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-rw-r--r--tools/testing/selftests/fpu/test_fpu.c61
1 files changed, 61 insertions, 0 deletions
diff --git a/tools/testing/selftests/fpu/test_fpu.c b/tools/testing/selftests/fpu/test_fpu.c
new file mode 100644
index 000000000..200238522
--- /dev/null
+++ b/tools/testing/selftests/fpu/test_fpu.c
@@ -0,0 +1,61 @@
+// 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;
+}