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