linux-kernel - Re: objtool crashes on clang output (drivers/hwmon/pmbus/adm1275.o)

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Date:   Thu, 11 Jul 2019 23:29:32 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Jann Horn <jannh@...gle.com>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: objtool crashes on clang output (drivers/hwmon/pmbus/adm1275.o)

On Thu, Jul 11, 2019 at 11:05 PM 'Jann Horn' via Clang Built Linux
<clang-built-linux@...glegroups.com> wrote:
> I was playing around with building the kernel with LLVM a few months
> ago and used this local patch, but didn't get around to submitting
> upstream because I couldn't reproduce the problem for some reason. I
> think the warnings you're getting sound like what I saw back then:
> https://gist.github.com/thejh/0434662728afb95d72455bf30ece5817
>
> Quoting the commit message from that patch:
>
> ====
> With clang from git master, code can be generated where a function contains
> two indirect jump instructions that use the same switch table. To deal with
> this case and similar ones properly, convert the switch table parsing to
> use two passes:
> ====
>
> Does that sound like what you're seeing?

Yes, that is exactly right, and your patch seems to address the problem
for the cases I tried so far (will know more after a night of randconfig
testing).

Tested-by: Arnd Bergmann <arnd@...db.de>

      Arnd