1// SPDX-License-Identifier: GPL-2.0 2/* 3 * KCSAN short boot-time selftests. 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/bitops.h> 12#include <linux/init.h> 13#include <linux/kcsan-checks.h> 14#include <linux/kernel.h> 15#include <linux/printk.h> 16#include <linux/random.h> 17#include <linux/sched.h> 18#include <linux/spinlock.h> 19#include <linux/types.h> 20 21#include "encoding.h" 22 23#define ITERS_PER_TEST 2000 24 25/* 26 * Test watchpoint encode and decode: check that encoding some access's info, 27 * and then subsequent decode preserves the access's info. 28 */ 29static bool __init test_encode_decode(void) 30{ 31 int i; 32 33 for (i = 0; i < ITERS_PER_TEST; ++i) { 34 size_t size = get_random_u32_inclusive(1, MAX_ENCODABLE_SIZE); 35 bool is_write = !!get_random_u32_below(2); 36 unsigned long verif_masked_addr; 37 long encoded_watchpoint; 38 bool verif_is_write; 39 unsigned long addr; 40 size_t verif_size; 41 42 get_random_bytes(&addr, sizeof(addr)); 43 if (addr < PAGE_SIZE) 44 addr = PAGE_SIZE; 45 46 if (WARN_ON(!check_encodable(addr, size))) 47 return false; 48 49 encoded_watchpoint = encode_watchpoint(addr, size, is_write); 50 51 /* Check special watchpoints */ 52 if (WARN_ON(decode_watchpoint(INVALID_WATCHPOINT, &verif_masked_addr, &verif_size, &verif_is_write))) 53 return false; 54 if (WARN_ON(decode_watchpoint(CONSUMED_WATCHPOINT, &verif_masked_addr, &verif_size, &verif_is_write))) 55 return false; 56 57 /* Check decoding watchpoint returns same data */ 58 if (WARN_ON(!decode_watchpoint(encoded_watchpoint, &verif_masked_addr, &verif_size, &verif_is_write))) 59 return false; 60 if (WARN_ON(verif_masked_addr != (addr & WATCHPOINT_ADDR_MASK))) 61 goto fail; 62 if (WARN_ON(verif_size != size)) 63 goto fail; 64 if (WARN_ON(is_write != verif_is_write)) 65 goto fail; 66 67 continue; 68fail: 69 pr_err("%s fail: %s %zu bytes @ %lx -> encoded: %lx -> %s %zu bytes @ %lx\n", 70 __func__, is_write ? "write" : "read", size, addr, encoded_watchpoint, 71 verif_is_write ? "write" : "read", verif_size, verif_masked_addr); 72 return false; 73 } 74 75 return true; 76} 77 78/* Test access matching function. */ 79static bool __init test_matching_access(void) 80{ 81 if (WARN_ON(!matching_access(10, 1, 10, 1))) 82 return false; 83 if (WARN_ON(!matching_access(10, 2, 11, 1))) 84 return false; 85 if (WARN_ON(!matching_access(10, 1, 9, 2))) 86 return false; 87 if (WARN_ON(matching_access(10, 1, 11, 1))) 88 return false; 89 if (WARN_ON(matching_access(9, 1, 10, 1))) 90 return false; 91 92 /* 93 * An access of size 0 could match another access, as demonstrated here. 94 * Rather than add more comparisons to 'matching_access()', which would 95 * end up in the fast-path for *all* checks, check_access() simply 96 * returns for all accesses of size 0. 97 */ 98 if (WARN_ON(!matching_access(8, 8, 12, 0))) 99 return false; 100 101 return true; 102} 103 104/* 105 * Correct memory barrier instrumentation is critical to avoiding false 106 * positives: simple test to check at boot certain barriers are always properly 107 * instrumented. See kcsan_test for a more complete test. 108 */ 109static DEFINE_SPINLOCK(test_spinlock); 110static bool __init test_barrier(void) 111{ 112#ifdef CONFIG_KCSAN_WEAK_MEMORY 113 struct kcsan_scoped_access *reorder_access = ¤t->kcsan_ctx.reorder_access; 114#else 115 struct kcsan_scoped_access *reorder_access = NULL; 116#endif 117 bool ret = true; 118 arch_spinlock_t arch_spinlock = __ARCH_SPIN_LOCK_UNLOCKED; 119 atomic_t dummy; 120 long test_var; 121 122 if (!reorder_access || !IS_ENABLED(CONFIG_SMP)) 123 return true; 124 125#define __KCSAN_CHECK_BARRIER(access_type, barrier, name) \ 126 do { \ 127 reorder_access->type = (access_type) | KCSAN_ACCESS_SCOPED; \ 128 reorder_access->size = 1; \ 129 barrier; \ 130 if (reorder_access->size != 0) { \ 131 pr_err("improperly instrumented type=(" #access_type "): " name "\n"); \ 132 ret = false; \ 133 } \ 134 } while (0) 135#define KCSAN_CHECK_READ_BARRIER(b) __KCSAN_CHECK_BARRIER(0, b, #b) 136#define KCSAN_CHECK_WRITE_BARRIER(b) __KCSAN_CHECK_BARRIER(KCSAN_ACCESS_WRITE, b, #b) 137#define KCSAN_CHECK_RW_BARRIER(b) __KCSAN_CHECK_BARRIER(KCSAN_ACCESS_WRITE | KCSAN_ACCESS_COMPOUND, b, #b) 138 139 kcsan_nestable_atomic_begin(); /* No watchpoints in called functions. */ 140 141 KCSAN_CHECK_READ_BARRIER(mb()); 142 KCSAN_CHECK_READ_BARRIER(rmb()); 143 KCSAN_CHECK_READ_BARRIER(smp_mb()); 144 KCSAN_CHECK_READ_BARRIER(smp_rmb()); 145 KCSAN_CHECK_READ_BARRIER(dma_rmb()); 146 KCSAN_CHECK_READ_BARRIER(smp_mb__before_atomic()); 147 KCSAN_CHECK_READ_BARRIER(smp_mb__after_atomic()); 148 KCSAN_CHECK_READ_BARRIER(smp_mb__after_spinlock()); 149 KCSAN_CHECK_READ_BARRIER(smp_store_mb(test_var, 0)); 150 KCSAN_CHECK_READ_BARRIER(smp_store_release(&test_var, 0)); 151 KCSAN_CHECK_READ_BARRIER(xchg(&test_var, 0)); 152 KCSAN_CHECK_READ_BARRIER(xchg_release(&test_var, 0)); 153 KCSAN_CHECK_READ_BARRIER(cmpxchg(&test_var, 0, 0)); 154 KCSAN_CHECK_READ_BARRIER(cmpxchg_release(&test_var, 0, 0)); 155 KCSAN_CHECK_READ_BARRIER(atomic_set_release(&dummy, 0)); 156 KCSAN_CHECK_READ_BARRIER(atomic_add_return(1, &dummy)); 157 KCSAN_CHECK_READ_BARRIER(atomic_add_return_release(1, &dummy)); 158 KCSAN_CHECK_READ_BARRIER(atomic_fetch_add(1, &dummy)); 159 KCSAN_CHECK_READ_BARRIER(atomic_fetch_add_release(1, &dummy)); 160 KCSAN_CHECK_READ_BARRIER(test_and_set_bit(0, &test_var)); 161 KCSAN_CHECK_READ_BARRIER(test_and_clear_bit(0, &test_var)); 162 KCSAN_CHECK_READ_BARRIER(test_and_change_bit(0, &test_var)); 163 KCSAN_CHECK_READ_BARRIER(clear_bit_unlock(0, &test_var)); 164 KCSAN_CHECK_READ_BARRIER(__clear_bit_unlock(0, &test_var)); 165 arch_spin_lock(&arch_spinlock); 166 KCSAN_CHECK_READ_BARRIER(arch_spin_unlock(&arch_spinlock)); 167 spin_lock(&test_spinlock); 168 KCSAN_CHECK_READ_BARRIER(spin_unlock(&test_spinlock)); 169 170 KCSAN_CHECK_WRITE_BARRIER(mb()); 171 KCSAN_CHECK_WRITE_BARRIER(wmb()); 172 KCSAN_CHECK_WRITE_BARRIER(smp_mb()); 173 KCSAN_CHECK_WRITE_BARRIER(smp_wmb()); 174 KCSAN_CHECK_WRITE_BARRIER(dma_wmb()); 175 KCSAN_CHECK_WRITE_BARRIER(smp_mb__before_atomic()); 176 KCSAN_CHECK_WRITE_BARRIER(smp_mb__after_atomic()); 177 KCSAN_CHECK_WRITE_BARRIER(smp_mb__after_spinlock()); 178 KCSAN_CHECK_WRITE_BARRIER(smp_store_mb(test_var, 0)); 179 KCSAN_CHECK_WRITE_BARRIER(smp_store_release(&test_var, 0)); 180 KCSAN_CHECK_WRITE_BARRIER(xchg(&test_var, 0)); 181 KCSAN_CHECK_WRITE_BARRIER(xchg_release(&test_var, 0)); 182 KCSAN_CHECK_WRITE_BARRIER(cmpxchg(&test_var, 0, 0)); 183 KCSAN_CHECK_WRITE_BARRIER(cmpxchg_release(&test_var, 0, 0)); 184 KCSAN_CHECK_WRITE_BARRIER(atomic_set_release(&dummy, 0)); 185 KCSAN_CHECK_WRITE_BARRIER(atomic_add_return(1, &dummy)); 186 KCSAN_CHECK_WRITE_BARRIER(atomic_add_return_release(1, &dummy)); 187 KCSAN_CHECK_WRITE_BARRIER(atomic_fetch_add(1, &dummy)); 188 KCSAN_CHECK_WRITE_BARRIER(atomic_fetch_add_release(1, &dummy)); 189 KCSAN_CHECK_WRITE_BARRIER(test_and_set_bit(0, &test_var)); 190 KCSAN_CHECK_WRITE_BARRIER(test_and_clear_bit(0, &test_var)); 191 KCSAN_CHECK_WRITE_BARRIER(test_and_change_bit(0, &test_var)); 192 KCSAN_CHECK_WRITE_BARRIER(clear_bit_unlock(0, &test_var)); 193 KCSAN_CHECK_WRITE_BARRIER(__clear_bit_unlock(0, &test_var)); 194 arch_spin_lock(&arch_spinlock); 195 KCSAN_CHECK_WRITE_BARRIER(arch_spin_unlock(&arch_spinlock)); 196 spin_lock(&test_spinlock); 197 KCSAN_CHECK_WRITE_BARRIER(spin_unlock(&test_spinlock)); 198 199 KCSAN_CHECK_RW_BARRIER(mb()); 200 KCSAN_CHECK_RW_BARRIER(wmb()); 201 KCSAN_CHECK_RW_BARRIER(rmb()); 202 KCSAN_CHECK_RW_BARRIER(smp_mb()); 203 KCSAN_CHECK_RW_BARRIER(smp_wmb()); 204 KCSAN_CHECK_RW_BARRIER(smp_rmb()); 205 KCSAN_CHECK_RW_BARRIER(dma_wmb()); 206 KCSAN_CHECK_RW_BARRIER(dma_rmb()); 207 KCSAN_CHECK_RW_BARRIER(smp_mb__before_atomic()); 208 KCSAN_CHECK_RW_BARRIER(smp_mb__after_atomic()); 209 KCSAN_CHECK_RW_BARRIER(smp_mb__after_spinlock()); 210 KCSAN_CHECK_RW_BARRIER(smp_store_mb(test_var, 0)); 211 KCSAN_CHECK_RW_BARRIER(smp_store_release(&test_var, 0)); 212 KCSAN_CHECK_RW_BARRIER(xchg(&test_var, 0)); 213 KCSAN_CHECK_RW_BARRIER(xchg_release(&test_var, 0)); 214 KCSAN_CHECK_RW_BARRIER(cmpxchg(&test_var, 0, 0)); 215 KCSAN_CHECK_RW_BARRIER(cmpxchg_release(&test_var, 0, 0)); 216 KCSAN_CHECK_RW_BARRIER(atomic_set_release(&dummy, 0)); 217 KCSAN_CHECK_RW_BARRIER(atomic_add_return(1, &dummy)); 218 KCSAN_CHECK_RW_BARRIER(atomic_add_return_release(1, &dummy)); 219 KCSAN_CHECK_RW_BARRIER(atomic_fetch_add(1, &dummy)); 220 KCSAN_CHECK_RW_BARRIER(atomic_fetch_add_release(1, &dummy)); 221 KCSAN_CHECK_RW_BARRIER(test_and_set_bit(0, &test_var)); 222 KCSAN_CHECK_RW_BARRIER(test_and_clear_bit(0, &test_var)); 223 KCSAN_CHECK_RW_BARRIER(test_and_change_bit(0, &test_var)); 224 KCSAN_CHECK_RW_BARRIER(clear_bit_unlock(0, &test_var)); 225 KCSAN_CHECK_RW_BARRIER(__clear_bit_unlock(0, &test_var)); 226 arch_spin_lock(&arch_spinlock); 227 KCSAN_CHECK_RW_BARRIER(arch_spin_unlock(&arch_spinlock)); 228 spin_lock(&test_spinlock); 229 KCSAN_CHECK_RW_BARRIER(spin_unlock(&test_spinlock)); 230 KCSAN_CHECK_RW_BARRIER(xor_unlock_is_negative_byte(1, &test_var)); 231 KCSAN_CHECK_READ_BARRIER(xor_unlock_is_negative_byte(1, &test_var)); 232 KCSAN_CHECK_WRITE_BARRIER(xor_unlock_is_negative_byte(1, &test_var)); 233 kcsan_nestable_atomic_end(); 234 235 return ret; 236} 237 238static int __init kcsan_selftest(void) 239{ 240 int passed = 0; 241 int total = 0; 242 243#define RUN_TEST(do_test) \ 244 do { \ 245 ++total; \ 246 if (do_test()) \ 247 ++passed; \ 248 else \ 249 pr_err("selftest: " #do_test " failed"); \ 250 } while (0) 251 252 RUN_TEST(test_encode_decode); 253 RUN_TEST(test_matching_access); 254 RUN_TEST(test_barrier); 255 256 pr_info("selftest: %d/%d tests passed\n", passed, total); 257 if (passed != total) 258 panic("selftests failed"); 259 return 0; 260} 261postcore_initcall(kcsan_selftest); 262