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From: Arvind Sankar <nivedita@alum.mit.edu>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Arvind Sankar <nivedita@alum.mit.edu>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andy Lutomirski <luto@amacapital.net>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Borislav Petkov <bp@suse.de>, Kalle Valo <kvalo@codeaurora.org>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	the arch/x86 maintainers <x86@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: gcc-10: kernel stack is corrupted and fails to boot
Date: Thu, 14 May 2020 11:50:28 -0400	[thread overview]
Message-ID: <20200514155028.GA2336285@rani.riverdale.lan> (raw)
In-Reply-To: <CAK8P3a1Cfzu7L30bFP-Sf2_GbkN_10CCJsbefTXyfnGF16uHMA@mail.gmail.com>

On Thu, May 14, 2020 at 10:40:44AM +0200, Arnd Bergmann wrote:
> On Thu, May 14, 2020 at 7:22 AM Arvind Sankar <nivedita@alum.mit.edu> wrote:
> > On Wed, May 13, 2020 at 09:52:07PM -0700, Linus Torvalds wrote:
> > > On Wed, May 13, 2020, 20:50 Andy Lutomirski <luto@amacapital.net> wrote:
> > The gcc docs [1,2] at least don't inspire much confidence that this will
> > continue working with plain asm("") though:
> >
> > "Note that GCC’s optimizers can move asm statements relative to other
> > code, including across jumps."
> > ...
> > "Note that the compiler can move even volatile asm instructions relative
> > to other code, including across jump instructions."
> >
> > Even if we don't include an instruction in it I think it should at least
> > have a memory clobber, to stop the compiler from deciding that it can be
> > moved before the call so it can do the tail-call optimization.
> 
> I think LTO would still be able to notice that cpu_startup_entry() can
> be annotated __attribute__((noreturn)) and optimize the callers
> accordingly, which in turn would allow a tail call again after dead code
> elimination.
> 
>      Arnd

Yes, with LTO the only solution is to actually compile the caller
without stack checking I think.  Although at present gcc actually
doesn't tail-call optimize calls to noreturn functions that could easily
change.

  parent reply	other threads:[~2020-05-14 15:50 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-09 12:06 [PATCH net-next 1/2] ath10k: fix gcc-10 zero-length-bounds warnings Arnd Bergmann
2020-05-09 12:06 ` [PATCH net-next 2/2] ath10k: fix ath10k_pci struct layout Arnd Bergmann
2020-05-11 12:05   ` Kalle Valo
2020-05-11 12:17     ` Kalle Valo
2020-05-11 12:39       ` Arnd Bergmann
2020-05-13  6:50       ` gcc-10: kernel stack is corrupted and fails to boot Kalle Valo
2020-05-13  8:49         ` Arnd Bergmann
2020-05-13 12:45           ` Kalle Valo
2020-05-13 13:45             ` Arnd Bergmann
2020-05-13 15:31               ` Kalle Valo
2020-05-13 16:00                 ` Arnd Bergmann
2020-05-13 16:07                   ` David Laight
2020-05-14  9:13                 ` Harald Arnesen
2020-05-13 15:48         ` Arvind Sankar
2020-05-13 21:28           ` Arnd Bergmann
2020-05-13 21:41             ` Borislav Petkov
2020-05-13 21:49               ` Arnd Bergmann
2020-05-13 22:20                 ` Borislav Petkov
2020-05-13 22:51                   ` Arvind Sankar
2020-05-13 23:13                   ` Linus Torvalds
2020-05-13 23:36                     ` Borislav Petkov
2020-05-14  0:11                       ` Linus Torvalds
2020-05-14  0:51                         ` Nick Desaulniers
2020-05-14  2:20                           ` Linus Torvalds
2020-05-14  3:50                             ` Andy Lutomirski
     [not found]                               ` <CAHk-=wgiGxRgJGS-zyer1C_x2MQUVo6iZn0=aJyuFTqJWk-mpA@mail.gmail.com>
2020-05-14  5:22                                 ` Arvind Sankar
2020-05-14  8:40                                   ` Arnd Bergmann
2020-05-14 13:27                                     ` [PATCH] x86: Fix early boot crash on gcc-10, third try Borislav Petkov
2020-05-14 14:45                                       ` Kalle Valo
2020-05-14 15:50                                     ` Arvind Sankar [this message]
2020-05-14  8:11                             ` gcc-10: kernel stack is corrupted and fails to boot David Laight
2020-05-13 23:07                 ` Linus Torvalds
2020-05-09 15:48 ` [PATCH net-next 1/2] ath10k: fix gcc-10 zero-length-bounds warnings Gustavo A. R. Silva
2020-05-11 12:02   ` Kalle Valo
2020-05-11 12:46     ` Arnd Bergmann
2020-05-11 13:09       ` Kalle Valo
2020-05-11 13:47         ` Arnd Bergmann
2020-05-12  7:33 ` Kalle Valo

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