From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH v2] misc: sram-exec: Use aligned fncpy instead of memcpy Date: Wed, 17 May 2017 12:43:07 +0100 Message-ID: <20170517114307.GU23750@n2100.armlinux.org.uk> References: <20170410145247.6023-1-d-gerlach@ti.com> <20170503185533.GS23750@n2100.armlinux.org.uk> <20170516160127.GH31418@atomide.com> <20170517091317.GA17902@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170517091317.GA17902@kroah.com> Sender: linux-kernel-owner@vger.kernel.org To: Greg Kroah-Hartman Cc: Tony Lindgren , Dave Gerlach , Arnd Bergmann , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, Shawn Guo , Alexandre Belloni , Keerthy J List-Id: linux-omap@vger.kernel.org On Wed, May 17, 2017 at 11:13:17AM +0200, Greg Kroah-Hartman wrote: > On Tue, May 16, 2017 at 09:01:27AM -0700, Tony Lindgren wrote: > > * Russell King - ARM Linux [170503 11:58]: > > > On Mon, Apr 10, 2017 at 09:52:47AM -0500, Dave Gerlach wrote: > > > > Currently the sram-exec functionality, which allows allocation of > > > > executable memory and provides an API to move code to it, is only > > > > selected in configs for the ARM architecture. Based on commit > > > > 5756e9dd0de6 ("ARM: 6640/1: Thumb-2: Symbol manipulation macros for > > > > function body copying") simply copying a C function pointer address > > > > using memcpy without consideration of alignment and Thumb is unsafe on > > > > ARM platforms. > > > > > > > > The aforementioned patch introduces the fncpy macro which is a safe way > > > > to copy executable code on ARM platforms, so let's make use of that here > > > > rather than the unsafe plain memcpy that was previously used by > > > > sram_exec_copy. Now sram_exec_copy will move the code to "dst" and > > > > return an address that is guaranteed to be safely callable. > > > > > > > > In the future, architectures hoping to make use of the sram-exec > > > > functionality must define an fncpy macro just as ARM has done to > > > > guarantee or check for safe copying to executable memory before allowing > > > > the arch to select CONFIG_SRAM_EXEC. > > > > > > > > Signed-off-by: Dave Gerlach > > > > > > Looks a lot saner, thanks. It's just a bit sad that we lose the type > > > checking. > > > > > > Acked-by: Russell King > > > > Looks like this is still pending so I'll add it into > > omap-for-v4.12/fixes so we can get this out of the way. > > It's a "fix"? Looked to be a 4.13 issue, sorry for the delay, otherwise > I would have queued it up earlier. Technically, it is a fix, but my greps for "sram_exec_copy" indicate that the code does not yet have any in-tree users. So I don't think there's any urgency to picking this up, and I think no need to back port to stable trees. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.