linux-kernel - Re: [PATCH v5 02/17] objtool: Better handle IRET

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Date:   Fri, 17 Apr 2020 14:25:53 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Miroslav Benes <mbenes@...e.cz>
Cc:     tglx@...utronix.de, jpoimboe@...hat.com,
        linux-kernel@...r.kernel.org, x86@...nel.org, mhiramat@...nel.org,
        jthierry@...hat.com, alexandre.chartre@...cle.com
Subject: Re: [PATCH v5 02/17] objtool: Better handle IRET

On Fri, Apr 17, 2020 at 01:29:32PM +0200, Miroslav Benes wrote:
> On Thu, 16 Apr 2020, Peter Zijlstra wrote:

> > +		case INSN_EXCEPTION_RETURN:
> > +			if (handle_insn_ops(insn, &state))
> > +				return 1;
> > +
> > +			/*
> > +			 * This handles x86's sync_core() case, where we use an
> > +			 * IRET to self. All 'normal' IRET instructions are in
> > +			 * STT_NOTYPE entry symbols.
> > +			 */
> > +			if (func)
> > +				break;
> > +
> > +			return 0;
> > +
> >  		case INSN_CONTEXT_SWITCH:
> >  			if (func && (!next_insn || !next_insn->hint)) {
> >  				WARN_FUNC("unsupported instruction in callable function",
> 
> It looks really simple.
> 
> Have you tried Julien's proposal about removing INSN_STACK altogether, 
> move the x86 to arch/x86/ and call handle_insn_ops() unconditionally, or 
> have you just postponed it? As I said, I think it could be better in the 
> long term, but the above looks good for now as well.

If you look at this other set I send yesterday:

  https://lkml.kernel.org/r/20200416150752.569029800@infradead.org

(also, sorry for not adding you to the Cc; also best look at the gitweb
version, the patches I send out are missing a hunk and lacking some
back-merges.. clearly I wasn't having a good day yesterday).

it has this intra_function_calls crud that needs explicit conditional
handle_insn_ops().