From: Martin KaFai Lau <martin.lau@linux.dev>
To: Kui-Feng Lee <sinquersw@gmail.com>, thinker.li@gmail.com
Cc: kuifeng@meta.com, bpf@vger.kernel.org, ast@kernel.org,
song@kernel.org, kernel-team@meta.com, andrii@kernel.org,
drosen@google.com
Subject: Re: [PATCH bpf-next v13 07/14] bpf: pass attached BTF to the bpf_struct_ops subsystem
Date: Sat, 16 Dec 2023 08:41:29 -0800 [thread overview]
Message-ID: <9dce9dca-f48b-4853-b1a5-a5ee0e22fc4a@linux.dev> (raw)
In-Reply-To: <390f3c92-2df6-4cea-aa78-ecc92a9fe8aa@gmail.com>
On 12/15/23 10:07 PM, Kui-Feng Lee wrote:
>
>
> On 12/15/23 21:55, Kui-Feng Lee wrote:
>>
>>
>> On 12/15/23 16:19, Martin KaFai Lau wrote:
>>> On 12/15/23 2:10 PM, Kui-Feng Lee wrote:
>>>>
>>>>
>>>> On 12/14/23 18:44, Martin KaFai Lau wrote:
>>>>> On 12/8/23 4:27 PM, thinker.li@gmail.com wrote:
>>>>>> @@ -681,15 +682,30 @@ static struct bpf_map
>>>>>> *bpf_struct_ops_map_alloc(union bpf_attr *attr)
>>>>>> struct bpf_struct_ops_map *st_map;
>>>>>> const struct btf_type *t, *vt;
>>>>>> struct bpf_map *map;
>>>>>> + struct btf *btf;
>>>>>> int ret;
>>>>>> - st_ops_desc = bpf_struct_ops_find_value(btf_vmlinux,
>>>>>> attr->btf_vmlinux_value_type_id);
>>>>>> - if (!st_ops_desc)
>>>>>> - return ERR_PTR(-ENOTSUPP);
>>>>>> + if (attr->value_type_btf_obj_fd) {
>>>>>> + /* The map holds btf for its whole life time. */
>>>>>> + btf = btf_get_by_fd(attr->value_type_btf_obj_fd);
>>>>>> + if (IS_ERR(btf))
>>>>>> + return ERR_PTR(PTR_ERR(btf));
>>>>>
>>>>> return ERR_CAST(btf);
>>>>>
>>>>> It needs to check for btf_is_module:
>>>>>
>>>>> if (!btf_is_module(btf)) {
>>>>> btf_put(btf);
>>>>> return ERR_PTR(-EINVAL);
>>>>> }
>>>>
>>>> Even btf is btf_vmlinux the kernel's btf, it still works.
>>>
>>> btf could be a bpf program's btf. It needs to ensure it is a kernel module
>>> btf here.
>>
>> Got it!
>
> Isn't btf_is_kernel() better here?
> User space may pass a fd to btf_vmlinux.
Limit it to btf_is_module. What is the benefit of supporting btf_vmlinux as a fd
while fd 0 already means btf_vmlinux?
kfunc does not support the btf_vmlinux as fd also, supporting in struct_ops
alone is confusing. I don't think the major user (libbpf) does this either, so
really not much usage other than a confusing API to have both fd == 0 and a
btf_vmlinux's fd to mean btf_vmlinux.
>
>>
>>>
>>>> Although libbpf pass 0 as the value of value_type_btf_obj_fd for
>>>> btf_vmlinux now, it should be OK for a user space loader to
>>>> pass a fd of btf_vmlinux.
>>>>
>>>> WDYT?
>>>
next prev parent reply other threads:[~2023-12-16 16:41 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-09 0:26 [PATCH bpf-next v13 00/14] Registrating struct_ops types from modules thinker.li
2023-12-09 0:26 ` [PATCH bpf-next v13 01/14] bpf: refactory struct_ops type initialization to a function thinker.li
2023-12-09 0:26 ` [PATCH bpf-next v13 02/14] bpf: get type information with BPF_ID_LIST thinker.li
2023-12-15 1:59 ` Martin KaFai Lau
2023-12-09 0:26 ` [PATCH bpf-next v13 03/14] bpf, net: introduce bpf_struct_ops_desc thinker.li
2023-12-15 2:05 ` Martin KaFai Lau
2023-12-09 0:26 ` [PATCH bpf-next v13 04/14] bpf: add struct_ops_tab to btf thinker.li
2023-12-15 2:22 ` Martin KaFai Lau
2023-12-15 21:42 ` Kui-Feng Lee
2023-12-16 1:19 ` Martin KaFai Lau
2023-12-16 5:43 ` Kui-Feng Lee
2023-12-16 16:48 ` Martin KaFai Lau
2023-12-17 7:09 ` Kui-Feng Lee
2023-12-09 0:27 ` [PATCH bpf-next v13 05/14] bpf: make struct_ops_map support btfs other than btf_vmlinux thinker.li
2023-12-09 0:27 ` [PATCH bpf-next v13 06/14] bpf: lookup struct_ops types from a given module BTF thinker.li
2023-12-09 0:27 ` [PATCH bpf-next v13 07/14] bpf: pass attached BTF to the bpf_struct_ops subsystem thinker.li
2023-12-15 2:44 ` Martin KaFai Lau
2023-12-15 22:10 ` Kui-Feng Lee
2023-12-16 0:19 ` Martin KaFai Lau
2023-12-16 5:55 ` Kui-Feng Lee
2023-12-16 6:07 ` Kui-Feng Lee
2023-12-16 16:41 ` Martin KaFai Lau [this message]
2023-12-16 19:38 ` Kui-Feng Lee
2023-12-09 0:27 ` [PATCH bpf-next v13 08/14] bpf: hold module for bpf_struct_ops_map thinker.li
2023-12-15 5:54 ` Martin KaFai Lau
2023-12-15 23:25 ` Kui-Feng Lee
2023-12-09 0:27 ` [PATCH bpf-next v13 09/14] bpf: validate value_type thinker.li
2023-12-15 6:02 ` Martin KaFai Lau
2023-12-15 23:52 ` Kui-Feng Lee
2023-12-09 0:27 ` [PATCH bpf-next v13 10/14] bpf, net: switch to dynamic registration thinker.li
2023-12-15 6:51 ` Martin KaFai Lau
2023-12-09 0:27 ` [PATCH bpf-next v13 11/14] libbpf: Find correct module BTFs for struct_ops maps and progs thinker.li
2023-12-09 0:27 ` [PATCH bpf-next v13 12/14] bpf: export btf_ctx_access to modules thinker.li
2023-12-09 0:27 ` [PATCH bpf-next v13 13/14] selftests/bpf: test case for register_bpf_struct_ops() thinker.li
2023-12-15 7:17 ` Martin KaFai Lau
2023-12-17 7:32 ` Kui-Feng Lee
2023-12-09 0:27 ` [PATCH bpf-next v13 14/14] bpf: pass btf object id in bpf_map_info thinker.li
2023-12-15 7:46 ` Martin KaFai Lau
2023-12-17 7:35 ` Kui-Feng Lee
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