linux-kernel - Re: [PATCH] arm64: change to use memmove in efi-stub

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Message-Id: <9B0C78A1-94BD-47F1-88CF-B78C3142C2DE@gmail.com>
Date:	Mon, 19 Oct 2015 10:11:55 +0800
From:	yalin wang <yalin.wang2010@...il.com>
To:	Mark Rutland <mark.rutland@....com>
Cc:	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	matt.fleming@...el.com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: change to use memmove in efi-stub

Got it ,

Thanks for your explanation .
> On Oct 16, 2015, at 18:57, Mark Rutland <mark.rutland@....com> wrote:
> 
> Hi,
> 
> On Fri, Oct 16, 2015 at 06:46:07PM +0800, yalin wang wrote:
>> Change to use memmove(), in case the dest address overlap with the
>> source address.
> 
> This cannot happen, and memove would not be sufficient if it did.
> 
> The destination is a region returned by EFI_BOOT_SERVICES.AllocatePages,
> which can only allocate pages which were free to begin with. Therefore
> the new region cannot overlap with the stub (whose pages are not free).
> 
> Were the new region to overlap with the stub, the memmove could corrupt
> the code/data in use by the stub, and things would explode shortly
> thereafter.
> 
> Thanks,
> Mark.
> 
>> 
>> Signed-off-by: yalin wang <yalin.wang2010@...il.com>
>> ---
>> arch/arm64/kernel/efi-stub.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/arch/arm64/kernel/efi-stub.c b/arch/arm64/kernel/efi-stub.c
>> index 816120e..b6dc44b 100644
>> --- a/arch/arm64/kernel/efi-stub.c
>> +++ b/arch/arm64/kernel/efi-stub.c
>> @@ -59,7 +59,7 @@ efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table_arg,
>> 			}
>> 			*image_addr = *reserve_addr + TEXT_OFFSET;
>> 		}
>> -		memcpy((void *)*image_addr, old_image_addr, kernel_size);
>> +		memmove((void *)*image_addr, old_image_addr, kernel_size);
>> 		*reserve_size = kernel_memsize;
>> 	}
>> 
>> -- 
>> 1.9.1
>> 

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