1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_S390_ALTERNATIVE_H
3 #define _ASM_S390_ALTERNATIVE_H
4
5 /*
6 * Each alternative comes with a 32 bit feature field:
7 * union {
8 * u32 feature;
9 * struct {
10 * u32 ctx : 4;
11 * u32 type : 8;
12 * u32 data : 20;
13 * };
14 * }
15 *
16 * @ctx is a bitfield, where only one bit must be set. Each bit defines
17 * in which context an alternative is supposed to be applied to the
18 * kernel image:
19 *
20 * - from the decompressor before the kernel itself is executed
21 * - from early kernel code from within the kernel
22 *
23 * @type is a number which defines the type and with that the type
24 * specific alternative patching.
25 *
26 * @data is additional type specific information which defines if an
27 * alternative should be applied.
28 */
29
30 #define ALT_CTX_EARLY 1
31 #define ALT_CTX_LATE 2
32 #define ALT_CTX_ALL (ALT_CTX_EARLY | ALT_CTX_LATE)
33
34 #define ALT_TYPE_FACILITY 0
35 #define ALT_TYPE_SPEC 1
36 #define ALT_TYPE_LOWCORE 2
37
38 #define ALT_DATA_SHIFT 0
39 #define ALT_TYPE_SHIFT 20
40 #define ALT_CTX_SHIFT 28
41
42 #define ALT_FACILITY_EARLY(facility) (ALT_CTX_EARLY << ALT_CTX_SHIFT | \
43 ALT_TYPE_FACILITY << ALT_TYPE_SHIFT | \
44 (facility) << ALT_DATA_SHIFT)
45
46 #define ALT_FACILITY(facility) (ALT_CTX_LATE << ALT_CTX_SHIFT | \
47 ALT_TYPE_FACILITY << ALT_TYPE_SHIFT | \
48 (facility) << ALT_DATA_SHIFT)
49
50 #define ALT_SPEC(facility) (ALT_CTX_LATE << ALT_CTX_SHIFT | \
51 ALT_TYPE_SPEC << ALT_TYPE_SHIFT | \
52 (facility) << ALT_DATA_SHIFT)
53
54 #define ALT_LOWCORE (ALT_CTX_EARLY << ALT_CTX_SHIFT | \
55 ALT_TYPE_LOWCORE << ALT_TYPE_SHIFT)
56
57 #ifndef __ASSEMBLY__
58
59 #include <linux/types.h>
60 #include <linux/stddef.h>
61 #include <linux/stringify.h>
62
63 struct alt_instr {
64 s32 instr_offset; /* original instruction */
65 s32 repl_offset; /* offset to replacement instruction */
66 union {
67 u32 feature; /* feature required for replacement */
68 struct {
69 u32 ctx : 4; /* context */
70 u32 type : 8; /* type of alternative */
71 u32 data : 20; /* patching information */
72 };
73 };
74 u8 instrlen; /* length of original instruction */
75 } __packed;
76
77 extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
78
79 void __apply_alternatives(struct alt_instr *start, struct alt_instr *end, unsigned int ctx);
80
81 static inline void apply_alternative_instructions(void)
82 {
83 __apply_alternatives(__alt_instructions, __alt_instructions_end, ALT_CTX_LATE);
84 }
85
86 static inline void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
87 {
88 __apply_alternatives(start, end, ALT_CTX_ALL);
89 }
90
91 /*
92 * +---------------------------------+
93 * |661: |662:
94 * | oldinstr |
95 * +---------------------------------+
96 *
97 * .altinstr_replacement section
98 * +---------------------------------+
99 * |6641: |6651:
100 * | alternative instr 1 |
101 * +---------------------------------+
102 * |6642: |6652:
103 * | alternative instr 2 |
104 * +---------------------------------+
105 *
106 * .altinstructions section
107 * +---------------------------------+
108 * | alt_instr entries for each |
109 * | alternative instr |
110 * +---------------------------------+
111 */
112
113 #define b_altinstr(num) "664"#num
114 #define e_altinstr(num) "665"#num
115 #define oldinstr_len "662b-661b"
116 #define altinstr_len(num) e_altinstr(num)"b-"b_altinstr(num)"b"
117
118 #define OLDINSTR(oldinstr) \
119 "661:\n\t" oldinstr "\n662:\n"
120
121 #define ALTINSTR_ENTRY(feature, num) \
122 "\t.long 661b - .\n" /* old instruction */ \
123 "\t.long " b_altinstr(num)"b - .\n" /* alt instruction */ \
124 "\t.long " __stringify(feature) "\n" /* feature */ \
125 "\t.byte " oldinstr_len "\n" /* instruction len */ \
126 "\t.org . - (" oldinstr_len ") & 1\n" \
127 "\t.org . - (" oldinstr_len ") + (" altinstr_len(num) ")\n" \
128 "\t.org . - (" altinstr_len(num) ") + (" oldinstr_len ")\n"
129
130 #define ALTINSTR_REPLACEMENT(altinstr, num) /* replacement */ \
131 b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n"
132
133 /* alternative assembly primitive: */
134 #define ALTERNATIVE(oldinstr, altinstr, feature) \
135 ".pushsection .altinstr_replacement, \"ax\"\n" \
136 ALTINSTR_REPLACEMENT(altinstr, 1) \
137 ".popsection\n" \
138 OLDINSTR(oldinstr) \
139 ".pushsection .altinstructions,\"a\"\n" \
140 ALTINSTR_ENTRY(feature, 1) \
141 ".popsection\n"
142
143 #define ALTERNATIVE_2(oldinstr, altinstr1, feature1, altinstr2, feature2)\
144 ".pushsection .altinstr_replacement, \"ax\"\n" \
145 ALTINSTR_REPLACEMENT(altinstr1, 1) \
146 ALTINSTR_REPLACEMENT(altinstr2, 2) \
147 ".popsection\n" \
148 OLDINSTR(oldinstr) \
149 ".pushsection .altinstructions,\"a\"\n" \
150 ALTINSTR_ENTRY(feature1, 1) \
151 ALTINSTR_ENTRY(feature2, 2) \
152 ".popsection\n"
153
154 /*
155 * Alternative instructions for different CPU types or capabilities.
156 *
157 * This allows to use optimized instructions even on generic binary
158 * kernels.
159 *
160 * oldinstr is padded with jump and nops at compile time if altinstr is
161 * longer. altinstr is padded with jump and nops at run-time during patching.
162 *
163 * For non barrier like inlines please define new variants
164 * without volatile and memory clobber.
165 */
166 #define alternative(oldinstr, altinstr, feature) \
167 asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, feature) : : : "memory")
168
169 #define alternative_2(oldinstr, altinstr1, feature1, altinstr2, feature2) \
170 asm_inline volatile(ALTERNATIVE_2(oldinstr, altinstr1, feature1, \
171 altinstr2, feature2) ::: "memory")
172
173 /* Alternative inline assembly with input. */
174 #define alternative_input(oldinstr, newinstr, feature, input...) \
175 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
176 : : input)
177
178 /* Like alternative_input, but with a single output argument */
179 #define alternative_io(oldinstr, altinstr, feature, output, input...) \
180 asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, feature) \
181 : output : input)
182
183 /* Use this macro if more than one output parameter is needed. */
184 #define ASM_OUTPUT2(a...) a
185
186 /* Use this macro if clobbers are needed without inputs. */
187 #define ASM_NO_INPUT_CLOBBER(clobber...) : clobber
188
189 #else /* __ASSEMBLY__ */
190
191 /*
192 * Issue one struct alt_instr descriptor entry (need to put it into
193 * the section .altinstructions, see below). This entry contains
194 * enough information for the alternatives patching code to patch an
195 * instruction. See apply_alternatives().
196 */
197 .macro alt_entry orig_start, orig_end, alt_start, alt_end, feature
198 .long \orig_start - .
199 .long \alt_start - .
200 .long \feature
201 .byte \orig_end - \orig_start
202 .org . - ( \orig_end - \orig_start ) & 1
203 .org . - ( \orig_end - \orig_start ) + ( \alt_end - \alt_start )
204 .org . - ( \alt_end - \alt_start ) + ( \orig_end - \orig_start )
205 .endm
206
207 /*
208 * Define an alternative between two instructions. If @feature is
209 * present, early code in apply_alternatives() replaces @oldinstr with
210 * @newinstr.
211 */
212 .macro ALTERNATIVE oldinstr, newinstr, feature
213 .pushsection .altinstr_replacement,"ax"
214 770: \newinstr
215 771: .popsection
216 772: \oldinstr
217 773: .pushsection .altinstructions,"a"
218 alt_entry 772b, 773b, 770b, 771b, \feature
219 .popsection
220 .endm
221
222 /*
223 * Define an alternative between two instructions. If @feature is
224 * present, early code in apply_alternatives() replaces @oldinstr with
225 * @newinstr.
226 */
227 .macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
228 .pushsection .altinstr_replacement,"ax"
229 770: \newinstr1
230 771: \newinstr2
231 772: .popsection
232 773: \oldinstr
233 774: .pushsection .altinstructions,"a"
234 alt_entry 773b, 774b, 770b, 771b,\feature1
235 alt_entry 773b, 774b, 771b, 772b,\feature2
236 .popsection
237 .endm
238
239 #endif /* __ASSEMBLY__ */
240
241 #endif /* _ASM_S390_ALTERNATIVE_H */
242
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