linux-kernel - Re: [PATCH v3 26/26] objtool: Add STT

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Message-ID: <20200324221616.2tdljgyay37aiw2t@treble>
Date:   Tue, 24 Mar 2020 17:16:16 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org, x86@...nel.org,
        mhiramat@...nel.org, mbenes@...e.cz, brgerst@...il.com
Subject: Re: [PATCH v3 26/26] objtool: Add STT_NOTYPE noinstr validation

On Tue, Mar 24, 2020 at 04:31:39PM +0100, Peter Zijlstra wrote:
> Make sure to also check STT_NOTYPE symbols for noinstr violations.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  tools/objtool/check.c |   19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
> 
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -2563,7 +2563,7 @@ static int validate_symbol(struct objtoo
>  		return 1;
>  	}
>  
> -	if (sym->pfunc != sym || sym->alias != sym)
> +	if ((sym->type == STT_FUNC && sym->pfunc != sym) || sym->alias != sym)
>  		return 0;
>  
>  	insn = find_insn(file, sec, sym->offset);
> @@ -2610,6 +2610,23 @@ static int validate_section(struct objto
>  		warnings += validate_symbol(file, sec, func, &state);
>  	}
>  
> +	if (state.noinstr) {
> +		/*
> +		 * In vmlinux mode we will not run validate_unwind_hints() by
> +		 * default which means we'll not otherwise visit STT_NOTYPE
> +		 * symbols.
> +		 *
> +		 * In case of --duplicate mode, insn->visited will avoid actual
> +		 * duplicate work being done.
> +		 */
> +		list_for_each_entry(func, &sec->symbol_list, list) {
> +			if (func->type != STT_NOTYPE)
> +				continue;
> +
> +			warnings += validate_symbol(file, sec, func, &state);
> +		}
> +	}
> +

I guess this is ok, but is there a valid reason why we don't just call
validate_unwind_hints()?

It's also slightly concerning that validate_reachable_instructions()
isn't called, I'm not 100% convinced all the code will get checked.

-- 
Josh