1/* SPDX-License-Identifier: GPL-2.0-only */
2/* Copyright(c) 2016-2020 Intel Corporation. All rights reserved. */
3
4#include <linux/linkage.h>
5#include <asm/asm.h>
6
7#ifndef CONFIG_UML
8
9#ifdef CONFIG_X86_MCE
10
11/*
12 * copy_mc_fragile - copy memory with indication if an exception / fault happened
13 *
14 * The 'fragile' version is opted into by platform quirks and takes
15 * pains to avoid unrecoverable corner cases like 'fast-string'
16 * instruction sequences, and consuming poison across a cacheline
17 * boundary. The non-fragile version is equivalent to memcpy()
18 * regardless of CPU machine-check-recovery capability.
19 */
20SYM_FUNC_START(copy_mc_fragile)
21 cmpl $8, %edx
22 /* Less than 8 bytes? Go to byte copy loop */
23 jb .L_no_whole_words
24
25 /* Check for bad alignment of source */
26 testl $7, %esi
27 /* Already aligned */
28 jz .L_8byte_aligned
29
30 /* Copy one byte at a time until source is 8-byte aligned */
31 movl %esi, %ecx
32 andl $7, %ecx
33 subl $8, %ecx
34 negl %ecx
35 subl %ecx, %edx
36.L_read_leading_bytes:
37 movb (%rsi), %al
38.L_write_leading_bytes:
39 movb %al, (%rdi)
40 incq %rsi
41 incq %rdi
42 decl %ecx
43 jnz .L_read_leading_bytes
44
45.L_8byte_aligned:
46 movl %edx, %ecx
47 andl $7, %edx
48 shrl $3, %ecx
49 jz .L_no_whole_words
50
51.L_read_words:
52 movq (%rsi), %r8
53.L_write_words:
54 movq %r8, (%rdi)
55 addq $8, %rsi
56 addq $8, %rdi
57 decl %ecx
58 jnz .L_read_words
59
60 /* Any trailing bytes? */
61.L_no_whole_words:
62 andl %edx, %edx
63 jz .L_done_memcpy_trap
64
65 /* Copy trailing bytes */
66 movl %edx, %ecx
67.L_read_trailing_bytes:
68 movb (%rsi), %al
69.L_write_trailing_bytes:
70 movb %al, (%rdi)
71 incq %rsi
72 incq %rdi
73 decl %ecx
74 jnz .L_read_trailing_bytes
75
76 /* Copy successful. Return zero */
77.L_done_memcpy_trap:
78 xorl %eax, %eax
79.L_done:
80 RET
81
82 /*
83 * Return number of bytes not copied for any failure. Note that
84 * there is no "tail" handling since the source buffer is 8-byte
85 * aligned and poison is cacheline aligned.
86 */
87.E_read_words:
88 shll $3, %ecx
89.E_leading_bytes:
90 addl %edx, %ecx
91.E_trailing_bytes:
92 mov %ecx, %eax
93 jmp .L_done
94
95 /*
96 * For write fault handling, given the destination is unaligned,
97 * we handle faults on multi-byte writes with a byte-by-byte
98 * copy up to the write-protected page.
99 */
100.E_write_words:
101 shll $3, %ecx
102 addl %edx, %ecx
103 movl %ecx, %edx
104 jmp copy_mc_fragile_handle_tail
105
106 _ASM_EXTABLE_TYPE(.L_read_leading_bytes, .E_leading_bytes, EX_TYPE_DEFAULT_MCE_SAFE)
107 _ASM_EXTABLE_TYPE(.L_read_words, .E_read_words, EX_TYPE_DEFAULT_MCE_SAFE)
108 _ASM_EXTABLE_TYPE(.L_read_trailing_bytes, .E_trailing_bytes, EX_TYPE_DEFAULT_MCE_SAFE)
109 _ASM_EXTABLE(.L_write_leading_bytes, .E_leading_bytes)
110 _ASM_EXTABLE(.L_write_words, .E_write_words)
111 _ASM_EXTABLE(.L_write_trailing_bytes, .E_trailing_bytes)
112
113SYM_FUNC_END(copy_mc_fragile)
114#endif /* CONFIG_X86_MCE */
115
116/*
117 * copy_mc_enhanced_fast_string - memory copy with exception handling
118 *
119 * Fast string copy + fault / exception handling. If the CPU does
120 * support machine check exception recovery, but does not support
121 * recovering from fast-string exceptions then this CPU needs to be
122 * added to the copy_mc_fragile_key set of quirks. Otherwise, absent any
123 * machine check recovery support this version should be no slower than
124 * standard memcpy.
125 */
126SYM_FUNC_START(copy_mc_enhanced_fast_string)
127 movq %rdi, %rax
128 movq %rdx, %rcx
129.L_copy:
130 rep movsb
131 /* Copy successful. Return zero */
132 xorl %eax, %eax
133 RET
134
135.E_copy:
136 /*
137 * On fault %rcx is updated such that the copy instruction could
138 * optionally be restarted at the fault position, i.e. it
139 * contains 'bytes remaining'. A non-zero return indicates error
140 * to copy_mc_generic() users, or indicate short transfers to
141 * user-copy routines.
142 */
143 movq %rcx, %rax
144 RET
145
146 _ASM_EXTABLE_TYPE(.L_copy, .E_copy, EX_TYPE_DEFAULT_MCE_SAFE)
147
148SYM_FUNC_END(copy_mc_enhanced_fast_string)
149#endif /* !CONFIG_UML */
150