From: tip-bot for Dave Martin <dave.martin@linaro.org>
Date: Fri, 18 Mar 2011 23:48:08 +0000 (-0700)
Subject: ARM: Thumb-2: Symbol manipulation macros for function body copying
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=19c4124e3f8931a82503f8a6c274b57e0cc31486;p=pandora-kernel.git

ARM: Thumb-2: Symbol manipulation macros for function body copying

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@linaro.org>
Tested-by: Jean Pihet <j-pihet@ti.com>
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