linux-kernel - [BUG] perf top reports not being able to resolve kernel symbols

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Message-ID: <Z3bd2uCdo2EAMSnG@x1>
Date: Thu, 2 Jan 2025 15:41:30 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Ian Rogers <irogers@...gle.com>,
	James Clark <james.clark@...aro.org>, Jiri Olsa <jolsa@...nel.org>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org
Subject: [BUG] perf top reports not being able to resolve kernel symbols

While investigating a report by Christophe I stumbled on this:

⬢ [acme@...lbox perf-tools-next]$ git bisect bad
77b004f4c5c3c90b20ad61c5fa2ba7d494c1dba1 is the first bad commit
commit 77b004f4c5c3c90b20ad61c5fa2ba7d494c1dba1 (HEAD)
Author: Namhyung Kim <namhyung@...nel.org>
Date:   Thu Sep 12 15:42:08 2024 -0700
    perf symbol: Do not fixup end address of labels

⬢ [acme@...lbox perf-tools-next]$ git tag --contains 77b004f4c5c3c90b20ad61c5fa2ba7d494c1dba1 | grep ^v6
v6.13-rc1
v6.13-rc2
v6.13-rc3
v6.13-rc4
v6.13-rc5
⬢ [acme@...lbox perf-tools-next]$ 
⬢ [acme@...lbox perf-tools-next]$ git merge perf-tools/perf-tools
Already up to date.
⬢ [acme@...lbox perf-tools-next]$ git merge perf-tools/tmp.perf-tools
Already up to date.
⬢ [acme@...lbox perf-tools-next]$

Running just:

# perf top --stdio
   PerfTop:       0 irqs/sec  kernel: 0.0%  exact:  0.0% lost: 0/0 drop: 0/0 [cpu_atom/cycles/P],  (all, 28 CPUs)
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Warning:
A vmlinux file was not found.
Kernel samples will not be resolved.
^C^C^C^Z
[1]+  Stopped                 perf top --stdio
root@...ber:/home/acme/git/pahole# 

But kernel addresses are being used and there is a matching vmlinux:

# pahole --running_kernel_vmlinux
/lib/modules/6.13.0-rc2/build/vmlinux
#

root@...ber:/home/acme/git/pahole# file /lib/modules/6.13.0-rc2/build/vmlinux
/lib/modules/6.13.0-rc2/build/vmlinux: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, BuildID[sha1]=d6f220b80bb50b35238aec50ed10f98df58849c0, with debug_info, not stripped
root@...ber:/home/acme/git/pahole# perf buildid-list --kernel
d6f220b80bb50b35238aec50ed10f98df58849c0
root@...ber:/home/acme/git/pahole# 
root@...ber:/home/acme/git/pahole# perf buildid-list -h --kernel

 Usage: perf buildid-list [<options>]

    -k, --kernel          Show current kernel build id

root@...ber:/home/acme/git/pahole#

I'm trying to figure this out now.

- Arnaldo