perf test 42 failure on x86

From: Thomas Richter <tmricht@linux.ibm.com>
To: "linux-perf-use." <linux-perf-users@vger.kernel.org>,
	Arnaldo de Melo <acme@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>,
	Sumanth Korikkar <sumanthk@linux.ibm.com>
Subject: perf test 42 failure on x86
Date: Mon, 14 Dec 2020 17:30:46 +0100	[thread overview]
Message-ID: <18a7ad32-1da7-f744-411d-d08ff4dfa91a@linux.ibm.com> (raw)

Hi,

I just installed Fedora 33 and its latest kernel on my x86_64 virtual machine and
ran into a perf test issue:

[root@f33 ~]# uname -a
Linux f33 5.9.13-200.fc33.x86_64 #1 SMP Tue Dec 8 15:42:52 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
[root@f33 ~]#[root@f33 ~]# perf test -F 42
42: BPF filter                                            :
42.1: Basic BPF filtering                                 : Ok
42.2: BPF pinning                                         : Ok
42.3: BPF prologue generation                             : Ok
42.4: BPF relocation checker                              : FAILED!
[root@f33 ~]# 

The last test fails due to unexpected success:
[root@f33 ~]# perf test -v -F 42
42: BPF filter                                            :
42.1: Basic BPF filtering                                 :
--- start ---
....
libbpf: skip section(9) .eh_frame
libbpf: section(10) .rel.eh_frame, size 16, link 12, flags 0, type=9
libbpf: skip relo .rel.eh_frame(10) for section(9)
libbpf: section(11) .llvm_addrsig, size 5, link 12, flags 80000000, type=1879002115
libbpf: skip section(11) .llvm_addrsig
libbpf: section(12) .symtab, size 192, link 1, flags 0, type=2
libbpf: looking for externs among 8 symbols...
libbpf: collected 0 externs total
libbpf: maps in [bpf_relocation_test]: 1 maps in 16 bytes
libbpf: map 'my_table' (legacy): at sec_idx 5, offset 0.
libbpf: map 6 is "my_table"
libbpf: map '_bpf_rel.bss' (global data): at sec_idx 6, offset 0, flags 400.
libbpf: map 1 is "_bpf_rel.bss"
libbpf: collecting relocating info for: 'func=sys_write'
libbpf: relo for shdr 6, symb 7, value 0, type 1, bind 1, name 26 ('this_is_a_global_val'), insn 7
libbpf: found data map 1 (_bpf_rel.bss, sec 6, off 0) for insn 7
Success unexpectedly: libbpf error when dealing with relocation
---- end ----
BPF filter subtest 4: FAILED!
[root@f33 ~]#

There is success when failure is expected. Has anybody already started to look into this?
--

Thomas Richter, Dept 3252, IBM s390 Linux Development, Boeblingen, Germany
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