0008581: perf: C++ symbol mangling support regressed/removed in Rocky 9.4 - Rocky Linux BugTracker

ID	Project	Category	View Status	Date Submitted	Last Update

0008581	Rocky-Linux-9	kernel	public	2024-12-13 16:56	2024-12-15 00:12

Reporter	Austin Kiekintveld	Assigned To	Louis Abel
Priority	normal	Severity	minor	Reproducibility	always
Status	closed	Resolution	not fixable
Platform	x86_64	OS	Rocky Linux	OS Version	Rocky 9.4

Summary	0008581: perf: C++ symbol mangling support regressed/removed in Rocky 9.4
Description	Hello! 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 Reproduce	1. 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.
Tags	No tags attached.

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.

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