1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _ASM_S390_ALTERNATIVE_ASM_H
3#define _ASM_S390_ALTERNATIVE_ASM_H
4
5#ifdef __ASSEMBLY__
6
7/*
8 * Check the length of an instruction sequence. The length may not be larger
9 * than 254 bytes and it has to be divisible by 2.
10 */
11.macro alt_len_check start,end
12	.if ( \end - \start ) > 254
13	.error "cpu alternatives does not support instructions blocks > 254 bytes\n"
14	.endif
15	.if ( \end - \start ) % 2
16	.error "cpu alternatives instructions length is odd\n"
17	.endif
18.endm
19
20/*
21 * Issue one struct alt_instr descriptor entry (need to put it into
22 * the section .altinstructions, see below). This entry contains
23 * enough information for the alternatives patching code to patch an
24 * instruction. See apply_alternatives().
25 */
26.macro alt_entry orig_start, orig_end, alt_start, alt_end, feature
27	.long	\orig_start - .
28	.long	\alt_start - .
29	.word	\feature
30	.byte	\orig_end - \orig_start
31	.byte	\alt_end - \alt_start
32.endm
33
34/*
35 * Fill up @bytes with nops. The macro emits 6-byte nop instructions
36 * for the bulk of the area, possibly followed by a 4-byte and/or
37 * a 2-byte nop if the size of the area is not divisible by 6.
38 */
39.macro alt_pad_fill bytes
40	.fill	( \bytes ) / 6, 6, 0xc0040000
41	.fill	( \bytes ) % 6 / 4, 4, 0x47000000
42	.fill	( \bytes ) % 6 % 4 / 2, 2, 0x0700
43.endm
44
45/*
46 * Fill up @bytes with nops. If the number of bytes is larger
47 * than 6, emit a jg instruction to branch over all nops, then
48 * fill an area of size (@bytes - 6) with nop instructions.
49 */
50.macro alt_pad bytes
51	.if ( \bytes > 0 )
52	.if ( \bytes > 6 )
53	jg	. + \bytes
54	alt_pad_fill \bytes - 6
55	.else
56	alt_pad_fill \bytes
57	.endif
58	.endif
59.endm
60
61/*
62 * Define an alternative between two instructions. If @feature is
63 * present, early code in apply_alternatives() replaces @oldinstr with
64 * @newinstr. ".skip" directive takes care of proper instruction padding
65 * in case @newinstr is longer than @oldinstr.
66 */
67.macro ALTERNATIVE oldinstr, newinstr, feature
68	.pushsection .altinstr_replacement,"ax"
69770:	\newinstr
70771:	.popsection
71772:	\oldinstr
72773:	alt_len_check 770b, 771b
73	alt_len_check 772b, 773b
74	alt_pad ( ( 771b - 770b ) - ( 773b - 772b ) )
75774:	.pushsection .altinstructions,"a"
76	alt_entry 772b, 774b, 770b, 771b, \feature
77	.popsection
78.endm
79
80/*
81 * Define an alternative between two instructions. If @feature is
82 * present, early code in apply_alternatives() replaces @oldinstr with
83 * @newinstr. ".skip" directive takes care of proper instruction padding
84 * in case @newinstr is longer than @oldinstr.
85 */
86.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
87	.pushsection .altinstr_replacement,"ax"
88770:	\newinstr1
89771:	\newinstr2
90772:	.popsection
91773:	\oldinstr
92774:	alt_len_check 770b, 771b
93	alt_len_check 771b, 772b
94	alt_len_check 773b, 774b
95	.if ( 771b - 770b > 772b - 771b )
96	alt_pad ( ( 771b - 770b ) - ( 774b - 773b ) )
97	.else
98	alt_pad ( ( 772b - 771b ) - ( 774b - 773b ) )
99	.endif
100775:	.pushsection .altinstructions,"a"
101	alt_entry 773b, 775b, 770b, 771b,\feature1
102	alt_entry 773b, 775b, 771b, 772b,\feature2
103	.popsection
104.endm
105
106#endif	/*  __ASSEMBLY__  */
107
108#endif /* _ASM_S390_ALTERNATIVE_ASM_H */
109