linux-kernel - Re: [PATCH v2 06/12] powerpc: Drop unnecessary initializations in __copy_inst_from_kernel

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Message-ID: <285e1504-a25a-452d-958e-9db3963a02cb@csgroup.eu>
Date: Fri, 22 Aug 2025 12:01:57 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Nathan Chancellor <nathan@...nel.org>, linux-kernel@...r.kernel.org
Cc: Arnd Bergmann <arnd@...db.de>, Kees Cook <kees@...nel.org>,
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
 llvm@...ts.linux.dev, patches@...ts.linux.dev,
 Madhavan Srinivasan <maddy@...ux.ibm.com>,
 Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>,
 linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2 06/12] powerpc: Drop unnecessary initializations in
 __copy_inst_from_kernel_nofault()



Le 21/08/2025 à 23:15, Nathan Chancellor a écrit :
> Now that the minimum supported version of LLVM for building the kernel
> has been bumped to 15.0.0, the zero initializations of val and suffix
> added by commit 0d76914a4c99 ("powerpc/inst: Optimise
> copy_inst_from_kernel_nofault()") to avoid a bogus case of
> -Wuninitialized can be dropped because the preprocessor condition is
> always false.
> 
> Reviewed-by: Kees Cook <kees@...nel.org>
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>

Reviewed-by: Christophe Leroy <christophe.leroy@...roup.eu>

> ---
> Cc: Madhavan Srinivasan <maddy@...ux.ibm.com>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Nicholas Piggin <npiggin@...il.com>
> Cc: Christophe Leroy <christophe.leroy@...roup.eu>
> Cc: linuxppc-dev@...ts.ozlabs.org
> ---
>   arch/powerpc/include/asm/inst.h | 4 ----
>   1 file changed, 4 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/inst.h b/arch/powerpc/include/asm/inst.h
> index 684d3f453282..ffa82167c860 100644
> --- a/arch/powerpc/include/asm/inst.h
> +++ b/arch/powerpc/include/asm/inst.h
> @@ -143,10 +143,6 @@ static inline int __copy_inst_from_kernel_nofault(ppc_inst_t *inst, u32 *src)
>   {
>   	unsigned int val, suffix;
>   
> -/* See https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FClangBuiltLinux%2Flinux%2Fissues%2F1521&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C23038335822b4dbe2adc08dde0f7f50e%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638914077769007882%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=EfgIB7nIdCB2e3KWeEvsXKG%2B8LrK%2FjpUrA4RIeMcreo%3D&reserved=0 */
> -#if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 140000
> -	val = suffix = 0;
> -#endif
>   	__get_kernel_nofault(&val, src, u32, Efault);
>   	if (IS_ENABLED(CONFIG_PPC64) && get_op(val) == OP_PREFIX) {
>   		__get_kernel_nofault(&suffix, src + 1, u32, Efault);
>