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"
69 770:	\newinstr
70 771:	.popsection
71 772:	\oldinstr
72 773:	alt_len_check 770b, 771b
73 	alt_len_check 772b, 773b
74 	alt_pad ( ( 771b - 770b ) - ( 773b - 772b ) )
75 774:	.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"
88 770:	\newinstr1
89 771:	\newinstr2
90 772:	.popsection
91 773:	\oldinstr
92 774:	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
100 775:	.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