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 (addr < PAGE_SIZE)
  37                         addr = PAGE_SIZE;
  38
  39                 if (WARN_ON(!check_encodable(addr, size)))
  40                         return false;
  41
  42                 /* Encode and decode */
  43                 {
  44                         const long encoded_watchpoint =
  45                                 encode_watchpoint(addr, size, is_write);
  46                         unsigned long verif_masked_addr;
  47                         size_t verif_size;
  48                         bool verif_is_write;
  49
  50                         /* Check special watchpoints */
  51                         if (WARN_ON(decode_watchpoint(
  52                                     INVALID_WATCHPOINT, &verif_masked_addr,
  53                                     &verif_size, &verif_is_write)))
  54                                 return false;
  55                         if (WARN_ON(decode_watchpoint(
  56                                     CONSUMED_WATCHPOINT, &verif_masked_addr,
  57                                     &verif_size, &verif_is_write)))
  58                                 return false;
  59
  60                         /* Check decoding watchpoint returns same data */
  61                         if (WARN_ON(!decode_watchpoint(
  62                                     encoded_watchpoint, &verif_masked_addr,
  63                                     &verif_size, &verif_is_write)))
  64                                 return false;
  65                         if (WARN_ON(verif_masked_addr !=
  66                                     (addr & WATCHPOINT_ADDR_MASK)))
  67                                 goto fail;
  68                         if (WARN_ON(verif_size != size))
  69                                 goto fail;
  70                         if (WARN_ON(is_write != verif_is_write))
  71                                 goto fail;
  72
  73                         continue;
  74 fail:
  75                         pr_err("%s fail: %s %zu bytes @ %lx -> encoded: %lx -> %s %zu bytes @ %lx\n",
  76                                __func__, is_write ? "write" : "read", size,
  77                                addr, encoded_watchpoint,
  78                                verif_is_write ? "write" : "read", verif_size,
  79                                verif_masked_addr);
  80                         return false;
  81                 }
  82         }
  83
  84         return true;
  85 }
  86
  87 /* Test access matching function. */
  88 static bool test_matching_access(void)
  89 {
  90         if (WARN_ON(!matching_access(10, 1, 10, 1)))
  91                 return false;
  92         if (WARN_ON(!matching_access(10, 2, 11, 1)))
  93                 return false;
  94         if (WARN_ON(!matching_access(10, 1, 9, 2)))
  95                 return false;
  96         if (WARN_ON(matching_access(10, 1, 11, 1)))
  97                 return false;
  98         if (WARN_ON(matching_access(9, 1, 10, 1)))
  99                 return false;
 100
 101         /*
 102          * An access of size 0 could match another access, as demonstrated here.
 103          * Rather than add more comparisons to 'matching_access()', which would
 104          * end up in the fast-path for *all* checks, check_access() simply
 105          * returns for all accesses of size 0.
 106          */
 107         if (WARN_ON(!matching_access(8, 8, 12, 0)))
 108                 return false;
 109
 110         return true;
 111 }
 112
 113 static int __init kcsan_selftest(void)
 114 {
 115         int passed = 0;
 116         int total = 0;
 117
 118 #define RUN_TEST(do_test)                                                      \
 119         do {                                                                   \
 120                 ++total;                                                       \
 121                 if (do_test())                                                 \
 122                         ++passed;                                              \
 123                 else                                                           \
 124                         pr_err("selftest: " #do_test " failed");               \
 125         } while (0)
 126
 127         RUN_TEST(test_requires);
 128         RUN_TEST(test_encode_decode);
 129         RUN_TEST(test_matching_access);
 130
 131         pr_info("selftest: %d/%d tests passed\n", passed, total);
 132         if (passed != total)
 133                 panic("selftests failed");
 134         return 0;
 135 }
 136 postcore_initcall(kcsan_selftest);