From mboxrd@z Thu Jan 1 00:00:00 1970 From: ard.biesheuvel@linaro.org (Ard Biesheuvel) Date: Thu, 16 Feb 2017 07:29:16 +0000 Subject: [PATCH v4] ARM: wire up HWCAP/HWCAP2 feature bits to the CPU modalias Message-ID: <1487230156-6016-1-git-send-email-ard.biesheuvel@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. Since it is non-trivial to transparantly support both HWCAP and HWCAP2 capabilities in the cpu_feature() macro (which allows a module's hwcap dependency and init routine to be declared using a single invocation of module_cpu_feature_match()), support only HWCAP2 for now, which covers the capabilities that are most likely to be useful in this manner. Module dependencies on HWCAP will need to be declared explicitly via a MODULE_DEVICE_TABLE(cpu, ...) declaration. Signed-off-by: Ard Biesheuvel --- v4: expose both elf_hwcap and elf_hwcap2 via the kernel modalias, and allow both to be used in MODULE_DEVICE_TABLE()s, but keep cpu_feature() as hwcap2 specific. 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 | 37 ++++++++++++++++++++ 2 files changed, 38 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..9ac822e927ac --- /dev/null +++ b/arch/arm/include/asm/cpufeature.h @@ -0,0 +1,37 @@ +/* + * Copyright (C) 2017 Linaro Ltd. + * + * 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 + +/* + * 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 hardware 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 cover those via the cpu_feature() + * convenience macro for now (which is used by module_cpu_feature_match()). + * However, all capabilities are exposed via the modalias, and can be matched + * using an explicit MODULE_DEVICE_TABLE() that uses __hwcap_feature() directly. + */ +#define MAX_CPU_FEATURES 64 +#define __hwcap_feature(x) ilog2(HWCAP_ ## x) +#define __hwcap2_feature(x) (32 + ilog2(HWCAP2_ ## x)) +#define cpu_feature(x) __hwcap2_feature(x) + +static inline bool cpu_have_feature(unsigned int num) +{ + return num < 32 ? elf_hwcap & BIT(num) : elf_hwcap2 & BIT(num - 32); +} + +#endif -- 2.7.4