From: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
To: Hari Bathini <hbathini@linux.ibm.com>
Cc: bpf@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
linux-kselftest@vger.kernel.org, Shuah Khan <shuah@kernel.org>
Subject: Re: [PATCH] selftests/bpf: test accounting of tail calls when prog is NULL
Date: Sat, 21 Feb 2026 09:18:43 +0530 [thread overview]
Message-ID: <112376c3-7cae-471b-b425-98ae17284c2b@linux.ibm.com> (raw)
In-Reply-To: <0cbbc97a-ebb8-41d8-ac88-2a954279d10c@linux.ibm.com>
On 16/02/26 8:31 pm, Venkat Rao Bagalkote wrote:
>
> On 16/02/26 4:41 pm, Hari Bathini wrote:
>>
>>
>> On 16/02/26 4:38 pm, Venkat wrote:
>>> Hello Hari,
>>>
>>> With this patch, tailcalls selftest is failing.
>>>
>>> # ./test_progs -t tailcalls
>>> tester_init:PASS:tester_log_buf 0 nsec
>>> process_subtest:PASS:obj_open_mem 0 nsec
>>> process_subtest:PASS:specs_alloc 0 nsec
>>> #448/1 tailcalls/tailcall_1:OK
>>> #448/2 tailcalls/tailcall_2:OK
>>> test_tailcall_count:PASS:tailcall 0 nsec
>>> test_tailcall_count:PASS:tailcall retval 0 nsec
>>> test_tailcall_count:PASS:tailcall count 0 nsec
>>> test_tailcall_count:FAIL:tailcall count unexpected tailcall count:
>>> actual 32 != expected 33
>>> test_tailcall_count:PASS:tailcall 0 nsec
>>> test_tailcall_count:PASS:tailcall retval 0 nsec
>>> #448/3 tailcalls/tailcall_3:FAIL
>>> #448/4 tailcalls/tailcall_4:OK
>>> #448/5 tailcalls/tailcall_5:OK
>>> #448/6 tailcalls/tailcall_6:OK
>>> #448/7 tailcalls/tailcall_bpf2bpf_1:OK
>>> #448/8 tailcalls/tailcall_bpf2bpf_2:OK
>>> #448/9 tailcalls/tailcall_bpf2bpf_3:OK
>>> #448/10 tailcalls/tailcall_bpf2bpf_4:OK
>>> #448/11 tailcalls/tailcall_bpf2bpf_5:OK
>>> #448/12 tailcalls/tailcall_bpf2bpf_6:OK
>>> #448/13 tailcalls/tailcall_bpf2bpf_fentry:OK
>>> #448/14 tailcalls/tailcall_bpf2bpf_fexit:OK
>>> #448/15 tailcalls/tailcall_bpf2bpf_fentry_fexit:OK
>>> #448/16 tailcalls/tailcall_bpf2bpf_fentry_entry:OK
>>> #448/17 tailcalls/tailcall_poke:OK
>>> #448/18 tailcalls/tailcall_bpf2bpf_hierarchy_1:OK
>>> #448/19 tailcalls/tailcall_bpf2bpf_hierarchy_fentry:OK
>>> #448/20 tailcalls/tailcall_bpf2bpf_hierarchy_fexit:OK
>>> #448/21 tailcalls/tailcall_bpf2bpf_hierarchy_fentry_fexit:OK
>>> #448/22 tailcalls/tailcall_bpf2bpf_hierarchy_fentry_entry:OK
>>> #448/23 tailcalls/tailcall_bpf2bpf_hierarchy_2:OK
>>> #448/24 tailcalls/tailcall_bpf2bpf_hierarchy_3:OK
>>> #448/25 tailcalls/tailcall_freplace:OK
>>> #448/26 tailcalls/tailcall_bpf2bpf_freplace:OK
>>> #448/27 tailcalls/tailcall_failure:OK
>>> #448/28 tailcalls/reject_tail_call_spin_lock:OK
>>> #448/29 tailcalls/reject_tail_call_rcu_lock:OK
>>> #448/30 tailcalls/reject_tail_call_preempt_lock:OK
>>> #448/31 tailcalls/reject_tail_call_ref:OK
>>> #448/32 tailcalls/tailcall_sleepable:OK
>>> #448 tailcalls:FAIL
>>>
>>> All error logs:
>>> tester_init:PASS:tester_log_buf 0 nsec
>>> process_subtest:PASS:obj_open_mem 0 nsec
>>> process_subtest:PASS:specs_alloc 0 nsec
>>> test_tailcall_count:PASS:tailcall 0 nsec
>>> test_tailcall_count:PASS:tailcall retval 0 nsec
>>> test_tailcall_count:PASS:tailcall count 0 nsec
>>> test_tailcall_count:FAIL:tailcall count unexpected tailcall count:
>>> actual 32 != expected 33
>>> test_tailcall_count:PASS:tailcall 0 nsec
>>> test_tailcall_count:PASS:tailcall retval 0 nsec
>>> #448/3 tailcalls/tailcall_3:FAIL
>>> #448 tailcalls:FAIL
>>> Summary: 0/31 PASSED, 0 SKIPPED, 1 FAILED
>>>
>>> Regards,
>>> Venkat.
>>>
>>>> On 16 Feb 2026, at 2:38 PM, Hari Bathini <hbathini@linux.ibm.com>
>>>> wrote:
>>>>
>>>> Test whether tail call count is incorrectly accounted for, when the
>>>> tail call fails due to a missing BPF program.
>>>>
>>>> Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
>>>> ---
>>>>
>>>> - powerpc64 BPF JIT has been incorrectly accounting for tailcall count
>>>> even when BPF program to tailcall into is missing. A simple change
>>>> to one of the tailcall selftests could have flagged it earlier.
>>>>
>>
>>>> https://lore.kernel.org/all/20260216065639.1750181-2-hbathini@linux.ibm.com/
>>>>
>
Tested by applying V2 version of above patch series, and tested this
patch, and the test passes.
Logs:
./test_progs -t tailcalls
#448/1 tailcalls/tailcall_1:OK
#448/2 tailcalls/tailcall_2:OK
#448/3 tailcalls/tailcall_3:OK
#448/4 tailcalls/tailcall_4:OK
#448/5 tailcalls/tailcall_5:OK
#448/6 tailcalls/tailcall_6:OK
#448/7 tailcalls/tailcall_bpf2bpf_1:OK
#448/8 tailcalls/tailcall_bpf2bpf_2:OK
#448/9 tailcalls/tailcall_bpf2bpf_3:OK
#448/10 tailcalls/tailcall_bpf2bpf_4:OK
#448/11 tailcalls/tailcall_bpf2bpf_5:OK
#448/12 tailcalls/tailcall_bpf2bpf_6:OK
#448/13 tailcalls/tailcall_bpf2bpf_fentry:OK
#448/14 tailcalls/tailcall_bpf2bpf_fexit:OK
#448/15 tailcalls/tailcall_bpf2bpf_fentry_fexit:OK
#448/16 tailcalls/tailcall_bpf2bpf_fentry_entry:OK
#448/17 tailcalls/tailcall_poke:OK
#448/18 tailcalls/tailcall_bpf2bpf_hierarchy_1:OK
#448/19 tailcalls/tailcall_bpf2bpf_hierarchy_fentry:OK
#448/20 tailcalls/tailcall_bpf2bpf_hierarchy_fexit:OK
#448/21 tailcalls/tailcall_bpf2bpf_hierarchy_fentry_fexit:OK
#448/22 tailcalls/tailcall_bpf2bpf_hierarchy_fentry_entry:OK
#448/23 tailcalls/tailcall_bpf2bpf_hierarchy_2:OK
#448/24 tailcalls/tailcall_bpf2bpf_hierarchy_3:OK
#448/25 tailcalls/tailcall_freplace:OK
#448/26 tailcalls/tailcall_bpf2bpf_freplace:OK
#448/27 tailcalls/tailcall_failure:OK
#448/28 tailcalls/reject_tail_call_spin_lock:OK
#448/29 tailcalls/reject_tail_call_rcu_lock:OK
#448/30 tailcalls/reject_tail_call_preempt_lock:OK
#448/31 tailcalls/reject_tail_call_ref:OK
#448/32 tailcalls/tailcall_sleepable:OK
#448 tailcalls:OK
Summary: 1/32 PASSED, 0 SKIPPED, 0 FAILED
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
My bad, I didnt apply the related patches, when I tested earlier.
Regards,
Venkat.
>
> Above patch was not applied, during the test.
>
>>
>> Hi Venkat,
>>
>> Can you confirm if the above kernel patch was used or not?
>
>
> Its with only below patch. Please refer git log.
>
>
> git log
> commit cb50b08d0c45e7f97e1364075a5ee399c63422d5 (HEAD -> master)
> Author: Hari Bathini <hbathini@linux.ibm.com>
> Date: Mon Feb 16 14:38:02 2026 +0530
>
> selftests/bpf: test accounting of tail calls when prog is NULL
>
> Test whether tail call count is incorrectly accounted for, when the
> tail call fails due to a missing BPF program.
>
> Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
>
> commit 0f2acd3148e0ef42bdacbd477f90e8533f96b2ac (origin/master,
> origin/HEAD)
> Merge: 26a4cfaff82a a16ac6ca46d6
> Author: Linus Torvalds <torvalds@linux-foundation.org>
> Date: Sun Feb 15 19:45:00 2026 -0800
>
>
> Regards,
>
> Venkat.
>
>>
>> - Hari
>>
next prev parent reply other threads:[~2026-02-21 3:49 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-16 9:08 [PATCH] selftests/bpf: test accounting of tail calls when prog is NULL Hari Bathini
2026-02-16 11:08 ` Venkat
2026-02-16 11:11 ` Hari Bathini
2026-02-16 15:01 ` Venkat Rao Bagalkote
2026-02-21 3:48 ` Venkat Rao Bagalkote [this message]
2026-02-17 12:53 ` Ilya Leoshkevich
2026-02-20 6:34 ` Hari Bathini
2026-02-25 1:20 ` patchwork-bot+netdevbpf
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