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 .rept ( \bytes ) / 6 41 brcl 0,0 42 .endr 43 .rept ( \bytes ) % 6 / 4 44 nop 45 .endr 46 .rept ( \bytes ) % 6 % 4 / 2 47 nopr 48 .endr 49 .endm 50 51 /* 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. 55 */ 56 .macro alt_pad bytes 57 .if ( \bytes > 0 ) 58 .if ( \bytes > 6 ) 59 jg . + \bytes 60 alt_pad_fill \bytes - 6 61 .else 62 alt_pad_fill \bytes 63 .endif 64 .endif 65 .endm 66 67 /* 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. 72 */ 73 .macro ALTERNATIVE oldinstr, newinstr, feature 74 .pushsection .altinstr_replacement,"ax" 75 770: \newinstr 76 771: .popsection 77 772: \oldinstr 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 83 .popsection 84 .endm 85 86 /* 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. 91 */ 92 .macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2 93 .pushsection .altinstr_replacement,"ax" 94 770: \newinstr1 95 771: \newinstr2 96 772: .popsection 97 773: \oldinstr 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 ) ) 103 .else 104 alt_pad ( ( 772b - 771b ) - ( 774b - 773b ) ) 105 .endif 106 775: .pushsection .altinstructions,"a" 107 alt_entry 773b, 775b, 770b, 771b,\feature1 108 alt_entry 773b, 775b, 771b, 772b,\feature2 109 .popsection 110 .endm 111 112 #endif /* __ASSEMBLY__ */ 113 114 #endif /* _ASM_S390_ALTERNATIVE_ASM_H */ 115