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1// SPDX-License-Identifier: GPL-2.0+2/*3 * Test cases for using floating point operations inside a kernel module.4 *5 * This tests kernel_fpu_begin() and kernel_fpu_end() functions, especially6 * when userland has modified the floating point control registers. The kernel7 * state might depend on the state set by the userland thread that was active8 * before a syscall.9 *10 * To facilitate the test, this module registers file11 * /sys/kernel/debug/selftest_helpers/test_fpu, which when read causes a12 * sequence of floating point operations. If the operations fail, either the13 * read returns error status or the kernel crashes.14 * If the operations succeed, the read returns "1\n".15 */16 17#include <linux/module.h>18#include <linux/kernel.h>19#include <linux/debugfs.h>20#include <linux/fpu.h>21 22#include "test_fpu.h"23 24static int test_fpu_get(void *data, u64 *val)25{26 int status = -EINVAL;27 28 kernel_fpu_begin();29 status = test_fpu();30 kernel_fpu_end();31 32 *val = 1;33 return status;34}35 36DEFINE_DEBUGFS_ATTRIBUTE(test_fpu_fops, test_fpu_get, NULL, "%lld\n");37static struct dentry *selftest_dir;38 39static int __init test_fpu_init(void)40{41 if (!kernel_fpu_available())42 return -EINVAL;43 44 selftest_dir = debugfs_create_dir("selftest_helpers", NULL);45 if (IS_ERR(selftest_dir))46 return -ENOMEM;47 48 debugfs_create_file_unsafe("test_fpu", 0444, selftest_dir, NULL,49 &test_fpu_fops);50 51 return 0;52}53 54static void __exit test_fpu_exit(void)55{56 debugfs_remove(selftest_dir);57}58 59module_init(test_fpu_init);60module_exit(test_fpu_exit);61 62MODULE_DESCRIPTION("Test cases for floating point operations");63MODULE_LICENSE("GPL");64