linux-kernel - Re: linux-next: Tree for Mar 18 (objtool)

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Date:   Thu, 19 Mar 2020 12:45:50 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: linux-next: Tree for Mar 18 (objtool)

On Thu, Mar 19, 2020 at 12:40:32PM -0500, Josh Poimboeuf wrote:
> On Thu, Mar 19, 2020 at 12:33:31PM -0500, Josh Poimboeuf wrote:
> > On Thu, Mar 19, 2020 at 12:31:05PM -0500, Josh Poimboeuf wrote:
> > > ... except the __builtin_trap() UD2 seems to be coming *after* the BUG
> > > UD2.  Could it be the BUG UD2 itself which is convincing UBSAN to add
> > > the __builtin_trap()?
> > 
> > Actually I suspect it's the __builtin_unreachable() annotation which is
> > making UBSAN add the __builtin_trap()...  because I don't see any double
> > UD2s for WARNs.
> 
> Scratch that theory, removing the __builtin_unreachable() from
> unreachable() doesn't make the double UD2 go away.

Actually, removing __builtin_unreachable() *does* make the extra UD2 go
away -- I forgot I had some silly debug code.

Not sure what the "fix" should be though.

-- 
Josh