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From: Will Deacon <will@kernel.org>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: ard.biesheuvel@linaro.org, ndesaulniers@google.com,
	linux-kernel@vger.kernel.org, tglx@linutronix.de,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 1/5] arm64: vdso32: Introduce COMPAT_CC_IS_GCC
Date: Tue, 1 Oct 2019 17:46:58 +0100	[thread overview]
Message-ID: <20191001164657.l2wz3ghq6icm3lim@willie-the-truck> (raw)
In-Reply-To: <20191001153056.GO41399@arrakis.emea.arm.com>

On Tue, Oct 01, 2019 at 04:30:56PM +0100, Catalin Marinas wrote:
> On Tue, Oct 01, 2019 at 03:43:54PM +0100, Will Deacon wrote:
> > > >>>> On Thu, Sep 26, 2019 at 10:43:38PM +0100, Vincenzo Frascino wrote:
> > > >>>>> +config COMPATCC_IS_ARM_GCC
> > > >>>>> +	def_bool $(success,$(COMPATCC) --version | head -n 1 | grep -q "arm-.*-gcc")
> [...]
> > My point was that we don't attempt to sanitise the compiler passed via
> > CROSS_COMPILE, so I don't think we should do anything special for COMPATCC
> > either.
> 
> What I really want from kbuild with this patch is:
> 
> 1. Not to warn me that I don't have a CROSS_COMPILE_COMPAT set
> 
> 2. Not to give me a compilation error if the makefile made up a COMPATCC
>    that doesn't work
> 
> Since we dropped the Kconfig option for the compat gcc prefix (which I
> didn't like anyway), COMPATCC is now initialised to
> (CROSS_COMPILE_COMPAT)gcc. This means that it is valid compiler (and
> it's an aarch64 compiler on my machine). The COMPATCC_IS_ARM_GCC
> silently disables the compat vDSO for this case rather than giving me a
> build error if we don't have such checks.
> 
> In the long run, I wouldn't mandate CROSS_COMPILE_COMPAT to always be
> set for the compat vDSO since with clang we could use the same compiler
> binary for both native and compat (with different flags). That's once we
> cleaned up the headers.

But we'll still need it even with clang so that the relevant triple can be
passed to the --target option. The top-level Makefile already does this:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Makefile#n544

so I think we should do the same thing for the compat vdso as well, which
would allow us to remove this complexity by requiring that
CROSS_COMPILE_COMPAT identifies the cross-compiler to use in exactly the
same way as CROSS_COMPILE does.

Am I missing something here?

Will

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  reply	other threads:[~2019-10-01 16:47 UTC|newest]

Thread overview: 60+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20190920142738.qlsjwguc6bpnez63@willie-the-truck>
2019-09-26  6:03 ` [PATCH 0/4] arm64: vdso32: Address various issues Vincenzo Frascino
2019-09-26  6:03   ` [PATCH 1/4] arm64: vdso32: Introduce COMPAT_CC_IS_GCC Vincenzo Frascino
2019-09-26  8:06     ` Catalin Marinas
2019-09-26 10:56       ` Vincenzo Frascino
2019-09-26 11:02         ` Vincenzo Frascino
2019-09-26 15:23           ` Catalin Marinas
2019-09-26 12:22         ` Vincenzo Frascino
2019-09-26 15:17           ` Catalin Marinas
2019-09-26 20:17             ` Vincenzo Frascino
2019-09-26  6:03   ` [PATCH 2/4] arm64: vdso32: Detect binutils support for dmb ishld Vincenzo Frascino
2019-09-26  8:30     ` Catalin Marinas
2019-09-26 10:59       ` Vincenzo Frascino
2019-09-26  6:03   ` [PATCH 3/4] arm64: vdso32: Fix compilation warning Vincenzo Frascino
2019-09-26  8:32     ` Catalin Marinas
2019-09-26 11:03       ` Vincenzo Frascino
2019-09-26  6:03   ` [PATCH 4/4] arm64: Remove gettimeofday.S Vincenzo Frascino
2019-09-26  8:34     ` Catalin Marinas
2019-09-26 13:38 ` [PATCH v2 0/4] arm64: vdso32: Address various issues Vincenzo Frascino
2019-09-26 13:38   ` [PATCH v2 1/4] arm64: vdso32: Introduce COMPAT_CC_IS_GCC Vincenzo Frascino
2019-09-26 15:13     ` Catalin Marinas
2019-09-26 13:38   ` [PATCH v2 2/4] arm64: vdso32: Detect binutils support for dmb ishld Vincenzo Frascino
2019-09-26 14:26     ` Catalin Marinas
2019-09-26 20:19       ` Vincenzo Frascino
2019-09-26 15:59     ` Catalin Marinas
2019-09-26 21:17       ` Vincenzo Frascino
2019-09-26 16:23     ` Nick Desaulniers
2019-09-26 13:38   ` [PATCH v2 3/4] arm64: vdso32: Fix compilation warning Vincenzo Frascino
2019-09-26 15:22     ` Catalin Marinas
2019-09-26 13:38   ` [PATCH v2 4/4] arm64: Remove gettimeofday.S Vincenzo Frascino
2019-09-26 15:31   ` [PATCH v2 0/4] arm64: vdso32: Address various issues Catalin Marinas
2019-09-26 20:29     ` Vincenzo Frascino
2019-09-26 21:43 ` [PATCH v3 0/5]arm64: " Vincenzo Frascino
2019-09-26 21:43   ` [PATCH v3 1/5] arm64: vdso32: Introduce COMPAT_CC_IS_GCC Vincenzo Frascino
2019-09-27  9:24     ` Catalin Marinas
2019-10-01 13:14     ` Will Deacon
2019-10-01 13:27       ` Catalin Marinas
2019-10-01 14:20         ` Vincenzo Frascino
2019-10-01 14:20           ` Will Deacon
2019-10-01 14:37             ` Vincenzo Frascino
2019-10-01 14:43               ` Will Deacon
2019-10-01 14:59                 ` Vincenzo Frascino
2019-10-01 15:30                 ` Catalin Marinas
2019-10-01 16:46                   ` Will Deacon [this message]
2019-10-01 16:59                     ` Nick Desaulniers
2019-10-01 17:07                       ` Will Deacon
2019-10-01 17:12                         ` Nick Desaulniers
2019-10-01 17:14                           ` Will Deacon
2019-09-26 21:43   ` [PATCH v3 2/5] arm64: vdso32: Detect binutils support for dmb ishld Vincenzo Frascino
2019-09-27  9:25     ` Catalin Marinas
2019-10-01 13:26     ` Will Deacon
2019-10-01 14:23       ` Vincenzo Frascino
2019-09-26 21:43   ` [PATCH v3 3/5] arm64: vdso32: Fix compilation warning Vincenzo Frascino
2019-09-27  9:26     ` Catalin Marinas
2019-10-01 13:21     ` Will Deacon
2019-10-01 14:41       ` Vincenzo Frascino
2019-09-26 21:43   ` [PATCH v3 4/5] arm64: Remove gettimeofday.S Vincenzo Frascino
2019-09-26 21:43   ` [PATCH v3 5/5] arm64: vdso32: Remove jump label config option in Makefile Vincenzo Frascino
2019-09-27  9:27     ` Catalin Marinas
2019-09-27 10:46   ` [PATCH v3 0/5]arm64: vdso32: Address various issues Catalin Marinas
2019-10-01 13:27   ` Will Deacon

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