linux/drivers/misc/lkdtm/cfi.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * This is for all the tests relating directly to Control Flow Integrity.
   4 */
   5#include "lkdtm.h"
   6
   7static int called_count;
   8
   9/* Function taking one argument, without a return value. */
  10static noinline void lkdtm_increment_void(int *counter)
  11{
  12        (*counter)++;
  13}
  14
  15/* Function taking one argument, returning int. */
  16static noinline int lkdtm_increment_int(int *counter)
  17{
  18        (*counter)++;
  19
  20        return *counter;
  21}
  22/*
  23 * This tries to call an indirect function with a mismatched prototype.
  24 */
  25void lkdtm_CFI_FORWARD_PROTO(void)
  26{
  27        /*
  28         * Matches lkdtm_increment_void()'s prototype, but not
  29         * lkdtm_increment_int()'s prototype.
  30         */
  31        void (*func)(int *);
  32
  33        pr_info("Calling matched prototype ...\n");
  34        func = lkdtm_increment_void;
  35        func(&called_count);
  36
  37        pr_info("Calling mismatched prototype ...\n");
  38        func = (void *)lkdtm_increment_int;
  39        func(&called_count);
  40
  41        pr_err("FAIL: survived mismatched prototype function call!\n");
  42        pr_expected_config(CONFIG_CFI_CLANG);
  43}
  44