[PATCH v4] ARM: Thumb-2: Symbol manipulation macros for function body copying

Dave Martin dave.martin at linaro.org
Mon Jan 24 08:50:49 EST 2011

On Thu, Jan 20, 2011 at 9:42 AM, Dave Martin <dave.martin at linaro.org> wrote:
> On Wed, Jan 19, 2011 at 10:29 PM, Kevin Hilman <khilman at ti.com> wrote:
>> Dave Martin <dave.martin at linaro.org> writes:
>>> In low-level board support code, there is sometimes a need to
>>> copy a function body to another location at run-time.
>>> A straightforward call to memcpy doesn't work in Thumb-2,
>>> because bit 0 of external Thumb function symbols is set to 1,
>>> indicating that the function is Thumb.  Without corrective
>>> measures, this will cause an off-by-one copy, and the copy
>>> may be called using the wrong instruction set.
>>> This patch adds an fncpy() macro to help with such copies.
>>> Particular care is needed, because C doesn't guarantee any
>>> defined behaviour when casting a function pointer to any other
>>> type.  This has been observed to lead to strange optimisation
>>> side-effects when doing the arithmetic which is required in
>>> order to copy/move function bodies correctly in Thumb-2.
>>> Thanks to Russell King and Nicolas Pitre for their input
>>> on this patch.
>>> Signed-off-by: Dave Martin <dave.martin at linaro.org>
>>> Tested-by: Jean Pihet <j-pihet at ti.com>
>> Tested-by: Kevin Hilman <khilman at ti.com>
>> along with Jean's OMAP patch on:
>> OMAP2420/n810: including basic suspend/resume test.
>> OMAP16xx/OSK: boot test only.
>> Kevin
> Thanks
> ---Dave

Any more comments on this patch?

I have no further changes so far.


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