linux-kernel - Re: [PATCH] powerpc/ptdump: don't entirely rebuild kernel when selecting CONFIG_PPC_DEBUG

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Date:   Tue, 14 Jan 2020 16:01:10 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Christophe Leroy <christophe.leroy@....fr>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc/ptdump: don't entirely rebuild kernel when selecting CONFIG_PPC_DEBUG_WX

Christophe Leroy <christophe.leroy@....fr> writes:
> Selecting CONFIG_PPC_DEBUG_WX only impacts ptdump and pgtable_32/64
> init calls. Declaring related functions in asm/pgtable.h implies
> rebuilding almost everything.
>
> Move ptdump_check_wx() declaration in a new dedicated header file.

Can you put it in arch/powerpc/mm/mmu_decl.h ? That already exists for
things that are private to arch/powerpc/mm, which this function is
AFAICT.

cheers

>  arch/powerpc/include/asm/pgtable.h |  6 ------
>  arch/powerpc/include/asm/ptdump.h  | 15 +++++++++++++++
>  arch/powerpc/mm/pgtable_32.c       |  1 +
>  arch/powerpc/mm/pgtable_64.c       |  1 +
>  arch/powerpc/mm/ptdump/ptdump.c    |  1 +
>  5 files changed, 18 insertions(+), 6 deletions(-)
>  create mode 100644 arch/powerpc/include/asm/ptdump.h
>
> diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
> index 0e4ec8cc37b7..8cc543ed114c 100644
> --- a/arch/powerpc/include/asm/pgtable.h
> +++ b/arch/powerpc/include/asm/pgtable.h
> @@ -94,12 +94,6 @@ void mark_initmem_nx(void);
>  static inline void mark_initmem_nx(void) { }
>  #endif
>  
> -#ifdef CONFIG_PPC_DEBUG_WX
> -void ptdump_check_wx(void);
> -#else
> -static inline void ptdump_check_wx(void) { }
> -#endif
> -
>  /*
>   * When used, PTE_FRAG_NR is defined in subarch pgtable.h
>   * so we are sure it is included when arriving here.
> diff --git a/arch/powerpc/include/asm/ptdump.h b/arch/powerpc/include/asm/ptdump.h
> new file mode 100644
> index 000000000000..246b92c21729
> --- /dev/null
> +++ b/arch/powerpc/include/asm/ptdump.h
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_POWERPC_PTDUMP_H
> +#define _ASM_POWERPC_PTDUMP_H
> +
> +#ifndef __ASSEMBLY__
> +
> +#ifdef CONFIG_PPC_DEBUG_WX
> +void ptdump_check_wx(void);
> +#else
> +static inline void ptdump_check_wx(void) { }
> +#endif
> +
> +#endif /* __ASSEMBLY__ */
> +
> +#endif /* _ASM_POWERPC_PTDUMP_H */
> diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
> index 73b84166d06a..6c866f1b1eeb 100644
> --- a/arch/powerpc/mm/pgtable_32.c
> +++ b/arch/powerpc/mm/pgtable_32.c
> @@ -29,6 +29,7 @@
>  #include <asm/fixmap.h>
>  #include <asm/setup.h>
>  #include <asm/sections.h>
> +#include <asm/ptdump.h>
>  
>  #include <mm/mmu_decl.h>
>  
> diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
> index e78832dce7bb..3686cd887c2f 100644
> --- a/arch/powerpc/mm/pgtable_64.c
> +++ b/arch/powerpc/mm/pgtable_64.c
> @@ -45,6 +45,7 @@
>  #include <asm/sections.h>
>  #include <asm/firmware.h>
>  #include <asm/dma.h>
> +#include <asm/ptdump.h>
>  
>  #include <mm/mmu_decl.h>
>  
> diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
> index 2f9ddc29c535..d7b02bcd0691 100644
> --- a/arch/powerpc/mm/ptdump/ptdump.c
> +++ b/arch/powerpc/mm/ptdump/ptdump.c
> @@ -23,6 +23,7 @@
>  #include <linux/const.h>
>  #include <asm/page.h>
>  #include <asm/pgalloc.h>
> +#include <asm/ptdump.h>
>  
>  #include "ptdump.h"
>  
> -- 
> 2.13.3