kernel/kcsan/selftest.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #define pr_fmt(fmt) "kcsan: " fmt
   4
   5 #include <linux/init.h>
   6 #include <linux/kernel.h>
   7 #include <linux/printk.h>
   8 #include <linux/random.h>
   9 #include <linux/types.h>
  10
  11 #include "encoding.h"
  12
  13 #define ITERS_PER_TEST 2000
  14
  15 /* Test requirements. */
  16 static bool test_requires(void)
  17 {
  18         /* random should be initialized for the below tests */
  19         return prandom_u32() + prandom_u32() != 0;
  20 }
  21
  22 /*
  23  * Test watchpoint encode and decode: check that encoding some access's info,
  24  * and then subsequent decode preserves the access's info.
  25  */
  26 static bool test_encode_decode(void)
  27 {
  28         int i;
  29
  30         for (i = 0; i < ITERS_PER_TEST; ++i) {
  31                 size_t size = prandom_u32_max(MAX_ENCODABLE_SIZE) + 1;
  32                 bool is_write = !!prandom_u32_max(2);
  33                 unsigned long addr;
  34
  35                 prandom_bytes(&addr, sizeof(addr));
  36                 if (WARN_ON(!check_encodable(addr, size)))
  37                         return false;
  38
  39                 /* Encode and decode */
  40                 {
  41                         const long encoded_watchpoint =
  42                                 encode_watchpoint(addr, size, is_write);
  43                         unsigned long verif_masked_addr;
  44                         size_t verif_size;
  45                         bool verif_is_write;
  46
  47                         /* Check special watchpoints */
  48                         if (WARN_ON(decode_watchpoint(
  49                                     INVALID_WATCHPOINT, &verif_masked_addr,
  50                                     &verif_size, &verif_is_write)))
  51                                 return false;
  52                         if (WARN_ON(decode_watchpoint(
  53                                     CONSUMED_WATCHPOINT, &verif_masked_addr,
  54                                     &verif_size, &verif_is_write)))
  55                                 return false;
  56
  57                         /* Check decoding watchpoint returns same data */
  58                         if (WARN_ON(!decode_watchpoint(
  59                                     encoded_watchpoint, &verif_masked_addr,
  60                                     &verif_size, &verif_is_write)))
  61                                 return false;
  62                         if (WARN_ON(verif_masked_addr !=
  63                                     (addr & WATCHPOINT_ADDR_MASK)))
  64                                 goto fail;
  65                         if (WARN_ON(verif_size != size))
  66                                 goto fail;
  67                         if (WARN_ON(is_write != verif_is_write))
  68                                 goto fail;
  69
  70                         continue;
  71 fail:
  72                         pr_err("%s fail: %s %zu bytes @ %lx -> encoded: %lx -> %s %zu bytes @ %lx\n",
  73                                __func__, is_write ? "write" : "read", size,
  74                                addr, encoded_watchpoint,
  75                                verif_is_write ? "write" : "read", verif_size,
  76                                verif_masked_addr);
  77                         return false;
  78                 }
  79         }
  80
  81         return true;
  82 }
  83
  84 /* Test access matching function. */
  85 static bool test_matching_access(void)
  86 {
  87         if (WARN_ON(!matching_access(10, 1, 10, 1)))
  88                 return false;
  89         if (WARN_ON(!matching_access(10, 2, 11, 1)))
  90                 return false;
  91         if (WARN_ON(!matching_access(10, 1, 9, 2)))
  92                 return false;
  93         if (WARN_ON(matching_access(10, 1, 11, 1)))
  94                 return false;
  95         if (WARN_ON(matching_access(9, 1, 10, 1)))
  96                 return false;
  97
  98         /*
  99          * An access of size 0 could match another access, as demonstrated here.
 100          * Rather than add more comparisons to 'matching_access()', which would
 101          * end up in the fast-path for *all* checks, check_access() simply
 102          * returns for all accesses of size 0.
 103          */
 104         if (WARN_ON(!matching_access(8, 8, 12, 0)))
 105                 return false;
 106
 107         return true;
 108 }
 109
 110 static int __init kcsan_selftest(void)
 111 {
 112         int passed = 0;
 113         int total = 0;
 114
 115 #define RUN_TEST(do_test)                                                      \
 116         do {                                                                   \
 117                 ++total;                                                       \
 118                 if (do_test())                                                 \
 119                         ++passed;                                              \
 120                 else                                                           \
 121                         pr_err("selftest: " #do_test " failed");               \
 122         } while (0)
 123
 124         RUN_TEST(test_requires);
 125         RUN_TEST(test_encode_decode);
 126         RUN_TEST(test_matching_access);
 127
 128         pr_info("selftest: %d/%d tests passed\n", passed, total);
 129         if (passed != total)
 130                 panic("selftests failed");
 131         return 0;
 132 }
 133 postcore_initcall(kcsan_selftest);