Re: x86 - clang / objtool status

From: Peter Zijlstra
Date: Wed Jul 24 2019 - 03:47:48 EST

On Tue, Jul 23, 2019 at 09:43:24PM -0500, Josh Poimboeuf wrote:
> On Thu, Jul 18, 2019 at 10:40:09PM +0200, Thomas Gleixner wrote:
> > drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x86: redundant UACCESS disable
> Looking at this one, I think I agree with objtool.
> PeterZ, Linus, I know y'all discussed this code a few months ago.
> __copy_from_user() already does a CLAC in its error path. So isn't the
> user_access_end() redundant for the __copy_from_user() error path?

Hmm, is this a result of your c705cecc8431 ("objtool: Track original function across branches") ?

I'm thinking it might've 'overlooked' the CLAC in the error path before
(because it didn't have a related function) and now it sees it and
worries about it.

Then again, I'm not seeing this warning on my GCC builds; so what's