From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Lindgren Subject: Re: [PATCH v4] ARM: Thumb-2: Symbol manipulation macros for function body copying Date: Wed, 19 Jan 2011 14:09:25 -0800 Message-ID: <20110119220925.GF4957@atomide.com> References: <1295039877-7976-1-git-send-email-dave.martin@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mho-02-ewr.mailhop.org ([204.13.248.72]:50484 "EHLO mho-02-ewr.mailhop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753690Ab1ASWJi (ORCPT ); Wed, 19 Jan 2011 17:09:38 -0500 Content-Disposition: inline In-Reply-To: <1295039877-7976-1-git-send-email-dave.martin@linaro.org> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Dave Martin Cc: linux-arm-kernel@lists.infradead.org, linux-omap@vger.kernel.org, Jean Pihet * 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