next-20241028: gcc-8-defconfig : ERROR: modpost: "__aeabi_uldivmod" [drivers/media/dvb-frontends/cxd2841er.ko] undefined!

next-20241028: gcc-8-defconfig : ERROR: modpost: "__aeabi_uldivmod" [drivers/media/dvb-frontends/cxd2841er.ko] undefined!

[Naresh Kamboju]

The arm builds failed with gcc-8 on Linux next-20241028
and builds pass with gcc-13.

First seen on Linux next-20241028 tag.
  Good: next-20241025
  Bad:  next-20241028

arm:
  build:
    * gcc-8-imx_v6_v7_defconfig
    * gcc-8-defconfig
    * gcc-8-omap2plus_defconfig
    * gcc-8-davinci_all_defconfig

Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>

Build log:
---------
ERROR: modpost: "__aeabi_uldivmod"
[drivers/media/dvb-frontends/cxd2841er.ko] undefined!
make[3]: *** [/builds/linux/scripts/Makefile.modpost:145:
Module.symvers] Error 1
make[3]: Target '__modpost' not remade because of errors.

Build image:
-----------
- https://storage.tuxsuite.com/public/linaro/lkft/builds/2o9bKKvq45ZlybLVnQ1Bl0hEVA5/
- https://storage.tuxsuite.com/public/linaro/lkft/builds/2o9bKKvq45ZlybLVnQ1Bl0hEVA5/build.log

Steps to reproduce:
------------
   - tuxmake --runtime podman --target-arch arm --toolchain gcc-8
--kconfig defconfig

metadata:
----
  git describe: next-20241030
  git repo: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
  git sha: 86e3904dcdc7e70e3257fc1de294a1b75f3d8d04
  kernel config:
https://storage.tuxsuite.com/public/linaro/lkft/builds/2o9bKKvq45ZlybLVnQ1Bl0hEVA5/config
  build url: https://storage.tuxsuite.com/public/linaro/lkft/builds/2o9bKKvq45ZlybLVnQ1Bl0hEVA5/
  toolchain: gcc-8
  config: defconfig
  arch: arm

--
Linaro LKFT
https://lkft.linaro.org

Re: next-20241028: gcc-8-defconfig : ERROR: modpost: "__aeabi_uldivmod" [drivers/media/dvb-frontends/cxd2841er.ko] undefined!

[Dan Carpenter]

Is it possible to tie this to a commit?

This is a u64 variable getting divided somewhere or maybe the divisor is a u64?
But there haven't been any recent changes to the driver so probably the change
happened in a header file?  I looked the differences between the preprocessed
.i files from before and after and nothing jumped out at me.

I don't have a copy of gcc-8...

regards,
dan carpenter

On Wed, Oct 30, 2024 at 06:53:01PM +0530, Naresh Kamboju wrote:
> The arm builds failed with gcc-8 on Linux next-20241028
> and builds pass with gcc-13.
> 
> First seen on Linux next-20241028 tag.
>   Good: next-20241025
>   Bad:  next-20241028
> 
> arm:
>   build:
>     * gcc-8-imx_v6_v7_defconfig
>     * gcc-8-defconfig
>     * gcc-8-omap2plus_defconfig
>     * gcc-8-davinci_all_defconfig
> 
> Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
> 
> Build log:
> ---------
> ERROR: modpost: "__aeabi_uldivmod"
> [drivers/media/dvb-frontends/cxd2841er.ko] undefined!
> make[3]: *** [/builds/linux/scripts/Makefile.modpost:145:
> Module.symvers] Error 1
> make[3]: Target '__modpost' not remade because of errors.
> 
> Build image:
> -----------
> - https://storage.tuxsuite.com/public/linaro/lkft/builds/2o9bKKvq45ZlybLVnQ1Bl0hEVA5/
> - https://storage.tuxsuite.com/public/linaro/lkft/builds/2o9bKKvq45ZlybLVnQ1Bl0hEVA5/build.log
> 
> Steps to reproduce:
> ------------
>    - tuxmake --runtime podman --target-arch arm --toolchain gcc-8
> --kconfig defconfig
> 
> metadata:
> ----
>   git describe: next-20241030
>   git repo: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
>   git sha: 86e3904dcdc7e70e3257fc1de294a1b75f3d8d04
>   kernel config:
> https://storage.tuxsuite.com/public/linaro/lkft/builds/2o9bKKvq45ZlybLVnQ1Bl0hEVA5/config
>   build url: https://storage.tuxsuite.com/public/linaro/lkft/builds/2o9bKKvq45ZlybLVnQ1Bl0hEVA5/
>   toolchain: gcc-8
>   config: defconfig
>   arch: arm
> 
> --
> Linaro LKFT
> https://lkft.linaro.org

Re: next-20241028: gcc-8-defconfig : ERROR: modpost: "__aeabi_uldivmod" [drivers/media/dvb-frontends/cxd2841er.ko] undefined!

[Dan Carpenter]

Arnd, can you take a look at this?

This patch fixes the build, but obviously breaks the kernel so don't apply it.
I don't know how do_div() works or what changed though.  All this code looks
ancient.

regards,
dan carpenter

diff --git a/drivers/media/dvb-frontends/cxd2841er.c b/drivers/media/dvb-frontends/cxd2841er.c
index d925ca24183b..e3131f5c6708 100644
--- a/drivers/media/dvb-frontends/cxd2841er.c
+++ b/drivers/media/dvb-frontends/cxd2841er.c
@@ -314,7 +314,7 @@ static u32 cxd2841er_calc_iffreq_xtal(enum cxd2841er_xtal xtal, u32 ifhz)
 	u64 tmp;
 
 	tmp = (u64) ifhz * 16777216;
-	do_div(tmp, ((xtal == SONY_XTAL_24000) ? 48000000 : 41000000));
+//	do_div(tmp, ((xtal == SONY_XTAL_24000) ? 48000000 : 41000000));
 
 	return (u32) tmp;
 }

Re: next-20241028: gcc-8-defconfig : ERROR: modpost: "__aeabi_uldivmod" [drivers/media/dvb-frontends/cxd2841er.ko] undefined!

[Arnd Bergmann]

On Thu, Oct 31, 2024, at 12:27, Dan Carpenter wrote:
> Arnd, can you take a look at this?
>
> diff --git a/drivers/media/dvb-frontends/cxd2841er.c 
> b/drivers/media/dvb-frontends/cxd2841er.c
> index d925ca24183b..e3131f5c6708 100644
> --- a/drivers/media/dvb-frontends/cxd2841er.c
> +++ b/drivers/media/dvb-frontends/cxd2841er.c
> @@ -314,7 +314,7 @@ static u32 cxd2841er_calc_iffreq_xtal(enum 
> cxd2841er_xtal xtal, u32 ifhz)
>  	u64 tmp;
> 
>  	tmp = (u64) ifhz * 16777216;
> -	do_div(tmp, ((xtal == SONY_XTAL_24000) ? 48000000 : 41000000));
> +//	do_div(tmp, ((xtal == SONY_XTAL_24000) ? 48000000 : 41000000));
> 
>  	return (u32) tmp;
>  }

Not sure what is happening exactly, probably something where
__builtin_constant_p() is inconclusive. The patch below seems
to address it without impairing readability.

      Arnd

--- a/drivers/media/dvb-frontends/cxd2841er.c
+++ b/drivers/media/dvb-frontends/cxd2841er.c
@@ -311,12 +311,8 @@ static int cxd2841er_set_reg_bits(struct cxd2841er_priv *priv,
 
 static u32 cxd2841er_calc_iffreq_xtal(enum cxd2841er_xtal xtal, u32 ifhz)
 {
-       u64 tmp;
-
-       tmp = (u64) ifhz * 16777216;
-       do_div(tmp, ((xtal == SONY_XTAL_24000) ? 48000000 : 41000000));
-
-       return (u32) tmp;
+       return div_u64(ifhz * 16777216ull,
+                       (xtal == SONY_XTAL_24000) ? 48000000 : 41000000);
 }
 
 static u32 cxd2841er_calc_iffreq(u32 ifhz)