linux-kernel - Re: [PATCH] objtool: Fix SLS checks

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Date:   Mon, 2 May 2022 13:09:46 -0700
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] objtool: Fix SLS checks

On Mon, May 02, 2022 at 10:01:53PM +0200, Peter Zijlstra wrote:
> On Mon, May 02, 2022 at 11:15:47AM -0700, Josh Poimboeuf wrote:
> > On Sat, Apr 30, 2022 at 12:50:02PM +0200, Peter Zijlstra wrote:
> > > 
> > > Fix the SLS validation; not having a next instruction is also a fail
> > > when the next instruction should be INSN_TRAP.
> > > 
> > > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > > ---
> > >  tools/objtool/check.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> > > index 3f6785415894..3354101ffe34 100644
> > > --- a/tools/objtool/check.c
> > > +++ b/tools/objtool/check.c
> > > @@ -3380,7 +3380,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
> > >  
> > >  		case INSN_RETURN:
> > >  			if (sls && !insn->retpoline_safe &&
> > > -			    next_insn && next_insn->type != INSN_TRAP) {
> > > +			    (!next_insn || (next_insn && next_insn->type != INSN_TRAP))) {
> > >  				WARN_FUNC("missing int3 after ret",
> > >  					  insn->sec, insn->offset);
> > >  			}
> > > @@ -3428,7 +3428,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
> > >  
> > >  		case INSN_JUMP_DYNAMIC:
> > >  			if (sls && !insn->retpoline_safe &&
> > > -			    next_insn && next_insn->type != INSN_TRAP) {
> > > +			    (!next_insn || (next_insn && next_insn->type != INSN_TRAP))) {
> > >  				WARN_FUNC("missing int3 after indirect jump",
> > >  					  insn->sec, insn->offset);
> > >  			}
> > 
> > My SLS rewrite in tip/objtool/core already fixed this, FWIW.  But this
> > could be good for -urgent.
> 
> Urgh, I should've looked at that indeed. This didn't find any new sites
> though; so I don't think this needs to go through urgent.

Well to be fair, it was easy to miss since I snuck it in with rewrite.

-- 
Josh