linux-kernel - Re: [PATCH] x86/retpoline/entry: Disable the entire SYSCALL64 fast path with retpolines on

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

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