drivers/misc/lkdtm/cfi.c

   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
   7 static int called_count;
   8
   9 /* Function taking one argument, without a return value. */
  10 static noinline void lkdtm_increment_void(int *counter)
  11 {
  12         (*counter)++;
  13 }
  14
  15 /* Function taking one argument, returning int. */
  16 static 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  */
  25 void 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_info("Fail: survived mismatched prototype function call!\n");
  42 }