linux-kernel - Re: [PATCH] x86, efi: initial the local variable of DataSize to zero

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Date:	Mon, 29 Apr 2013 18:25:11 +0800
From:	joeyli <jlee@...e.com>
To:	matt.fleming@...el.com, mjg59@...f.ucam.org
Cc:	linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Matthew Garrett <mjg@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86, efi: initial the local variable of DataSize to
 zero

於 六，2013-04-27 於 01:19 +0800，Lee, Chun-Yi 提到：
> That will be better initial the value of DataSize to zero for the input of
> GetVariable(), otherwise we will feed a random value. The debug log of input
> DataSize like this:
> 
> ...
> [  195.915612] EFI Variables Facility v0.08 2004-May-17
> [  195.915819] efi: size: 18446744071581821342
> [  195.915969] efi:  size': 18446744071581821342
> [  195.916324] efi: size: 18446612150714306560
> [  195.916632] efi:  size': 18446612150714306560
> [  195.917159] efi: size: 18446612150714306560
> [  195.917453] efi:  size': 18446612150714306560
> ...

After applied patch, the log of size like this:

[   82.442042] EFI Variables Facility v0.08 2004-May-17
[   82.442202] efi: size: 0
[   82.442360] efi:  size': 1039
[   82.443828] efi: size: 0
[   82.444127] efi:  size': 2616
[   82.447057] efi: size: 0
[   82.447356] efi:  size': 5832
[   82.452669] efi: size: 0
[   82.453128] efi:  size': 1
[   82.454339] efi: size: 0
[   82.454843] efi:  size': 1
[   82.456173] efi: size: 0
[   82.456764] efi:  size': 8
[   82.458194] efi: size: 0
[   82.458905] efi:  size': 4

The size' is the return value of Acer BIOS, it return right size value
then we feed zero DataSize.


Thanks a lot!
Joey Lee

> 
> Found on Acer Aspire V3 BIOS, it will not return the size of data if we input a
> non-zero DataSize.
> 
> Cc: Matthew Garrett <mjg@...hat.com>
> Cc: Matt Fleming <matt.fleming@...el.com>
> Cc: H. Peter Anvin <hpa@...or.com>
> Signed-off-by: Lee, Chun-Yi <jlee@...e.com>
> ---
>  arch/x86/platform/efi/efi.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> index e4a86a6..cb59732 100644
> --- a/arch/x86/platform/efi/efi.c
> +++ b/arch/x86/platform/efi/efi.c
> @@ -204,7 +204,7 @@ static efi_status_t virt_efi_get_next_variable(unsigned long *name_size,
>  	}
>  
>  	if (boot_used_size && !finished) {
> -		unsigned long size;
> +		unsigned long size = 0;
>  		u32 attr;
>  		efi_status_t s;
>  		void *tmp;


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