Messages in this thread | | | Date | Wed, 25 Mar 2020 09:39:15 -0500 | From | Josh Poimboeuf <> | Subject | Re: [PATCH v3 18/26] objtool: Fix !CFI insn_state propagation |
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On Wed, Mar 25, 2020 at 12:00:10AM +0100, Peter Zijlstra wrote: > On Tue, Mar 24, 2020 at 11:11:09PM +0100, Peter Zijlstra wrote: > > On Tue, Mar 24, 2020 at 04:40:06PM -0500, Josh Poimboeuf wrote: > > > On Tue, Mar 24, 2020 at 04:31:31PM +0100, Peter Zijlstra wrote: > > > > > > + if (!save_insn->visited) { > > > > + /* > > > > + * Oops, no state to copy yet. > > > > + * Hopefully we can reach this > > > > + * instruction from another branch > > > > + * after the save insn has been > > > > + * visited. > > > > + */ > > > > + if (insn == first) > > > > + return 0; // XXX > > > > > > Yeah, moving this code out to apply_insn_hint() seems like a nice idea, > > > but it wouldn't be worth it if it breaks this case. TBH I don't > > > remember if this check was for a real-world case. Might be worth > > > looking at... If this case doesn't exist in reality then we could just > > > remove this check altogether. > > > > I'll go run a bunch of builds with a print on it, that should tell us I > > suppose. > > I can a bunch of builds, including an allmodconfig with the below on top > and it 'works'. > > So I suppose we can remove this special case. > > --- > --- a/tools/objtool/check.c > +++ b/tools/objtool/check.c > @@ -2134,11 +2134,13 @@ static int apply_insn_hint(struct objtoo > * after the save insn has been > * visited. > */ > - if (insn == first) > - return 0; // XXX > > WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo", > sec, insn->offset); > + > + if (insn == first) > + return -1; > +
I think all the validate_branch() callers aren't prepared to handle a -1 return code.
We can just be lazy and remove this 'insn == first' check and consider it a non-fatal warning.
-- Josh
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