1 // SPDX-License-Identifier: GPL-2.0
3 #define pr_fmt(fmt) "kcsan: " fmt
5 #include <linux/atomic.h>
6 #include <linux/bsearch.h>
8 #include <linux/debugfs.h>
9 #include <linux/init.h>
10 #include <linux/kallsyms.h>
11 #include <linux/sched.h>
12 #include <linux/seq_file.h>
13 #include <linux/slab.h>
14 #include <linux/sort.h>
15 #include <linux/string.h>
16 #include <linux/uaccess.h>
20 atomic_long_t kcsan_counters[KCSAN_COUNTER_COUNT];
21 static const char *const counter_names[] = {
22 [KCSAN_COUNTER_USED_WATCHPOINTS] = "used_watchpoints",
23 [KCSAN_COUNTER_SETUP_WATCHPOINTS] = "setup_watchpoints",
24 [KCSAN_COUNTER_DATA_RACES] = "data_races",
25 [KCSAN_COUNTER_ASSERT_FAILURES] = "assert_failures",
26 [KCSAN_COUNTER_NO_CAPACITY] = "no_capacity",
27 [KCSAN_COUNTER_REPORT_RACES] = "report_races",
28 [KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN] = "races_unknown_origin",
29 [KCSAN_COUNTER_UNENCODABLE_ACCESSES] = "unencodable_accesses",
30 [KCSAN_COUNTER_ENCODING_FALSE_POSITIVES] = "encoding_false_positives",
32 static_assert(ARRAY_SIZE(counter_names) == KCSAN_COUNTER_COUNT);
35 * Addresses for filtering functions from reporting. This list can be used as a
36 * whitelist or blacklist.
39 unsigned long *addrs; /* array of addresses */
40 size_t size; /* current size */
41 int used; /* number of elements used */
42 bool sorted; /* if elements are sorted */
43 bool whitelist; /* if list is a blacklist or whitelist */
44 } report_filterlist = {
46 .size = 8, /* small initial size */
49 .whitelist = false, /* default is blacklist */
51 static DEFINE_SPINLOCK(report_filterlist_lock);
54 * The microbenchmark allows benchmarking KCSAN core runtime only. To run
55 * multiple threads, pipe 'microbench=<iters>' from multiple tasks into the
56 * debugfs file. This will not generate any conflicts, and tests fast-path only.
58 static noinline void microbenchmark(unsigned long iters)
60 const struct kcsan_ctx ctx_save = current->kcsan_ctx;
61 const bool was_enabled = READ_ONCE(kcsan_enabled);
64 /* We may have been called from an atomic region; reset context. */
65 memset(¤t->kcsan_ctx, 0, sizeof(current->kcsan_ctx));
67 * Disable to benchmark fast-path for all accesses, and (expected
68 * negligible) call into slow-path, but never set up watchpoints.
70 WRITE_ONCE(kcsan_enabled, false);
72 pr_info("%s begin | iters: %lu\n", __func__, iters);
74 cycles = get_cycles();
76 unsigned long addr = iters & ((PAGE_SIZE << 8) - 1);
77 int type = !(iters & 0x7f) ? KCSAN_ACCESS_ATOMIC :
78 (!(iters & 0xf) ? KCSAN_ACCESS_WRITE : 0);
79 __kcsan_check_access((void *)addr, sizeof(long), type);
81 cycles = get_cycles() - cycles;
83 pr_info("%s end | cycles: %llu\n", __func__, cycles);
85 WRITE_ONCE(kcsan_enabled, was_enabled);
87 current->kcsan_ctx = ctx_save;
90 static int cmp_filterlist_addrs(const void *rhs, const void *lhs)
92 const unsigned long a = *(const unsigned long *)rhs;
93 const unsigned long b = *(const unsigned long *)lhs;
95 return a < b ? -1 : a == b ? 0 : 1;
98 bool kcsan_skip_report_debugfs(unsigned long func_addr)
100 unsigned long symbolsize, offset;
104 if (!kallsyms_lookup_size_offset(func_addr, &symbolsize, &offset))
106 func_addr -= offset; /* Get function start */
108 spin_lock_irqsave(&report_filterlist_lock, flags);
109 if (report_filterlist.used == 0)
112 /* Sort array if it is unsorted, and then do a binary search. */
113 if (!report_filterlist.sorted) {
114 sort(report_filterlist.addrs, report_filterlist.used,
115 sizeof(unsigned long), cmp_filterlist_addrs, NULL);
116 report_filterlist.sorted = true;
118 ret = !!bsearch(&func_addr, report_filterlist.addrs,
119 report_filterlist.used, sizeof(unsigned long),
120 cmp_filterlist_addrs);
121 if (report_filterlist.whitelist)
125 spin_unlock_irqrestore(&report_filterlist_lock, flags);
129 static void set_report_filterlist_whitelist(bool whitelist)
133 spin_lock_irqsave(&report_filterlist_lock, flags);
134 report_filterlist.whitelist = whitelist;
135 spin_unlock_irqrestore(&report_filterlist_lock, flags);
138 /* Returns 0 on success, error-code otherwise. */
139 static ssize_t insert_report_filterlist(const char *func)
142 unsigned long addr = kallsyms_lookup_name(func);
146 pr_err("could not find function: '%s'\n", func);
150 spin_lock_irqsave(&report_filterlist_lock, flags);
152 if (report_filterlist.addrs == NULL) {
153 /* initial allocation */
154 report_filterlist.addrs =
155 kmalloc_array(report_filterlist.size,
156 sizeof(unsigned long), GFP_ATOMIC);
157 if (report_filterlist.addrs == NULL) {
161 } else if (report_filterlist.used == report_filterlist.size) {
162 /* resize filterlist */
163 size_t new_size = report_filterlist.size * 2;
164 unsigned long *new_addrs =
165 krealloc(report_filterlist.addrs,
166 new_size * sizeof(unsigned long), GFP_ATOMIC);
168 if (new_addrs == NULL) {
169 /* leave filterlist itself untouched */
174 report_filterlist.size = new_size;
175 report_filterlist.addrs = new_addrs;
178 /* Note: deduplicating should be done in userspace. */
179 report_filterlist.addrs[report_filterlist.used++] =
180 kallsyms_lookup_name(func);
181 report_filterlist.sorted = false;
184 spin_unlock_irqrestore(&report_filterlist_lock, flags);
189 static int show_info(struct seq_file *file, void *v)
195 seq_printf(file, "enabled: %i\n", READ_ONCE(kcsan_enabled));
196 for (i = 0; i < KCSAN_COUNTER_COUNT; ++i) {
197 seq_printf(file, "%s: %ld\n", counter_names[i],
198 atomic_long_read(&kcsan_counters[i]));
201 /* show filter functions, and filter type */
202 spin_lock_irqsave(&report_filterlist_lock, flags);
203 seq_printf(file, "\n%s functions: %s\n",
204 report_filterlist.whitelist ? "whitelisted" : "blacklisted",
205 report_filterlist.used == 0 ? "none" : "");
206 for (i = 0; i < report_filterlist.used; ++i)
207 seq_printf(file, " %ps\n", (void *)report_filterlist.addrs[i]);
208 spin_unlock_irqrestore(&report_filterlist_lock, flags);
213 static int debugfs_open(struct inode *inode, struct file *file)
215 return single_open(file, show_info, NULL);
219 debugfs_write(struct file *file, const char __user *buf, size_t count, loff_t *off)
221 char kbuf[KSYM_NAME_LEN];
223 int read_len = count < (sizeof(kbuf) - 1) ? count : (sizeof(kbuf) - 1);
225 if (copy_from_user(kbuf, buf, read_len))
227 kbuf[read_len] = '\0';
228 arg = strstrip(kbuf);
230 if (!strcmp(arg, "on")) {
231 WRITE_ONCE(kcsan_enabled, true);
232 } else if (!strcmp(arg, "off")) {
233 WRITE_ONCE(kcsan_enabled, false);
234 } else if (str_has_prefix(arg, "microbench=")) {
237 if (kstrtoul(&arg[strlen("microbench=")], 0, &iters))
239 microbenchmark(iters);
240 } else if (!strcmp(arg, "whitelist")) {
241 set_report_filterlist_whitelist(true);
242 } else if (!strcmp(arg, "blacklist")) {
243 set_report_filterlist_whitelist(false);
244 } else if (arg[0] == '!') {
245 ssize_t ret = insert_report_filterlist(&arg[1]);
256 static const struct file_operations debugfs_ops =
259 .open = debugfs_open,
260 .write = debugfs_write,
261 .release = single_release
264 void __init kcsan_debugfs_init(void)
266 debugfs_create_file("kcsan", 0644, NULL, NULL, &debugfs_ops);