It is useful to pass down MIDR register down to userland if all of the online cores are all the same type. This adds AT_ARM64_MIDR aux vector type and passes down the midr system register.
This is alternative to MIDR_EL1 part of http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/358995.html. It allows for faster access to midr_el1 than going through a trap and does not exist if the set of cores are not the same. Signed-off-by: Andrew Pinski <apin...@cavium.com> --- arch/arm64/include/asm/cpu.h | 1 + arch/arm64/include/asm/elf.h | 6 ++++++ arch/arm64/kernel/cpuinfo.c | 22 ++++++++++++++++++++++ 3 files changed, 29 insertions(+) diff --git a/arch/arm64/include/asm/cpu.h b/arch/arm64/include/asm/cpu.h index 8e797b2..fab0aa1 100644 --- a/arch/arm64/include/asm/cpu.h +++ b/arch/arm64/include/asm/cpu.h @@ -62,5 +62,6 @@ DECLARE_PER_CPU(struct cpuinfo_arm64, cpu_data); void cpuinfo_store_cpu(void); void __init cpuinfo_store_boot_cpu(void); +u32 get_arm64_midr(void); #endif /* __ASM_CPU_H */ diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h index faad6df..d3549de 100644 --- a/arch/arm64/include/asm/elf.h +++ b/arch/arm64/include/asm/elf.h @@ -17,6 +17,7 @@ #define __ASM_ELF_H #include <asm/hwcap.h> +#include <asm/cpu.h> /* * ELF register definitions.. @@ -138,8 +139,13 @@ typedef struct user_fpsimd_state elf_fpregset_t; #define ARCH_DLINFO \ do { \ + u32 midr; \ + \ NEW_AUX_ENT(AT_SYSINFO_EHDR, \ (elf_addr_t)current->mm->context.vdso); \ + midr = get_arm64_midr(); \ + if (midr != 0) \ + NEW_AUX_ENT(AT_ARM64_MIDR, (elf_addr_t)midr); \ } while (0) #define ARCH_HAS_SETUP_ADDITIONAL_PAGES diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c index 75d5a86..b14c87d 100644 --- a/arch/arm64/kernel/cpuinfo.c +++ b/arch/arm64/kernel/cpuinfo.c @@ -254,3 +254,25 @@ void __init cpuinfo_store_boot_cpu(void) boot_cpu_data = *info; } + +u32 get_arm64_midr(void) +{ + int i; + u32 midr = 0; + + for_each_online_cpu(i) { + struct cpuinfo_arm64 *cpuinfo = &per_cpu(cpu_data, i); + u32 oldmidr = midr; + + midr = cpuinfo->reg_midr; + /* + * If there are cpus which have a different + * midr just return 0. + */ + if (oldmidr && oldmidr != midr) + return 0; + } + + return midr; +} + -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
