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e039ee4e AP |
1 | #ifndef __ASM_ALTERNATIVE_H |
2 | #define __ASM_ALTERNATIVE_H | |
3 | ||
272d01bd | 4 | #include <asm/cpucaps.h> |
792d4737 | 5 | #include <asm/insn.h> |
57f4959b | 6 | |
8d883b23 MZ |
7 | #ifndef __ASSEMBLY__ |
8 | ||
ef5e724b | 9 | #include <linux/init.h> |
e039ee4e AP |
10 | #include <linux/types.h> |
11 | #include <linux/stddef.h> | |
12 | #include <linux/stringify.h> | |
13 | ||
14 | struct alt_instr { | |
15 | s32 orig_offset; /* offset to original instruction */ | |
16 | s32 alt_offset; /* offset to replacement instruction */ | |
17 | u16 cpufeature; /* cpufeature bit set for replacement */ | |
18 | u8 orig_len; /* size of original instruction(s) */ | |
19 | u8 alt_len; /* size of new instruction(s), <= orig_len */ | |
20 | }; | |
21 | ||
ef5e724b | 22 | void __init apply_alternatives_all(void); |
932ded4b | 23 | void apply_alternatives(void *start, size_t length); |
e039ee4e AP |
24 | |
25 | #define ALTINSTR_ENTRY(feature) \ | |
26 | " .word 661b - .\n" /* label */ \ | |
27 | " .word 663f - .\n" /* new instruction */ \ | |
28 | " .hword " __stringify(feature) "\n" /* feature bit */ \ | |
29 | " .byte 662b-661b\n" /* source len */ \ | |
30 | " .byte 664f-663f\n" /* replacement len */ | |
31 | ||
eb7c11ee MZ |
32 | /* |
33 | * alternative assembly primitive: | |
34 | * | |
35 | * If any of these .org directive fail, it means that insn1 and insn2 | |
36 | * don't have the same length. This used to be written as | |
37 | * | |
38 | * .if ((664b-663b) != (662b-661b)) | |
39 | * .error "Alternatives instruction length mismatch" | |
40 | * .endif | |
41 | * | |
42 | * but most assemblers die if insn1 or insn2 have a .inst. This should | |
43 | * be fixed in a binutils release posterior to 2.25.51.0.2 (anything | |
44 | * containing commit 4e4d08cf7399b606 or c1baaddf8861). | |
45 | */ | |
91a5cefa JM |
46 | #define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled) \ |
47 | ".if "__stringify(cfg_enabled)" == 1\n" \ | |
e039ee4e AP |
48 | "661:\n\t" \ |
49 | oldinstr "\n" \ | |
50 | "662:\n" \ | |
51 | ".pushsection .altinstructions,\"a\"\n" \ | |
52 | ALTINSTR_ENTRY(feature) \ | |
53 | ".popsection\n" \ | |
54 | ".pushsection .altinstr_replacement, \"a\"\n" \ | |
55 | "663:\n\t" \ | |
56 | newinstr "\n" \ | |
57 | "664:\n\t" \ | |
58 | ".popsection\n\t" \ | |
eb7c11ee | 59 | ".org . - (664b-663b) + (662b-661b)\n\t" \ |
91a5cefa JM |
60 | ".org . - (662b-661b) + (664b-663b)\n" \ |
61 | ".endif\n" | |
62 | ||
63 | #define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...) \ | |
64 | __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg)) | |
e039ee4e | 65 | |
8d883b23 MZ |
66 | #else |
67 | ||
57f4959b JM |
68 | #include <asm/assembler.h> |
69 | ||
8d883b23 MZ |
70 | .macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len |
71 | .word \orig_offset - . | |
72 | .word \alt_offset - . | |
73 | .hword \feature | |
74 | .byte \orig_len | |
75 | .byte \alt_len | |
76 | .endm | |
77 | ||
91a5cefa JM |
78 | .macro alternative_insn insn1, insn2, cap, enable = 1 |
79 | .if \enable | |
8d883b23 MZ |
80 | 661: \insn1 |
81 | 662: .pushsection .altinstructions, "a" | |
82 | altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f | |
83 | .popsection | |
84 | .pushsection .altinstr_replacement, "ax" | |
85 | 663: \insn2 | |
86 | 664: .popsection | |
eb7c11ee MZ |
87 | .org . - (664b-663b) + (662b-661b) |
88 | .org . - (662b-661b) + (664b-663b) | |
91a5cefa | 89 | .endif |
8d883b23 MZ |
90 | .endm |
91 | ||
63e40815 | 92 | /* |
792d4737 MR |
93 | * Alternative sequences |
94 | * | |
95 | * The code for the case where the capability is not present will be | |
96 | * assembled and linked as normal. There are no restrictions on this | |
97 | * code. | |
98 | * | |
99 | * The code for the case where the capability is present will be | |
100 | * assembled into a special section to be used for dynamic patching. | |
101 | * Code for that case must: | |
102 | * | |
103 | * 1. Be exactly the same length (in bytes) as the default code | |
104 | * sequence. | |
63e40815 | 105 | * |
792d4737 MR |
106 | * 2. Not contain a branch target that is used outside of the |
107 | * alternative sequence it is defined in (branches into an | |
108 | * alternative sequence are not fixed up). | |
109 | */ | |
110 | ||
111 | /* | |
112 | * Begin an alternative code sequence. | |
63e40815 | 113 | */ |
b82bfa47 | 114 | .macro alternative_if_not cap |
792d4737 | 115 | .set .Lasm_alt_mode, 0 |
63e40815 DT |
116 | .pushsection .altinstructions, "a" |
117 | altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f | |
118 | .popsection | |
119 | 661: | |
120 | .endm | |
121 | ||
792d4737 MR |
122 | .macro alternative_if cap |
123 | .set .Lasm_alt_mode, 1 | |
124 | .pushsection .altinstructions, "a" | |
125 | altinstruction_entry 663f, 661f, \cap, 664f-663f, 662f-661f | |
126 | .popsection | |
127 | .pushsection .altinstr_replacement, "ax" | |
128 | .align 2 /* So GAS knows label 661 is suitably aligned */ | |
129 | 661: | |
130 | .endm | |
131 | ||
63e40815 | 132 | /* |
792d4737 | 133 | * Provide the other half of the alternative code sequence. |
63e40815 | 134 | */ |
b82bfa47 | 135 | .macro alternative_else |
792d4737 MR |
136 | 662: |
137 | .if .Lasm_alt_mode==0 | |
138 | .pushsection .altinstr_replacement, "ax" | |
139 | .else | |
140 | .popsection | |
141 | .endif | |
63e40815 DT |
142 | 663: |
143 | .endm | |
144 | ||
145 | /* | |
146 | * Complete an alternative code sequence. | |
147 | */ | |
b82bfa47 | 148 | .macro alternative_endif |
792d4737 MR |
149 | 664: |
150 | .if .Lasm_alt_mode==0 | |
151 | .popsection | |
152 | .endif | |
63e40815 DT |
153 | .org . - (664b-663b) + (662b-661b) |
154 | .org . - (662b-661b) + (664b-663b) | |
155 | .endm | |
156 | ||
792d4737 MR |
157 | /* |
158 | * Provides a trivial alternative or default sequence consisting solely | |
159 | * of NOPs. The number of NOPs is chosen automatically to match the | |
160 | * previous case. | |
161 | */ | |
162 | .macro alternative_else_nop_endif | |
163 | alternative_else | |
164 | nops (662b-661b) / AARCH64_INSN_SIZE | |
165 | alternative_endif | |
166 | .endm | |
167 | ||
91a5cefa JM |
168 | #define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \ |
169 | alternative_insn insn1, insn2, cap, IS_ENABLED(cfg) | |
170 | ||
290622ef AP |
171 | .macro user_alt, label, oldinstr, newinstr, cond |
172 | 9999: alternative_insn "\oldinstr", "\newinstr", \cond | |
173 | _ASM_EXTABLE 9999b, \label | |
174 | .endm | |
91a5cefa | 175 | |
57f4959b JM |
176 | /* |
177 | * Generate the assembly for UAO alternatives with exception table entries. | |
178 | * This is complicated as there is no post-increment or pair versions of the | |
179 | * unprivileged instructions, and USER() only works for single instructions. | |
180 | */ | |
181 | #ifdef CONFIG_ARM64_UAO | |
182 | .macro uao_ldp l, reg1, reg2, addr, post_inc | |
183 | alternative_if_not ARM64_HAS_UAO | |
184 | 8888: ldp \reg1, \reg2, [\addr], \post_inc; | |
185 | 8889: nop; | |
186 | nop; | |
187 | alternative_else | |
188 | ldtr \reg1, [\addr]; | |
189 | ldtr \reg2, [\addr, #8]; | |
190 | add \addr, \addr, \post_inc; | |
191 | alternative_endif | |
192 | ||
6c94f27a AB |
193 | _asm_extable 8888b,\l; |
194 | _asm_extable 8889b,\l; | |
57f4959b JM |
195 | .endm |
196 | ||
197 | .macro uao_stp l, reg1, reg2, addr, post_inc | |
198 | alternative_if_not ARM64_HAS_UAO | |
199 | 8888: stp \reg1, \reg2, [\addr], \post_inc; | |
200 | 8889: nop; | |
201 | nop; | |
202 | alternative_else | |
203 | sttr \reg1, [\addr]; | |
204 | sttr \reg2, [\addr, #8]; | |
205 | add \addr, \addr, \post_inc; | |
206 | alternative_endif | |
207 | ||
6c94f27a AB |
208 | _asm_extable 8888b,\l; |
209 | _asm_extable 8889b,\l; | |
57f4959b JM |
210 | .endm |
211 | ||
212 | .macro uao_user_alternative l, inst, alt_inst, reg, addr, post_inc | |
213 | alternative_if_not ARM64_HAS_UAO | |
214 | 8888: \inst \reg, [\addr], \post_inc; | |
215 | nop; | |
216 | alternative_else | |
217 | \alt_inst \reg, [\addr]; | |
218 | add \addr, \addr, \post_inc; | |
219 | alternative_endif | |
220 | ||
6c94f27a | 221 | _asm_extable 8888b,\l; |
57f4959b JM |
222 | .endm |
223 | #else | |
224 | .macro uao_ldp l, reg1, reg2, addr, post_inc | |
225 | USER(\l, ldp \reg1, \reg2, [\addr], \post_inc) | |
226 | .endm | |
227 | .macro uao_stp l, reg1, reg2, addr, post_inc | |
228 | USER(\l, stp \reg1, \reg2, [\addr], \post_inc) | |
229 | .endm | |
230 | .macro uao_user_alternative l, inst, alt_inst, reg, addr, post_inc | |
231 | USER(\l, \inst \reg, [\addr], \post_inc) | |
232 | .endm | |
233 | #endif | |
234 | ||
8d883b23 MZ |
235 | #endif /* __ASSEMBLY__ */ |
236 | ||
91a5cefa JM |
237 | /* |
238 | * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature)); | |
239 | * | |
240 | * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature, CONFIG_FOO)); | |
241 | * N.B. If CONFIG_FOO is specified, but not selected, the whole block | |
242 | * will be omitted, including oldinstr. | |
243 | */ | |
244 | #define ALTERNATIVE(oldinstr, newinstr, ...) \ | |
245 | _ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1) | |
246 | ||
e039ee4e | 247 | #endif /* __ASM_ALTERNATIVE_H */ |