From mboxrd@z Thu Jan 1 00:00:00 1970 From: szabolcs.nagy@arm.com (Szabolcs Nagy) Date: Fri, 3 Aug 2018 10:12:24 +0100 Subject: framebuffer corruption due to overlapping stp instructions on arm64 In-Reply-To: <9acdacdb-3bd5-b71a-3003-e48132ee1371@redhat.com> References: <9acdacdb-3bd5-b71a-3003-e48132ee1371@redhat.com> Message-ID: <2d7cddbe-6523-f388-339b-382231514f6f@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 03/08/18 08:53, Florian Weimer wrote: > On 08/03/2018 09:11 AM, Andrew Pinski wrote: >> Yes fix Links not to use memcpy on the framebuffer. >> It is undefined behavior to use device memory with memcpy. > > Some (de facto) ABIs require that it is supported, though.? For example, the POWER string functions avoid unaligned loads and stores for this > reason because the platform has the same issue with device memory.? And yes, GCC will expand memcpy on POWER to something that is incompatible > with device memory. 8-( > i think it's not reasonable to require libc memcpy to work on device memory. i think if device memory is exposed to regular userspace applications that should be fixed. > If we don't want people to use memcpy, we probably need to provide a credible alternative. > > Thanks, > Florian