On Tue, Apr 28, 2020 at 09:25:51AM -0700, Sean Christopherson wrote: > On Tue, Apr 28, 2020 at 10:54:13AM -0500, Josh Poimboeuf wrote: > > On Tue, Apr 28, 2020 at 10:49:09AM -0500, Josh Poimboeuf wrote: > > > On Tue, Apr 28, 2020 at 05:25:52PM +0200, Peter Zijlstra wrote: > > > > On Tue, Apr 28, 2020 at 09:31:57AM -0500, Josh Poimboeuf wrote: > > > > > That's quite the monstrosity, and I still don't see the point. I > > > > > thought we decided to just disallow CFI changes in alternatives > > > > > anyway? > > > > > That can be done much simpler. > > > > > > > > Something like so then ? > > > > > > > > --- > > > > diff --git a/tools/objtool/check.c b/tools/objtool/check.c > > > > index 8443ec690051..d14d83e6edb0 100644 > > > > --- a/tools/objtool/check.c > > > > +++ b/tools/objtool/check.c > > > > @@ -940,6 +940,7 @@ static int handle_group_alt(struct objtool_file > > > > *file, > > > > > > > > last_new_insn = insn; > > > > > > > > + insn->alt_group = true; > > > > insn->ignore = orig_insn->ignore_alts; > > > > insn->func = orig_insn->func; > > > > > > > > @@ -2242,6 +2243,11 @@ static int handle_insn_ops(struct instruction > > > > *insn, struct insn_state *state) > > > > list_for_each_entry(op, &insn->stack_ops, list) { > > > > int res; > > > > > > > > + if (insn->alt_group) { > > > > + WARN_FUNC("alternative has CFI", insn->sec, > > > > insn->offset); > > > > + return 1; > > > > + } > > > > + > > > > > > ACK (separate patch) > > > > BTW, since most people don't know what CFI is, how about something like > > > > "unsupported stack change in alternatives code" > > Would it be accurate to print > > "unsupported CFI stack change in alternatives code"? > > to give the developer something more explicit to plug into their search > engine?
I don't have a strong opinion either way, though this warning is going to be documented in stack-validation.txt anyway right Peter? :-) -- Josh