1 // SPDX-License-Identifier: GPL-2.0 2 3 #define pr_fmt(fmt) "kcsan: " fmt 4 5 #include <linux/atomic.h> 6 #include <linux/bsearch.h> 7 #include <linux/bug.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> 17 18 #include "kcsan.h" 19 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", 31 }; 32 static_assert(ARRAY_SIZE(counter_names) == KCSAN_COUNTER_COUNT); 33 34 /* 35 * Addresses for filtering functions from reporting. This list can be used as a 36 * whitelist or blacklist. 37 */ 38 static struct { 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 = { 45 .addrs = NULL, 46 .size = 8, /* small initial size */ 47 .used = 0, 48 .sorted = false, 49 .whitelist = false, /* default is blacklist */ 50 }; 51 static DEFINE_SPINLOCK(report_filterlist_lock); 52 53 /* 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. 57 */ 58 static noinline void microbenchmark(unsigned long iters) 59 { 60 const struct kcsan_ctx ctx_save = current->kcsan_ctx; 61 const bool was_enabled = READ_ONCE(kcsan_enabled); 62 cycles_t cycles; 63 64 /* We may have been called from an atomic region; reset context. */ 65 memset(¤t->kcsan_ctx, 0, sizeof(current->kcsan_ctx)); 66 /* 67 * Disable to benchmark fast-path for all accesses, and (expected 68 * negligible) call into slow-path, but never set up watchpoints. 69 */ 70 WRITE_ONCE(kcsan_enabled, false); 71 72 pr_info("%s begin | iters: %lu\n", __func__, iters); 73 74 cycles = get_cycles(); 75 while (iters--) { 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); 80 } 81 cycles = get_cycles() - cycles; 82 83 pr_info("%s end | cycles: %llu\n", __func__, cycles); 84 85 WRITE_ONCE(kcsan_enabled, was_enabled); 86 /* restore context */ 87 current->kcsan_ctx = ctx_save; 88 } 89 90 static int cmp_filterlist_addrs(const void *rhs, const void *lhs) 91 { 92 const unsigned long a = *(const unsigned long *)rhs; 93 const unsigned long b = *(const unsigned long *)lhs; 94 95 return a < b ? -1 : a == b ? 0 : 1; 96 } 97 98 bool kcsan_skip_report_debugfs(unsigned long func_addr) 99 { 100 unsigned long symbolsize, offset; 101 unsigned long flags; 102 bool ret = false; 103 104 if (!kallsyms_lookup_size_offset(func_addr, &symbolsize, &offset)) 105 return false; 106 func_addr -= offset; /* Get function start */ 107 108 spin_lock_irqsave(&report_filterlist_lock, flags); 109 if (report_filterlist.used == 0) 110 goto out; 111 112 /* 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; 117 } 118 ret = !!bsearch(&func_addr, report_filterlist.addrs, 119 report_filterlist.used, sizeof(unsigned long), 120 cmp_filterlist_addrs); 121 if (report_filterlist.whitelist) 122 ret = !ret; 123 124 out: 125 spin_unlock_irqrestore(&report_filterlist_lock, flags); 126 return ret; 127 } 128 129 static void set_report_filterlist_whitelist(bool whitelist) 130 { 131 unsigned long flags; 132 133 spin_lock_irqsave(&report_filterlist_lock, flags); 134 report_filterlist.whitelist = whitelist; 135 spin_unlock_irqrestore(&report_filterlist_lock, flags); 136 } 137 138 /* Returns 0 on success, error-code otherwise. */ 139 static ssize_t insert_report_filterlist(const char *func) 140 { 141 unsigned long flags; 142 unsigned long addr = kallsyms_lookup_name(func); 143 ssize_t ret = 0; 144 145 if (!addr) { 146 pr_err("could not find function: '%s'\n", func); 147 return -ENOENT; 148 } 149 150 spin_lock_irqsave(&report_filterlist_lock, flags); 151 152 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) { 158 ret = -ENOMEM; 159 goto out; 160 } 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); 167 168 if (new_addrs == NULL) { 169 /* leave filterlist itself untouched */ 170 ret = -ENOMEM; 171 goto out; 172 } 173 174 report_filterlist.size = new_size; 175 report_filterlist.addrs = new_addrs; 176 } 177 178 /* Note: deduplicating should be done in userspace. */ 179 report_filterlist.addrs[report_filterlist.used++] = 180 kallsyms_lookup_name(func); 181 report_filterlist.sorted = false; 182 183 out: 184 spin_unlock_irqrestore(&report_filterlist_lock, flags); 185 186 return ret; 187 } 188 189 static int show_info(struct seq_file *file, void *v) 190 { 191 int i; 192 unsigned long flags; 193 194 /* show stats */ 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])); 199 } 200 201 /* 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); 209 210 return 0; 211 } 212 213 static int debugfs_open(struct inode *inode, struct file *file) 214 { 215 return single_open(file, show_info, NULL); 216 } 217 218 static ssize_t 219 debugfs_write(struct file *file, const char __user *buf, size_t count, loff_t *off) 220 { 221 char kbuf[KSYM_NAME_LEN]; 222 char *arg; 223 int read_len = count < (sizeof(kbuf) - 1) ? count : (sizeof(kbuf) - 1); 224 225 if (copy_from_user(kbuf, buf, read_len)) 226 return -EFAULT; 227 kbuf[read_len] = '\0'; 228 arg = strstrip(kbuf); 229 230 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=")) { 235 unsigned long iters; 236 237 if (kstrtoul(&arg[strlen("microbench=")], 0, &iters)) 238 return -EINVAL; 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]); 246 247 if (ret < 0) 248 return ret; 249 } else { 250 return -EINVAL; 251 } 252 253 return count; 254 } 255 256 static const struct file_operations debugfs_ops = 257 { 258 .read = seq_read, 259 .open = debugfs_open, 260 .write = debugfs_write, 261 .release = single_release 262 }; 263 264 void __init kcsan_debugfs_init(void) 265 { 266 debugfs_create_file("kcsan", 0644, NULL, NULL, &debugfs_ops); 267 } 268