Re: [PATCH] objtool: prefer memory clobber & %= to volatile & __COUNTER__

[Josh Poimboeuf]

On Tue, Jan 18, 2022 at 11:22:59AM -0800, Josh Poimboeuf wrote:
> On Sun, Jan 16, 2022 at 02:32:59PM +0100, Borislav Petkov wrote:
> > so I like the local label and how it is more readable this way.
> > 
> > So, provided the memory clobber works (I wonder here if Josh has some
> > concrete failing cases which could be tested with your version) and
> > after the nitpicks have been addressed
> > 
> > Acked-by: Borislav Petkov <bp@xxxxxxx>
> 
> I think Nick was already able to recreate the original issue.  I'll run
> it through some more testing.
> 
> I wanted to make this change years ago, but couldn't because of legacy
> toolchains.  Here's hoping this is the final solution for those @#$%^
> macros.
> 
> Boris, thanks for looping Nick in, I should have done so to begin with.

Apparently this patch isn't going to work after all :-(

  https://lkml.kernel.org/r/202201190632.lhlaiCBk-lkp@xxxxxxxxx

With the two WARN_ONs in media_request_object_complete(), GCC apparently
considers the two reachable() asm statements as duplicates, and it
removes the second one.

-- 
Josh