linux-kernel - Re: [PATCH v2 5/9] objtool: Add verbose option for disassembling affected functions

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Message-ID: <20230413080527.GG4253@hirez.programming.kicks-ass.net>
Date:   Thu, 13 Apr 2023 10:05:27 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...nel.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Miroslav Benes <mbenes@...e.cz>
Subject: Re: [PATCH v2 5/9] objtool: Add verbose option for disassembling
 affected functions

On Wed, Apr 12, 2023 at 12:03:20PM -0700, Josh Poimboeuf wrote:
> When a warning is associated with a function, add an option to
> disassemble that function.
> 
> This makes it easier for reporters to submit the information needed to
> diagnose objtool warnings.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
> ---
>  tools/objtool/Documentation/objtool.txt |  5 ++
>  tools/objtool/builtin-check.c           |  5 ++
>  tools/objtool/check.c                   | 77 +++++++++++++++++++++++++
>  tools/objtool/include/objtool/builtin.h |  1 +
>  4 files changed, 88 insertions(+)
> 
> diff --git a/tools/objtool/Documentation/objtool.txt b/tools/objtool/Documentation/objtool.txt
> index 8e53fc6735ef..4d6c5acde7a3 100644
> --- a/tools/objtool/Documentation/objtool.txt
> +++ b/tools/objtool/Documentation/objtool.txt
> @@ -244,6 +244,11 @@ To achieve the validation, objtool enforces the following rules:
>  Objtool warnings
>  ----------------
>  
> +NOTE: When requesting help with an objtool warning, please recreate with
> +OBJTOOL_VERBOSE=1 (e.g., "make OBJTOOL_VERBOSE=1") and send the full
> +output, including any disassembly below the warning, to the objtool
> +maintainers.
> +
>  For asm files, if you're getting an error which doesn't make sense,
>  first make sure that the affected code follows the above rules.
>  
> diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
> index 7c175198d09f..5e21cfb7661d 100644
> --- a/tools/objtool/builtin-check.c
> +++ b/tools/objtool/builtin-check.c
> @@ -93,6 +93,7 @@ static const struct option check_options[] = {
>  	OPT_BOOLEAN(0, "no-unreachable", &opts.no_unreachable, "skip 'unreachable instruction' warnings"),
>  	OPT_BOOLEAN(0, "sec-address", &opts.sec_address, "print section addresses in warnings"),
>  	OPT_BOOLEAN(0, "stats", &opts.stats, "print statistics"),
> +	OPT_BOOLEAN('v', "verbose", &opts.verbose, "verbose warnings"),
>  
>  	OPT_END(),
>  };
> @@ -118,6 +119,10 @@ int cmd_parse_options(int argc, const char **argv, const char * const usage[])
>  		parse_options(envc, envv, check_options, env_usage, 0);
>  	}
>  
> +	env = getenv("OBJTOOL_VERBOSE");
> +	if (env && !strcmp(env, "1"))
> +		opts.verbose = true;
> +
>  	argc = parse_options(argc, argv, check_options, usage, 0);
>  	if (argc != 1)
>  		usage_with_options(usage, check_options);

No real objection; but I do feel obliged to point out that:
OBJTOOL_ARGS="-v" achieves much the same.