From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kevin Hilman Subject: Re: [PATCH v4] ARM: Thumb-2: Symbol manipulation macros for function body copying Date: Wed, 19 Jan 2011 14:29:00 -0800 Message-ID: <87bp3cr0ib.fsf@ti.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 na3sys009aog110.obsmtp.com ([74.125.149.203]:44935 "EHLO na3sys009aog110.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754893Ab1ASW3J (ORCPT ); Wed, 19 Jan 2011 17:29:09 -0500 Received: by mail-qw0-f53.google.com with SMTP id 5so1390768qwe.12 for ; Wed, 19 Jan 2011 14:29:04 -0800 (PST) In-Reply-To: <1295039877-7976-1-git-send-email-dave.martin@linaro.org> (Dave Martin's message of "Fri, 14 Jan 2011 15:17:57 -0600") 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 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 > Tested-by: Jean Pihet Tested-by: Kevin Hilman along with Jean's OMAP patch on: OMAP2420/n810: including basic suspend/resume test. OMAP16xx/OSK: boot test only. Kevin