Re: [PATCH 3/5] objtool: Support Clang non-section symbols in ORC generation

[Josh Poimboeuf]

On Fri, Apr 03, 2020 at 10:58:20AM +0200, Miroslav Benes wrote:
> > +	if (insn_sec->sym) {
> > +		rela->sym = insn_sec->sym;
> > +		rela->addend = insn_off;
> > +	} else {
> > +		/*
> > +		 * The Clang assembler doesn't produce section symbols, so we
> > +		 * have to reference the function symbol instead:
> > +		 */
> > +		rela->sym = find_symbol_containing(insn_sec, insn_off);
> > +		if (!rela->sym) {
> > +			/*
> > +			 * Hack alert.  This happens when we need to reference
> > +			 * the NOP pad insn immediately after the function.
> > +			 */
> > +			rela->sym = find_symbol_containing(insn_sec,
> > +							   insn_off - 1);
> > +		}
> 
> I suppose there is always just one NOP pad insn, right? Anyway, it would 
> be better to get rid of it as you proposed.

There can actually be multiple NOPs because functions are aligned on a
16-byte boundary.  But the undefined ORC entry is always at the first
NOP because objtool merges duplicate entries.

-- 
Josh