LXR linux/tools/testing/selftests/powerpc/math/fpu

   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * Copyright IBM Corp. 2020
   4 *
   5 * This test attempts to cause a FP denormal exception on POWER8 CPUs. Unfortunately
   6 * if the denormal handler is not configured or working properly, this can cause a bad
   7 * crash in kernel mode when the kernel tries to save FP registers when the process
   8 * exits.
   9 */
  10
  11#include <stdio.h>
  12#include <string.h>
  13
  14#include "utils.h"
  15
  16static int test_denormal_fpu(void)
  17{
  18        unsigned int m32;
  19        unsigned long m64;
  20        volatile float f;
  21        volatile double d;
  22
  23        /* try to induce lfs <denormal> ; stfd */
  24
  25        m32 = 0x00715fcf; /* random denormal */
  26        memcpy((float *)&f, &m32, sizeof(f));
  27        d = f;
  28        memcpy(&m64, (double *)&d, sizeof(d));
  29
  30        FAIL_IF((long)(m64 != 0x380c57f3c0000000)); /* renormalised value */
  31
  32        return 0;
  33}
  34
  35int main(int argc, char *argv[])
  36{
  37        return test_harness(test_denormal_fpu, "fpu_denormal");
  38}
  39