linux-kernel - Re: [RFC PATCH 02/11] arm64: Move arch-specific prctls out of core code

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Date:   Mon, 21 May 2018 19:30:14 +0100
From:   Will Deacon <will.deacon@....com>
To:     Dave Martin <Dave.Martin@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>, marc.zyngier@....com
Subject: Re: [RFC PATCH 02/11] arm64: Move arch-specific prctls out of core
 code

On Mon, May 14, 2018 at 06:14:18PM +0100, Dave Martin wrote:
> This patch moves the arm64-specific prctl call implementations out
> of core code and removes redundant boilerplate associated with
> them.
> 
> No functional change.
> 
> Signed-off-by: Dave Martin <Dave.Martin@....com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> ---
>  arch/arm64/Kconfig                 |  1 +
>  arch/arm64/include/asm/processor.h |  4 ----
>  arch/arm64/kernel/sys.c            | 15 +++++++++++++++
>  kernel/sys.c                       | 12 ------------
>  4 files changed, 16 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index eb2cf49..6b706af 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -123,6 +123,7 @@ config ARM64
>  	select HAVE_PERF_EVENTS
>  	select HAVE_PERF_REGS
>  	select HAVE_PERF_USER_STACK_DUMP
> +	select HAVE_PRCTL_ARCH
>  	select HAVE_REGS_AND_STACK_ACCESS_API
>  	select HAVE_RCU_TABLE_FREE
>  	select HAVE_SYSCALL_TRACEPOINTS
> diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
> index 7675989..b1d262f 100644
> --- a/arch/arm64/include/asm/processor.h
> +++ b/arch/arm64/include/asm/processor.h
> @@ -244,9 +244,5 @@ void cpu_enable_pan(const struct arm64_cpu_capabilities *__unused);
>  void cpu_enable_cache_maint_trap(const struct arm64_cpu_capabilities *__unused);
>  void cpu_clear_disr(const struct arm64_cpu_capabilities *__unused);
>  
> -/* Userspace interface for PR_SVE_{SET,GET}_VL prctl()s: */
> -#define SVE_SET_VL(arg)	sve_set_current_vl(arg)
> -#define SVE_GET_VL()	sve_get_current_vl()
> -
>  #endif /* __ASSEMBLY__ */
>  #endif /* __ASM_PROCESSOR_H */
> diff --git a/arch/arm64/kernel/sys.c b/arch/arm64/kernel/sys.c
> index 72981ba..597ff35 100644
> --- a/arch/arm64/kernel/sys.c
> +++ b/arch/arm64/kernel/sys.c
> @@ -22,10 +22,12 @@
>  #include <linux/fs.h>
>  #include <linux/mm.h>
>  #include <linux/export.h>
> +#include <linux/prctl.h>
>  #include <linux/sched.h>
>  #include <linux/slab.h>
>  #include <linux/syscalls.h>
>  #include <asm/cpufeature.h>
> +#include <asm/fpsimd.h>
>  
>  asmlinkage long sys_mmap(unsigned long addr, unsigned long len,
>  			 unsigned long prot, unsigned long flags,
> @@ -45,6 +47,19 @@ SYSCALL_DEFINE1(arm64_personality, unsigned int, personality)
>  	return sys_personality(personality);
>  }
>  
> +int prctl_arch(int option, unsigned long arg2, unsigned long arg3,
> +	       unsigned long arg4, unsigned long arg5)
> +{
> +	switch (option) {
> +	case PR_SVE_SET_VL:
> +		return sve_set_current_vl(arg2);
> +	case PR_SVE_GET_VL:
> +		return sve_get_current_vl();
> +	default:
> +		return -EINVAL;
> +	}
> +}

If we think this might grow, then it might be worth adding a prctl.c to
collect these together. Anyhow:

Acked-by: Will Deacon <will.deacon@....com>

Will