[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAK8P3a0ko9E91jok0fSnwQ__vO8nzBpmki768t_-Z9MhZ_f-JQ@mail.gmail.com>
Date: Tue, 6 Mar 2018 22:47:54 +0100
From: Arnd Bergmann <arnd@...db.de>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>, 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>,
Borislav Petkov <bp@...en8.de>, Richard Sandiford <richard.sandiford@....com>,
Thomas Gleixner <tglx@...utronix.de>, "H . Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>, "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>, 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>, 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 6, 2018 at 10:36 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Tue, 6 Mar 2018 13:01:20 -0800
> Linus Torvalds <torvalds@...ux-foundation.org> wrote:
>
>> Then the optimization passes will just remove the initialization in
>> 99.9% of all cases. Only very occasionally - when gcc cannot see it
>> being overwritten - would it remain. And those are exactly the cases
>> where you *want* it to remain.
>
> You mean have gcc fill in the variables that it thinks is used
> uninitialized with zeros? As long as it still warns about it, because
> that usually catches some real bugs where zeroing the variable doesn't
> actually fix the bug.
>
> I also tried the example Arnd posted with:
>
>
> int g(int c)
> {
> int i;
> if (c) /* gcc optimizes out the condition as nothing else sets i */
> i = 1;
> return i;
> }
>
> And he's right. -O2 doesn't warn :-( I think that it should.
See this bug that has been open since 2004 and the 31 bugs
that have been marked as duplicates since then:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=18501
I don't really understand it myself, but I do understand that
the gcc developers think this is a hard problem to solve.
Arnd
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.
