Petteri Aimonen | 4185b3b | 2020-06-18 16:37:37 +0200 | [diff] [blame] | 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, 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 Holland | 790a4a3 | 2024-03-29 00:18:30 -0700 | [diff] [blame] | 20 | #include <linux/fpu.h> |
Petteri Aimonen | 4185b3b | 2020-06-18 16:37:37 +0200 | [diff] [blame] | 21 | |
Samuel Holland | 9613736 | 2024-03-29 00:18:29 -0700 | [diff] [blame] | 22 | #include "test_fpu.h" |
Petteri Aimonen | 4185b3b | 2020-06-18 16:37:37 +0200 | [diff] [blame] | 23 | |
| 24 | static 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 robot | 443121b | 2020-10-25 11:20:04 +0100 | [diff] [blame] | 36 | DEFINE_DEBUGFS_ATTRIBUTE(test_fpu_fops, test_fpu_get, NULL, "%lld\n"); |
Petteri Aimonen | 4185b3b | 2020-06-18 16:37:37 +0200 | [diff] [blame] | 37 | static struct dentry *selftest_dir; |
| 38 | |
| 39 | static int __init test_fpu_init(void) |
| 40 | { |
Samuel Holland | 790a4a3 | 2024-03-29 00:18:30 -0700 | [diff] [blame] | 41 | if (!kernel_fpu_available()) |
| 42 | return -EINVAL; |
| 43 | |
Petteri Aimonen | 4185b3b | 2020-06-18 16:37:37 +0200 | [diff] [blame] | 44 | selftest_dir = debugfs_create_dir("selftest_helpers", NULL); |
| 45 | if (!selftest_dir) |
| 46 | return -ENOMEM; |
| 47 | |
kernel test robot | 443121b | 2020-10-25 11:20:04 +0100 | [diff] [blame] | 48 | debugfs_create_file_unsafe("test_fpu", 0444, selftest_dir, NULL, |
| 49 | &test_fpu_fops); |
Petteri Aimonen | 4185b3b | 2020-06-18 16:37:37 +0200 | [diff] [blame] | 50 | |
| 51 | return 0; |
| 52 | } |
| 53 | |
| 54 | static void __exit test_fpu_exit(void) |
| 55 | { |
| 56 | debugfs_remove(selftest_dir); |
| 57 | } |
| 58 | |
| 59 | module_init(test_fpu_init); |
| 60 | module_exit(test_fpu_exit); |
| 61 | |
Jeff Johnson | 2a49c8b6 | 2024-06-22 07:55:05 -0700 | [diff] [blame] | 62 | MODULE_DESCRIPTION("Test cases for floating point operations"); |
Petteri Aimonen | 4185b3b | 2020-06-18 16:37:37 +0200 | [diff] [blame] | 63 | MODULE_LICENSE("GPL"); |