include/asm/cpufeature.h

0001 /* SPDX-License-Identifier: GPL-2.0-only */
0002 /*
0003  * Copyright (C) 2017 Linaro Ltd. <ard.biesheuvel@linaro.org>
0004  */
0005
0006 #ifndef __ASM_CPUFEATURE_H
0007 #define __ASM_CPUFEATURE_H
0008
0009 #include <linux/log2.h>
0010 #include <asm/hwcap.h>
0011
0012 /*
0013  * Due to the fact that ELF_HWCAP is a 32-bit type on ARM, and given the number
0014  * of optional CPU features it defines, ARM's CPU hardware capability bits have
0015  * been distributed over separate elf_hwcap and elf_hwcap2 variables, each of
0016  * which covers a subset of the available CPU features.
0017  *
0018  * Currently, only a few of those are suitable for automatic module loading
0019  * (which is the primary use case of this facility) and those happen to be all
0020  * covered by HWCAP2. So let's only cover those via the cpu_feature()
0021  * convenience macro for now (which is used by module_cpu_feature_match()).
0022  * However, all capabilities are exposed via the modalias, and can be matched
0023  * using an explicit MODULE_DEVICE_TABLE() that uses __hwcap_feature() directly.
0024  */
0025 #define MAX_CPU_FEATURES    64
0026 #define __hwcap_feature(x)  ilog2(HWCAP_ ## x)
0027 #define __hwcap2_feature(x) (32 + ilog2(HWCAP2_ ## x))
0028 #define cpu_feature(x)      __hwcap2_feature(x)
0029
0030 static inline bool cpu_have_feature(unsigned int num)
0031 {
0032     return num < 32 ? elf_hwcap & BIT(num) : elf_hwcap2 & BIT(num - 32);
0033 }
0034
0035 #endif