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From: Daniel Borkmann <daniel@iogearbox.net>
To: Alexei Starovoitov <ast@kernel.org>
Cc: davem@davemloft.net, x86@kernel.org, netdev@vger.kernel.org,
	bpf@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH v3 bpf-next 00/11] bpf: revolutionize bpf tracing
Date: Thu, 17 Oct 2019 17:14:45 +0200	[thread overview]
Message-ID: <20191017151445.GB26267@pc-63.home> (raw)
In-Reply-To: <20191016032505.2089704-1-ast@kernel.org>

On Tue, Oct 15, 2019 at 08:24:54PM -0700, Alexei Starovoitov wrote:
> v2->v3:
> - while trying to adopt btf-based tracing in production service realized
>   that disabling bpf_probe_read() was premature. The real tracing program
>   needs to see much more than this type safe tracking can provide.
>   With these patches the verifier will be able to see that skb->data
>   is a pointer to 'u8 *', but it cannot possibly know how many bytes
>   of it is readable. Hence bpf_probe_read() is necessary to do basic
>   packet reading from tracing program. Some helper can be introduced to
>   solve this particular problem, but there are other similar structures.
>   Another issue is bitfield reading. The support for bitfields
>   is coming to llvm. libbpf will be supporting it eventually as well,
>   but there will be corner cases where bpf_probe_read() is necessary.
>   The long term goal is still the same: get rid of probe_read eventually.
> - fixed build issue with clang reported by Nathan Chancellor.
> - addressed a ton of comments from Andrii.
>   bitfields and arrays are explicitly unsupported in btf-based tracking.
>   This will be improved in the future.
>   Right now the verifier is more strict than necessary.
>   In some cases it can fall back to 'scalar' instead of rejecting
>   the program, but rejection today allows to make better decisions
>   in the future.
> - adjusted testcase to demo bitfield and skb->data reading.

Applied, thanks!

      parent reply	other threads:[~2019-10-17 15:14 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-16  3:24 [PATCH v3 bpf-next 00/11] bpf: revolutionize bpf tracing Alexei Starovoitov
2019-10-16  3:24 ` [PATCH v3 bpf-next 01/11] bpf: add typecast to raw_tracepoints to help BTF generation Alexei Starovoitov
2019-10-16  3:24 ` [PATCH v3 bpf-next 02/11] bpf: add typecast to bpf helpers " Alexei Starovoitov
2019-10-16  3:24 ` [PATCH v3 bpf-next 03/11] bpf: process in-kernel BTF Alexei Starovoitov
2019-10-16  3:24 ` [PATCH v3 bpf-next 04/11] bpf: add attach_btf_id attribute to program load Alexei Starovoitov
2019-10-16 19:45   ` Andrii Nakryiko
2019-10-16 19:50     ` Alexei Starovoitov
2019-10-16  3:24 ` [PATCH v3 bpf-next 05/11] libbpf: auto-detect btf_id of BTF-based raw_tracepoints Alexei Starovoitov
2019-10-16 19:49   ` Andrii Nakryiko
2019-10-16  3:25 ` [PATCH v3 bpf-next 06/11] bpf: implement accurate raw_tp context access via BTF Alexei Starovoitov
2019-10-16 20:09   ` Andrii Nakryiko
2019-10-16 21:21   ` Daniel Borkmann
2019-10-16 21:28     ` Alexei Starovoitov
2019-10-16 22:08       ` Daniel Borkmann
2019-10-16 23:52         ` Alexei Starovoitov
2019-10-16  3:25 ` [PATCH v3 bpf-next 07/11] bpf: attach raw_tp program with BTF via type name Alexei Starovoitov
2019-10-16 20:13   ` Andrii Nakryiko
2019-10-16  3:25 ` [PATCH v3 bpf-next 08/11] bpf: add support for BTF pointers to interpreter Alexei Starovoitov
2019-10-16  3:25 ` [PATCH v3 bpf-next 09/11] bpf: add support for BTF pointers to x86 JIT Alexei Starovoitov
2019-10-16 20:15   ` Andrii Nakryiko
2019-10-16  3:25 ` [PATCH v3 bpf-next 10/11] bpf: check types of arguments passed into helpers Alexei Starovoitov
2019-10-16  3:25 ` [PATCH v3 bpf-next 11/11] selftests/bpf: add kfree_skb raw_tp test Alexei Starovoitov
2019-10-16 18:01 ` [PATCH v3 bpf-next 00/11] bpf: revolutionize bpf tracing Martin Lau
2019-10-17 15:14 ` Daniel Borkmann [this message]

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