mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
89 lines
2.0 KiB
89 lines
2.0 KiB
// 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 <asm/fpu/api.h> |
|
|
|
static int test_fpu(void) |
|
{ |
|
/* |
|
* This sequence of operations tests that rounding mode is |
|
* to nearest and that denormal numbers are supported. |
|
* Volatile variables are used to avoid compiler optimizing |
|
* the calculations away. |
|
*/ |
|
volatile double a, b, c, d, e, f, g; |
|
|
|
a = 4.0; |
|
b = 1e-15; |
|
c = 1e-310; |
|
|
|
/* Sets precision flag */ |
|
d = a + b; |
|
|
|
/* Result depends on rounding mode */ |
|
e = a + b / 2; |
|
|
|
/* Denormal and very large values */ |
|
f = b / c; |
|
|
|
/* Depends on denormal support */ |
|
g = a + c * f; |
|
|
|
if (d > a && e > a && g > a) |
|
return 0; |
|
else |
|
return -EINVAL; |
|
} |
|
|
|
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) |
|
{ |
|
selftest_dir = debugfs_create_dir("selftest_helpers", NULL); |
|
if (!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_LICENSE("GPL");
|
|
|