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/init.h>
  11 #include <linux/kernel.h>
  12 #include <linux/printk.h>
  13 #include <linux/random.h>
  14 #include <linux/types.h>
  15
  16 #include "encoding.h"
  17
  18 #define ITERS_PER_TEST 2000
  19
  20 /* Test requirements. */
  21 static bool test_requires(void)
  22 {
  23         /* random should be initialized for the below tests */
  24         return prandom_u32() + prandom_u32() != 0;
  25 }
  26
  27 /*
  28  * Test watchpoint encode and decode: check that encoding some access's info,
  29  * and then subsequent decode preserves the access's info.
  30  */
  31 static bool test_encode_decode(void)
  32 {
  33         int i;
  34
  35         for (i = 0; i < ITERS_PER_TEST; ++i) {
  36                 size_t size = prandom_u32_max(MAX_ENCODABLE_SIZE) + 1;
  37                 bool is_write = !!prandom_u32_max(2);
  38                 unsigned long addr;
  39
  40                 prandom_bytes(&addr, sizeof(addr));
  41                 if (addr < PAGE_SIZE)
  42                         addr = PAGE_SIZE;
  43
  44                 if (WARN_ON(!check_encodable(addr, size)))
  45                         return false;
  46
  47                 /* Encode and decode */
  48                 {
  49                         const long encoded_watchpoint =
  50                                 encode_watchpoint(addr, size, is_write);
  51                         unsigned long verif_masked_addr;
  52                         size_t verif_size;
  53                         bool verif_is_write;
  54
  55                         /* Check special watchpoints */
  56                         if (WARN_ON(decode_watchpoint(
  57                                     INVALID_WATCHPOINT, &verif_masked_addr,
  58                                     &verif_size, &verif_is_write)))
  59                                 return false;
  60                         if (WARN_ON(decode_watchpoint(
  61                                     CONSUMED_WATCHPOINT, &verif_masked_addr,
  62                                     &verif_size, &verif_is_write)))
  63                                 return false;
  64
  65                         /* Check decoding watchpoint returns same data */
  66                         if (WARN_ON(!decode_watchpoint(
  67                                     encoded_watchpoint, &verif_masked_addr,
  68                                     &verif_size, &verif_is_write)))
  69                                 return false;
  70                         if (WARN_ON(verif_masked_addr !=
  71                                     (addr & WATCHPOINT_ADDR_MASK)))
  72                                 goto fail;
  73                         if (WARN_ON(verif_size != size))
  74                                 goto fail;
  75                         if (WARN_ON(is_write != verif_is_write))
  76                                 goto fail;
  77
  78                         continue;
  79 fail:
  80                         pr_err("%s fail: %s %zu bytes @ %lx -> encoded: %lx -> %s %zu bytes @ %lx\n",
  81                                __func__, is_write ? "write" : "read", size,
  82                                addr, encoded_watchpoint,
  83                                verif_is_write ? "write" : "read", verif_size,
  84                                verif_masked_addr);
  85                         return false;
  86                 }
  87         }
  88
  89         return true;
  90 }
  91
  92 /* Test access matching function. */
  93 static bool test_matching_access(void)
  94 {
  95         if (WARN_ON(!matching_access(10, 1, 10, 1)))
  96                 return false;
  97         if (WARN_ON(!matching_access(10, 2, 11, 1)))
  98                 return false;
  99         if (WARN_ON(!matching_access(10, 1, 9, 2)))
 100                 return false;
 101         if (WARN_ON(matching_access(10, 1, 11, 1)))
 102                 return false;
 103         if (WARN_ON(matching_access(9, 1, 10, 1)))
 104                 return false;
 105
 106         /*
 107          * An access of size 0 could match another access, as demonstrated here.
 108          * Rather than add more comparisons to 'matching_access()', which would
 109          * end up in the fast-path for *all* checks, check_access() simply
 110          * returns for all accesses of size 0.
 111          */
 112         if (WARN_ON(!matching_access(8, 8, 12, 0)))
 113                 return false;
 114
 115         return true;
 116 }
 117
 118 static int __init kcsan_selftest(void)
 119 {
 120         int passed = 0;
 121         int total = 0;
 122
 123 #define RUN_TEST(do_test)                                                      \
 124         do {                                                                   \
 125                 ++total;                                                       \
 126                 if (do_test())                                                 \
 127                         ++passed;                                              \
 128                 else                                                           \
 129                         pr_err("selftest: " #do_test " failed");               \
 130         } while (0)
 131
 132         RUN_TEST(test_requires);
 133         RUN_TEST(test_encode_decode);
 134         RUN_TEST(test_matching_access);
 135
 136         pr_info("selftest: %d/%d tests passed\n", passed, total);
 137         if (passed != total)
 138                 panic("selftests failed");
 139         return 0;
 140 }
 141 postcore_initcall(kcsan_selftest);