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Message-ID: <20180306172927.7a975cee@vmware.local.home>
Date: Tue, 6 Mar 2018 17:29:27 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Arnd Bergmann <arnd@...db.de>, 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, 6 Mar 2018 13:47:11 -0800
Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> But that's no different from "static variables initialize to zero" and
> nobody sane expects a warning from that. It's just what it is.
Yeah but I would argue that static variables are different. They are
either used in multiple functions or are used for the same function
that maintains its value for multiple calls to that function. Either
way the semantics of a static variable is that it has to be initialized
to something, because you don't know when the first one sets it.
Local variables on the other hand are only in scope of one logical
function algorithm. I've done lots of stupid errors where I may
initialize a local variable in a loop and forget that the loop may
never execute. Sometimes the original value shouldn't be zero, although
most times it is. But that warning has saved me, especially when the
value isn't supposed to be zero.
-- Steve
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