kernel/kcsan/selftest.c

   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  */
  29 static 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;
  68 fail:
  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. */
  79 static 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  */
 109 static DEFINE_SPINLOCK(test_spinlock);
 110 static bool __init test_barrier(void)
 111 {
 112 #ifdef CONFIG_KCSAN_WEAK_MEMORY
 113         struct kcsan_scoped_access *reorder_access = &current->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
 231 #ifdef clear_bit_unlock_is_negative_byte
 232         KCSAN_CHECK_RW_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
 233         KCSAN_CHECK_READ_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
 234         KCSAN_CHECK_WRITE_BARRIER(clear_bit_unlock_is_negative_byte(0, &test_var));
 235 #endif
 236         kcsan_nestable_atomic_end();
 237
 238         return ret;
 239 }
 240
 241 static int __init kcsan_selftest(void)
 242 {
 243         int passed = 0;
 244         int total = 0;
 245
 246 #define RUN_TEST(do_test)                                                      \
 247         do {                                                                   \
 248                 ++total;                                                       \
 249                 if (do_test())                                                 \
 250                         ++passed;                                              \
 251                 else                                                           \
 252                         pr_err("selftest: " #do_test " failed");               \
 253         } while (0)
 254
 255         RUN_TEST(test_encode_decode);
 256         RUN_TEST(test_matching_access);
 257         RUN_TEST(test_barrier);
 258
 259         pr_info("selftest: %d/%d tests passed\n", passed, total);
 260         if (passed != total)
 261                 panic("selftests failed");
 262         return 0;
 263 }
 264 postcore_initcall(kcsan_selftest);