linux-kernel - Re: [PATCH] parisc: use -fno-strict-aliasing for decompressor

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Message-ID: <5849978b-7330-1dae-0896-7ecbc6083d34@gmx.de>
Date:   Fri, 8 May 2020 23:40:37 +0200
From:   Helge Deller <deller@....de>
To:     Arnd Bergmann <arnd@...db.de>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>
Cc:     kbuild test robot <lkp@...el.com>, linux-parisc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] parisc: use -fno-strict-aliasing for decompressor

On 08.05.20 11:35, Arnd Bergmann wrote:
> An experimental patch series of mine reworks how warnings are processed
> in Kbuild. A side effect is a new warning about a harmless aliasing
> rule violation in an inline function:
>
> In file included from
> include/linux/rhashtable-types.h:15:0,
>                  from include/linux/ipc.h:7,
>                  from include/uapi/linux/sem.h:5,
>                  from include/linux/sem.h:5,
>                  from include/linux/sched.h:15,
>                  from include/linux/uaccess.h:6,
>                  from arch/parisc/boot/compressed/misc.c:7:
> include/linux/workqueue.h: In function 'work_static':
> include/linux/workqueue.h:212:2: warning: dereferencing
> type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
>   return *work_data_bits(work) & WORK_STRUCT_STATIC;
>
> Make the decompressor use -fno-strict-aliasing like the rest of
> the kernel for consistency, and to ensure this warning never makes
> it into a release.
>
> Reported-by: kbuild test robot <lkp@...el.com>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Acked-by: Helge Deller <deller@....de>

Arnd, will you take it through your trees when you push your experimental
patches, or do you want me to take it through the parisc tree?

Helge

> ---
>  arch/parisc/boot/compressed/Makefile | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/parisc/boot/compressed/Makefile b/arch/parisc/boot/compressed/Makefile
> index 1e5879c6a752..dff453687530 100644
> --- a/arch/parisc/boot/compressed/Makefile
> +++ b/arch/parisc/boot/compressed/Makefile
> @@ -16,6 +16,7 @@ targets += real2.S firmware.c
>
>  KBUILD_CFLAGS := -D__KERNEL__ -O2 -DBOOTLOADER
>  KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
> +KBUILD_CFLAGS += -fno-strict-aliasing
>  KBUILD_CFLAGS += $(cflags-y) -fno-delete-null-pointer-checks -fno-builtin-printf
>  KBUILD_CFLAGS += -fno-PIE -mno-space-regs -mdisable-fpregs -Os
>  ifndef CONFIG_64BIT
>