From: Linus Walleij > Sent: 03 March 2021 15:19 > > On Tue, Feb 23, 2021 at 11:05 AM Will Deacon <w...@kernel.org> wrote: > > On Mon, Feb 22, 2021 at 01:50:06PM -0800, Jian Cai wrote: > > > I am not sure if there are any plans to protect assembly code and I > > > will leave it to the Arm folks since they know a whole lot better. But > > > even without that part, we should still have better protection, > > > especially when overhead does not look too bad: I did some preliminary > > > experiments on ChromeOS, code size of vmlinux increased 3%, and there > > > were no noticeable changes to run-time performance of the benchmarks I > > > used. > > > > If the mitigation is required, I'm not sure I see a lot of point in only > > doing a half-baked job of it. It feels a bit like a box-ticking exercise, > > in which case any overhead is too much. > > I wrote some suggestions on follow-ups in my reply, and I can > help out doing some of the patches, I think. > > Since ARM32 RET is mov pc, <> > git grep 'mov.*pc,' | wc -l gives 93 sites in arch/arm. > I suppose these need to come out: > > mov pc, lr > dsb(nsh); > isb();
Won't that go horribly wrong for conditional returns? David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)