Messages in this thread | | | Subject | Re: [PATCH bpf-next v4 1/3] libbpf: Introduce 'btf_custom_path' to 'bpf_obj_open_opts' | From | Shuyi Cheng <> | Date | Sat, 17 Jul 2021 09:15:50 +0800 |
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On 7/16/21 12:51 PM, Andrii Nakryiko wrote: > On Tue, Jul 13, 2021 at 5:43 AM Shuyi Cheng > <chengshuyi@linux.alibaba.com> 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@mail.gmail.com/#t >> [1]https://yhbt.net/lore/all/CAEf4Bzbgw49w2PtowsrzKQNcxD4fZRE6AKByX-5-dMo-+oWHHA@mail.gmail.com/ >> >> Signed-off-by: Shuyi Cheng <chengshuyi@linux.alibaba.com> >> --- >> 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
You're right. 👍
regards, Shuyi > >> + >> return false; >> } >> > > [...] >
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