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/instrumented.h>
8#include <linux/string.h>
9#include <linux/types.h>
10
11#include <asm/mce.h>
12
13#ifdef CONFIG_X86_MCE
14static DEFINE_STATIC_KEY_FALSE(copy_mc_fragile_key);
15
16void enable_copy_mc_fragile(void)
17{
18 static_branch_inc(&copy_mc_fragile_key);
19}
20#define copy_mc_fragile_enabled (static_branch_unlikely(&copy_mc_fragile_key))
21
22/*
23 * Similar to copy_user_handle_tail, probe for the write fault point, or
24 * source exception point.
25 */
26__visible notrace unsigned long
27copy_mc_fragile_handle_tail(char *to, char *from, unsigned len)
28{
29 for (; len; --len, to++, from++)
30 if (copy_mc_fragile(dst: to, src: from, cnt: 1))
31 break;
32 return len;
33}
34#else
35/*
36 * No point in doing careful copying, or consulting a static key when
37 * there is no #MC handler in the CONFIG_X86_MCE=n case.
38 */
39void enable_copy_mc_fragile(void)
40{
41}
42#define copy_mc_fragile_enabled (0)
43#endif
44
45unsigned long copy_mc_enhanced_fast_string(void *dst, const void *src, unsigned len);
46
47/**
48 * copy_mc_to_kernel - memory copy that handles source exceptions
49 *
50 * @dst: destination address
51 * @src: source address
52 * @len: number of bytes to copy
53 *
54 * Call into the 'fragile' version on systems that benefit from avoiding
55 * corner case poison consumption scenarios, For example, accessing
56 * poison across 2 cachelines with a single instruction. Almost all
57 * other uses case can use copy_mc_enhanced_fast_string() for a fast
58 * recoverable copy, or fallback to plain memcpy.
59 *
60 * Return 0 for success, or number of bytes not copied if there was an
61 * exception.
62 */
63unsigned long __must_check copy_mc_to_kernel(void *dst, const void *src, unsigned len)
64{
65 unsigned long ret;
66
67 if (copy_mc_fragile_enabled) {
68 instrument_memcpy_before(to: dst, from: src, n: len);
69 ret = copy_mc_fragile(dst, src, cnt: len);
70 instrument_memcpy_after(to: dst, from: src, n: len, left: ret);
71 return ret;
72 }
73 if (static_cpu_has(X86_FEATURE_ERMS)) {
74 instrument_memcpy_before(to: dst, from: src, n: len);
75 ret = copy_mc_enhanced_fast_string(dst, src, len);
76 instrument_memcpy_after(to: dst, from: src, n: len, left: ret);
77 return ret;
78 }
79 memcpy(to: dst, from: src, len);
80 return 0;
81}
82EXPORT_SYMBOL_GPL(copy_mc_to_kernel);
83
84unsigned long __must_check copy_mc_to_user(void __user *dst, const void *src, unsigned len)
85{
86 unsigned long ret;
87
88 if (copy_mc_fragile_enabled) {
89 instrument_copy_to_user(to: dst, from: src, n: len);
90 __uaccess_begin();
91 ret = copy_mc_fragile(dst: (__force void *)dst, src, cnt: len);
92 __uaccess_end();
93 return ret;
94 }
95
96 if (static_cpu_has(X86_FEATURE_ERMS)) {
97 instrument_copy_to_user(to: dst, from: src, n: len);
98 __uaccess_begin();
99 ret = copy_mc_enhanced_fast_string(dst: (__force void *)dst, src, len);
100 __uaccess_end();
101 return ret;
102 }
103
104 return copy_user_generic(to: (__force void *)dst, from: src, len);
105}
106