From: Jiri Olsa <jolsa@redhat.com>
To: Yonghong Song <yhs@fb.com>
Cc: Jiri Olsa <jolsa@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
Song Liu <songliubraving@fb.com>, Martin KaFai Lau <kafai@fb.com>,
David Miller <davem@redhat.com>,
John Fastabend <john.fastabend@gmail.com>,
Wenbo Zhang <ethercflow@gmail.com>,
KP Singh <kpsingh@chromium.org>, Andrii Nakryiko <andriin@fb.com>,
Brendan Gregg <bgregg@netflix.com>,
Florent Revest <revest@chromium.org>,
Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v4 bpf-next 05/14] bpf: Remove btf_id helpers resolving
Date: Sun, 28 Jun 2020 22:16:08 +0200 [thread overview]
Message-ID: <20200628201608.GG2988321@krava> (raw)
In-Reply-To: <7480f7b2-01f0-f575-7e4f-cf3bde851c3f@fb.com>
On Fri, Jun 26, 2020 at 02:36:37PM -0700, Yonghong Song wrote:
SNIP
> > - }
> > -
> > - t = btf_type_by_id(btf_vmlinux, t->type);
> > - if (!btf_type_is_ptr(t))
> > - return -EFAULT;
> > - t = btf_type_by_id(btf_vmlinux, t->type);
> > - if (!btf_type_is_func_proto(t))
> > - return -EFAULT;
> > -
> > - args = (const struct btf_param *)(t + 1);
> > - if (arg >= btf_type_vlen(t)) {
> > - bpf_log(log, "bpf helper %s doesn't have %d-th argument\n",
> > - fnname, arg);
> > + if (WARN_ON_ONCE(!fn->btf_id))
>
> The original code does not have this warning. It directly did
> "ret = READ_ONCE(*btf_id);" after testing reg arg type ARG_PTR_TO_BTF_ID.
not sure why I put it in there, it's probably enough guarded
by arg_type having ARG_PTR_TO_BTF_ID, will remove
>
> > return -EINVAL;
> > - }
> > - t = btf_type_by_id(btf_vmlinux, args[arg].type);
> > - if (!btf_type_is_ptr(t) || !t->type) {
> > - /* anything but the pointer to struct is a helper config bug */
> > - bpf_log(log, "ARG_PTR_TO_BTF is misconfigured\n");
> > - return -EFAULT;
> > - }
> > - btf_id = t->type;
> > - t = btf_type_by_id(btf_vmlinux, t->type);
> > - /* skip modifiers */
> > - while (btf_type_is_modifier(t)) {
> > - btf_id = t->type;
> > - t = btf_type_by_id(btf_vmlinux, t->type);
> > - }
> > - if (!btf_type_is_struct(t)) {
> > - bpf_log(log, "ARG_PTR_TO_BTF is not a struct\n");
> > - return -EFAULT;
> > - }
> > - bpf_log(log, "helper %s arg%d has btf_id %d struct %s\n", fnname + 4,
> > - arg, btf_id, __btf_name_by_offset(btf_vmlinux, t->name_off));
> > - return btf_id;
> > -}
> > + id = fn->btf_id[arg];
>
> The corresponding BTF_ID definition here is:
> BTF_ID_LIST(bpf_skb_output_btf_ids)
> BTF_ID(struct, sk_buff)
>
> The bpf helper writer needs to ensure proper declarations
> of BTF_IDs like the above matching helpers definition.
> Support we have arg1 and arg3 as BTF_ID. then the list
> definition may be
>
> BTF_ID_LIST(bpf_skb_output_btf_ids)
> BTF_ID(struct, sk_buff)
> BTF_ID(struct, __unused)
> BTF_ID(struct, task_struct)
>
> This probably okay, I guess.
right, AFAIK we don't have such case yet, but would be good
to be ready and have something like
BTF_ID(struct, __unused)
maybe adding new type for that will be better:
BTF_ID(none, unused)
jirka
next prev parent reply other threads:[~2020-06-28 20:16 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-25 22:12 [PATCH v4 bpf-next 00/14] bpf: Add d_path helper Jiri Olsa
2020-06-25 22:12 ` [PATCH v4 bpf-next 01/14] bpf: Add resolve_btfids tool to resolve BTF IDs in ELF object Jiri Olsa
2020-06-26 20:53 ` Andrii Nakryiko
2020-06-26 21:09 ` Yonghong Song
2020-06-28 19:09 ` Alexei Starovoitov
2020-06-28 19:35 ` Jiri Olsa
2020-06-28 20:53 ` Yonghong Song
2020-06-25 22:12 ` [PATCH v4 bpf-next 02/14] bpf: Compile resolve_btfids tool at kernel compilation start Jiri Olsa
2020-06-26 21:28 ` Andrii Nakryiko
2020-06-28 19:48 ` Jiri Olsa
2020-06-25 22:12 ` [PATCH v4 bpf-next 03/14] bpf: Add BTF_ID_LIST/BTF_ID macros Jiri Olsa
2020-06-26 21:32 ` Andrii Nakryiko
2020-06-28 19:50 ` Jiri Olsa
2020-06-25 22:12 ` [PATCH v4 bpf-next 04/14] bpf: Resolve BTF IDs in vmlinux image Jiri Olsa
2020-06-26 21:34 ` Andrii Nakryiko
2020-06-25 22:12 ` [PATCH v4 bpf-next 05/14] bpf: Remove btf_id helpers resolving Jiri Olsa
2020-06-26 21:36 ` Yonghong Song
2020-06-26 21:40 ` Andrii Nakryiko
2020-06-26 23:29 ` Yonghong Song
2020-06-28 18:50 ` Alexei Starovoitov
2020-06-28 20:00 ` Andrii Nakryiko
2020-06-28 20:16 ` Jiri Olsa [this message]
2020-06-28 20:59 ` Yonghong Song
2020-06-28 21:20 ` Jiri Olsa
2020-06-25 22:12 ` [PATCH v4 bpf-next 06/14] bpf: Use BTF_ID to resolve bpf_ctx_convert struct Jiri Olsa
2020-06-26 21:44 ` Andrii Nakryiko
2020-06-26 21:44 ` Yonghong Song
2020-06-28 19:52 ` Jiri Olsa
2020-06-25 22:12 ` [PATCH v4 bpf-next 07/14] bpf: Allow nested BTF object to be refferenced by BTF object + offset Jiri Olsa
2020-06-30 1:52 ` Andrii Nakryiko
2020-06-30 13:54 ` Jiri Olsa
2020-06-30 20:05 ` Andrii Nakryiko
2020-06-30 20:07 ` Andrii Nakryiko
2020-07-02 10:08 ` Jiri Olsa
2020-07-06 23:15 ` Andrii Nakryiko
2020-06-25 22:12 ` [PATCH v4 bpf-next 08/14] bpf: Add BTF_SET_START/END macros Jiri Olsa
2020-06-26 21:49 ` Andrii Nakryiko
2020-06-25 22:12 ` [PATCH v4 bpf-next 09/14] bpf: Add info about .BTF.ids section to btf.rst Jiri Olsa
2020-06-25 22:13 ` [PATCH v4 bpf-next 10/14] bpf: Add d_path helper Jiri Olsa
2020-06-26 20:38 ` Andrii Nakryiko
2020-06-28 19:42 ` Jiri Olsa
2020-07-16 23:13 ` KP Singh
2020-07-17 8:28 ` Jiri Olsa
2020-06-25 22:13 ` [PATCH v4 bpf-next 11/14] tools headers: Adopt verbatim copy of btf_ids.h from kernel sources Jiri Olsa
2020-06-26 21:51 ` Andrii Nakryiko
2020-06-25 22:13 ` [PATCH v4 bpf-next 12/14] selftests/bpf: Add verifier test for d_path helper Jiri Olsa
2020-06-30 1:30 ` Andrii Nakryiko
2020-06-25 22:13 ` [PATCH v4 bpf-next 13/14] selftests/bpf: Add " Jiri Olsa
2020-06-26 21:55 ` Andrii Nakryiko
2020-06-28 19:55 ` Jiri Olsa
2020-06-25 22:13 ` [PATCH v4 bpf-next 14/14] selftests/bpf: Add test for resolve_btfids Jiri Olsa
2020-06-30 1:43 ` Andrii Nakryiko
2020-06-30 14:27 ` Jiri Olsa
2020-06-30 18:13 ` Andrii Nakryiko
2020-06-30 1:54 ` [PATCH v4 bpf-next 00/14] bpf: Add d_path helper Andrii Nakryiko
2020-06-30 13:55 ` Jiri Olsa
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