1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
|
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __ASM_ALTERNATIVE_MACROS_H
#define __ASM_ALTERNATIVE_MACROS_H
#include <linux/const.h>
#include <vdso/bits.h>
#include <asm/cpucaps.h>
#include <asm/insn-def.h>
/*
* Binutils 2.27.0 can't handle a 'UL' suffix on constants, so for the assembly
* macros below we must use we must use `(1 << ARM64_CB_SHIFT)`.
*/
#define ARM64_CB_SHIFT 15
#define ARM64_CB_BIT BIT(ARM64_CB_SHIFT)
#if ARM64_NCAPS >= ARM64_CB_BIT
#error "cpucaps have overflown ARM64_CB_BIT"
#endif
#ifndef __ASSEMBLY__
#include <linux/stringify.h>
#define ALTINSTR_ENTRY(cpucap) \
" .word 661b - .\n" /* label */ \
" .word 663f - .\n" /* new instruction */ \
" .hword " __stringify(cpucap) "\n" /* cpucap */ \
" .byte 662b-661b\n" /* source len */ \
" .byte 664f-663f\n" /* replacement len */
#define ALTINSTR_ENTRY_CB(cpucap, cb) \
" .word 661b - .\n" /* label */ \
" .word " __stringify(cb) "- .\n" /* callback */ \
" .hword " __stringify(cpucap) "\n" /* cpucap */ \
" .byte 662b-661b\n" /* source len */ \
" .byte 664f-663f\n" /* replacement len */
/*
* alternative assembly primitive:
*
* If any of these .org directive fail, it means that insn1 and insn2
* don't have the same length. This used to be written as
*
* .if ((664b-663b) != (662b-661b))
* .error "Alternatives instruction length mismatch"
* .endif
*
* but most assemblers die if insn1 or insn2 have a .inst. This should
* be fixed in a binutils release posterior to 2.25.51.0.2 (anything
* containing commit 4e4d08cf7399b606 or c1baaddf8861).
*
* Alternatives with callbacks do not generate replacement instructions.
*/
#define __ALTERNATIVE_CFG(oldinstr, newinstr, cpucap, cfg_enabled) \
".if "__stringify(cfg_enabled)" == 1\n" \
"661:\n\t" \
oldinstr "\n" \
"662:\n" \
".pushsection .altinstructions,\"a\"\n" \
ALTINSTR_ENTRY(cpucap) \
".popsection\n" \
".subsection 1\n" \
"663:\n\t" \
newinstr "\n" \
"664:\n\t" \
".org . - (664b-663b) + (662b-661b)\n\t" \
".org . - (662b-661b) + (664b-663b)\n\t" \
".previous\n" \
".endif\n"
#define __ALTERNATIVE_CFG_CB(oldinstr, cpucap, cfg_enabled, cb) \
".if "__stringify(cfg_enabled)" == 1\n" \
"661:\n\t" \
oldinstr "\n" \
"662:\n" \
".pushsection .altinstructions,\"a\"\n" \
ALTINSTR_ENTRY_CB(cpucap, cb) \
".popsection\n" \
"663:\n\t" \
"664:\n\t" \
".endif\n"
#define _ALTERNATIVE_CFG(oldinstr, newinstr, cpucap, cfg, ...) \
__ALTERNATIVE_CFG(oldinstr, newinstr, cpucap, IS_ENABLED(cfg))
#define ALTERNATIVE_CB(oldinstr, cpucap, cb) \
__ALTERNATIVE_CFG_CB(oldinstr, (1 << ARM64_CB_SHIFT) | (cpucap), 1, cb)
#else
#include <asm/assembler.h>
.macro altinstruction_entry orig_offset alt_offset cpucap orig_len alt_len
.word \orig_offset - .
.word \alt_offset - .
.hword (\cpucap)
.byte \orig_len
.byte \alt_len
.endm
.macro alternative_insn insn1, insn2, cap, enable = 1
.if \enable
661: \insn1
662: .pushsection .altinstructions, "a"
altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f
.popsection
.subsection 1
663: \insn2
664: .org . - (664b-663b) + (662b-661b)
.org . - (662b-661b) + (664b-663b)
.previous
.endif
.endm
/*
* Alternative sequences
*
* The code for the case where the capability is not present will be
* assembled and linked as normal. There are no restrictions on this
* code.
*
* The code for the case where the capability is present will be
* assembled into a special section to be used for dynamic patching.
* Code for that case must:
*
* 1. Be exactly the same length (in bytes) as the default code
* sequence.
*
* 2. Not contain a branch target that is used outside of the
* alternative sequence it is defined in (branches into an
* alternative sequence are not fixed up).
*/
/*
* Begin an alternative code sequence.
*/
.macro alternative_if_not cap
.set .Lasm_alt_mode, 0
.pushsection .altinstructions, "a"
altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f
.popsection
661:
.endm
.macro alternative_if cap
.set .Lasm_alt_mode, 1
.pushsection .altinstructions, "a"
altinstruction_entry 663f, 661f, \cap, 664f-663f, 662f-661f
.popsection
.subsection 1
.align 2 /* So GAS knows label 661 is suitably aligned */
661:
.endm
.macro alternative_cb cap, cb
.set .Lasm_alt_mode, 0
.pushsection .altinstructions, "a"
altinstruction_entry 661f, \cb, (1 << ARM64_CB_SHIFT) | \cap, 662f-661f, 0
.popsection
661:
.endm
/*
* Provide the other half of the alternative code sequence.
*/
.macro alternative_else
662:
.if .Lasm_alt_mode==0
.subsection 1
.else
.previous
.endif
663:
.endm
/*
* Complete an alternative code sequence.
*/
.macro alternative_endif
664:
.org . - (664b-663b) + (662b-661b)
.org . - (662b-661b) + (664b-663b)
.if .Lasm_alt_mode==0
.previous
.endif
.endm
/*
* Callback-based alternative epilogue
*/
.macro alternative_cb_end
662:
.endm
/*
* Provides a trivial alternative or default sequence consisting solely
* of NOPs. The number of NOPs is chosen automatically to match the
* previous case.
*/
.macro alternative_else_nop_endif
alternative_else
nops (662b-661b) / AARCH64_INSN_SIZE
alternative_endif
.endm
#define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \
alternative_insn insn1, insn2, cap, IS_ENABLED(cfg)
#endif /* __ASSEMBLY__ */
/*
* Usage: asm(ALTERNATIVE(oldinstr, newinstr, cpucap));
*
* Usage: asm(ALTERNATIVE(oldinstr, newinstr, cpucap, CONFIG_FOO));
* N.B. If CONFIG_FOO is specified, but not selected, the whole block
* will be omitted, including oldinstr.
*/
#define ALTERNATIVE(oldinstr, newinstr, ...) \
_ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1)
#ifndef __ASSEMBLY__
#include <linux/types.h>
static __always_inline bool
alternative_has_cap_likely(const unsigned long cpucap)
{
if (!cpucap_is_possible(cpucap))
return false;
asm goto(
ALTERNATIVE_CB("b %l[l_no]", %[cpucap], alt_cb_patch_nops)
:
: [cpucap] "i" (cpucap)
:
: l_no);
return true;
l_no:
return false;
}
static __always_inline bool
alternative_has_cap_unlikely(const unsigned long cpucap)
{
if (!cpucap_is_possible(cpucap))
return false;
asm goto(
ALTERNATIVE("nop", "b %l[l_yes]", %[cpucap])
:
: [cpucap] "i" (cpucap)
:
: l_yes);
return false;
l_yes:
return true;
}
#endif /* __ASSEMBLY__ */
#endif /* __ASM_ALTERNATIVE_MACROS_H */
|
