On Tue, Jul 13, 2021 at 5:43 AM Shuyi Cheng <chengshuyi@xxxxxxxxxxxxxxxxx> wrote: > > btf_custom_path allows developers to load custom BTF, and subsequent > CO-RE will use custom BTF for relocation. > > Learn from Andrii's comments in [0], add the btf_custom_path parameter > to bpf_obj_open_opts, you can directly use the skeleton's > <objname>_bpf__open_opts function to pass in the btf_custom_path > parameter. > > Prior to this, there was also a developer who provided a patch with > similar functions. It is a pity that the follow-up did not continue to > advance. See [1]. > > [0]https://lore.kernel.org/bpf/CAEf4BzbJZLjNoiK8_VfeVg_Vrg=9iYFv+po-38SMe=UzwDKJ=Q@xxxxxxxxxxxxxx/#t > [1]https://yhbt.net/lore/all/CAEf4Bzbgw49w2PtowsrzKQNcxD4fZRE6AKByX-5-dMo-+oWHHA@xxxxxxxxxxxxxx/ > > Signed-off-by: Shuyi Cheng <chengshuyi@xxxxxxxxxxxxxxxxx> > --- > tools/lib/bpf/libbpf.c | 36 ++++++++++++++++++++++++++++++------ > tools/lib/bpf/libbpf.h | 9 ++++++++- > 2 files changed, 38 insertions(+), 7 deletions(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 1e04ce7..6e11a7b 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -498,6 +498,13 @@ struct bpf_object { > * it at load time. > */ > struct btf *btf_vmlinux; > + /* Path to the custom BTF to be used for BPF CO-RE relocations. > + * This custom BTF completely replaces the use of vmlinux BTF > + * for the purpose of CO-RE relocations. > + * NOTE: any other BPF feature (e.g., fentry/fexit programs, > + * struct_ops, etc) will need actual kernel BTF at /sys/kernel/btf/vmlinux. > + */ this comment completely duplicates the one from bpf_object_open_opts, I'll remove or shorten it > + char *btf_custom_path; > /* vmlinux BTF override for CO-RE relocations */ > struct btf *btf_vmlinux_override; > /* Lazily initialized kernel module BTFs */ > @@ -2645,10 +2652,6 @@ static bool obj_needs_vmlinux_btf(const struct bpf_object *obj) > struct bpf_program *prog; > int i; > > - /* CO-RE relocations need kernel BTF */ > - if (obj->btf_ext && obj->btf_ext->core_relo_info.len) > - return true; > - > /* Support for typed ksyms needs kernel BTF */ > for (i = 0; i < obj->nr_extern; i++) { > const struct extern_desc *ext; > @@ -2665,6 +2668,13 @@ static bool obj_needs_vmlinux_btf(const struct bpf_object *obj) > return true; > } > > + /* CO-RE relocations need kernel BTF, only when btf_custom_path > + * is not specified > + */ > + if (obj->btf_ext && obj->btf_ext->core_relo_info.len > + && !obj->btf_custom_path) > + return true; not sure why you moved it, I'll move it back to minimize code churn > + > return false; > } > [...]
