From: Michael Matz <matz@suse.de>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Jakub Jelinek <jakub@redhat.com>, Borislav Petkov <bp@alien8.de>,
Sergei Trofimovich <slyfox@gentoo.org>,
LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH v2] x86: fix early boot crash on gcc-10
Date: Mon, 20 Apr 2020 14:04:06 +0000 (UTC) [thread overview]
Message-ID: <alpine.LSU.2.21.2004201401120.11688@wotan.suse.de> (raw)
In-Reply-To: <CAKwvOdkkbWgWmNthq5KijCdtatM9PEAaCknaq8US9w4qaDuwug@mail.gmail.com>
Hello,
On Fri, 17 Apr 2020, Nick Desaulniers wrote:
> Ah seems we do have __attribute__((no_selector))
> (https://reviews.llvm.org/D46300,
> https://releases.llvm.org/7.0.0/tools/clang/docs/AttributeReference.html#no-stack-protector-clang-no-stack-protector-clang-no-stack-protector)
> which differs from GCC attribute name.
As you will discover upthread that was tried with GCC and found
insufficient, as GCC is a bit surprising with optimize attributes: it
resets every -f option from the command line and applies only the ones
from the attributes. Including a potential -fno-omit-frame-pointer,
causing all kinds of itches :)
(The similar attribute in clang might work less surprising of course).
Ciao,
Michael.
>
> I'm still catching up on the thread (and my cat is insistent about
> sleeping on my lap while I'm trying to use my laptop), but I like
> https://lore.kernel.org/lkml/20200417190607.GY2424@tucnak/T/#m23d197d3a66a6c7d04c5444af4f51d940895b412
> if it additionally defined __no_stack_protector for compiler-clang.h.
>
> On Fri, Apr 17, 2020 at 12:06 PM Jakub Jelinek <jakub@redhat.com> wrote:
> >
> > On Fri, Apr 17, 2020 at 11:22:25AM -0700, Nick Desaulniers wrote:
> > > > Sorry, I don't quite follow. The idea is that an empty asm statement
> > > > in foo() should prevent foo() from being inlined into bar()?
> > >
> > > s/inlined/tail called/
> >
> > Yeah. The thing is, the caller changes the stack protector guard base
> > value, so at the start of the function it saves a different value then
> > it compares at the end. But, the function that it calls at the end
> > actually doesn't return, so this isn't a problem.
> > If it is tail called though, the stack protector guard checking is done
> > before the tail call and it crashes.
> > If the called function is marked with noreturn attribute or _Noreturn,
> > at least GCC will also not tail call it and all is fine, but not sure
> > what LLVM does in that case.
>
> Seems fine? https://godbolt.org/z/VEoEfw
> (try commenting out the __attribute__((noreturn)) to observe the tail calls.
>
next prev parent reply other threads:[~2020-04-20 14:04 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-14 16:44 [PATCH] x86: fix early boot crash on gcc-10 Sergei Trofimovich
2020-03-16 13:04 ` Peter Zijlstra
2020-03-16 13:26 ` Jakub Jelinek
2020-03-16 13:42 ` Peter Zijlstra
2020-03-16 17:54 ` Borislav Petkov
2020-03-16 18:03 ` Jakub Jelinek
2020-03-17 14:36 ` Borislav Petkov
2020-03-17 14:39 ` Jakub Jelinek
2020-03-17 14:49 ` Borislav Petkov
2020-03-17 16:35 ` David Laight
2020-03-25 13:31 ` Borislav Petkov
2020-03-26 21:54 ` Sergei Trofimovich
2020-03-26 22:35 ` Borislav Petkov
2020-03-28 8:48 ` [PATCH v2] " Sergei Trofimovich
2020-04-13 14:15 ` [tip: x86/urgent] x86: Fix " tip-bot2 for Sergei Trofimovich
2020-04-13 16:35 ` [PATCH v2] x86: fix " Borislav Petkov
2020-04-14 13:50 ` Michael Matz
2020-04-15 7:48 ` Borislav Petkov
2020-04-15 14:53 ` Michael Matz
2020-04-15 22:19 ` Sergei Trofimovich
2020-04-17 7:57 ` Borislav Petkov
2020-04-17 8:07 ` Jakub Jelinek
2020-04-17 8:42 ` Borislav Petkov
2020-04-17 8:58 ` Jakub Jelinek
2020-04-17 9:09 ` Borislav Petkov
2020-04-17 18:15 ` Nick Desaulniers
2020-04-17 18:22 ` Nick Desaulniers
2020-04-17 19:06 ` Jakub Jelinek
2020-04-17 19:49 ` Nick Desaulniers
2020-04-17 19:53 ` Nick Desaulniers
2020-04-20 14:04 ` Michael Matz [this message]
2020-04-22 10:23 ` Borislav Petkov
2020-04-22 11:40 ` Peter Zijlstra
2020-04-22 13:49 ` Borislav Petkov
2020-04-22 13:55 ` Jakub Jelinek
2020-04-22 14:16 ` Martin Liška
2020-04-22 15:06 ` Michael Matz
2020-04-22 16:53 ` Borislav Petkov
2020-04-22 17:02 ` Jakub Jelinek
2020-04-22 18:47 ` Nick Desaulniers
2020-04-22 18:55 ` Nick Desaulniers
2020-04-22 19:21 ` Borislav Petkov
2020-04-22 21:05 ` Nick Desaulniers
2020-04-22 21:26 ` Borislav Petkov
2020-04-22 22:57 ` Nick Desaulniers
2020-04-23 12:53 ` Borislav Petkov
2020-04-23 16:12 ` [PATCH] x86: Fix early boot crash on gcc-10, next try Borislav Petkov
2020-04-23 17:30 ` Borislav Petkov
2020-04-23 18:02 ` Nick Desaulniers
2020-04-23 18:27 ` Borislav Petkov
2020-04-27 11:37 ` [tip: x86/build] x86/build: Check whether the compiler is sane tip-bot2 for Borislav Petkov
2020-04-23 19:40 ` [PATCH] x86: Fix early boot crash on gcc-10, next try Kees Cook
2020-04-25 1:46 ` Arvind Sankar
2020-04-25 8:57 ` Borislav Petkov
2020-04-25 11:09 ` Jürgen Groß
2020-04-25 15:04 ` Arvind Sankar
2020-04-25 17:31 ` Borislav Petkov
2020-04-25 17:52 ` Borislav Petkov
2020-04-27 17:07 ` David Laight
2020-04-25 18:37 ` Segher Boessenkool
2020-04-25 18:53 ` Borislav Petkov
2020-04-25 19:15 ` Segher Boessenkool
2020-04-25 22:17 ` Borislav Petkov
2020-04-25 22:25 ` Arvind Sankar
2020-04-17 10:38 ` [PATCH v2] x86: fix early boot crash on gcc-10 Peter Zijlstra
2020-04-18 13:12 ` David Laight
2020-04-17 10:41 ` Peter Zijlstra
2020-03-16 18:20 ` [PATCH] " Arvind Sankar
2020-03-16 18:54 ` Arvind Sankar
2020-03-16 19:53 ` Arvind Sankar
2020-03-16 20:08 ` Jakub Jelinek
2020-03-16 20:40 ` Arvind Sankar
2020-03-16 22:12 ` Sergei Trofimovich
2020-03-17 11:46 ` Jakub Jelinek
2020-03-17 18:10 ` Sergei Trofimovich
2020-03-16 18:22 ` Arvind Sankar
2020-03-26 23:16 ` [PATCH v2] " Sergei Trofimovich
2020-04-27 11:37 ` [tip: x86/build] x86: Fix early boot crash on gcc-10, next try tip-bot2 for Borislav Petkov
2020-05-15 11:20 ` [tip: x86/urgent] x86: Fix early boot crash on gcc-10, third try tip-bot2 for Borislav Petkov
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