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 
16 static 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 
35 int main(int argc, char *argv[])
36 {
37 	return test_harness(test_denormal_fpu, "fpu_denormal");
38 }
39