265 lines
6.5 KiB
C
265 lines
6.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __ASM_ALTERNATIVE_MACROS_H
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#define __ASM_ALTERNATIVE_MACROS_H
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#include <linux/const.h>
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#include <vdso/bits.h>
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#include <asm/cpucaps.h>
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#include <asm/insn-def.h>
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/*
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* Binutils 2.27.0 can't handle a 'UL' suffix on constants, so for the assembly
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* macros below we must use we must use `(1 << ARM64_CB_SHIFT)`.
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*/
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#define ARM64_CB_SHIFT 15
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#define ARM64_CB_BIT BIT(ARM64_CB_SHIFT)
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#if ARM64_NCAPS >= ARM64_CB_BIT
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#error "cpucaps have overflown ARM64_CB_BIT"
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#endif
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#ifndef __ASSEMBLY__
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#include <linux/stringify.h>
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#define ALTINSTR_ENTRY(feature) \
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" .word 661b - .\n" /* label */ \
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" .word 663f - .\n" /* new instruction */ \
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" .hword " __stringify(feature) "\n" /* feature bit */ \
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" .byte 662b-661b\n" /* source len */ \
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" .byte 664f-663f\n" /* replacement len */
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#define ALTINSTR_ENTRY_CB(feature, cb) \
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" .word 661b - .\n" /* label */ \
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" .word " __stringify(cb) "- .\n" /* callback */ \
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" .hword " __stringify(feature) "\n" /* feature bit */ \
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" .byte 662b-661b\n" /* source len */ \
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" .byte 664f-663f\n" /* replacement len */
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/*
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* alternative assembly primitive:
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*
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* If any of these .org directive fail, it means that insn1 and insn2
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* don't have the same length. This used to be written as
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*
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* .if ((664b-663b) != (662b-661b))
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* .error "Alternatives instruction length mismatch"
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* .endif
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*
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* but most assemblers die if insn1 or insn2 have a .inst. This should
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* be fixed in a binutils release posterior to 2.25.51.0.2 (anything
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* containing commit 4e4d08cf7399b606 or c1baaddf8861).
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*
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* Alternatives with callbacks do not generate replacement instructions.
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*/
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#define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled) \
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".if "__stringify(cfg_enabled)" == 1\n" \
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"661:\n\t" \
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oldinstr "\n" \
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"662:\n" \
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".pushsection .altinstructions,\"a\"\n" \
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ALTINSTR_ENTRY(feature) \
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".popsection\n" \
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".subsection 1\n" \
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"663:\n\t" \
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newinstr "\n" \
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"664:\n\t" \
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".org . - (664b-663b) + (662b-661b)\n\t" \
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".org . - (662b-661b) + (664b-663b)\n\t" \
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".previous\n" \
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".endif\n"
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#define __ALTERNATIVE_CFG_CB(oldinstr, feature, cfg_enabled, cb) \
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".if "__stringify(cfg_enabled)" == 1\n" \
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"661:\n\t" \
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oldinstr "\n" \
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"662:\n" \
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".pushsection .altinstructions,\"a\"\n" \
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ALTINSTR_ENTRY_CB(feature, cb) \
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".popsection\n" \
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"663:\n\t" \
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"664:\n\t" \
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".endif\n"
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#define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...) \
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__ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg))
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#define ALTERNATIVE_CB(oldinstr, feature, cb) \
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__ALTERNATIVE_CFG_CB(oldinstr, (1 << ARM64_CB_SHIFT) | (feature), 1, cb)
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#else
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#include <asm/assembler.h>
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.macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len
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.word \orig_offset - .
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.word \alt_offset - .
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.hword (\feature)
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.byte \orig_len
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.byte \alt_len
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.endm
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.macro alternative_insn insn1, insn2, cap, enable = 1
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.if \enable
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661: \insn1
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662: .pushsection .altinstructions, "a"
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altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f
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.popsection
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.subsection 1
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663: \insn2
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664: .org . - (664b-663b) + (662b-661b)
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.org . - (662b-661b) + (664b-663b)
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.previous
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.endif
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.endm
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/*
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* Alternative sequences
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*
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* The code for the case where the capability is not present will be
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* assembled and linked as normal. There are no restrictions on this
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* code.
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*
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* The code for the case where the capability is present will be
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* assembled into a special section to be used for dynamic patching.
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* Code for that case must:
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*
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* 1. Be exactly the same length (in bytes) as the default code
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* sequence.
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*
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* 2. Not contain a branch target that is used outside of the
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* alternative sequence it is defined in (branches into an
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* alternative sequence are not fixed up).
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*/
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/*
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* Begin an alternative code sequence.
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*/
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.macro alternative_if_not cap
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.set .Lasm_alt_mode, 0
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.pushsection .altinstructions, "a"
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altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f
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.popsection
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661:
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.endm
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.macro alternative_if cap
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.set .Lasm_alt_mode, 1
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.pushsection .altinstructions, "a"
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altinstruction_entry 663f, 661f, \cap, 664f-663f, 662f-661f
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.popsection
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.subsection 1
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.align 2 /* So GAS knows label 661 is suitably aligned */
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661:
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.endm
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.macro alternative_cb cap, cb
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.set .Lasm_alt_mode, 0
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.pushsection .altinstructions, "a"
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altinstruction_entry 661f, \cb, (1 << ARM64_CB_SHIFT) | \cap, 662f-661f, 0
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.popsection
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661:
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.endm
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/*
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* Provide the other half of the alternative code sequence.
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*/
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.macro alternative_else
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662:
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.if .Lasm_alt_mode==0
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.subsection 1
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.else
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.previous
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.endif
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663:
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.endm
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/*
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* Complete an alternative code sequence.
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*/
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.macro alternative_endif
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664:
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.org . - (664b-663b) + (662b-661b)
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.org . - (662b-661b) + (664b-663b)
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.if .Lasm_alt_mode==0
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.previous
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.endif
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.endm
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/*
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* Callback-based alternative epilogue
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*/
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.macro alternative_cb_end
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662:
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.endm
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/*
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* Provides a trivial alternative or default sequence consisting solely
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* of NOPs. The number of NOPs is chosen automatically to match the
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* previous case.
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*/
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.macro alternative_else_nop_endif
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alternative_else
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nops (662b-661b) / AARCH64_INSN_SIZE
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alternative_endif
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.endm
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#define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \
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alternative_insn insn1, insn2, cap, IS_ENABLED(cfg)
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#endif /* __ASSEMBLY__ */
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/*
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* Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature));
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*
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* Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature, CONFIG_FOO));
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* N.B. If CONFIG_FOO is specified, but not selected, the whole block
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* will be omitted, including oldinstr.
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*/
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#define ALTERNATIVE(oldinstr, newinstr, ...) \
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_ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1)
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#ifndef __ASSEMBLY__
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#include <linux/types.h>
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static __always_inline bool
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alternative_has_feature_likely(unsigned long feature)
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{
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compiletime_assert(feature < ARM64_NCAPS,
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"feature must be < ARM64_NCAPS");
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asm goto(
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ALTERNATIVE_CB("b %l[l_no]", %[feature], alt_cb_patch_nops)
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:
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: [feature] "i" (feature)
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:
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: l_no);
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return true;
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l_no:
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return false;
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}
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static __always_inline bool
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alternative_has_feature_unlikely(unsigned long feature)
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{
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compiletime_assert(feature < ARM64_NCAPS,
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"feature must be < ARM64_NCAPS");
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asm goto(
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ALTERNATIVE("nop", "b %l[l_yes]", %[feature])
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:
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: [feature] "i" (feature)
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:
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: l_yes);
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return false;
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l_yes:
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return true;
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}
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#endif /* __ASSEMBLY__ */
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#endif /* __ASM_ALTERNATIVE_MACROS_H */
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