linux-kernel - Re: [PATCH 1/3] ARM: use arch_extension directive instead of arch argument

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Message-ID: <yw1xa7hlzihi.fsf@mansr.com>
Date:   Sat, 23 Mar 2019 16:02:49 +0000
From:   Måns Rullgård <mans@...sr.com>
To:     Stefan Agner <stefan@...er.ch>
Cc:     linux@...linux.org.uk, arnd@...db.de, ard.biesheuvel@...aro.org,
        robin.murphy@....com, nicolas.pitre@...aro.org,
        f.fainelli@...il.com, rjui@...adcom.com, sbranden@...adcom.com,
        bcm-kernel-feedback-list@...adcom.com, kgene@...nel.org,
        krzk@...nel.org, robh@...nel.org, ssantosh@...nel.org,
        jason@...edaemon.net, andrew@...n.ch, gregory.clement@...tlin.com,
        sebastian.hesselbarth@...il.com, tony@...mide.com,
        marc.w.gonzalez@...e.fr, ndesaulniers@...gle.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] ARM: use arch_extension directive instead of arch argument

Stefan Agner <stefan@...er.ch> writes:

> 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 a 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.
>
> 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@...er.ch>
> ---
>  arch/arm/mach-bcm/Makefile         | 3 ---
>  arch/arm/mach-bcm/bcm_kona_smc.c   | 2 --
>  arch/arm/mach-exynos/Makefile      | 4 ----
>  arch/arm/mach-exynos/exynos-smc.S  | 2 +-
>  arch/arm/mach-exynos/sleep.S       | 2 +-
>  arch/arm/mach-highbank/Makefile    | 3 ---
>  arch/arm/mach-highbank/smc.S       | 2 +-
>  arch/arm/mach-keystone/Makefile    | 3 ---
>  arch/arm/mach-keystone/smc.S       | 1 +
>  arch/arm/mach-omap2/Makefile       | 8 --------
>  arch/arm/mach-omap2/omap-headsmp.S | 1 +
>  arch/arm/mach-omap2/omap-smc.S     | 2 +-
>  arch/arm/mach-omap2/sleep34xx.S    | 1 +
>  arch/arm/mach-omap2/sleep43xx.S    | 1 +
>  arch/arm/mach-omap2/sleep44xx.S    | 1 +
>  arch/arm/mach-tango/Makefile       | 3 ---
>  arch/arm/mach-tango/smc.S          | 1 +
>  17 files changed, 10 insertions(+), 30 deletions(-)

[...]

> diff --git a/arch/arm/mach-tango/Makefile b/arch/arm/mach-tango/Makefile
> index da6c633d3cc0..97cd04508fa1 100644
> --- a/arch/arm/mach-tango/Makefile
> +++ b/arch/arm/mach-tango/Makefile
> @@ -1,7 +1,4 @@
>  # SPDX-License-Identifier: GPL-2.0
> -plus_sec := $(call as-instr,.arch_extension sec,+sec)
> -AFLAGS_smc.o := -Wa,-march=armv7-a$(plus_sec)
> -
>  obj-y += setup.o smc.o
>  obj-$(CONFIG_SMP) += platsmp.o
>  obj-$(CONFIG_SUSPEND) += pm.o
> diff --git a/arch/arm/mach-tango/smc.S b/arch/arm/mach-tango/smc.S
> index 361a8dc89804..cf2d21e5226c 100644
> --- a/arch/arm/mach-tango/smc.S
> +++ b/arch/arm/mach-tango/smc.S
> @@ -1,6 +1,7 @@
>  /* SPDX-License-Identifier: GPL-2.0 */
>  #include <linux/linkage.h>
>
> +	.arch_extension sec
>  ENTRY(tango_smc)
>  	push	{lr}
>  	mov	ip, r1

For Tango:

Acked-by: Mans Rullgard <mans@...sr.com>

-- 
Måns Rullgård