From mboxrd@z Thu Jan 1 00:00:00 1970 From: tony@atomide.com (Tony Lindgren) Date: Wed, 19 Jan 2011 14:09:25 -0800 Subject: [PATCH v4] ARM: Thumb-2: Symbol manipulation macros for function body copying In-Reply-To: <1295039877-7976-1-git-send-email-dave.martin@linaro.org> References: <1295039877-7976-1-git-send-email-dave.martin@linaro.org> Message-ID: <20110119220925.GF4957@atomide.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org * Dave Martin [110114 13:17]: > 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 > Tested-by: Jean Pihet Boot tested on osk5912 and n800: Tested-by: Tony Lindgren