[PATCH 1/2] arm64/hwcap: Document allocation of upper bits of AT_HWCAP
From: Mark Brown <broonie@kernel.org> commit d3e4a9d30804a78387bfcb383371209417e05c9a upstream. The top two bits of AT_HWCAP are reserved for use by glibc and the rest of the top 32 bits are being kept unallocated for potential use by glibc. Document this in the header. Signed-off-by: Mark Brown <broonie@kernel.org> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Szabolcs Nagy <szabolcs.nagy@arm.com> Link: https://lore.kernel.org/r/20220707103632.12745-2-broonie@kernel.org Signed-off-by: Will Deacon <will@kernel.org> Signed-off-by: Qi Xi <xiqi2@huawei.com> --- arch/arm64/include/uapi/asm/hwcap.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/arm64/include/uapi/asm/hwcap.h b/arch/arm64/include/uapi/asm/hwcap.h index ff5e42430799..94869846bfef 100644 --- a/arch/arm64/include/uapi/asm/hwcap.h +++ b/arch/arm64/include/uapi/asm/hwcap.h @@ -19,6 +19,9 @@ /* * HWCAP flags - for AT_HWCAP + * + * Bits 62 and 63 are reserved for use by libc. + * Bits 32-61 are unallocated for potential use by libc. */ #define HWCAP_FP (1 << 0) #define HWCAP_ASIMD (1 << 1) -- 2.33.0
commit 60c868eff2bc59656ff449258d30da23adae544a upstream. When we added support for AT_HWCAP2 we took advantage of the fact that we have limited hwcaps to the low 32 bits and stored it along with AT_HWCAP in a single unsigned integer. Thanks to the ever expanding capabilities of the architecture we have now allocated all 64 of the bits in an unsigned long so in preparation for adding more hwcaps convert elf_hwcap to be a bitmap instead, with 64 bits allocated to each AT_HWCAP. There should be no functional change from this patch. Signed-off-by: Mark Brown <broonie@kernel.org> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Link: https://lore.kernel.org/r/20220707103632.12745-3-broonie@kernel.org Signed-off-by: Will Deacon <will@kernel.org> Signed-off-by: Qi Xi <xiqi2@huawei.com> --- arch/arm64/include/asm/cpufeature.h | 2 +- arch/arm64/include/asm/hwcap.h | 2 +- arch/arm64/kernel/cpufeature.c | 12 +++++------- 3 files changed, 7 insertions(+), 9 deletions(-) diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 266ebca324ea..32494de9073c 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -11,7 +11,7 @@ #include <asm/hwcap.h> #include <asm/sysreg.h> -#define MAX_CPU_FEATURES 64 +#define MAX_CPU_FEATURES 128 #define cpu_feature(x) KERNEL_HWCAP_ ## x #ifndef __ASSEMBLY__ diff --git a/arch/arm64/include/asm/hwcap.h b/arch/arm64/include/asm/hwcap.h index 2155094ef9f7..2ca9f11347ad 100644 --- a/arch/arm64/include/asm/hwcap.h +++ b/arch/arm64/include/asm/hwcap.h @@ -85,7 +85,7 @@ #define KERNEL_HWCAP_PACA __khwcap_feature(PACA) #define KERNEL_HWCAP_PACG __khwcap_feature(PACG) -#define __khwcap2_feature(x) (const_ilog2(HWCAP2_ ## x) + 32) +#define __khwcap2_feature(x) (const_ilog2(HWCAP2_ ## x) + 64) #define KERNEL_HWCAP_DCPODP __khwcap2_feature(DCPODP) #define KERNEL_HWCAP_SVE2 __khwcap2_feature(SVE2) #define KERNEL_HWCAP_SVEAES __khwcap2_feature(SVEAES) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index dc37d667b41d..efdf2a17297e 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -92,7 +92,7 @@ #include <asm/virt.h> /* Kernel representation of AT_HWCAP and AT_HWCAP2 */ -static unsigned long elf_hwcap __read_mostly; +static DECLARE_BITMAP(elf_hwcap, MAX_CPU_FEATURES) __read_mostly; #ifdef CONFIG_COMPAT #define COMPAT_ELF_HWCAP_DEFAULT \ @@ -2965,15 +2965,13 @@ static bool __maybe_unused __system_matches_cap(unsigned int n) void cpu_set_feature(unsigned int num) { - WARN_ON(num >= MAX_CPU_FEATURES); - elf_hwcap |= BIT(num); + set_bit(num, elf_hwcap); } EXPORT_SYMBOL_GPL(cpu_set_feature); bool cpu_have_feature(unsigned int num) { - WARN_ON(num >= MAX_CPU_FEATURES); - return elf_hwcap & BIT(num); + return test_bit(num, elf_hwcap); } EXPORT_SYMBOL_GPL(cpu_have_feature); @@ -2984,12 +2982,12 @@ unsigned long cpu_get_elf_hwcap(void) * note that for userspace compatibility we guarantee that bits 62 * and 63 will always be returned as 0. */ - return lower_32_bits(elf_hwcap); + return elf_hwcap[0]; } unsigned long cpu_get_elf_hwcap2(void) { - return upper_32_bits(elf_hwcap); + return elf_hwcap[1]; } static void __init setup_system_capabilities(void) -- 2.33.0
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Qi Xi