linux-kernel - Re: [PATCH] [v2] arm64/io: add constant-argument check

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Date: Tue, 4 Jun 2024 16:55:37 +0100
From: Will Deacon <will@...nel.org>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
	Baoquan He <bhe@...hat.com>,
	Kefeng Wang <wangkefeng.wang@...wei.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Mark Rutland <mark.rutland@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [v2] arm64/io: add constant-argument check

On Tue, May 28, 2024 at 05:37:11PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> In some configurations __const_iowrite32_copy() does not get inlined
> and gcc runs into the BUILD_BUG():
> 
> In file included from <command-line>:
> In function '__const_memcpy_toio_aligned32',
>     inlined from '__const_iowrite32_copy' at arch/arm64/include/asm/io.h:203:3,
>     inlined from '__const_iowrite32_copy' at arch/arm64/include/asm/io.h:199:20:
> include/linux/compiler_types.h:487:45: error: call to '__compiletime_assert_538' declared with attribute error: BUILD_BUG failed
>   487 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
>       |                                             ^
> include/linux/compiler_types.h:468:25: note: in definition of macro '__compiletime_assert'
>   468 |                         prefix ## suffix();                             \
>       |                         ^~~~~~
> include/linux/compiler_types.h:487:9: note: in expansion of macro '_compiletime_assert'
>   487 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
>       |         ^~~~~~~~~~~~~~~~~~~
> include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
>    39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
>       |                                     ^~~~~~~~~~~~~~~~~~
> include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG'
>    59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
>       |                     ^~~~~~~~~~~~~~~~
> arch/arm64/include/asm/io.h:193:17: note: in expansion of macro 'BUILD_BUG'
>   193 |                 BUILD_BUG();
>       |                 ^~~~~~~~~
> 
> Move the check for constant arguments into the inline function to ensure
> it is still constant if the compiler decides against inlining it.
> 
> Fixes: ead79118dae6 ("arm64/io: Provide a WC friendly __iowriteXX_copy()")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> v2:
>  - fix both 32-bit and 64-bit copies
>  - remove now-redundant macros
> ---
>  arch/arm64/include/asm/io.h | 24 +++++++++---------------
>  1 file changed, 9 insertions(+), 15 deletions(-)

I think this is superseded by Mark's diff in reply to v1, right?

https://lore.kernel.org/r/ZlcODqVXTDh6n0h-@J2N7QTR9R3

If so, Mark, please can you post that as a proper patch so that we can
get this fixed?

Cheers,

Will