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

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Message-ID: <202003261133.814BEE9F@keescook>
Date:   Thu, 26 Mar 2020 11:36:10 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        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>
Subject: Re: linux-next: Tree for Mar 18 (objtool)

On Thu, Mar 26, 2020 at 11:31:10AM -0500, Josh Poimboeuf wrote:
> On Wed, Mar 25, 2020 at 10:57:02PM -0700, Kees Cook wrote:
> > > In the meantime I can still change objtool to ignore unreachable UD2s if
> > > there aren't any better ideas.
> > 
> > It'll still need the objtool change for CONFIG_UBSAN_TRAP, though based on
> > the clang bug discussion, I'll probably _also_ be adding CONFIG_UBSAN_WARN
> > which won't have an unreachable (and won't bloat the kernel). Testing
> > still under way... it is possible that CONFIG_UBSAN_TRAP will go away
> > in the future, though. If that happens, should I also remove the change
> > at that time?
> 
> I'll go ahead and make the patch and post it soon.  It should be pretty
> trivial.  We can always revert it if CONFIG_UBSAN_TRAP goes away.

Awesome, thanks very much. After digging into the WARN-style option,
it seems that TRAP is unlikely to go away because it's Clang only;
GCC doesn't support the "minimal runtime" option. Yay compilers.

Anyway, I'll still get the WARN mode sent out. Thanks for looking at this;
can you CC me on the patch? I'm trying to get more familiar with objtool
so I don't have to bug you when objtool is angered by crazy stuff I do. ;)

-- 
Kees Cook