On Thu, Nov 11, 2021 at 9:02 PM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> From: Alexei Starovoitov <ast@xxxxxxxxxx>
>
> Without lskel the CO-RE relocations are processed by libbpf before any other
> work is done. Instead, when lksel is needed, remember relocation as RELO_CORE
typo: lskel
> kind. Then when loader prog is generated for a given bpf program pass CO-RE
> relos of that program to gen loader via bpf_gen__record_relo_core(). The gen
> loader will remember them as-is and pass it later as-is into the kernel.
>
> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> ---
> tools/lib/bpf/bpf_gen_internal.h | 3 +
> tools/lib/bpf/gen_loader.c | 41 +++++++++++-
> tools/lib/bpf/libbpf.c | 104 +++++++++++++++++++++++--------
> 3 files changed, 119 insertions(+), 29 deletions(-)
>
> diff --git a/tools/lib/bpf/bpf_gen_internal.h b/tools/lib/bpf/bpf_gen_internal.h
> index 75ca9fb857b2..ed162fdeecf6 100644
> --- a/tools/lib/bpf/bpf_gen_internal.h
> +++ b/tools/lib/bpf/bpf_gen_internal.h
> @@ -39,6 +39,8 @@ struct bpf_gen {
> int error;
> struct ksym_relo_desc *relos;
> int relo_cnt;
> + struct bpf_core_relo *core_relo;
this is named as a singular pointer to one relocation, core_relos
would be a more natural name for an array?
> + int core_relo_cnt;
> char attach_target[128];
> int attach_kind;
> struct ksym_desc *ksyms;
> @@ -61,5 +63,6 @@ void bpf_gen__map_freeze(struct bpf_gen *gen, int map_idx);
> void bpf_gen__record_attach_target(struct bpf_gen *gen, const char *name, enum bpf_attach_type type);
> void bpf_gen__record_extern(struct bpf_gen *gen, const char *name, bool is_weak,
> bool is_typeless, int kind, int insn_idx);
[...]
> @@ -6581,6 +6623,16 @@ static int bpf_program__record_externs(struct bpf_program *prog)
> ext->is_weak, false, BTF_KIND_FUNC,
> relo->insn_idx);
> break;
> + case RELO_CORE: {
This is not an extern, it doesn't make sense to have it here. But I
also don't understand why we need to add RELO_CORE and extend struct
relo_desc in the first place, just to pass it as bpf_core_relo into
gen_loader. Why can't gen_loader just record this directly at the
place of record_relo_core() call?
> + struct bpf_core_relo cr = {
> + .insn_off = relo->insn_idx * 8,
> + .type_id = relo->type_id,
> + .access_str_off = relo->access_str_off,
> + .kind = relo->kind,
> + };
> + bpf_gen__record_relo_core(obj->gen_loader, &cr);
> + break;
> + }
> default:
> continue;
> }
> --
> 2.30.2
>
