mm/rodata_test.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * rodata_test.c: functional test for mark_rodata_ro function
   4  *
   5  * (C) Copyright 2008 Intel Corporation
   6  * Author: Arjan van de Ven <arjan@linux.intel.com>
   7  */
   8 #define pr_fmt(fmt) "rodata_test: " fmt
   9
  10 #include <linux/rodata_test.h>
  11 #include <linux/uaccess.h>
  12 #include <asm/sections.h>
  13
  14 static const int rodata_test_data = 0xC3;
  15
  16 void rodata_test(void)
  17 {
  18         unsigned long start, end;
  19         int zero = 0;
  20
  21         /* test 1: read the value */
  22         /* If this test fails, some previous testrun has clobbered the state */
  23         if (!rodata_test_data) {
  24                 pr_err("test 1 fails (start data)\n");
  25                 return;
  26         }
  27
  28         /* test 2: write to the variable; this should fault */
  29         if (!copy_to_kernel_nofault((void *)&rodata_test_data,
  30                                 (void *)&zero, sizeof(zero))) {
  31                 pr_err("test data was not read only\n");
  32                 return;
  33         }
  34
  35         /* test 3: check the value hasn't changed */
  36         if (rodata_test_data == zero) {
  37                 pr_err("test data was changed\n");
  38                 return;
  39         }
  40
  41         /* test 4: check if the rodata section is PAGE_SIZE aligned */
  42         start = (unsigned long)__start_rodata;
  43         end = (unsigned long)__end_rodata;
  44         if (start & (PAGE_SIZE - 1)) {
  45                 pr_err("start of .rodata is not page size aligned\n");
  46                 return;
  47         }
  48         if (end & (PAGE_SIZE - 1)) {
  49                 pr_err("end of .rodata is not page size aligned\n");
  50                 return;
  51         }
  52
  53         pr_info("all tests were successful\n");
  54 }