| 1 | |
| 2 | |
| 3 | * Test cases for using floating point operations inside a kernel module.
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| 4 | *
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| 5 | * This tests kernel_fpu_begin() and kernel_fpu_end() functions, especially
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| 6 | * when userland has modified the floating point control registers. The kernel
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| 7 | * state might depend on the state set by the userland thread that was active
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| 8 | * before a syscall.
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| 9 | *
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| 10 | * To facilitate the test, this module registers file
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| 11 | * /sys/kernel/debug/selftest_helpers/test_fpu, which when read causes a
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| 12 | * sequence of floating point operations. If the operations fail, either the
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| 13 | * read returns error status or the kernel crashes.
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| 14 | * If the operations succeed, the read returns "1\n".
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| 15 |
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| 16 |
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| 17 | #include <linux/module.h>
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| 18 | #include <linux/kernel.h>
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| 19 | #include <linux/debugfs.h>
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| 20 | #include <linux/fpu.h>
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| 21 |
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| 22 | #include "test_fpu.h"
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| 23 |
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| 24 | static int test_fpu_get(void *data, u64 *val)
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| 25 | {
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| 26 | int status = -EINVAL;
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| 27 |
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| 28 | kernel_fpu_begin();
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| 29 | status = test_fpu();
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| 30 | kernel_fpu_end();
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| 31 |
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| 32 | *val = 1;
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| 33 | return status;
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| 34 | }
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| 35 |
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| 36 | DEFINE_DEBUGFS_ATTRIBUTE(test_fpu_fops, test_fpu_get, NULL, "%lld\n");
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| 37 | static struct dentry *selftest_dir;
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| 38 |
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| 39 | static int __init test_fpu_init(void)
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| 40 | {
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| 41 | if (!kernel_fpu_available())
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| 42 | return -EINVAL;
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| 43 |
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| 44 | selftest_dir = debugfs_create_dir("selftest_helpers", NULL);
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| 45 | if (IS_ERR(selftest_dir))
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| 46 | return -ENOMEM;
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| 47 |
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| 48 | debugfs_create_file_unsafe("test_fpu", 0444, selftest_dir, NULL,
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| 49 | &test_fpu_fops);
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| 50 |
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| 51 | return 0;
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| 52 | }
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| 53 |
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| 54 | static void __exit test_fpu_exit(void)
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| 55 | {
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| 56 | debugfs_remove(selftest_dir);
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| 57 | }
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| 58 |
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| 59 | module_init(test_fpu_init);
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| 60 | module_exit(test_fpu_exit);
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| 61 |
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| 62 | MODULE_DESCRIPTION("Test cases for floating point operations");
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| 63 | MODULE_LICENSE("GPL");
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