[PATCHv2] ARM64: Add AT_ARM64_MIDR to the aux vector
From: Andrew Pinski <hidden>
Date: 2015-08-29 18:46:32
Also in:
lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
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. Changes from v1: Forgot to include the auxvec.h part. Signed-off-by: Andrew Pinski <redacted> --- arch/arm64/include/asm/cpu.h | 1 + arch/arm64/include/asm/elf.h | 6 ++++++ arch/arm64/include/uapi/asm/auxvec.h | 3 +++ arch/arm64/kernel/cpuinfo.c | 22 ++++++++++++++++++++++ 4 files changed, 32 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/include/uapi/asm/auxvec.h b/arch/arm64/include/uapi/asm/auxvec.h
index 22d6d88..dc55c56 100644
--- a/arch/arm64/include/uapi/asm/auxvec.h
+++ b/arch/arm64/include/uapi/asm/auxvec.h@@ -19,4 +19,7 @@ /* vDSO location */ #define AT_SYSINFO_EHDR 33 +/* Machine IDenfier Register (MDIR). */ +#define AT_ARM64_MIDR 38 + #endif
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; +} +
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1.7.10.4