1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * KCSAN debugfs interface. |
4 | * |
5 | * Copyright (C) 2019, Google LLC. |
6 | */ |
7 | |
8 | #define pr_fmt(fmt) "kcsan: " fmt |
9 | |
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> |
16 | #include <linux/sched.h> |
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 | |
25 | atomic_long_t kcsan_counters[KCSAN_COUNTER_COUNT]; |
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); |
38 | |
39 | /* |
40 | * Addresses for filtering functions from reporting. This list can be used as a |
41 | * whitelist or blacklist. |
42 | */ |
43 | static struct { |
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 */ |
49 | } report_filterlist = { |
50 | .addrs = NULL, |
51 | .size = 8, /* small initial size */ |
52 | .used = 0, |
53 | .sorted = false, |
54 | .whitelist = false, /* default is blacklist */ |
55 | }; |
56 | static DEFINE_SPINLOCK(report_filterlist_lock); |
57 | |
58 | /* |
59 | * The microbenchmark allows benchmarking KCSAN core runtime only. To run |
60 | * multiple threads, pipe 'microbench=<iters>' from multiple tasks into the |
61 | * debugfs file. This will not generate any conflicts, and tests fast-path only. |
62 | */ |
63 | static noinline void microbenchmark(unsigned long iters) |
64 | { |
65 | const struct kcsan_ctx ctx_save = current->kcsan_ctx; |
66 | const bool was_enabled = READ_ONCE(kcsan_enabled); |
67 | u64 cycles; |
68 | |
69 | /* We may have been called from an atomic region; reset context. */ |
70 | memset(¤t->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 | |
77 | pr_info("%s begin | iters: %lu\n" , __func__, iters); |
78 | |
79 | cycles = get_cycles(); |
80 | while (iters--) { |
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(ptr: (void *)addr, size: sizeof(long), type); |
85 | } |
86 | cycles = get_cycles() - cycles; |
87 | |
88 | pr_info("%s end | cycles: %llu\n" , __func__, cycles); |
89 | |
90 | WRITE_ONCE(kcsan_enabled, was_enabled); |
91 | /* restore context */ |
92 | current->kcsan_ctx = ctx_save; |
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(addr: func_addr, symbolsize: &symbolsize, offset: &offset)) |
110 | return false; |
111 | func_addr -= offset; /* Get function start */ |
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(base: report_filterlist.addrs, num: report_filterlist.used, |
120 | size: sizeof(unsigned long), cmp_func: cmp_filterlist_addrs, NULL); |
121 | report_filterlist.sorted = true; |
122 | } |
123 | ret = !!bsearch(key: &func_addr, base: report_filterlist.addrs, |
124 | num: report_filterlist.used, size: sizeof(unsigned long), |
125 | cmp: cmp_filterlist_addrs); |
126 | if (report_filterlist.whitelist) |
127 | ret = !ret; |
128 | |
129 | out: |
130 | spin_unlock_irqrestore(lock: &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(lock: &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(name: func); |
148 | ssize_t ret = 0; |
149 | |
150 | if (!addr) { |
151 | pr_err("could not find function: '%s'\n" , func); |
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(n: report_filterlist.size, |
161 | size: sizeof(unsigned long), GFP_ATOMIC); |
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(objp: report_filterlist.addrs, |
171 | new_size: new_size * sizeof(unsigned long), GFP_ATOMIC); |
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(name: func); |
186 | report_filterlist.sorted = false; |
187 | |
188 | out: |
189 | spin_unlock_irqrestore(lock: &report_filterlist_lock, flags); |
190 | |
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(m: file, fmt: "enabled: %i\n" , READ_ONCE(kcsan_enabled)); |
201 | for (i = 0; i < KCSAN_COUNTER_COUNT; ++i) { |
202 | seq_printf(m: file, fmt: "%s: %ld\n" , counter_names[i], |
203 | atomic_long_read(v: &kcsan_counters[i])); |
204 | } |
205 | |
206 | /* show filter functions, and filter type */ |
207 | spin_lock_irqsave(&report_filterlist_lock, flags); |
208 | seq_printf(m: file, fmt: "\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(m: file, fmt: " %ps\n" , (void *)report_filterlist.addrs[i]); |
213 | spin_unlock_irqrestore(lock: &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 | |
223 | static ssize_t |
224 | debugfs_write(struct file *file, const char __user *buf, size_t count, loff_t *off) |
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(to: kbuf, from: buf, n: read_len)) |
231 | return -EFAULT; |
232 | kbuf[read_len] = '\0'; |
233 | arg = strstrip(str: 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); |
239 | } else if (str_has_prefix(str: arg, prefix: "microbench=" )) { |
240 | unsigned long iters; |
241 | |
242 | if (kstrtoul(s: &arg[strlen("microbench=" )], base: 0, res: &iters)) |
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(func: &arg[1]); |
251 | |
252 | if (ret < 0) |
253 | return ret; |
254 | } else { |
255 | return -EINVAL; |
256 | } |
257 | |
258 | return count; |
259 | } |
260 | |
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 | }; |
268 | |
269 | static int __init kcsan_debugfs_init(void) |
270 | { |
271 | debugfs_create_file(name: "kcsan" , mode: 0644, NULL, NULL, fops: &debugfs_ops); |
272 | return 0; |
273 | } |
274 | |
275 | late_initcall(kcsan_debugfs_init); |
276 | |