From: Yonghong Song <yhs@fb.com>
To: Qais Yousef <qais.yousef@arm.com>, <netdev@vger.kernel.org>,
<bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Steven Rostedt <rostedt@goodmis.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 bpf-next 1/2] trace: bpf: Allow bpf to attach to bare tracepoints
Date: Sat, 16 Jan 2021 18:03:37 -0800 [thread overview]
Message-ID: <2e63b638-1500-c323-0fec-1aecfef5f033@fb.com> (raw)
In-Reply-To: <20210116182133.2286884-2-qais.yousef@arm.com>
On 1/16/21 10:21 AM, Qais Yousef wrote:
> Some subsystems only have bare tracepoints (a tracepoint with no
> associated trace event) to avoid the problem of trace events being an
> ABI that can't be changed.
>
> From bpf presepective, bare tracepoints are what it calls
> RAW_TRACEPOINT().
>
> Since bpf assumed there's 1:1 mapping, it relied on hooking to
> DEFINE_EVENT() macro to create bpf mapping of the tracepoints. Since
> bare tracepoints use DECLARE_TRACE() to create the tracepoint, bpf had
> no knowledge about their existence.
>
> By teaching bpf_probe.h to parse DECLARE_TRACE() in a similar fashion to
> DEFINE_EVENT(), bpf can find and attach to the new raw tracepoints.
>
> Enabling that comes with the contract that changes to raw tracepoints
> don't constitute a regression if they break existing bpf programs.
> We need the ability to continue to morph and modify these raw
> tracepoints without worrying about any ABI.
>
> Update Documentation/bpf/bpf_design_QA.rst to document this contract.
>
> Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Acked-by: Yonghong Song <yhs@fb.com>
next prev parent reply other threads:[~2021-01-17 2:05 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-16 18:21 [PATCH v2 bpf-next 0/2] Allow attaching to bare tracepoints Qais Yousef
2021-01-16 18:21 ` [PATCH v2 bpf-next 1/2] trace: bpf: Allow bpf to attach " Qais Yousef
2021-01-17 2:03 ` Yonghong Song [this message]
2021-01-16 18:21 ` [PATCH v2 bpf-next 2/2] selftests: bpf: Add a new test for " Qais Yousef
2021-01-17 2:11 ` Yonghong Song
2021-01-18 12:18 ` Qais Yousef
2021-01-18 17:48 ` Yonghong Song
2021-01-19 9:57 ` Qais Yousef
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