linux-kernel - Re: [PATCH v5 12/15] objtool: Add support for more complex UACCESS control

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Message-ID: <20250116092832.GG8362@noisy.programming.kicks-ass.net>
Date: Thu, 16 Jan 2025 10:28:32 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Josh Poimboeuf <jpoimboe@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Julien Thierry <jthierry@...hat.com>,
	Miroslav Benes <mbenes@...e.cz>,
	Raphael Gault <raphael.gault@....com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Naveen N Rao <naveen@...nel.org>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	llvm@...ts.linux.dev
Subject: Re: [PATCH v5 12/15] objtool: Add support for more complex UACCESS
 control

On Wed, Jan 15, 2025 at 11:42:52PM +0100, Christophe Leroy wrote:

> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index 91436f4b3622..54625f09d831 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -2422,6 +2422,14 @@ static int __annotate_late(struct objtool_file *file, int type, struct instructi
>  		insn->dead_end = false;
>  		break;
>  
> +	case ANNOTYPE_UACCESS_BEGIN:
> +		insn->type = INSN_STAC;
> +		break;
> +
> +	case ANNOTYPE_UACCESS_END:
> +		insn->type = INSN_CLAC;
> +		break;

I would feel better if this had something like:

	if (insn->type != INSN_OTHER)
		WARN_INSN(insn, "over-riding instruction type: %d", insn->type);

Adding these annotations to control flow instruction would be bad etc.