LXR linux/arch/x86/kernel/test

   1/*
   2 * test_rodata.c: functional test for mark_rodata_ro function
   3 *
   4 * (C) Copyright 2008 Intel Corporation
   5 * Author: Arjan van de Ven <arjan@linux.intel.com>
   6 *
   7 * This program is free software; you can redistribute it and/or
   8 * modify it under the terms of the GNU General Public License
   9 * as published by the Free Software Foundation; version 2
  10 * of the License.
  11 */
  12#include <linux/module.h>
  13#include <asm/cacheflush.h>
  14#include <asm/sections.h>
  15#include <asm/asm.h>
  16
  17int rodata_test(void)
  18{
  19        unsigned long result;
  20        unsigned long start, end;
  21
  22        /* test 1: read the value */
  23        /* If this test fails, some previous testrun has clobbered the state */
  24        if (!rodata_test_data) {
  25                printk(KERN_ERR "rodata_test: test 1 fails (start data)\n");
  26                return -ENODEV;
  27        }
  28
  29        /* test 2: write to the variable; this should fault */
  30        /*
  31         * If this test fails, we managed to overwrite the data
  32         *
  33         * This is written in assembly to be able to catch the
  34         * exception that is supposed to happen in the correct
  35         * case
  36         */
  37
  38        result = 1;
  39        asm volatile(
  40                "0:     mov %[zero],(%[rodata_test])\n"
  41                "       mov %[zero], %[rslt]\n"
  42                "1:\n"
  43                ".section .fixup,\"ax\"\n"
  44                "2:     jmp 1b\n"
  45                ".previous\n"
  46                _ASM_EXTABLE(0b,2b)
  47                : [rslt] "=r" (result)
  48                : [rodata_test] "r" (&rodata_test_data), [zero] "r" (0UL)
  49        );
  50
  51
  52        if (!result) {
  53                printk(KERN_ERR "rodata_test: test data was not read only\n");
  54                return -ENODEV;
  55        }
  56
  57        /* test 3: check the value hasn't changed */
  58        /* If this test fails, we managed to overwrite the data */
  59        if (!rodata_test_data) {
  60                printk(KERN_ERR "rodata_test: Test 3 failes (end data)\n");
  61                return -ENODEV;
  62        }
  63        /* test 4: check if the rodata section is 4Kb aligned */
  64        start = (unsigned long)__start_rodata;
  65        end = (unsigned long)__end_rodata;
  66        if (start & (PAGE_SIZE - 1)) {
  67                printk(KERN_ERR "rodata_test: .rodata is not 4k aligned\n");
  68                return -ENODEV;
  69        }
  70        if (end & (PAGE_SIZE - 1)) {
  71                printk(KERN_ERR "rodata_test: .rodata end is not 4k aligned\n");
  72                return -ENODEV;
  73        }
  74
  75        return 0;
  76}
  77
  78MODULE_LICENSE("GPL");
  79MODULE_DESCRIPTION("Testcase for the DEBUG_RODATA infrastructure");
  80MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>");
  81