1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_S390_ALTERNATIVE_ASM_H
3 #define _ASM_S390_ALTERNATIVE_ASM_H
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.
11 .macro alt_len_check start,end
12 .if ( \end - \start ) > 254
13 .error "cpu alternatives does not support instructions blocks > 254 bytes\n"
15 .if ( \end - \start ) % 2
16 .error "cpu alternatives instructions length is odd\n"
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().
26 .macro alt_entry orig_start, orig_end, alt_start, alt_end, feature
30 .byte \orig_end - \orig_start
31 .byte \alt_end - \alt_start
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.
39 .macro alt_pad_fill bytes
43 .rept ( \bytes ) % 6 / 4
46 .rept ( \bytes ) % 6 % 4 / 2
52 * Fill up @bytes with nops. If the number of bytes is larger
53 * than 6, emit a jg instruction to branch over all nops, then
54 * fill an area of size (@bytes - 6) with nop instructions.
60 alt_pad_fill \bytes - 6
68 * Define an alternative between two instructions. If @feature is
69 * present, early code in apply_alternatives() replaces @oldinstr with
70 * @newinstr. ".skip" directive takes care of proper instruction padding
71 * in case @newinstr is longer than @oldinstr.
73 .macro ALTERNATIVE oldinstr, newinstr, feature
74 .pushsection .altinstr_replacement,"ax"
78 773: alt_len_check 770b, 771b
79 alt_len_check 772b, 773b
80 alt_pad ( ( 771b - 770b ) - ( 773b - 772b ) )
81 774: .pushsection .altinstructions,"a"
82 alt_entry 772b, 774b, 770b, 771b, \feature
87 * Define an alternative between two instructions. If @feature is
88 * present, early code in apply_alternatives() replaces @oldinstr with
89 * @newinstr. ".skip" directive takes care of proper instruction padding
90 * in case @newinstr is longer than @oldinstr.
92 .macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
93 .pushsection .altinstr_replacement,"ax"
98 774: alt_len_check 770b, 771b
99 alt_len_check 771b, 772b
100 alt_len_check 773b, 774b
101 .if ( 771b - 770b > 772b - 771b )
102 alt_pad ( ( 771b - 770b ) - ( 774b - 773b ) )
104 alt_pad ( ( 772b - 771b ) - ( 774b - 773b ) )
106 775: .pushsection .altinstructions,"a"
107 alt_entry 773b, 775b, 770b, 771b,\feature1
108 alt_entry 773b, 775b, 771b, 772b,\feature2
112 #endif /* __ASSEMBLY__ */
114 #endif /* _ASM_S390_ALTERNATIVE_ASM_H */