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From: Catalin Marinas <catalin.marinas@arm.com>
To: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Will Deacon <will@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] arm64: Allow disabling of the compat vDSO
Date: Thu, 26 Sep 2019 16:51:47 +0100	[thread overview]
Message-ID: <20190926155147.GL9689@arrakis.emea.arm.com> (raw)
In-Reply-To: <20190926074717.GA26802@iMac.local>

On Thu, Sep 26, 2019 at 08:47:18AM +0100, Catalin Marinas wrote:
> On Thu, Sep 26, 2019 at 01:06:50AM +0100, Vincenzo Frascino wrote:
> > On 9/25/19 6:08 PM, Catalin Marinas wrote:
> > > On Wed, Sep 25, 2019 at 09:53:16AM -0700, Nick Desaulniers wrote:
> > >> On Wed, Sep 25, 2019 at 6:09 AM Catalin Marinas <catalin.marinas@arm.com> wrote:
> > >>> - clean up the headers includes; vDSO should not include kernel-only
> > >>>   headers that may even contain code patched at run-time
> > >>
> > >> This is a big one; Clang validates the inline asm constraints for
> > >> extended inline assembly, GCC does not for dead code.  So Clang chokes
> > >> on the inclusion of arm64 headers using extended inline assembly when
> > >> being compiled for arm-linux-gnueabi.
> > > 
> > > Whether clang or gcc, I'd like this fixed anyway. At some point we may
> > > inadvertently rely on some code which is patched at boot time for the
> > > kernel code but not for the vDSO.
> > 
> > Do we have any code of this kind in header files?
> > 
> > The vDSO library uses only a subset of the headers (mainly Macros) hence all the
> > unused symbols should be compiled out. Is your concern only theoretical or do
> > you have an example on where this could be happening?
> 
> At the moment it's rather theoretical.

Actually, it's not. The moment the compat vdso Makefile needs the line
below, we are doing it wrong:

VDSO_CFLAGS += -D__uint128_t='void*'

-- 
Catalin

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WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Will Deacon <will@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] arm64: Allow disabling of the compat vDSO
Date: Thu, 26 Sep 2019 16:51:47 +0100	[thread overview]
Message-ID: <20190926155147.GL9689@arrakis.emea.arm.com> (raw)
In-Reply-To: <20190926074717.GA26802@iMac.local>

On Thu, Sep 26, 2019 at 08:47:18AM +0100, Catalin Marinas wrote:
> On Thu, Sep 26, 2019 at 01:06:50AM +0100, Vincenzo Frascino wrote:
> > On 9/25/19 6:08 PM, Catalin Marinas wrote:
> > > On Wed, Sep 25, 2019 at 09:53:16AM -0700, Nick Desaulniers wrote:
> > >> On Wed, Sep 25, 2019 at 6:09 AM Catalin Marinas <catalin.marinas@arm.com> wrote:
> > >>> - clean up the headers includes; vDSO should not include kernel-only
> > >>>   headers that may even contain code patched at run-time
> > >>
> > >> This is a big one; Clang validates the inline asm constraints for
> > >> extended inline assembly, GCC does not for dead code.  So Clang chokes
> > >> on the inclusion of arm64 headers using extended inline assembly when
> > >> being compiled for arm-linux-gnueabi.
> > > 
> > > Whether clang or gcc, I'd like this fixed anyway. At some point we may
> > > inadvertently rely on some code which is patched at boot time for the
> > > kernel code but not for the vDSO.
> > 
> > Do we have any code of this kind in header files?
> > 
> > The vDSO library uses only a subset of the headers (mainly Macros) hence all the
> > unused symbols should be compiled out. Is your concern only theoretical or do
> > you have an example on where this could be happening?
> 
> At the moment it's rather theoretical.

Actually, it's not. The moment the compat vdso Makefile needs the line
below, we are doing it wrong:

VDSO_CFLAGS += -D__uint128_t='void*'

-- 
Catalin

  reply	other threads:[~2019-09-26 15:51 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-25 13:09 [PATCH] arm64: Allow disabling of the compat vDSO Catalin Marinas
2019-09-25 13:09 ` Catalin Marinas
2019-09-25 16:53 ` Nick Desaulniers
2019-09-25 16:53   ` Nick Desaulniers
2019-09-25 17:08   ` Catalin Marinas
2019-09-25 17:08     ` Catalin Marinas
2019-09-25 17:31     ` Nick Desaulniers
2019-09-25 17:31       ` Nick Desaulniers
2019-09-25 23:35       ` Vincenzo Frascino
2019-09-25 23:35         ` Vincenzo Frascino
2019-09-26  0:06     ` Vincenzo Frascino
2019-09-26  0:06       ` Vincenzo Frascino
2019-09-26  7:47       ` Catalin Marinas
2019-09-26  7:47         ` Catalin Marinas
2019-09-26 15:51         ` Catalin Marinas [this message]
2019-09-26 15:51           ` Catalin Marinas
2019-09-26 16:40           ` Nick Desaulniers
2019-09-26 16:40             ` Nick Desaulniers
2019-09-26 16:38         ` Nick Desaulniers
2019-09-26 16:38           ` Nick Desaulniers

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