View Issue Details

Jump to NotesJump to History
IDProjectCategoryView StatusDate SubmittedLast Update
0008581Rocky-Linux-9kernelpublic2024-12-13 16:562025-01-06 15:47
ReporterAustin Kiekintveld Assigned ToLouis Abel  
PrioritynormalSeverityminorReproducibilityalways
Status assignedResolutionreopened 
Platformx86_64OSRocky LinuxOS VersionRocky 9.4
Summary0008581: perf: C++ symbol mangling support regressed/removed in Rocky 9.4
DescriptionHello! I ran into an issue when using perf from Rocky 9.4 (perf version 5.14.0-427.31.1.el9_4.x86_64) where perf does not properly demangle C++ symbol names. Prior to this I was using Rocky 9.3 (perf version 5.14.0-362.8.1.el9_3.x86_64) and the demangling support works fine there. I suspect there was a change in the build environment that caused this, as perf only builds in support for C++ demangling when binutils-devel is present. I also found what appears to be a similar bug in Ubuntu that details how the build dependencies work in their packages: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1396654.
Steps To Reproduce1. Put the contents of the below code snippet in a file called "example.cpp". The purpose of `foo` is to spin in a loop long enough to be sampled at least once by perf.
```
void foo() {
  volatile int x = 0;
  while (x++ != 10000000);
}

int main() {
  foo();
}
```
2. Run `c++ example.cpp` (On my machine that used c++ (GCC) 11.4.1 20231218 (Red Hat 11.4.1-3)).
2. Run `perf record ./a.out` with perf version 5.14.0-427.31.1.el9_4.x86_64.
3. Run `perf report`.
4. Observe that instead of seeing the demangled symbol name `foo` on the report, instead the mangled symbol name `_Z3foov` appears.
5. Repeat the above with perf version to 5.14.0-362.8.1.el9_3.x86_64.
6. Observe that the demangled name `foo` appears as expected.
TagsNo tags attached.

Activities

Louis Abel

Louis Abel

2024-12-15 00:12

administrator   ~0009109

Thank you for the report.

>I suspect there was a change in the build environment that caused this, as perf only builds in support for C++ demangling when binutils-devel is present.

You will find that binutils-devel is brought in as a dependency. https://git.rockylinux.org/staging/rpms/kernel/-/blob/r9/SPECS/kernel.spec?ref_type=heads#L674

In addition, you can review the changes of the kernel spec file here: https://git.rockylinux.org/staging/rpms/kernel/-/commits/r9/ and you can also view the CentOS Stream 9 kernels, the basis of Enterprise Linux kernels, here https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9 and here https://gitlab.com/redhat/centos-stream/rpms/kernel/-/tree/c9s

--

What you are reporting is reproducible in CentOS Stream 9. My recommendation is that you spin up RHEL 9.5 and CentOS Stream 9, reproduce your findings, and report it to https://issues.redhat.com

--

Please note that Rocky Linux 9.4 is no longer supported. You are recommended to update your systems to 9.5. https://wiki.rockylinux.org/rocky/version/#__tabbed_1_2

Closing.
Austin Kiekintveld

Austin Kiekintveld

2025-01-06 15:42

reporter   ~0009241

Reopening just in case anyone else wants to follow along, it looks like this issue was noticed upstream in Fedora 40 and is being fixed there, so the fix should flow down eventually here: https://bugzilla.redhat.com/show_bug.cgi?id=2256856
Austin Kiekintveld

Austin Kiekintveld

2025-01-06 15:47

reporter   ~0009242

Feel free to close again, sorry I couldn't find a way to add a note without reopening.

Issue History

Date Modified Username Field Change
2024-12-13 16:56 Austin Kiekintveld New Issue
2024-12-15 00:12 Louis Abel Assigned To => Louis Abel
2024-12-15 00:12 Louis Abel Status new => closed
2024-12-15 00:12 Louis Abel Resolution open => not fixable
2024-12-15 00:12 Louis Abel Note Added: 0009109
2025-01-06 15:42 Austin Kiekintveld Status closed => feedback
2025-01-06 15:42 Austin Kiekintveld Resolution not fixable => reopened
2025-01-06 15:42 Austin Kiekintveld Note Added: 0009241
2025-01-06 15:47 Austin Kiekintveld Note Added: 0009242
2025-01-06 15:47 Austin Kiekintveld Status feedback => assigned