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Date:   Mon, 25 Oct 2021 16:56:37 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Josh Poimboeuf <jpoimboe@redhat.com>
Cc:     Rob Landley <rob@landley.net>,
        Masahiro Yamada <masahiroy@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>
Subject: Re: Commit 0d989ac2c90b broke my x86-64 build.
Message-ID: <YXbFpfJwXJXABDup@hirez.programming.kicks-ass.net>
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On Mon, Oct 25, 2021 at 07:46:56AM -0700, Josh Poimboeuf wrote:
> On Mon, Oct 25, 2021 at 11:04:33AM +0200, Peter Zijlstra wrote:
> > On Sun, Oct 24, 2021 at 09:51:45PM -0500, Rob Landley wrote:
> > > > Unfortunately I think CONFIG_STACK_VALIDATION is no longer optional on
> > > > x86-64 these days, because of static calls and retpolines.
> > > 
> > > Does it need stack validation, or just a frame unwinder?
> > 
> > static_calls rely on objtool to find all "call __SCT*" instructions and
> > write their location in a .static_call_sites section.
> > 
> > The having of static calls is not optional on x86_64, and I have zero
> > interest in trying to work out what not having static_call() does, or to
> > maintain that option.
> 
> What I meant was, make STATIC_CALL_INLINE optional.  Then it would use
> out-of-line static calls which should just work, no?

Yeah, I suppose so... I think we're then missing a STACK_VALIDATION
dependency for KCOV. We rely on objtool to nop out those
__sanitizer_cov_* calls.

I had really hoped to just make objtool an unconditional part of x86_64.