterlist_lock, flags);	return ret;} static void set_report_filterlist_whitelist(bool whitelist){	unsigned long flags; 	raw_spin_lock_irqsave(&report_filterlist_lock, flags);	report_filterlist.whitelist = whitelist;	raw_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);	unsigned long *delay_free = NULL;	unsigned long *new_addrs = NULL;	size_t new_size = 0;	ssize_t ret = 0; 	if (!addr) {		pr_err("could not find function: '%s'\n", func);		return -ENOENT;	} retry_alloc:	/*	 * Check if we need an allocation, and re-validate under the lock. Since	 * the report_filterlist_lock is a raw, cannot allocate under the lock.	 */	if (data_race(report_filterlist.used == report_filterlist.size)) {		new_size = (report_filterlist.size ?: 4) * 2;		delay_free = new_addrs = kmalloc_array(new_size, sizeof(unsigned long), GFP_KERNEL);		if (!new_addrs)			return -ENOMEM;	} 	raw_spin_lock_irqsave(&report_filterlist_lock, flags);	if (report_filterlist.used == report_filterlist.size) {		/* Check we pre-allocated enough, and retry if not. */		if (report_filterlist.used >= new_size) {			raw_spin_unlock_irqrestore(&report_filterlist_lock, flags);			kfree(new_addrs); /* kfree(NULL) is safe */			delay_free = new_addrs = NULL;			goto retry_alloc;		} 		if (report_filterlist.used)			memcpy(new_addrs, report_filterlist.addrs, report_filterlist.used * sizeof(unsigned long));		delay_free = report_filterlist.addrs; /* free the old list */		report_filterlist.addrs = new_addrs;  /* switch to the new list */		report_filterlist.size = new_size;	} 	/* Note: deduplicating should be done in userspace. */	report_filterlist.addrs[report_filterlist.used++] = addr;	report_filterlist.sorted = false; 	raw_spin_unlock_irqrestore(&report_filterlist_lock, flags); 	kfree(delay_free);	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 */	raw_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]);	raw_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;	const size_t read_len = min(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);