15f0fc91e1
may_use_simd() should only be called by code that may use FP/SIMD when it is available, and so checking whether the system supports FP/SIMD in the first place should be redundant - the caller in question (e.g., a SIMD crypto algorithm) should never be initialized in the first place. Checking the system capability involves jump labels and therefore code patching, which interferes with our ability to perform an integrity check on some of the crypto code. So let's get rid of the capability check altogether. Bug: 153614920 Bug: 188620248 Change-Id: Ia8df624f4648cc980a12a44eeb82e8f186d5f961 Signed-off-by: Ard Biesheuvel <ardb@google.com>
51 lines
1.4 KiB
C
51 lines
1.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2017 Linaro Ltd. <ard.biesheuvel@linaro.org>
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*/
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#ifndef __ASM_SIMD_H
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#define __ASM_SIMD_H
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#include <linux/compiler.h>
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#include <linux/irqflags.h>
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#include <linux/percpu.h>
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#include <linux/preempt.h>
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#include <linux/types.h>
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DECLARE_PER_CPU(bool, fpsimd_context_busy);
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#ifdef CONFIG_KERNEL_MODE_NEON
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/*
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* may_use_simd - whether it is allowable at this time to issue SIMD
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* instructions or access the SIMD register file
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*
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* Callers must not assume that the result remains true beyond the next
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* preempt_enable() or return from softirq context.
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*/
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static __must_check inline bool may_use_simd(void)
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{
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/*
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* We must make sure that the SVE has been initialized properly
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* before using the SIMD in kernel.
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* fpsimd_context_busy is only set while preemption is disabled,
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* and is clear whenever preemption is enabled. Since
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* this_cpu_read() is atomic w.r.t. preemption, fpsimd_context_busy
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* cannot change under our feet -- if it's set we cannot be
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* migrated, and if it's clear we cannot be migrated to a CPU
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* where it is set.
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*/
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return !in_irq() && !irqs_disabled() && !in_nmi() &&
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!this_cpu_read(fpsimd_context_busy);
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}
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#else /* ! CONFIG_KERNEL_MODE_NEON */
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static __must_check inline bool may_use_simd(void) {
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return false;
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}
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#endif /* ! CONFIG_KERNEL_MODE_NEON */
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#endif
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