linux-kernel - Re: [PATCH 13/13] objtool: Add CONFIG_OBJTOOL

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Message-ID: <Z9YeR20Vua8GQIiW@gmail.com>
Date: Sun, 16 Mar 2025 01:41:43 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Brendan Jackman <jackmanb@...gle.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 13/13] objtool: Add CONFIG_OBJTOOL_WERROR


* Josh Poimboeuf <jpoimboe@...nel.org> wrote:

> Objtool warnings can be indicative of crashes, broken live patching, or
> even boot failures.  Ignoring them is not recommended.
> 
> Add CONFIG_OBJTOOL_WERROR to upgrade objtool warnings to errors by
> enabling the objtool --Werror option.  Also set --backtrace to print the
> branches leading up to the warning, which can help considerably when
> debugging certain warnings.
> 
> To avoid breaking bots too badly for now, make it the default for real
> world builds only (!COMPILE_TEST).
> 
> Co-developed-by: Brendan Jackman <jackmanb@...gle.com>
> Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
> ---
>  lib/Kconfig.debug    | 12 ++++++++++++
>  scripts/Makefile.lib |  1 +
>  2 files changed, 13 insertions(+)
> 
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 35796c290ca3..bbfb9d575f97 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -545,6 +545,18 @@ config FRAME_POINTER
>  config OBJTOOL
>  	bool
>  
> +config OBJTOOL_WERROR
> +	bool "Upgrade objtool warnings to errors"
> +	default y
> +	depends on OBJTOOL && !COMPILE_TEST
> +	help
> +	  Fail the build on objtool warnings.

This is *way* too aggressive: objtool false positives are still common, 
and an 'allmodconfig' should not fail the build IMO.

Thanks,

	Ingo