[PATCH] tools/perf: Fix bpf__probe to set bpf_prog_type type only if differs from the desired one

[Sachin Sant]

> On 07-Aug-2023, at 10:22 AM, Athira Rajeev <atrajeev at linux.vnet.ibm.com> wrote:
> 
> The test "BPF prologue generation" fails as below:
> 
>   Writing event: p:perf_bpf_probe/func _text+10423200 f_mode=+20(%gpr3):x32 offset=%gpr4:s64 orig=%gpr5:s32
>   In map_prologue, ntevs=1
>   mapping[0]=0
>   libbpf: prog 'bpf_func__null_lseek': BPF program load failed: Permission denied
>   libbpf: prog 'bpf_func__null_lseek': -- BEGIN PROG LOAD LOG --
>   btf_vmlinux is malformed
>   reg type unsupported for arg#0 function bpf_func__null_lseek#5
>   0: R1=ctx(off=0,imm=0) R10=fp0
>   ;
>   0: (57) r3 &= 2
>   R3 !read_ok
>   processed 1 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
>   -- END PROG LOAD LOG --
>   libbpf: prog 'bpf_func__null_lseek': failed to load: -13
>   libbpf: failed to load object '[bpf_prologue_test]'
>   bpf: load objects failed: err=-13: (Permission denied)
>   Failed to add events selected by BPF
> 
> This fails occurs after this commit:
> commit d6e6286a12e7 ("libbpf: disassociate section handler
> on explicit bpf_program__set_type() call")'
> 
> With this change, SEC_DEF handler libbpf which is determined
> initially based on program's SEC() is set to NULL. The change
> is made because sec_def is not valid when user sets the program
> type with bpf_program__set_type function. This commit also fixed
> bpf_prog_test_load() helper in selftests/bpf to force-set program
> type only if it differs from the desired one.
> 
> The "bpf__probe" function in util/bpf-loader.c, also calls
> bpf_program__set_type to set bpf_prog_type. Add similar fix in
> here as well to avoid setting sec_def to NULL.
> 
> Reported-by: Sachin Sant <sachinp at linux.vnet.ibm.com>
> Signed-off-by: Athira Rajeev <atrajeev at linux.vnet.ibm.com>
> ---

Thanks Athira for the fix.
With this patch applied perf BPF prologue sub test works correctly.

 42: BPF filter                                                     :
 42.1: Basic BPF filtering                                    : Ok
 42.2: BPF pinning                                              : Ok
 42.3: BPF prologue generation                          : Ok

Tested-by: Sachin Sant <sachinp at linux.ibm.com>

Can you please use the above mentioned id(without vnet) in the reported-by ?

- Sachin