Nvidia jetson 35.1 Linux 5.10.104 - build will fail if CONFIG_DEBUG_INFO_BTF=y

Robotics & Edge Computing Jetson & Embedded Systems Jetson AGX Orin
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1

I can build the kernel v5.10.104 which came along with jetson 35.1 development kit with the tegra default kernel config. However, if I customized the default config by adding CONFIG_DEBUG_INFO_BTF=y, the build would end up this error :

LD .tmp_vmlinux.kallsyms1
KSYMS .tmp_vmlinux.kallsyms1.S
AS .tmp_vmlinux.kallsyms1.S
LD .tmp_vmlinux.kallsyms2
KSYMS .tmp_vmlinux.kallsyms2.S
AS .tmp_vmlinux.kallsyms2.S
LD vmlinux
BTFIDS vmlinux
FAILED unresolved symbol netlink_sock

I did some initial analysis. if I enabled this same config for a upstream v5.10.104, the build can complete successfully. Further more, if I removed all the Nvidia patches from the v5.10.104 kernel which is delivered with Jetson 35.1, then the build could succeed as well.

So I believe this error is caused by some of these Nvidia patches which patched the kernel v5.10.104.

Hope Nvidia will investigate and fix this problem.

3

Hi,
Thanks for reporting it. We will try to reproduce the issue and do investigation.

And could you share the purpose of enabling CONFIG_DEBUG_INFO_BTF? We don’t have experience in enabling the config. Would be great if you can share more information.

4

Thanks for responding to this issue.
Basically BTF is bpf type format. After the kernel or kernel modules are built, a couple new sections named .BTF .BTF_ids will be created in each elf file. You can use objdump -h | grep BTF to see that and you can use objdump -s -j .BTF to see the contents. The reason that we need BTF is because the size of the trace type info is much smaller than the previous dwarf format.

7

Hi,
Please modify

kernel/kernel-5.10/net/netlink/af_netlink.c

to add this line:

...

+ BTF_ID(struct, netlink_sock)
#if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_PROC_FS)
BTF_ID_LIST(btf_netlink_sock_id)
BTF_ID(struct, netlink_sock)

...
1 Like
8

Hello Dane,

The code change you proposed fixed the problem. Thank you so much!

Johnny

10

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