Bug 201551 - perf no longer resolves module symbols
Summary: perf no longer resolves module symbols
Status: NEW
Alias: None
Product: Tracing/Profiling
Classification: Unclassified
Component: Perf tool (show other bugs)
Hardware: All Linux
: P1 normal
Assignee: Arnaldo Carvalho de Melo
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2018-10-29 02:40 UTC by Souvik Banerjee
Modified: 2018-10-30 02:43 UTC (History)
1 user (show)

See Also:
Kernel Version: 4.19
Subsystem:
Regression: Yes
Bisected commit-id:

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Description Souvik Banerjee 2018-10-29 02:40:44 UTC 
I am using perf to record both kernel and user data. This worked with perf 4.18. With perf 4.19, I noticed that kernel module symbols were no longer being resolved. They appear as [unknown] in `perf report` and have a hexadecimal address. The modules I am interested in are ext4 and xfs, but I've noticed this happening for every module.


I bisected this bug to the following commit: 

commit edeb0c90df3581b821a764052d185df985f8b8dc
Author: Arnaldo Carvalho de Melo <acme@redhat.com>
Date:   Tue Oct 16 17:08:29 2018 -0300

    perf tools: Stop fallbacking to kallsyms for vdso symbols lookup
Comment 1 Arnaldo Carvalho de Melo 2018-10-29 18:02:56 UTC 
Can you try with 'perf script' to see if the backtraces are ok? I've reproduced the problem with 'perf report --stdio' and I'm debugging this now.
Comment 2 Souvik Banerjee 2018-10-30 02:43:21 UTC 
It looks like `perf script` is ok. It's able to resolve addresses to symbols+offsets.

The command I am using is:

perf record --all-kernel -g --call-graph dwarf [workload]
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