// SPDX-License-Identifier: GPL-2.0+
/* This testcase operates with the test_fpu kernel driver.
 * It modifies the FPU control register in user mode and calls the kernel
 * module to perform floating point operations in the kernel. The control
 * register value should be independent between kernel and user mode.
 */

#define _GNU_SOURCE
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <fenv.h>
#include <unistd.h>
#include <fcntl.h>

const char *test_fpu_path = "/sys/kernel/debug/selftest_helpers/test_fpu";

int main(void)
{
        char dummy[1];
        int fd = open(test_fpu_path, O_RDONLY);

        if (fd < 0) {
                printf("[SKIP]\tcan't access %s: %s\n",
                       test_fpu_path, strerror(errno));
                return 0;
        }

        if (read(fd, dummy, 1) < 0) {
                printf("[FAIL]\taccess with default rounding mode failed\n");
                return 1;
        }

        fesetround(FE_DOWNWARD);
        if (read(fd, dummy, 1) < 0) {
                printf("[FAIL]\taccess with downward rounding mode failed\n");
                return 2;
        }
        if (fegetround() != FE_DOWNWARD) {
                printf("[FAIL]\tusermode rounding mode clobbered\n");
                return 3;
        }

        /* Note: the tests up to this point are quite safe and will only return
         * an error. But the exception mask setting can cause misbehaving kernel
         * to crash.
         */
        feclearexcept(FE_ALL_EXCEPT);
        feenableexcept(FE_ALL_EXCEPT);
        if (read(fd, dummy, 1) < 0) {
                printf("[FAIL]\taccess with fpu exceptions unmasked failed\n");
                return 4;
        }
        if (fegetexcept() != FE_ALL_EXCEPT) {
                printf("[FAIL]\tusermode fpu exception mask clobbered\n");
                return 5;
        }

        printf("[OK]\ttest_fpu\n");
        return 0;
}