linux-kernel - Re: [PATCH] x86, efi: Fix unaligned access and endian issues

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Message-ID: <4F4527D3.9040906@zytor.com>
Date:	Wed, 22 Feb 2012 09:37:23 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Nick Bowler <nbowler@...iptictech.com>
CC:	Matt Fleming <matt@...sole-pimps.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Matt Fleming <matt.fleming@...el.com>
Subject: Re: [PATCH] x86, efi: Fix unaligned access and endian issues

On 02/22/2012 08:44 AM, Nick Bowler wrote:
> On 2012-02-22 14:00 +0000, Matt Fleming wrote:
>> From: Matt Fleming<matt.fleming@...el.com>
>>
>> We need to read from and write to 'buf' a byte at a time otherwise
>> it's possible we'll perform an unaligned access, which can lead to a
>> segfault when cross-building an x86 kernel on risc architectures.
>>
>> Also, we may need to convert the endianness of the data we read
>> from/write to buf, so let's add some helper functions to do that.
> [...]
>> +static inline u32 read32_le(u8 *src)
>> +{
>> +	u32 data;
>> +
>> +	data = *src++;
>> +	data |= *src++<<  8;
>> +	data |= *src++<<  16;
>> +	data |= *src++<<  24;
>> +
>> +	return data;
>> +}
>
> We already have get_unaligned_le32 in<asm/unaligned.h>  for this.
>
>> +
>> +static inline void write32_le(u8 *dst, u32 data)
>> +{
>> +	*dst++ = data;
>> +	*dst++ = data>>  8;
>> +	*dst++ = data>>  16;
>> +	*dst++ = data>>  24;
>> +}
>
> Similarly, put_unaligned_le32.
>

This is user space; those headers are not exported.  However, sticking 
to the same name would be good.

I'm wondering if this is the kind of things that should be put in 
usr/include?

	-hpa


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