linux-kernel - Re: [PATCH v4 07/14] arm64: Add support for suppressing warning backtraces

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Message-ID: <20250313122503.GA7438@willie-the-truck>
Date: Thu, 13 Mar 2025 12:25:04 +0000
From: Will Deacon <will@...nel.org>
To: Alessandro Carminati <acarmina@...hat.com>
Cc: linux-kselftest@...r.kernel.org, David Airlie <airlied@...il.com>,
	Arnd Bergmann <arnd@...db.de>,
	Maíra Canal <mcanal@...lia.com>,
	Dan Carpenter <dan.carpenter@...aro.org>,
	Kees Cook <keescook@...omium.org>,
	Daniel Diaz <daniel.diaz@...aro.org>,
	David Gow <davidgow@...gle.com>,
	Arthur Grillo <arthurgrillo@...eup.net>,
	Brendan Higgins <brendan.higgins@...ux.dev>,
	Naresh Kamboju <naresh.kamboju@...aro.org>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Maxime Ripard <mripard@...nel.org>,
	Ville Syrjälä <ville.syrjala@...ux.intel.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Guenter Roeck <linux@...ck-us.net>,
	Alessandro Carminati <alessandro.carminati@...il.com>,
	Jani Nikula <jani.nikula@...el.com>,
	dri-devel@...ts.freedesktop.org, kunit-dev@...glegroups.com,
	linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
	linux-sh@...r.kernel.org, loongarch@...ts.linux.dev, x86@...nel.org,
	Linux Kernel Functional Testing <lkft@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH v4 07/14] arm64: Add support for suppressing warning
 backtraces

On Thu, Mar 13, 2025 at 11:43:22AM +0000, Alessandro Carminati wrote:
> diff --git a/arch/arm64/include/asm/bug.h b/arch/arm64/include/asm/bug.h
> index 28be048db3f6..044c5e24a17d 100644
> --- a/arch/arm64/include/asm/bug.h
> +++ b/arch/arm64/include/asm/bug.h
> @@ -11,8 +11,14 @@
>  
>  #include <asm/asm-bug.h>
>  
> +#ifdef HAVE_BUG_FUNCTION
> +# define __BUG_FUNC	__func__
> +#else
> +# define __BUG_FUNC	NULL
> +#endif
> +
>  #define __BUG_FLAGS(flags)				\
> -	asm volatile (__stringify(ASM_BUG_FLAGS(flags)));
> +	asm volatile (__stringify(ASM_BUG_FLAGS(flags, %c0)) : : "i" (__BUG_FUNC));

Why is 'i' the right asm constraint to use here? It seems a bit odd to
use that for a pointer.

Will