linux-kernel - Re: [PATCH] [RFC] Revert "bpf: Fix ORC unwinding in non-JIT BPF code"

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Date:   Mon, 8 Jul 2019 15:17:31 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Networking <netdev@...r.kernel.org>, bpf@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [RFC] Revert "bpf: Fix ORC unwinding in non-JIT BPF code"

On Mon, Jul 8, 2019 at 3:11 PM Josh Poimboeuf <jpoimboe@...hat.com> wrote:
>
> On Mon, Jul 08, 2019 at 02:45:23PM +0200, Arnd Bergmann wrote:
> > Apparently this was a bit premature, at least I still get this
> > warning with gcc-8.1:
> >
> > kernel/bpf/core.o: warning: objtool: ___bpf_prog_run()+0x44d2: sibling call from callable instruction with modified stack frame
> >
> > This reverts commit b22cf36c189f31883ad0238a69ccf82aa1f3b16b.
> >
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
>
> Yes, I have been working on a fix.
>
> The impact is that ORC unwinding is broken in this function for
> CONFIG_RETPOLINE=n.
>
> I don't think we want to revert this patch though, because that will
> broaden the impact to the CONFIG_RETPOLINE=y case.  Anyway I hope to
> have fixes soon.

Ok, sounds good. Thanks,

     Arnd