1// SPDX-License-Identifier: GPL-2.0
2/* Copyright(c) 2016-2020 Intel Corporation. All rights reserved. */
3
4#include <linux/jump_label.h>
5#include <linux/uaccess.h>
6#include <linux/export.h>
7#include <linux/string.h>
8#include <linux/types.h>
9
10#include <asm/mce.h>
11
12#ifdef CONFIG_X86_MCE
13static DEFINE_STATIC_KEY_FALSE(copy_mc_fragile_key);
14
15void enable_copy_mc_fragile(void)
16{
17	static_branch_inc(&copy_mc_fragile_key);
18}
19#define copy_mc_fragile_enabled (static_branch_unlikely(&copy_mc_fragile_key))
20
21/*
22 * Similar to copy_user_handle_tail, probe for the write fault point, or
23 * source exception point.
24 */
25__visible notrace unsigned long
26copy_mc_fragile_handle_tail(char *to, char *from, unsigned len)
27{
28	for (; len; --len, to++, from++)
29		if (copy_mc_fragile(to, from, 1))
30			break;
31	return len;
32}
33#else
34/*
35 * No point in doing careful copying, or consulting a static key when
36 * there is no #MC handler in the CONFIG_X86_MCE=n case.
37 */
38void enable_copy_mc_fragile(void)
39{
40}
41#define copy_mc_fragile_enabled (0)
42#endif
43
44unsigned long copy_mc_enhanced_fast_string(void *dst, const void *src, unsigned len);
45
46/**
47 * copy_mc_to_kernel - memory copy that handles source exceptions
48 *
49 * @dst:	destination address
50 * @src:	source address
51 * @len:	number of bytes to copy
52 *
53 * Call into the 'fragile' version on systems that benefit from avoiding
54 * corner case poison consumption scenarios, For example, accessing
55 * poison across 2 cachelines with a single instruction. Almost all
56 * other uses case can use copy_mc_enhanced_fast_string() for a fast
57 * recoverable copy, or fallback to plain memcpy.
58 *
59 * Return 0 for success, or number of bytes not copied if there was an
60 * exception.
61 */
62unsigned long __must_check copy_mc_to_kernel(void *dst, const void *src, unsigned len)
63{
64	if (copy_mc_fragile_enabled)
65		return copy_mc_fragile(dst, src, len);
66	if (static_cpu_has(X86_FEATURE_ERMS))
67		return copy_mc_enhanced_fast_string(dst, src, len);
68	memcpy(dst, src, len);
69	return 0;
70}
71EXPORT_SYMBOL_GPL(copy_mc_to_kernel);
72
73unsigned long __must_check copy_mc_to_user(void __user *dst, const void *src, unsigned len)
74{
75	unsigned long ret;
76
77	if (copy_mc_fragile_enabled) {
78		__uaccess_begin();
79		ret = copy_mc_fragile((__force void *)dst, src, len);
80		__uaccess_end();
81		return ret;
82	}
83
84	if (static_cpu_has(X86_FEATURE_ERMS)) {
85		__uaccess_begin();
86		ret = copy_mc_enhanced_fast_string((__force void *)dst, src, len);
87		__uaccess_end();
88		return ret;
89	}
90
91	return copy_user_generic((__force void *)dst, src, len);
92}
93