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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:49:45 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:49:45 +0000 |
commit | 2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch) | |
tree | 848558de17fb3008cdf4d861b01ac7781903ce39 /lib/test_fpu.c | |
parent | Initial commit. (diff) | |
download | linux-upstream/6.1.76.tar.xz linux-upstream/6.1.76.zip |
Adding upstream version 6.1.76.upstream/6.1.76upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | lib/test_fpu.c | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/lib/test_fpu.c b/lib/test_fpu.c new file mode 100644 index 000000000..e82db19fe --- /dev/null +++ b/lib/test_fpu.c @@ -0,0 +1,89 @@ +// 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"); |