Re: [PATCH 13/13] objtool: Add CONFIG_OBJTOOL_WERROR

[Josh Poimboeuf]

On Sun, Mar 16, 2025 at 01:41:43AM +0100, Ingo Molnar wrote:
> > +config OBJTOOL_WERROR
> > +	bool "Upgrade objtool warnings to errors"
> > +	default y
> > +	depends on OBJTOOL && !COMPILE_TEST
> > +	help
> > +	  Fail the build on objtool warnings.
> 
> This is *way* too aggressive: objtool false positives are still common, 

I'm not sure what false positives you'd be referring to, these days the
vast majority of warnings I see are actual bugs.

> and an 'allmodconfig' should not fail the build IMO.

In fact it doesn't: allmodconfig sets COMPILE_TEST which prevents
OBJTOOL_WERROR.

I've had complaints from people who spent days debugging a broken kernel
only to discover it was related to an ignored objtool warning.

For non-bot builds which actually get run on a system, many of the
warnings should most definitely not be ignored.  Especially since
objtool is directly involved in some critical kernel infrastructure like
static calls/jumps and CPU mitigations.

All that said, I really don't know whether this default is too
aggressive.  But I do wonder if running it through a linux-next cycle
after the next merge window might help answer that question.

-- 
Josh