iovisor/bcc

Unresolved symbols in profile co-re version

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#5,349 opened on Jul 3, 2025

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bughelp wanted

Description

Hello,

Why does the profile utility from the libbpf-tool return less detailed stack traces compared to the old version?

  • libbpf-tool (10 samples):
$ /opt/bcc/bin/profile -F49 -d --stack-storage-size=$((1024*1024)) -f -p 1087382 10

Could not open /usr/lib/x86_64-linux-gnu/libc.so.6 (deleted)
Could not open /usr/lib/x86_64-linux-gnu/libpthread.so.0 (deleted)
Could not open /usr/lib/x86_64-linux-gnu/libresolv.so.2 (deleted)
Could not open /usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2 (deleted)
Sampling at 49 Hertz of PID [1087382] by user + kernel for 10 secs.
    [unknown]
    [unknown]
    [unknown]
    [unknown]
    [unknown]
    [unknown]
    -                kubelet (1087382)
        2

    [unknown]
    [unknown]
    [unknown]
    [unknown]
    [unknown]
    -                kubelet (1087382)
...
  • python (154 samples):
$ python3 /opt/bcc/share/bcc/tools/profile -F49 -d --stack-storage-size=$((1024*1024)) -fa -p 1087382 10

Sampling at 49 Hertz of PID [1087382] by user + kernel stack for 10 secs.

    __switch_to+0x165 [kernel]
    __switch_to+0x165 [kernel]
    __schedule+0x2b7 [kernel]
    schedule+0x68 [kernel]
    futex_wait_queue+0x66 [kernel]
    futex_wait+0x151 [kernel]
    do_futex+0x178 [kernel]
    __x64_sys_futex+0x78 [kernel]
    do_syscall_64+0x59 [kernel]
    entry_SYSCALL_64_after_hwframe+0x73 [kernel]
    --
    [unknown] [kubelet]
    [unknown] [kubelet]
    [unknown] [kubelet]
    [unknown] [kubelet]
    [unknown] [kubelet]
    [unknown] [kubelet]
    [unknown] [kubelet]
    [unknown] [kubelet]
    [unknown] [kubelet]
    [unknown] [kubelet]
    [unknown] [kubelet]
    [unknown] [kubelet]
    [unknown] [kubelet]
    [unknown] [kubelet]
    -                kubelet (1087382)
        1
...

Why so huge difference between python based profile and libbpf based versions?

OS: Ubuntu Jammy 22.04 Linux: 6.2.0

Contributor guide

Tech stack
cpython
Domain
backendobservabilityperformance
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
BCCeBPFLinux profiling
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Investigate the symbol resolution code in libbpf tool's profile utility at /src/cc/libbpf tools/profile.c. Compare with the Python version's approach using BCC Python bindings to understand why symbols are unresolved. Look into the comment thread for possible clues about changes in library handling or kernel versions on Ubuntu 22.04 with Linux 6.2.0. The root cause may be missing debug info or incorrect symbol lookup in the new libbpf based version.
Unresolved symbols in profile co-re version · iovisor/bcc#5349 | Good First Issue