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