blob: eef282a2715f218aee94cb2cf5bca40baec28a4c [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0+
* Test cases for using floating point operations inside a kernel module.
* This tests kernel_fpu_begin() and kernel_fpu_end() functions, especially
* when userland has modified the floating point control registers. The kernel
* state might depend on the state set by the userland thread that was active
* before a syscall.
* To facilitate the test, this module registers file
* /sys/kernel/debug/selftest_helpers/test_fpu, which when read causes a
* sequence of floating point operations. If the operations fail, either the
* read returns error status or the kernel crashes.
* If the operations succeed, the read returns "1\n".
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/debugfs.h>
#include <linux/fpu.h>
#include "test_fpu.h"
static int test_fpu_get(void *data, u64 *val)
int status = -EINVAL;
status = test_fpu();
*val = 1;
return status;
DEFINE_DEBUGFS_ATTRIBUTE(test_fpu_fops, test_fpu_get, NULL, "%lld\n");
static struct dentry *selftest_dir;
static int __init test_fpu_init(void)
if (!kernel_fpu_available())
return -EINVAL;
selftest_dir = debugfs_create_dir("selftest_helpers", NULL);
if (!selftest_dir)
return -ENOMEM;
debugfs_create_file_unsafe("test_fpu", 0444, selftest_dir, NULL,
return 0;
static void __exit test_fpu_exit(void)