1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_S390_ALTERNATIVE_H
3 #define _ASM_S390_ALTERNATIVE_H
4
5 #ifndef __ASSEMBLY__
6
7 #include <linux/types.h>
8 #include <linux/stddef.h>
9 #include <linux/stringify.h>
10
11 struct alt_instr {
12 s32 instr_offset; /* original instruction */
13 s32 repl_offset; /* offset to replacement instruction */
14 u16 facility; /* facility bit set for replacement */
15 u8 instrlen; /* length of original instruction */
16 u8 replacementlen; /* length of new instruction */
17 } __packed;
18
19 void apply_alternative_instructions(void);
20 void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
21
22 /*
23 * |661: |662: |6620 |663:
24 * +-----------+---------------------+
25 * | oldinstr | oldinstr_padding |
26 * | +----------+----------+
27 * | | | |
28 * | | >6 bytes |6/4/2 nops|
29 * | |6 bytes jg----------->
30 * +-----------+---------------------+
31 * ^^ static padding ^^
32 *
33 * .altinstr_replacement section
34 * +---------------------+-----------+
35 * |6641: |6651:
36 * | alternative instr 1 |
37 * +-----------+---------+- - - - - -+
38 * |6642: |6652: |
39 * | alternative instr 2 | padding
40 * +---------------------+- - - - - -+
41 * ^ runtime ^
42 *
43 * .altinstructions section
44 * +---------------------------------+
45 * | alt_instr entries for each |
46 * | alternative instr |
47 * +---------------------------------+
48 */
49
50 #define b_altinstr(num) "664"#num
51 #define e_altinstr(num) "665"#num
52
53 #define e_oldinstr_pad_end "663"
54 #define oldinstr_len "662b-661b"
55 #define oldinstr_total_len e_oldinstr_pad_end"b-661b"
56 #define altinstr_len(num) e_altinstr(num)"b-"b_altinstr(num)"b"
57 #define oldinstr_pad_len(num) \
58 "-(((" altinstr_len(num) ")-(" oldinstr_len ")) > 0) * " \
59 "((" altinstr_len(num) ")-(" oldinstr_len "))"
60
61 #define INSTR_LEN_SANITY_CHECK(len) \
62 ".if " len " > 254\n" \
63 "\t.error \"cpu alternatives does not support instructions " \
64 "blocks > 254 bytes\"\n" \
65 ".endif\n" \
66 ".if (" len ") %% 2\n" \
67 "\t.error \"cpu alternatives instructions length is odd\"\n" \
68 ".endif\n"
69
70 #define OLDINSTR_PADDING(oldinstr, num) \
71 ".if " oldinstr_pad_len(num) " > 6\n" \
72 "\tjg " e_oldinstr_pad_end "f\n" \
73 "6620:\n" \
74 "\t.fill (" oldinstr_pad_len(num) " - (6620b-662b)) / 2, 2, 0x0700\n" \
75 ".else\n" \
76 "\t.fill " oldinstr_pad_len(num) " / 6, 6, 0xc0040000\n" \
77 "\t.fill " oldinstr_pad_len(num) " %% 6 / 4, 4, 0x47000000\n" \
78 "\t.fill " oldinstr_pad_len(num) " %% 6 %% 4 / 2, 2, 0x0700\n" \
79 ".endif\n"
80
81 #define OLDINSTR(oldinstr, num) \
82 "661:\n\t" oldinstr "\n662:\n" \
83 OLDINSTR_PADDING(oldinstr, num) \
84 e_oldinstr_pad_end ":\n" \
85 INSTR_LEN_SANITY_CHECK(oldinstr_len)
86
87 #define OLDINSTR_2(oldinstr, num1, num2) \
88 "661:\n\t" oldinstr "\n662:\n" \
89 ".if " altinstr_len(num1) " < " altinstr_len(num2) "\n" \
90 OLDINSTR_PADDING(oldinstr, num2) \
91 ".else\n" \
92 OLDINSTR_PADDING(oldinstr, num1) \
93 ".endif\n" \
94 e_oldinstr_pad_end ":\n" \
95 INSTR_LEN_SANITY_CHECK(oldinstr_len)
96
97 #define ALTINSTR_ENTRY(facility, num) \
98 "\t.long 661b - .\n" /* old instruction */ \
99 "\t.long " b_altinstr(num)"b - .\n" /* alt instruction */ \
100 "\t.word " __stringify(facility) "\n" /* facility bit */ \
101 "\t.byte " oldinstr_total_len "\n" /* source len */ \
102 "\t.byte " altinstr_len(num) "\n" /* alt instruction len */
103
104 #define ALTINSTR_REPLACEMENT(altinstr, num) /* replacement */ \
105 b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n" \
106 INSTR_LEN_SANITY_CHECK(altinstr_len(num))
107
108 /* alternative assembly primitive: */
109 #define ALTERNATIVE(oldinstr, altinstr, facility) \
110 ".pushsection .altinstr_replacement, \"ax\"\n" \
111 ALTINSTR_REPLACEMENT(altinstr, 1) \
112 ".popsection\n" \
113 OLDINSTR(oldinstr, 1) \
114 ".pushsection .altinstructions,\"a\"\n" \
115 ALTINSTR_ENTRY(facility, 1) \
116 ".popsection\n"
117
118 #define ALTERNATIVE_2(oldinstr, altinstr1, facility1, altinstr2, facility2)\
119 ".pushsection .altinstr_replacement, \"ax\"\n" \
120 ALTINSTR_REPLACEMENT(altinstr1, 1) \
121 ALTINSTR_REPLACEMENT(altinstr2, 2) \
122 ".popsection\n" \
123 OLDINSTR_2(oldinstr, 1, 2) \
124 ".pushsection .altinstructions,\"a\"\n" \
125 ALTINSTR_ENTRY(facility1, 1) \
126 ALTINSTR_ENTRY(facility2, 2) \
127 ".popsection\n"
128
129 /*
130 * Alternative instructions for different CPU types or capabilities.
131 *
132 * This allows to use optimized instructions even on generic binary
133 * kernels.
134 *
135 * oldinstr is padded with jump and nops at compile time if altinstr is
136 * longer. altinstr is padded with jump and nops at run-time during patching.
137 *
138 * For non barrier like inlines please define new variants
139 * without volatile and memory clobber.
140 */
141 #define alternative(oldinstr, altinstr, facility) \
142 asm volatile(ALTERNATIVE(oldinstr, altinstr, facility) : : : "memory")
143
144 #define alternative_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \
145 asm volatile(ALTERNATIVE_2(oldinstr, altinstr1, facility1, \
146 altinstr2, facility2) ::: "memory")
147
148 #endif /* __ASSEMBLY__ */
149
150 #endif /* _ASM_S390_ALTERNATIVE_H */