netdev - Re: bpf: btf: Change how section is supported in btf

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Message-ID: <CACT4Y+YzC15pw=30uS3Vo27-cZp=V=CdnG5vYDYrULVLKvj=YQ@mail.gmail.com>
Date:   Tue, 11 Sep 2018 18:40:05 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Martin KaFai Lau <kafai@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>
Subject: Re: bpf: btf: Change how section is supported in btf_header

Hi Martin,

I am looking at the subj commit:

 static int btf_add_type(struct btf_verifier_env *env, struct btf_type *t)
@@ -1754,9 +1756,9 @@ static int btf_check_all_metas(struct
btf_verifier_env *env)
        struct btf_header *hdr;
        void *cur, *end;

-       hdr = btf->hdr;
+       hdr = &btf->hdr;
        cur = btf->nohdr_data + hdr->type_off;
-       end = btf->nohdr_data + hdr->str_off;
+       end = btf->nohdr_data + hdr->type_len;

Shouldn't this be:

+       end = cur + hdr->type_len;

? Or otherwise I am having trouble understanding meaning of fields.

On a related note, what's between header and type_off? Is type_off
supposed to be 0 always?

Thanks