Re: gpu: drm_fb_cma_helper.c:46: undefined reference to `drm_gem_fb_get_obj'

[Randy Dunlap]

On 10/26/21 11:21 AM, Thomas Zimmermann wrote:
> Hi
>
> Am 25.10.21 um 14:13 schrieb Naresh Kamboju:
> > Regression found on arm gcc-11 built with multi_v5_defconfig
> > Following build warnings / errors reported on linux next 20211025.
> >
> > metadata:
> >      git_describe: next-20211025
> >      git_repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next
> >      git_short_log: 9ae1fbdeabd3 (\"Add linux-next specific files for 20211025\")
> >      target_arch: arm
> >      toolchain: gcc-11
> >      config: multi_v5_defconfig
> >
> > build error :
> > --------------
> > arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: in
> > function `drm_fb_cma_get_gem_obj':
> > drivers/gpu/drm/drm_fb_cma_helper.c:46: undefined reference to
> > `drm_gem_fb_get_obj'
> > arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46:
> > undefined reference to `drm_gem_fb_get_obj'
> > arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46:
> > undefined reference to `drm_gem_fb_get_obj'
> > arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: in
> > function `drm_fb_cma_sync_non_coherent':
> > drivers/gpu/drm/drm_fb_cma_helper.c:133: undefined reference to
> > `drm_atomic_helper_damage_iter_init'
> > arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:135:
> > undefined reference to `drm_atomic_helper_damage_iter_next'
> > make[1]: *** [Makefile:1252: vmlinux] Error 1
> > make[1]: Target '__all' not remade because of errors.
> > make: *** [Makefile:226: __sub-make] Error 2
> >
> > Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>
> >
> >
> > build link:
> > -----------
> > https://builds.tuxbuild.com/1zzgFZBGjpQ5R0lawQFW9iJ39Hp/build.log
> >
> > build config:
> > -------------
> > https://builds.tuxbuild.com/1zzgFZBGjpQ5R0lawQFW9iJ39Hp/config
>
> Looking at this config, there is:
>
> CONFIG_DRM=y
> # CONFIG_DRM_DP_AUX_CHARDEV is not set
> # CONFIG_DRM_DEBUG_MM is not set
> # CONFIG_DRM_DEBUG_SELFTEST is not set
> CONFIG_DRM_KMS_HELPER=m
> # CONFIG_DRM_LOAD_EDID_FIRMWARE is not set
> # CONFIG_DRM_DP_CEC is not set
> CONFIG_DRM_GEM_CMA_HELPER=y
> CONFIG_DRM_KMS_CMA_HELPER=y
>
> GEM_CMA_HELPER depends on KMS_HELPER, but the latter is a module. That's probably the cause of the problem. Is it intentionally set this way?

The only drivers that select DRM_KMS_HELPER are both =m, so that's how
DRM_KMS_HELPER is set also.

Symbol: DRM_KMS_HELPER [=m]
Type : tristate
Defined at drivers/gpu/drm/Kconfig:82
Depends on: HAS_IOMEM [=y] && DRM [=y]
Selected by [m]:
- DRM_ATMEL_HLCDC [=m] && HAS_IOMEM [=y] && DRM [=y] && OF [=y] && COMMON_CLK [=y] && MFD_ATMEL_HLCDC [=y] && ARM [=y]
- DRM_ASPEED_GFX [=m] && HAS_IOMEM [=y] && DRM [=y] && OF [=y] && (COMPILE_TEST [=n] || ARCH_ASPEED [=y]) && MMU [=y]


I did the ARM cross-build and also see the linker error.
I didn't understand why -- and still don't, but here is a little
speculation:

In the past (e.g. 10 years ago), we have to move some .o files
in lib/ from lib-y to obj-y so that they would always be included
in the final object file and not cause their user/caller object
files to suffer from undefined references.
These happened because unused functions(?) in lib-y files are
stripped out of the final object files.
The same thing could be happening here (still just guessing).

Does that help any?  I dunno.

Adding Arnd to Cc: to see if he has any ideas...

> > # To install tuxmake on your system globally
> > # sudo pip3 install -U tuxmake
> > tuxmake --runtime podman --target-arch arm --toolchain gcc-11
> > --kconfig multi_v5_defconfig
> >
> > --
> > Linaro LKFT
> > https://lkft.linaro.org



--
~Randy