linux-kernel - Re: [PATCH 1/1] arm64: fix flush_cache_range

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Date:	Tue, 24 May 2016 12:37:27 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Zhen Lei <thunder.leizhen@...wei.com>
Cc:	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Xinwei Hu <huxinwei@...wei.com>, Zefan Li <lizefan@...wei.com>,
	Hanjun Guo <guohanjun@...wei.com>,
	Tianhong Ding <dingtianhong@...wei.com>
Subject: Re: [PATCH 1/1] arm64: fix flush_cache_range

On Tue, May 24, 2016 at 07:16:37PM +0800, Zhen Lei wrote:
> When we ran mprotect04(a test case in LTP) infinitely, it would always
> failed after a few seconds. The case can be described briefly that: copy
> a empty function from code area into a new memory area(created by mmap),
> then call mprotect to change the protection to PROT_EXEC. The syscall
> sys_mprotect will finally invoke flush_cache_range, but this function
> currently only invalid icache, the operation of flush dcache is missed.

In the LTP code I see powerpc-specific D-cache / I-cache synchronisation
(i.e. d-cache cleaning followed by I-cache invalidation), so there
appears to be some expectation of userspace maintenance. Hoever, there
is no such ARM-specific I-cache maintenance.

It looks like the test may be missing I-cache maintenance regardless of
the semantics of mprotect in this case.

I have not yet devled into flush_cache_range and how it is called.

Thanks,
Mark.

> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> ---
>  arch/arm64/mm/flush.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c
> index dbd12ea..eda4124 100644
> --- a/arch/arm64/mm/flush.c
> +++ b/arch/arm64/mm/flush.c
> @@ -31,7 +31,7 @@ void flush_cache_range(struct vm_area_struct *vma, unsigned long start,
>  		       unsigned long end)
>  {
>  	if (vma->vm_flags & VM_EXEC)
> -		__flush_icache_all();
> +		flush_icache_range(start, end);
>  }
> 
>  static void sync_icache_aliases(void *kaddr, unsigned long len)
> --
> 2.5.0
> 
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

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