linux-kernel - Re: ERROR: modpost: "__divsi3_table" [lib/lz4/lz4

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Message-ID: <CAK8P3a0wboR0evmNGL_VEsNNdLd9x_v8k3APH70t5gfu9D=A6w@mail.gmail.com>
Date:   Mon, 6 Dec 2021 12:01:47 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     kernel test robot <lkp@...el.com>
Cc:     Arnd Bergmann <arnd@...db.de>, kbuild-all@...ts.01.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        "open list:TENSILICA XTENSA PORT (xtensa)" 
        <linux-xtensa@...ux-xtensa.org>, Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>
Subject: Re: ERROR: modpost: "__divsi3_table" [lib/lz4/lz4_compress.ko] undefined!

On Mon, Dec 6, 2021 at 11:30 AM kernel test robot <lkp@...el.com> wrote:
> First bad commit (maybe != root cause):
> commit: 570a82b9c36f76a5959b5e47900629b0d413931d media: i2c: select V4L2_ASYNC where needed

Right, that is clearly unrelated.

> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
>
> All errors (new ones prefixed by >>, old ones prefixed by <<):
>
> >> ERROR: modpost: "__divsi3_table" [lib/lz4/lz4_compress.ko] undefined!

lz4 was recently updated, and apparently now does a 32-bit division. I
assume this
is the decompressor, as arch/mips had similar problems.

The possible fixes are:

- disable lz4 compressed kernels on xtensa
- change lz4 to not perform any division
- change the xtensa decompressor to include the divsi3 helper code from the
  main kernel, see fbf3bce45821 ("MIPS: boot/compressed/: add __ashldi3 to
  target for ZSTD compression")

        Arnd