kernel/kcsan/selftest.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include <linux/init.h>
   4 #include <linux/kernel.h>
   5 #include <linux/printk.h>
   6 #include <linux/random.h>
   7 #include <linux/types.h>
   8
   9 #include "encoding.h"
  10
  11 #define ITERS_PER_TEST 2000
  12
  13 /* Test requirements. */
  14 static bool test_requires(void)
  15 {
  16         /* random should be initialized for the below tests */
  17         return prandom_u32() + prandom_u32() != 0;
  18 }
  19
  20 /*
  21  * Test watchpoint encode and decode: check that encoding some access's info,
  22  * and then subsequent decode preserves the access's info.
  23  */
  24 static bool test_encode_decode(void)
  25 {
  26         int i;
  27
  28         for (i = 0; i < ITERS_PER_TEST; ++i) {
  29                 size_t size = prandom_u32_max(MAX_ENCODABLE_SIZE) + 1;
  30                 bool is_write = !!prandom_u32_max(2);
  31                 unsigned long addr;
  32
  33                 prandom_bytes(&addr, sizeof(addr));
  34                 if (WARN_ON(!check_encodable(addr, size)))
  35                         return false;
  36
  37                 /* Encode and decode */
  38                 {
  39                         const long encoded_watchpoint =
  40                                 encode_watchpoint(addr, size, is_write);
  41                         unsigned long verif_masked_addr;
  42                         size_t verif_size;
  43                         bool verif_is_write;
  44
  45                         /* Check special watchpoints */
  46                         if (WARN_ON(decode_watchpoint(
  47                                     INVALID_WATCHPOINT, &verif_masked_addr,
  48                                     &verif_size, &verif_is_write)))
  49                                 return false;
  50                         if (WARN_ON(decode_watchpoint(
  51                                     CONSUMED_WATCHPOINT, &verif_masked_addr,
  52                                     &verif_size, &verif_is_write)))
  53                                 return false;
  54
  55                         /* Check decoding watchpoint returns same data */
  56                         if (WARN_ON(!decode_watchpoint(
  57                                     encoded_watchpoint, &verif_masked_addr,
  58                                     &verif_size, &verif_is_write)))
  59                                 return false;
  60                         if (WARN_ON(verif_masked_addr !=
  61                                     (addr & WATCHPOINT_ADDR_MASK)))
  62                                 goto fail;
  63                         if (WARN_ON(verif_size != size))
  64                                 goto fail;
  65                         if (WARN_ON(is_write != verif_is_write))
  66                                 goto fail;
  67
  68                         continue;
  69 fail:
  70                         pr_err("%s fail: %s %zu bytes @ %lx -> encoded: %lx -> %s %zu bytes @ %lx\n",
  71                                __func__, is_write ? "write" : "read", size,
  72                                addr, encoded_watchpoint,
  73                                verif_is_write ? "write" : "read", verif_size,
  74                                verif_masked_addr);
  75                         return false;
  76                 }
  77         }
  78
  79         return true;
  80 }
  81
  82 /* Test access matching function. */
  83 static bool test_matching_access(void)
  84 {
  85         if (WARN_ON(!matching_access(10, 1, 10, 1)))
  86                 return false;
  87         if (WARN_ON(!matching_access(10, 2, 11, 1)))
  88                 return false;
  89         if (WARN_ON(!matching_access(10, 1, 9, 2)))
  90                 return false;
  91         if (WARN_ON(matching_access(10, 1, 11, 1)))
  92                 return false;
  93         if (WARN_ON(matching_access(9, 1, 10, 1)))
  94                 return false;
  95
  96         /*
  97          * An access of size 0 could match another access, as demonstrated here.
  98          * Rather than add more comparisons to 'matching_access()', which would
  99          * end up in the fast-path for *all* checks, check_access() simply
 100          * returns for all accesses of size 0.
 101          */
 102         if (WARN_ON(!matching_access(8, 8, 12, 0)))
 103                 return false;
 104
 105         return true;
 106 }
 107
 108 static int __init kcsan_selftest(void)
 109 {
 110         int passed = 0;
 111         int total = 0;
 112
 113 #define RUN_TEST(do_test)                                                      \
 114         do {                                                                   \
 115                 ++total;                                                       \
 116                 if (do_test())                                                 \
 117                         ++passed;                                              \
 118                 else                                                           \
 119                         pr_err("KCSAN selftest: " #do_test " failed");         \
 120         } while (0)
 121
 122         RUN_TEST(test_requires);
 123         RUN_TEST(test_encode_decode);
 124         RUN_TEST(test_matching_access);
 125
 126         pr_info("KCSAN selftest: %d/%d tests passed\n", passed, total);
 127         if (passed != total)
 128                 panic("KCSAN selftests failed");
 129         return 0;
 130 }
 131 postcore_initcall(kcsan_selftest);