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