Date: Thu, 25 Jan 2018 13:08:38 -0800 From: Andy Lutomirski <luto@...nel.org> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Andy Lutomirski <luto@...nel.org>, "the arch/x86 maintainers" <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Alan Cox <alan@...ux.intel.com>, Jann Horn <jannh@...gle.com>, Samuel Neves <samuel.c.p.neves@...il.com>, Dan Williams <dan.j.williams@...el.com>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Borislav Petkov <bp@...en8.de> Subject: Re: [PATCH] x86/retpoline/entry: Disable the entire SYSCALL64 fast path with retpolines on On Thu, Jan 25, 2018 at 1:06 PM, Linus Torvalds <torvalds@...ux-foundation.org> wrote: > On Thu, Jan 25, 2018 at 1:02 PM, Andy Lutomirski <luto@...nel.org> wrote: >> >> Feel free to Acked-by: Andy Lutomirski <luto@...nel.org> that patch. >> >> Or I can grab it and send it to -tip. > > I'm not going to apply it for 4.15, I just wanted to see how it > looked, and do some minimal profiling. > > From the profiles, as mentioned, moving 'status' from thread_struct to > thread_info is probably worth doing. But I didn't look at the impact > of that at all. > > So it should go through all the normal channels in -tip for 4.16. > > I'll happily sign off on the patch, but it was really pretty mindless, > so I'm not sure I need the authorship either. > >> Re: the trampoline not showing up: if I find some time, I'll try to >> wire it up correctly in kallsyms. > > That would be lovely. Right now the system call exit shows up pretty > clearly in profiles, and most of it is (obviously) the cr3 write. So > the missing entry trampoline is not insignificant. > With retpoline, the retpoline in the trampoline sucks. I don't need perf for that -- I've benchmarked it both ways. It sucks. I'll fix it, but it'll be kind of complicated. --Andy
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