Date: Thu, 25 Jan 2018 22:05:05 +0100 (CET) From: Thomas Gleixner <tglx@...utronix.de> To: Andy Lutomirski <luto@...nel.org> cc: Linus Torvalds <torvalds@...ux-foundation.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, 25 Jan 2018, Andy Lutomirski wrote: > On Thu, Jan 25, 2018 at 10:48 AM, Linus Torvalds > <torvalds@...ux-foundation.org> wrote: > > On Mon, Jan 22, 2018 at 10:55 AM, Linus Torvalds > > <torvalds@...ux-foundation.org> wrote: > >> > >> Honestly, I'd rather get rid of the fast-path entirely. Compared to > >> all the PTI mess, it's not even noticeable. > > > > So I looked at how that would be. > > > > Patch attached. Not really "tested", but I'm running the kernel with > > this patch now, and 'strace' etc works, and honestly, it seems very > > obvious. > > > > Also, code generation for 'do_syscall_64()' does not look horrible. In > > fact, it doesn't look all that much worse than the fast-path ever did. > > > > So the biggest impact of this is the extra register saves > > (SAVE_EXTRA_REGS) from setting up the full ptregs. And honestly, I > > hate how that stupid macro still uses "movq reg,off(%rsp)" instead of > > "pushq %reg". > > > > Considering the diffstat: > > > > 2 files changed, 2 insertions(+), 121 deletions(-) > > > > and how those 100+ lines are nasty assembly code, I do think we should > > just do it. > > Feel free to Acked-by: Andy Lutomirski <luto@...nel.org> that patch. > > Or I can grab it and send it to -tip. That would be nice, so we can route it through x86/pti which provides it for backporting cleanly. Thanks, tglx
Powered by blists - more mailing lists
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.