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

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Date:	Wed, 22 Feb 2012 11:44:02 -0500
From:	Nick Bowler <nbowler@...iptictech.com>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	Stephen Rothwell <sfr@...b.auug.org.au>, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Matt Fleming <matt.fleming@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86, efi: Fix unaligned access and endian issues

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.

Cheers,
-- 
Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/)

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