From: Yonghong Song <yhs@fb.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andrii Nakryiko <andriin@fb.com>, <bpf@vger.kernel.org>,
Martin KaFai Lau <kafai@fb.com>, <netdev@vger.kernel.org>,
Alexei Starovoitov <ast@fb.com>,
Daniel Borkmann <daniel@iogearbox.net>, <kernel-team@fb.com>
Subject: Re: [PATCH bpf-next v4 12/21] bpf: add PTR_TO_BTF_ID_OR_NULL support
Date: Sat, 9 May 2020 22:18:37 -0700 [thread overview]
Message-ID: <d5b04ac9-3e3c-3e32-4058-afc29e3d34ce@fb.com> (raw)
In-Reply-To: <20200510005059.d3zocagerrnsspez@ast-mbp>
On 5/9/20 5:50 PM, Alexei Starovoitov wrote:
> On Sat, May 09, 2020 at 10:59:12AM -0700, Yonghong Song wrote:
>> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
>> index a2cfba89a8e1..c490fbde22d4 100644
>> --- a/kernel/bpf/btf.c
>> +++ b/kernel/bpf/btf.c
>> @@ -3790,7 +3790,10 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
>> return true;
>>
>> /* this is a pointer to another type */
>> - info->reg_type = PTR_TO_BTF_ID;
>> + if (off != 0 && prog->aux->btf_id_or_null_non0_off)
>> + info->reg_type = PTR_TO_BTF_ID_OR_NULL;
>> + else
>> + info->reg_type = PTR_TO_BTF_ID;
>
> I think the verifier should be smarter than this.
> It's too specific and inflexible. All ctx fields of bpf_iter execpt first
> will be such ? let's figure out a different way to tell verifier about this.
> How about using typedef with specific suffix? Like:
> typedef struct bpf_map *bpf_map_or_null;
> struct bpf_iter__bpf_map {
> struct bpf_iter_meta *meta;
> bpf_map_or_null map;
> };
> or use a union with specific second member? Like:
> struct bpf_iter__bpf_map {
> struct bpf_iter_meta *meta;
> union {
> struct bpf_map *map;
> long null;
> };
> };
I have an alternative approach to refactor this for future
support for map elements as well.
For example, for bpf_map_elements iterator the prog context type
can be
struct bpf_iter_bpf_map_elem {
struct bpf_iter_meta *meta;
strruct bpf_map *map;
<key type> *key;
<value type> *val;
};
target will pass the following information to bpf_iter registration:
arg 1: PTR_TO_BTF_ID
arg 2: PTR_TO_BTF_ID_OR_NULL
arg 3: PTR_TO_BUFFER
arg 4: PTR_TO_BUFFER
verifier will retrieve the reg_type from target.
next prev parent reply other threads:[~2020-05-10 5:19 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-09 17:58 [PATCH bpf-next v4 00/21] bpf: implement bpf iterator for kernel data Yonghong Song
2020-05-09 17:58 ` [PATCH bpf-next v4 01/21] bpf: implement an interface to register bpf_iter targets Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 02/21] bpf: allow loading of a bpf_iter program Yonghong Song
2020-05-10 0:41 ` Alexei Starovoitov
2020-05-10 5:07 ` Yonghong Song
2020-05-12 15:41 ` Yonghong Song
2020-05-12 16:25 ` Alexei Starovoitov
2020-05-12 16:29 ` Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 03/21] bpf: support bpf tracing/iter programs for BPF_LINK_CREATE Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 04/21] bpf: support bpf tracing/iter programs for BPF_LINK_UPDATE Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 05/21] bpf: implement bpf_seq_read() for bpf iterator Yonghong Song
2020-05-10 0:30 ` Alexei Starovoitov
2020-05-10 4:51 ` Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 06/21] bpf: create anonymous " Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 07/21] bpf: create file " Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 08/21] bpf: implement common macros/helpers for target iterators Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 09/21] bpf: add bpf_map iterator Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 10/21] net: bpf: add netlink and ipv6_route bpf_iter targets Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 11/21] bpf: add task and task/file iterator targets Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 12/21] bpf: add PTR_TO_BTF_ID_OR_NULL support Yonghong Song
2020-05-10 0:50 ` Alexei Starovoitov
2020-05-10 5:18 ` Yonghong Song [this message]
2020-05-10 16:11 ` Alexei Starovoitov
2020-05-10 17:05 ` Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 13/21] bpf: add bpf_seq_printf and bpf_seq_write helpers Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 14/21] bpf: handle spilled PTR_TO_BTF_ID properly when checking stack_boundary Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 15/21] bpf: support variable length array in tracing programs Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 16/21] tools/libbpf: add bpf_iter support Yonghong Song
2020-05-10 0:35 ` Alexei Starovoitov
2020-05-10 5:06 ` Yonghong Song
2020-05-10 16:09 ` Alexei Starovoitov
2020-05-10 17:04 ` Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 17/21] tools/libpf: add offsetof/container_of macro in bpf_helpers.h Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 18/21] tools/bpftool: add bpf_iter support for bptool Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 19/21] tools/bpf: selftests: add iterator programs for ipv6_route and netlink Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 20/21] tools/bpf: selftests: add iter progs for bpf_map/task/task_file Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 21/21] tools/bpf: selftests: add bpf_iter selftests Yonghong Song
2020-05-10 0:34 ` Alexei Starovoitov
2020-05-10 5:01 ` Yonghong Song
2020-05-10 16:14 ` Alexei Starovoitov
2020-05-10 0:27 ` [PATCH bpf-next v4 00/21] bpf: implement bpf iterator for kernel data Alexei Starovoitov
2020-05-10 4:47 ` Yonghong Song
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