90 lines
2.0 KiB
C
90 lines
2.0 KiB
C
|
// 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");
|