Working with third party fork of linux kernel
First let me say: this is not your problem. It is mine and Xilinx's problem.
The code is here: https://github.com/Xilinx/linux-xlnx
It is based on version 6.1.0 of the official kernel repo.
I'm debugging the displayport output of a Xilinx MPSOC development board (specifically the Avnet UltraZed EV Carrier Board).
The display port out works on boot up once in a while. There are very few messages in dmesg when it doesn't work.
The code I am debugging is custom and written by Xilinx engineers. It is written to be kernel modules, but was by default set to be compiled in.
I changed the code to [M] so I could delay loading it until after boot to help with timing and to make debugging the code easier. (also because I thought there might be a race condition that is handled by the time the system is booted)
Changing to [M]odule required MODULE_LICENSE to be added to three C source codes and around 60 EXPORT_SYMBOL directives to be added.
However, after doing all that the kernel won't compile and because I'm a kernel novice I don't know what's going on. Here are the compiler errors:
LD [M] drivers/gpu/drm/xlnx/zynqmp-dpsub.ko LD .tmp_vmlinux.kallsyms1 ld: Unexpected GOT/PLT entries detected! ld: Unexpected run-time procedure linkages detected! ld: ID map text too big or misaligned ld: drivers/gpu/drm/display/drm_dp_mst_topology.o: in function `drm_dp_mst_duplicate_state': /usr/src/linux/drivers/gpu/drm/display/drm_dp_mst_topology.c:4951: undefined reference to `__drm_atomic_helper_private_obj_duplicate_state' ld: drivers/gpu/drm/display/drm_dp_mst_topology.o: in function `drm_dp_delayed_destroy_work': /usr/src/linux/drivers/gpu/drm/display/drm_dp_mst_topology.c:4937: undefined reference to `drm_kms_helper_hotplug_event' ld: drivers/gpu/drm/display/drm_dp_mst_topology.o: in function `drm_dp_mst_up_req_work': /usr/src/linux/drivers/gpu/drm/display/drm_dp_mst_topology.c:3979: undefined reference to `drm_kms_helper_hotplug_event' ld: drivers/gpu/drm/display/drm_dp_mst_topology.o: in function `drm_dp_mst_link_probe_work': /usr/src/linux/drivers/gpu/drm/display/drm_dp_mst_topology.c:2689: undefined reference to `drm_kms_helper_hotplug_event' make[1]: *** [scripts/Makefile.vmlinux:34: vmlinux] Error 1 make: *** [Makefile:1236: vmlinux] Error 2
I have checked and those references are defined in actual headers and in c code. I verified the the .o files have at least the text of those references.
I'm hoping one of you will have mercy on a newb and help me out.
I'm using gcc:
ultrazed ~ # gcc -v Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/libexec/gcc/aarch64-unknown-linux-gnu/12/lto-wrapper Target: aarch64-unknown-linux-gnu Configured with: /var/tmp/portage/sys-devel/gcc-12.3.1_p20230526/work/gcc-12-20230526/configure --host=aarch64-unknown-linux-gnu --build=aarch64-unknown-linux-gnu --prefix=/usr --bindir=/usr/aarch64-unknown-linux-gnu/gcc-bin/12 --includedir=/usr/lib/gcc/aarch64-unknown-linux-gnu/12/include --datadir=/usr/share/gcc-data/aarch64-unknown-linux-gnu/12 --mandir=/usr/share/gcc-data/aarch64-unknown-linux-gnu/12/man --infodir=/usr/share/gcc-data/aarch64-unknown-linux-gnu/12/info --with-gxx-include-dir=/usr/lib/gcc/aarch64-unknown-linux-gnu/12/include/g++-v12 --with-python-dir=/share/gcc-data/aarch64-unknown-linux-gnu/12/python --enable-languages=c,c++,fortran --enable-obsolete --enable-secureplt --disable-werror --with-system-zlib --enable-nls --without-included-gettext --disable-libunwind-exceptions --enable-checking=release --with-bugurl=https://bugs.gentoo.org/ --with-pkgversion='Gentoo 12.3.1_p20230526 p2' --with-gcc-major-version-only --enable-libstdcxx-time --enable-lto --disable-libstdcxx-pch --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu --disable-multilib --disable-fixed-point --enable-libgomp --disable-libssp --disable-libada --disable-cet --disable-systemtap --disable-valgrind-annotations --disable-vtable-verify --disable-libvtv --without-zstd --without-isl --enable-default-pie --enable-default-ssp Thread model: posix Supported LTO compression algorithms: zlib gcc version 12.3.1 20230526 (Gentoo 12.3.1_p20230526 p2)
Answers
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So I'm learning more about Kconfig. I think I found an issue related to this.
The Xilinx GPU driver is using select DRM_KMS_HELPER in it's Kconfig, which is setting DRM_KMS_HELPER=m which causes the Makefile to exclude the very files that are needed.
# # Modesetting helpers # drm_kms_helper-y := drm_bridge_connector.o drm_crtc_helper.o \ drm_encoder_slave.o drm_flip_work.o \ drm_probe_helper.o \ drm_plane_helper.o drm_atomic_helper.o \ drm_kms_helper_common.o \ drm_simple_kms_helper.o drm_modeset_helper.o \ drm_gem_atomic_helper.o \ drm_gem_framebuffer_helper.o \ drm_atomic_state_helper.o drm_damage_helper.o \ drm_format_helper.o drm_self_refresh_helper.o drm_rect.o drm_kms_helper-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
I'm trying to figure out how to get DRM_KMS_HELPER=y but google hasn't shown me the light yet.
Can someone point me the right direction?
Nevermind I changed Makefile to assign this: drm_kms_helper-($CONFIG_DRM_KMS_HELPER)) and it still generated the same error messages.
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