// 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; 	kernel_fpu_begin();	status = test_fpu();	kernel_fpu_end(); 	*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 (IS_ERR(selftest_dir))		return -ENOMEM; 	debugfs_create_file_unsafe("test_fpu", 0444, selftest_dir, NULL,				   &test_fpu_fops); 	return 0;} static void __exit test_fpu_exit(void){	debugfs_remove(selftest_dir);} module_init(test_fpu_init);module_exit(test_fpu_exit); MODULE_DESCRIPTION("Test cases for floating point operations");MODULE_LICENSE("GPL");