Re: [PATCH v4 1/2] ARM: use arch_extension directive instead of arch argument

From: Olof Johansson <olof@lixom.net>
To: Stefan Agner <stefan@agner.ch>
Cc: andrew@lunn.ch, mans@mansr.com, tony@atomide.com,
	robh@kernel.org, f.fainelli@gmail.com,
	gregory.clement@bootlin.com, linux@armlinux.org.uk,
	krzk@kernel.org, arm@kernel.org,
	bcm-kernel-feedback-list@broadcom.com,
	sebastian.hesselbarth@gmail.com, jason@lakedaemon.net,
	arnd@arndb.de, marc.w.gonzalez@free.fr, rjui@broadcom.com,
	ssantosh@kernel.org, linux-arm-kernel@lists.infradead.org,
	sbranden@broadcom.com, nico@fluxnic.net,
	ard.biesheuvel@linaro.org, ndesaulniers@google.com,
	linux-kernel@vger.kernel.org, kgene@kernel.org,
	robin.murphy@arm.com
Subject: Re: [PATCH v4 1/2] ARM: use arch_extension directive instead of arch argument
Date: Wed, 19 Jun 2019 10:33:54 -0700	[thread overview]
Message-ID: <20190619173354.z5znqao6iveoffc7@localhost> (raw)
In-Reply-To: <c0ca465daa7c7663c19b0bcb848c70e8da22baff.1558996564.git.stefan@agner.ch>

On Tue, May 28, 2019 at 12:40:50AM +0200, Stefan Agner wrote:
> The LLVM Target parser currently does not allow to specify the security
> extension as part of -march (see also LLVM Bug 40186 [0]). When trying
> to use Clang with LLVM's integrated assembler, this leads to build
> errors such as this:
>   clang-8: error: the clang compiler does not support '-Wa,-march=armv7-a+sec'
> 
> Use ".arch_extension sec" to enable the security extension in a more
> portable fasion. Also make sure to use ".arch armv7-a" in case a v6/v7
> multi-platform kernel is being built.
> 
> Note that this is technically not exactly the same as the old code
> checked for availabilty of the security extension by calling as-instr.
> However, there are already other sites which use ".arch_extension sec"
> unconditionally, hence de-facto we need an assembler capable of
> ".arch_extension sec" already today (arch/arm/mm/proc-v7.S). The
> arch extension "sec" is available since binutils 2.21 according to
> its documentation [1].
> 
> [0] https://bugs.llvm.org/show_bug.cgi?id=40186
> [1] https://sourceware.org/binutils/docs-2.21/as/ARM-Options.html
> 
> Signed-off-by: Stefan Agner <stefan@agner.ch>
> Acked-by: Mans Rullgard <mans@mansr.com>
> Acked-by: Arnd Bergmann <arnd@arndb.de>
> Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
> ---
> Changes since v1:
> - Explicitly specify assembler architecture as armv7-a to avoid
>   build issues when bulding v6/v7 multi arch kernel.
> 
> Changes since v2:
> - Add armv7-a also in mach-tango
> - Move .arch armv7-a outside of ifdef'ed area in sleep44xx.S
>   to make the kernel compile also without CONFIG_SMP/PM.
> 
> Changes since v3:
> - Rebase on top of v5.2-rc2

Thanks, applied to arm/soc.

-Olof

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