[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20180306190720.GK25181@hirez.programming.kicks-ass.net>
Date: Tue, 6 Mar 2018 20:07:20 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Daniel Micay <danielmicay@...il.com>, Ingo Molnar <mingo@...nel.org>,
Kees Cook <keescook@...omium.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Alexander Popov <alex.popov@...ux.com>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
PaX Team <pageexec@...email.hu>,
Brad Spengler <spender@...ecurity.net>,
Andy Lutomirski <luto@...nel.org>, Tycho Andersen <tycho@...ho.ws>,
Laura Abbott <labbott@...hat.com>,
Mark Rutland <mark.rutland@....com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Borislav Petkov <bp@...en8.de>,
Richard Sandiford <richard.sandiford@....com>,
Thomas Gleixner <tglx@...utronix.de>,
"H . Peter Anvin" <hpa@...or.com>,
"Dmitry V . Levin" <ldv@...linux.org>,
Emese Revfy <re.emese@...il.com>, Jonathan Corbet <corbet@....net>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
Thomas Garnier <thgarnie@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Alexei Starovoitov <ast@...nel.org>, Josef Bacik <jbacik@...com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Nicholas Piggin <npiggin@...il.com>,
Al Viro <viro@...iv.linux.org.uk>,
"David S . Miller" <davem@...emloft.net>,
Ding Tianhong <dingtianhong@...wei.com>,
David Woodhouse <dwmw@...zon.co.uk>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Steven Rostedt <rostedt@...dmis.org>,
Dominik Brodowski <linux@...inikbrodowski.net>,
Juergen Gross <jgross@...e.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Dan Williams <dan.j.williams@...el.com>,
Mathias Krause <minipli@...glemail.com>,
Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
Kyle Huey <me@...ehuey.com>,
Dmitry Safonov <dsafonov@...tuozzo.com>,
Will Deacon <will.deacon@....com>, Arnd Bergmann <arnd@...db.de>,
X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v9 4/7] x86/entry: Erase kernel stack in
syscall_trace_enter()
On Tue, Mar 06, 2018 at 10:56:58AM -0800, Linus Torvalds wrote:
> On Tue, Mar 6, 2018 at 7:16 AM, Daniel Micay <danielmicay@...il.com> wrote:
> >
> > Zeroing locals isn't very expensive because the compiler has a chance
> > to optimize it out when it can figure out it isn't needed and they're
> > almost always used.
>
> I thought I saw Kees with some stats, and it wasn't even noticeable.
> But maybe I mis-remember.
>
> I definitely like the "zero local variables", and would actually
> prefer something even stronger than GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
> (although I can't actually read gcc plugins, so I'm just going by
> name).
>
> It's not necessarily just struct, it can very much be arrays and
> regular automatic variables too.
>
> And yes, we might want to have some override switch for individual
> variables ("I really know what I'm doing and I promise I fill it
> myself, but the compiler doesn't understand me, look here:").
Right, I have one case in perf where we very carefully pass a partially
initialized structure around for performance raisins. So I would
definitely like to have that attribute that allows us to over-ride that
BYREF_ALL thing.
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.
