From: Martin KaFai Lau <martin.lau@linux.dev>
To: Kui-Feng Lee <kuifeng@meta.com>
Cc: bpf@vger.kernel.org, ast@kernel.org, song@kernel.org,
kernel-team@meta.com, andrii@kernel.org, sdf@google.com
Subject: Re: [PATCH bpf-next v9 4/8] libbpf: Create a bpf_link in bpf_map__attach_struct_ops().
Date: Tue, 21 Mar 2023 10:49:16 -0700 [thread overview]
Message-ID: <6157e6c1-1085-b4da-120b-98ccbdfa411d@linux.dev> (raw)
In-Reply-To: <20230320195644.1953096-5-kuifeng@meta.com>
On 3/20/23 12:56 PM, Kui-Feng Lee wrote:
> struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
> {
> - struct bpf_struct_ops *st_ops;
> - struct bpf_link *link;
> - __u32 i, zero = 0;
> - int err;
> + struct bpf_link_struct_ops *link;
> + __u32 zero = 0;
> + int err, fd;
>
> if (!bpf_map__is_struct_ops(map) || map->fd == -1)
> return libbpf_err_ptr(-EINVAL);
> @@ -11596,31 +11637,32 @@ struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
> if (!link)
> return libbpf_err_ptr(-EINVAL);
>
> - st_ops = map->st_ops;
> - for (i = 0; i < btf_vlen(st_ops->type); i++) {
> - struct bpf_program *prog = st_ops->progs[i];
> - void *kern_data;
> - int prog_fd;
> + /* kern_vdata should be prepared during the loading phase. */
> + err = bpf_map_update_elem(map->fd, &zero, map->st_ops->kern_vdata, 0);
> + if (err && err != -EBUSY) {
> + free(link);
> + return libbpf_err_ptr(err);
> + }
>
> - if (!prog)
> - continue;
> + link->link.detach = bpf_link__detach_struct_ops;
>
> - prog_fd = bpf_program__fd(prog);
> - kern_data = st_ops->kern_vdata + st_ops->kern_func_off[i];
> - *(unsigned long *)kern_data = prog_fd;
> + if (!(map->def.map_flags & BPF_F_LINK)) {
hmm... This still does not look right. 'err' could be -EBUSY here and should not
be treated as success for non BPF_F_LINK case. The above 'err && err != -EBUSY'
check should also consider the BPF_F_LINK map_flags.
[ Replied on the wrong v9, so copy-and-paste the reply back to this v9. ]
> + /* w/o a real link */
> + link->link.fd = map->fd;
> + link->map_fd = -1;
> + return &link->link;
> }
>
> - err = bpf_map_update_elem(map->fd, &zero, st_ops->kern_vdata, 0);
> - if (err) {
> - err = -errno;
> + fd = bpf_link_create(map->fd, 0, BPF_STRUCT_OPS, NULL);
> + if (fd < 0) {
> free(link);
> - return libbpf_err_ptr(err);
> + return libbpf_err_ptr(fd);
> }
>
> - link->detach = bpf_link__detach_struct_ops;
> - link->fd = map->fd;
> + link->link.fd = fd;
> + link->map_fd = map->fd;
>
> - return link;
> + return &link->link;
> }
>
> typedef enum bpf_perf_event_ret (*bpf_perf_event_print_t)(struct perf_event_header *hdr,
next prev parent reply other threads:[~2023-03-21 17:49 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-20 19:56 [PATCH bpf-next v9 0/8] Transit between BPF TCP congestion controls Kui-Feng Lee
2023-03-20 19:56 ` [PATCH bpf-next v9 1/8] bpf: Retire the struct_ops map kvalue->refcnt Kui-Feng Lee
2023-03-20 19:56 ` [PATCH bpf-next v9 2/8] net: Update an existing TCP congestion control algorithm Kui-Feng Lee
2023-03-20 19:56 ` [PATCH bpf-next v9 3/8] bpf: Create links for BPF struct_ops maps Kui-Feng Lee
2023-03-20 19:56 ` [PATCH bpf-next v9 4/8] libbpf: Create a bpf_link in bpf_map__attach_struct_ops() Kui-Feng Lee
2023-03-21 17:49 ` Martin KaFai Lau [this message]
2023-03-21 23:03 ` Kui-Feng Lee
2023-03-20 19:56 ` [PATCH bpf-next v9 5/8] bpf: Update the struct_ops of a bpf_link Kui-Feng Lee
2023-03-21 18:18 ` Martin KaFai Lau
2023-03-21 23:04 ` Kui-Feng Lee
2023-03-20 19:56 ` [PATCH bpf-next v9 6/8] libbpf: Update a bpf_link with another struct_ops Kui-Feng Lee
2023-03-21 21:04 ` Martin KaFai Lau
2023-03-21 23:04 ` Kui-Feng Lee
2023-03-20 19:56 ` [PATCH bpf-next v9 7/8] libbpf: Use .struct_ops.link section to indicate a struct_ops with a link Kui-Feng Lee
2023-03-20 19:56 ` [PATCH bpf-next v9 8/8] selftests/bpf: Test switching TCP Congestion Control algorithms Kui-Feng Lee
2023-03-21 21:05 ` Martin KaFai Lau
2023-03-21 23:05 ` Kui-Feng Lee
-- strict thread matches above, loose matches on Subject: below --
2023-03-20 19:24 [PATCH bpf-next v9 0/8] Transit between BPF TCP congestion controls Kui-Feng Lee
2023-03-20 19:24 ` [PATCH bpf-next v9 4/8] libbpf: Create a bpf_link in bpf_map__attach_struct_ops() Kui-Feng Lee
2023-03-21 17:36 ` Martin KaFai Lau
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