[PATCH v3] ARM: wire up HWCAP2 feature bits to the CPU modalias
From: Ard Biesheuvel <hidden>
Date: 2017-02-15 21:37:18
Subsystem:
arm port, the rest · Maintainers:
Russell King, Linus Torvalds
Wire up the generic support for exposing CPU feature bits via the
modalias in /sys/device/system/cpu. This allows udev to automatically
load modules for things like crypto algorithms that are implemented
using optional instructions.
Signed-off-by: Ard Biesheuvel <redacted>
---
v3: add offset of 32 so that ELF_HWCAP could be added in the future as
well
arch/arm/Kconfig | 1 +
arch/arm/include/asm/cpufeature.h | 32 ++++++++++++++++++++
2 files changed, 33 insertions(+)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 186c4c214e0a..53689e386c47 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig@@ -21,6 +21,7 @@ config ARM select GENERIC_ALLOCATOR select GENERIC_ATOMIC64 if (CPU_V7M || CPU_V6 || !CPU_32v6K || !AEABI) select GENERIC_CLOCKEVENTS_BROADCAST if SMP + select GENERIC_CPU_AUTOPROBE select GENERIC_EARLY_IOREMAP select GENERIC_IDLE_POLL_SETUP select GENERIC_IRQ_PROBE
diff --git a/arch/arm/include/asm/cpufeature.h b/arch/arm/include/asm/cpufeature.h
new file mode 100644
index 000000000000..ec3ad45761aa
--- /dev/null
+++ b/arch/arm/include/asm/cpufeature.h@@ -0,0 +1,32 @@ +/* + * Copyright (C) 2017 Linaro Ltd. <ard.biesheuvel@linaro.org> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#ifndef __ASM_CPUFEATURE_H +#define __ASM_CPUFEATURE_H + +#include <asm/hwcap.h> + +/* + * Due to the fact that ELF_HWCAP is a 32-bit type on ARM, and given the number + * of optional CPU features it defines, ARM's CPU capability bits have been + * distributed over separate elf_hwcap and elf_hwcap2 variables, each of which + * covers a subset of the available CPU features. + * + * Currently, only a few of those are suitable for automatic module loading + * (which is the primary use case of this facility) and those happen to be all + * covered by HWCAP2. So let's only expose those via the CPU modalias for now. + */ +#define MAX_CPU_FEATURES 64 +#define cpu_feature(x) (32 + ilog2(HWCAP2_ ## x)) + +static inline bool cpu_have_feature(unsigned int num) +{ + return elf_hwcap2 & (1UL << (num - 32)); +} + +#endif
--
2.7.4