linux-kernel - Re: [RFC 5/8] ARM64: Re-factor flush_ptrace

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Message-ID: <20150102175115.GB6761@redhat.com>
Date:	Fri, 2 Jan 2015 18:51:15 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Pratyush Anand <panand@...hat.com>
Cc:	linux-arm-kernel@...ts.infradead.org, linux@....linux.org.uk,
	tixy@...aro.org, ananth@...ibm.com, sandeepa.prabhu@...aro.org,
	catalin.marinas@....com, will.deacon@....com,
	linux-kernel@...r.kernel.org, anil.s.keshavamurthy@...el.com,
	masami.hiramatsu.pt@...achi.com, wcohen@...hat.com
Subject: Re: [RFC 5/8] ARM64: Re-factor flush_ptrace_access

On 12/31, Pratyush Anand wrote:
>
> Re-factor flush_ptrace_access to reuse vma independent part.

But for what? The changelog should explain this.

> Signed-off-by: Pratyush Anand <panand@...hat.com>
> ---
>  arch/arm64/mm/flush.c | 24 +++++++++++++++---------
>  1 file changed, 15 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c
> index b6f14e8d2121..9a4dd6f39cfb 100644
> --- a/arch/arm64/mm/flush.c
> +++ b/arch/arm64/mm/flush.c
> @@ -34,19 +34,25 @@ void flush_cache_range(struct vm_area_struct *vma, unsigned long start,
>  		__flush_icache_all();
>  }
>
> +static void __flush_ptrace_access(struct page *page, unsigned long uaddr,
> +		void *kaddr, unsigned long len)
> +{
> +	unsigned long addr = (unsigned long)kaddr;
> +
> +	if (icache_is_aliasing()) {
> +		__flush_dcache_area(kaddr, len);
> +		__flush_icache_all();
> +	} else {
> +		flush_icache_range(addr, addr + len);
> +	}
> +}
> +
>  static void flush_ptrace_access(struct vm_area_struct *vma, struct page *page,
>  				unsigned long uaddr, void *kaddr,
>  				unsigned long len)
>  {
> -	if (vma->vm_flags & VM_EXEC) {
> -		unsigned long addr = (unsigned long)kaddr;
> -		if (icache_is_aliasing()) {
> -			__flush_dcache_area(kaddr, len);
> -			__flush_icache_all();
> -		} else {
> -			flush_icache_range(addr, addr + len);
> -		}
> -	}
> +	if (vma->vm_flags & VM_EXEC)
> +		__flush_ptrace_access(page, uaddr, kaddr, len);
>  }

So why uprobes can't use flush_ptrace_access() ? flush_uprobe_xol_access() is
called by arch_uprobe_copy_ixol(), and xol vma has VM_EXEC bit set.

Oleg.

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