From: John Fastabend <john.fastabend@gmail.com>
To: Andrii Nakryiko <andrii@kernel.org>,
bpf@vger.kernel.org, netdev@vger.kernel.org,
paul@paul-moore.com, brauner@kernel.org
Cc: linux-fsdevel@vger.kernel.org,
linux-security-module@vger.kernel.org, keescook@chromium.org,
kernel-team@meta.com, sargun@sargun.me
Subject: RE: [PATCH bpf-next 3/8] libbpf: further decouple feature checking logic from bpf_object
Date: Mon, 11 Dec 2023 13:41:00 -0800 [thread overview]
Message-ID: <657781ec1712_edaa208f5@john.notmuch> (raw)
In-Reply-To: <20231207185443.2297160-4-andrii@kernel.org>
Andrii Nakryiko wrote:
> Add feat_supported() helper that accepts feature cache instead of
> bpf_object. This allows low-level code in bpf.c to not know or care
> about higher-level concept of bpf_object, yet it will be able to utilize
> custom feature checking in cases where BPF token might influence the
> outcome.
>
> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
> ---
...
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index a6b8d6f70918..af5e777efcbd 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -637,6 +637,7 @@ struct elf_state {
> };
>
> struct usdt_manager;
> +struct kern_feature_cache;
>
> struct bpf_object {
> char name[BPF_OBJ_NAME_LEN];
> @@ -5063,17 +5064,14 @@ static struct kern_feature_desc {
> },
> };
>
> -bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
> +bool feat_supported(struct kern_feature_cache *cache, enum kern_feature_id feat_id)
> {
> struct kern_feature_desc *feat = &feature_probes[feat_id];
> - struct kern_feature_cache *cache = &feature_cache;
> int ret;
>
> - if (obj && obj->gen_loader)
> - /* To generate loader program assume the latest kernel
> - * to avoid doing extra prog_load, map_create syscalls.
> - */
> - return true;
> + /* assume global feature cache, unless custom one is provided */
> + if (!cache)
> + cache = &feature_cache;
Why expose a custom cache at all? Where would that be used? I guess we are
looking at libbpf_internal APIs so maybe not a big deal.
>
> if (READ_ONCE(cache->res[feat_id]) == FEAT_UNKNOWN) {
> ret = feat->probe();
> @@ -5090,6 +5088,17 @@ bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
> return READ_ONCE(cache->res[feat_id]) == FEAT_SUPPORTED;
> }
Acked-by: John Fastabend <john.fastabend@gmail.com>
next prev parent reply other threads:[~2023-12-11 21:41 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-07 18:54 [PATCH bpf-next 0/8] BPF token support in libbpf's BPF object Andrii Nakryiko
2023-12-07 18:54 ` [PATCH bpf-next 1/8] bpf: fail BPF_TOKEN_CREATE if no delegation option was set on BPF FS Andrii Nakryiko
2023-12-08 21:49 ` Christian Brauner
2023-12-08 22:42 ` Andrii Nakryiko
2023-12-11 21:33 ` John Fastabend
2023-12-07 18:54 ` [PATCH bpf-next 2/8] libbpf: split feature detectors definitions from cached results Andrii Nakryiko
2023-12-11 21:38 ` John Fastabend
2023-12-07 18:54 ` [PATCH bpf-next 3/8] libbpf: further decouple feature checking logic from bpf_object Andrii Nakryiko
2023-12-10 15:31 ` Eduard Zingerman
2023-12-11 18:20 ` Andrii Nakryiko
2023-12-11 21:41 ` John Fastabend [this message]
2023-12-11 22:50 ` Andrii Nakryiko
2023-12-07 18:54 ` [PATCH bpf-next 4/8] libbpf: move feature detection code into its own file Andrii Nakryiko
2023-12-11 21:41 ` John Fastabend
2023-12-07 18:54 ` [PATCH bpf-next 5/8] libbpf: wire up token_fd into feature probing logic Andrii Nakryiko
2023-12-11 21:44 ` John Fastabend
2023-12-07 18:54 ` [PATCH bpf-next 6/8] libbpf: wire up BPF token support at BPF object level Andrii Nakryiko
2023-12-11 22:56 ` John Fastabend
2023-12-12 0:05 ` Andrii Nakryiko
2023-12-12 0:26 ` John Fastabend
2023-12-07 18:54 ` [PATCH bpf-next 7/8] selftests/bpf: add BPF object loading tests with explicit token passing Andrii Nakryiko
2023-12-11 22:59 ` John Fastabend
2023-12-07 18:54 ` [PATCH bpf-next 8/8] selftests/bpf: add tests for BPF object load with implicit token Andrii Nakryiko
2023-12-11 23:00 ` John Fastabend
2023-12-10 15:30 ` [PATCH bpf-next 0/8] BPF token support in libbpf's BPF object Eduard Zingerman
2023-12-11 18:21 ` Andrii Nakryiko
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