linux-kernel - Re: [PATCH v4 02/13] objtool: Factor out CFI hints

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Message-ID: <20200325194100.GL20713@hirez.programming.kicks-ass.net>
Date:   Wed, 25 Mar 2020 20:41:00 +0100
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
Subject: Re: [PATCH v4 02/13] objtool: Factor out CFI hints

On Wed, Mar 25, 2020 at 07:26:06PM +0100, Miroslav Benes wrote:
> On Wed, 25 Mar 2020, Peter Zijlstra wrote:
> 
> > Move the application of CFI hints into it's own function.
> > No functional changes intended.
> > 
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>
> > ---
> >  tools/objtool/check.c |   67 ++++++++++++++++++++++++++++----------------------
> >  1 file changed, 38 insertions(+), 29 deletions(-)
> > 
> > --- a/tools/objtool/check.c
> > +++ b/tools/objtool/check.c
> > @@ -2033,6 +2033,41 @@ static int validate_return(struct symbol
> >  	return 0;
> >  }
> >  
> > +static int apply_insn_hint(struct objtool_file *file, struct section *sec,
> > +			   struct symbol *func, struct instruction *insn,
> > +			   struct insn_state *state)
> > +{
> > +	if (insn->restore) {
> > +		struct instruction *save_insn, *i;
> > +
> > +		i = insn;
> > +		save_insn = NULL;
> > +		sym_for_each_insn_continue_reverse(file, func, i) {
> > +			if (i->save) {
> > +				save_insn = i;
> > +				break;
> > +			}
> > +		}
> > +
> > +		if (!save_insn) {
> > +			WARN_FUNC("no corresponding CFI save for CFI restore",
> > +				  sec, insn->offset);
> > +			return 1;
> > +		}
> > +
> > +		if (!save_insn->visited) {
> > +			WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
> > +				  sec, insn->offset);
> > +			return 1;
> > +		}
> > +
> > +		insn->state = save_insn->state;
> > +	}
> > +
> > +	state = insn->state;
> 
> It does not matter, because it will change later again, but there should 
> be
> 
> *state = insn->state;
> 
> here, right?

Argh, yes.  Let me go edit the patches.