linux-kernel - Re: [PATCH] x86: select ARCH_WANT_FRAME_POINTERS again when UNWINDER_FRAME

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Date: Thu, 21 Mar 2024 00:30:33 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: x86@...nel.org
Cc: Josh Poimboeuf <jpoimboe@...nel.org>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, 
	Ingo Molnar <mingo@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: select ARCH_WANT_FRAME_POINTERS again when UNWINDER_FRAME_POINTER=y

Ping?


On Sun, Feb 4, 2024 at 9:20 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> It took me some time to understand the purpose of the tricky code at
> the end of arch/x86/Kconfig.debug.
>
> Without it, the following would be shown:
>
>   WARNING: unmet direct dependencies detected for FRAME_POINTER
>
> because commit 81d387190039 ("x86/kconfig: Consolidate unwinders into
> multiple choice selection") removed 'select ARCH_WANT_FRAME_POINTERS'.
>
> The correct and more straightforward approach should have been to move
> it where 'select FRAME_POINTER' is located.
>
> Several architectures properly handle the conditional selection of
> ARCH_WANT_FRAME_POINTERS. For example, 'config UNWINDER_FRAME_POINTER'
> in arch/arm/Kconfig.debug.
>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>
>  arch/x86/Kconfig.debug | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
> index c5d614d28a75..74777a97e394 100644
> --- a/arch/x86/Kconfig.debug
> +++ b/arch/x86/Kconfig.debug
> @@ -248,6 +248,7 @@ config UNWINDER_ORC
>
>  config UNWINDER_FRAME_POINTER
>         bool "Frame pointer unwinder"
> +       select ARCH_WANT_FRAME_POINTERS
>         select FRAME_POINTER
>         help
>           This option enables the frame pointer unwinder for unwinding kernel
> @@ -271,7 +272,3 @@ config UNWINDER_GUESS
>           overhead.
>
>  endchoice
> -
> -config FRAME_POINTER
> -       depends on !UNWINDER_ORC && !UNWINDER_GUESS
> -       bool
> --
> 2.40.1
>


-- 
Best Regards
Masahiro Yamada