From: Simon Horman Subject: Re: [PATCH] ARM: convert all "mov.* pc, reg" to "bx reg" for ARMv6+ Date: Mon, 7 Jul 2014 11:21:42 +0200 Message-ID: <20140707092142.GC3118@verge.net.au> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Andrew Lunn , kvm@vger.kernel.org, linux-sh@vger.kernel.org, Kevin Hilman , Sekhar Nori , linux-tegra@vger.kernel.org, Thierry Reding , kvmarm@lists.cs.columbia.edu, Kukjin Kim , Herbert Xu , Stefano Stabellini , Magnus Damm , Gleb Natapov , Tony Lindgren , linux-arm-kernel@lists.infradead.org, xen-devel@lists.xenproject.org, Sebastian Hesselbarth , Jason Cooper , Stephen Warren , Marc Zyngier , Hans Ulli Kroll , Haojian Zhuang , linux-samsung-soc@vger.kernel.org, Ben Dooks Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org List-Id: linux-crypto.vger.kernel.org On Tue, Jul 01, 2014 at 04:58:24PM +0100, Russell King wrote: > ARMv6 and greater introduced a new instruction ("bx") which can be used > to return from function calls. Recent CPUs perform better when the > "bx lr" instruction is used rather than the "mov pc, lr" instruction, > and this sequence is strongly recommended to be used by the ARM > architecture manual (section A.4.1.1). > > We provide a new macro "ret" with all its variants for the condition > code which will resolve to the appropriate instruction. > > Rather than doing this piecemeal, and miss some instances, change all > the "mov pc" instances to use the new macro, with the exception of > the "movs" instruction and the kprobes code. This allows us to detect > the "mov pc, lr" case and fix it up - and also gives us the possibility > of deploying this for other registers depending on the CPU selection. > > Signed-off-by: Russell King A conflict in next notification from Stephen Rothwell tells me that this has made it there but regardless I would like to note that I have successfully tested this on the following shmobile boards: Genmai, Koelsh, Lager, Marzen, Bockw, APE6EVM, KZM9D, KZM9G, Armadillo800 EVA and Mackerel. This covers all but one board (I do not have access to a Henninger) and all SoCs supported in mainline. Accordingly, the shmobile portion: Tested-by: Simon Horman