tools/testing/selftests/fpu/test_fpu.c

   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
  16 const char *test_fpu_path = "/sys/kernel/debug/selftest_helpers/test_fpu";
  17
  18 int 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 }