Re: [PATCH bpf-next v5] selftests/bpf: trace_helpers.c: optimize kallsyms cache

[Yonghong Song]

On 8/18/23 8:36 AM, Rong Tao wrote:
> Hi, jirka
>
> Sadly, we can't include libbpf_internal.h in trace_helpers.{h,c}.
> we only have the following headers when compile samples/bpf/:
>
> tree of samples/bpf/libbpf/
>      +-- bpf_helper_defs.h
>      +-- include
>      |   '-- bpf
>      |       +-- bpf_core_read.h
>      |       +-- bpf_endian.h
>      |       +-- bpf.h
>      |       +-- bpf_helper_defs.h
>      |       +-- bpf_helpers.h
>      |       +-- bpf_tracing.h
>      |       +-- btf.h
>      |       +-- libbpf_common.h
>      |       +-- libbpf.h
>      |       +-- libbpf_legacy.h
>      |       +-- libbpf_version.h
>      |       +-- skel_internal.h
>      |       '-- usdt.bpf.h
>      +-- libbpf.a
>
> No libbpf_internal.h here.
>
> What if we add a declaration to libbpf_ensure_mem() in trace_helpers.c?

[~/work/bpf-next/tools/testing/selftests/bpf/prog_tests (master)]$ grep 
libbpf_internal.h *
cpu_mask.c:#include "bpf/libbpf_internal.h"
kprobe_multi_test.c:#include "bpf/libbpf_internal.h"
kprobe_multi_testmod_test.c:#include "bpf/libbpf_internal.h"
module_fentry_shadow.c:#include "bpf/libbpf_internal.h"
perf_branches.c:#include "bpf/libbpf_internal.h"
perf_buffer.c:#include "bpf/libbpf_internal.h"
raw_tp_test_run.c:#include "bpf/libbpf_internal.h"
[~/work/bpf-next/tools/testing/selftests/bpf/prog_tests (master)]$ grep 
libbpf_ensure_mem *.c
kprobe_multi_test.c:            err = libbpf_ensure_mem((void **) &syms, 
&cap,
[~/work/bpf-next/tools/testing/selftests/bpf/prog_tests (master)]$

Looks like it is already used for selftets.

The libbpf_internal.h exists in the following directory when you build
the selftest.

[~/work/bpf-next/tools/testing/selftests/bpf/tools/include/bpf (master)]$ ls
bpf_core_read.h  bpf.h              bpf_helpers.h  btf.h 
libbpf_common.h  libbpf_internal.h  libbpf_version.h  relo_core.h 
usdt.bpf.h
bpf_endian.h     bpf_helper_defs.h  bpf_tracing.h  hashmap.h  libbpf.h 
      libbpf_legacy.h    nlattr.h          skel_internal.h


> Good Day,
> Rong Tao