Re: [PATCH] selftests/bpf: test accounting of tail calls when prog is NULL

[Hari Bathini <hbathini@linux.ibm.com>]

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/

Hi Venkat,

Can you confirm if the above kernel patch was used or not?

- Hari