blob: 074f30301f2999de59294dc18e4a6a604a250f22 [file] [log] [blame]
Petteri Aimonen4185b3b2020-06-18 16:37:37 +02001// 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, especially
6 * when userland has modified the floating point control registers. The kernel
7 * state might depend on the state set by the userland thread that was active
8 * before a syscall.
9 *
10 * To facilitate the test, this module registers file
11 * /sys/kernel/debug/selftest_helpers/test_fpu, which when read causes a
12 * sequence of floating point operations. If the operations fail, either the
13 * 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>
Samuel Holland790a4a32024-03-29 00:18:30 -070020#include <linux/fpu.h>
Petteri Aimonen4185b3b2020-06-18 16:37:37 +020021
Samuel Holland96137362024-03-29 00:18:29 -070022#include "test_fpu.h"
Petteri Aimonen4185b3b2020-06-18 16:37:37 +020023
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
kernel test robot443121b2020-10-25 11:20:04 +010036DEFINE_DEBUGFS_ATTRIBUTE(test_fpu_fops, test_fpu_get, NULL, "%lld\n");
Petteri Aimonen4185b3b2020-06-18 16:37:37 +020037static struct dentry *selftest_dir;
38
39static int __init test_fpu_init(void)
40{
Samuel Holland790a4a32024-03-29 00:18:30 -070041 if (!kernel_fpu_available())
42 return -EINVAL;
43
Petteri Aimonen4185b3b2020-06-18 16:37:37 +020044 selftest_dir = debugfs_create_dir("selftest_helpers", NULL);
45 if (!selftest_dir)
46 return -ENOMEM;
47
kernel test robot443121b2020-10-25 11:20:04 +010048 debugfs_create_file_unsafe("test_fpu", 0444, selftest_dir, NULL,
49 &test_fpu_fops);
Petteri Aimonen4185b3b2020-06-18 16:37:37 +020050
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
Jeff Johnson2a49c8b62024-06-22 07:55:05 -070062MODULE_DESCRIPTION("Test cases for floating point operations");
Petteri Aimonen4185b3b2020-06-18 16:37:37 +020063MODULE_LICENSE("GPL");