linux-kernel - Can this be a invalid memory access? (was: Re: [PATCH] spi/xilinx: Cast ioread32/iowrite32 function pointers)

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Date:	Mon, 2 Feb 2015 13:49:20 +0100
From:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
To:	Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Can this be a invalid memory access? (was: Re: [PATCH] spi/xilinx:
 Cast ioread32/iowrite32 function pointers)

Hello

Regarding ioread8 et al.

On include/asm-generic/io.h is defined as:
extern unsigned int ioread8(void __iomem *);

On include/asm-generic/io.h:
static inline u8 ioread8(const volatile void __iomem *addr)

Please ignore the qualifiers right now. The first function returns an
unsigned integer, the second a u8.

Through #ifdefs, different arches uses the first or the second definitions.

If we consider this code:

u8 varA;
u8 varB;
u8 varC;
void * pvar=varB;
*pvar = ioread8(valid_memory);

Depending if ioread8 returns a u8 or a unsigned int, aren't we also
accessing varC?

Could not this be a problem?

If I decide to send a patch and fix it, is there a clever script that
I can run on my x86 computer to test if the patch works on all arches?

Thanks

-- 
Ricardo Ribalda
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