1// SPDX-License-Identifier: GPL-2.0+
2/* This testcase operates with the test_fpu kernel driver.
3 * It modifies the FPU control register in user mode and calls the kernel
4 * module to perform floating point operations in the kernel. The control
5 * register value should be independent between kernel and user mode.
6 */
7
8#define _GNU_SOURCE
9#include <stdio.h>
10#include <errno.h>
11#include <string.h>
12#include <fenv.h>
13#include <unistd.h>
14#include <fcntl.h>
15
16const char *test_fpu_path = "/sys/kernel/debug/selftest_helpers/test_fpu";
17
18int main(void)
19{
20	char dummy[1];
21	int fd = open(test_fpu_path, O_RDONLY);
22
23	if (fd < 0) {
24		printf("[SKIP]\tcan't access %s: %s\n",
25		       test_fpu_path, strerror(errno));
26		return 0;
27	}
28
29	if (read(fd, dummy, 1) < 0) {
30		printf("[FAIL]\taccess with default rounding mode failed\n");
31		return 1;
32	}
33
34	fesetround(FE_DOWNWARD);
35	if (read(fd, dummy, 1) < 0) {
36		printf("[FAIL]\taccess with downward rounding mode failed\n");
37		return 2;
38	}
39	if (fegetround() != FE_DOWNWARD) {
40		printf("[FAIL]\tusermode rounding mode clobbered\n");
41		return 3;
42	}
43
44	/* Note: the tests up to this point are quite safe and will only return
45	 * an error. But the exception mask setting can cause misbehaving kernel
46	 * to crash.
47	 */
48	feclearexcept(FE_ALL_EXCEPT);
49	feenableexcept(FE_ALL_EXCEPT);
50	if (read(fd, dummy, 1) < 0) {
51		printf("[FAIL]\taccess with fpu exceptions unmasked failed\n");
52		return 4;
53	}
54	if (fegetexcept() != FE_ALL_EXCEPT) {
55		printf("[FAIL]\tusermode fpu exception mask clobbered\n");
56		return 5;
57	}
58
59	printf("[OK]\ttest_fpu\n");
60	return 0;
61}
62