linux-kernel - Re: [PATCH v2 02/16] powerpc: override __ALIGN() and __ALIGN

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Date:   Mon, 5 Sep 2022 13:03:21 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Sathvika Vasireddy <sv@...ux.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, jpoimboe@...hat.com,
        linux-kernel@...r.kernel.org, aik@...abs.ru, mpe@...erman.id.au,
        mingo@...hat.com, christophe.leroy@...roup.eu, rostedt@...dmis.org,
        mbenes@...e.cz, npiggin@...il.com, chenzhongjin@...wei.com,
        naveen.n.rao@...ux.vnet.ibm.com
Subject: Re: [PATCH v2 02/16] powerpc: override __ALIGN() and __ALIGN_STR()
 macros

On Mon, Aug 29, 2022 at 11:22:09AM +0530, Sathvika Vasireddy wrote:
> Powerpc instructions must be word-aligned. Currently,
> there is an alignment of 16 bytes (by default), and it is
> much more than what is required for powerpc (4 bytes).
> 
> The default expansion of __ALIGN() macro is:
> #define __ALIGN       .align 4,0x90
> 
> Since Powerpc Linux does not require a 16 byte alignment,
> override __ALIGN() and __ALIGN_STR() macros to use required
> 4 byte alignment.
> 
> Signed-off-by: Sathvika Vasireddy <sv@...ux.ibm.com>
> ---
>  arch/powerpc/include/asm/linkage.h | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/linkage.h b/arch/powerpc/include/asm/linkage.h
> index b71b9582e754..8df88fe61438 100644
> --- a/arch/powerpc/include/asm/linkage.h
> +++ b/arch/powerpc/include/asm/linkage.h
> @@ -2,8 +2,12 @@
>  #ifndef _ASM_POWERPC_LINKAGE_H
>  #define _ASM_POWERPC_LINKAGE_H
>  
> +#include <linux/stringify.h>
>  #include <asm/types.h>
>  
> +#define __ALIGN			.align 2
> +#define __ALIGN_STR		__stringify(__ALIGN)


Related thread:

  https://lkml.kernel.org/r/YxXJswK9QjhCGmPN@hirez.programming.kicks-ass.net