From: Yonghong Song <yhs@fb.com>
To: Hou Tao <houtao1@huawei.com>, Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
<bpf@vger.kernel.org>, <netdev@vger.kernel.org>
Subject: Re: [PATCH 1/3] bpf: support writable context for bare tracepoint
Date: Fri, 17 Sep 2021 07:48:53 -0700 [thread overview]
Message-ID: <3001e875-9a74-8e22-3a7c-be3d280cd866@fb.com> (raw)
In-Reply-To: <b76d4051-abff-5e75-c812-41c6f283327f@huawei.com>
On 9/17/21 6:45 AM, Hou Tao wrote:
> Hi,
>
> On 9/17/2021 7:16 AM, Yonghong Song wrote:
>>
>>
>> On 9/16/21 6:55 AM, Hou Tao wrote:
>>> Commit 9df1c28bb752 ("bpf: add writable context for raw tracepoints")
>>> supports writable context for tracepoint, but it misses the support
>>> for bare tracepoint which has no associated trace event.
>>>
>>> Bare tracepoint is defined by DECLARE_TRACE(), so adding a corresponding
>>> DECLARE_TRACE_WRITABLE() macro to generate a definition in __bpf_raw_tp_map
>>> section for bare tracepoint in a similar way to DEFINE_TRACE_WRITABLE().
>>>
>>> Signed-off-by: Hou Tao <houtao1@huawei.com>
>>> ---
>>> include/trace/bpf_probe.h | 19 +++++++++++++++----
>>> 1 file changed, 15 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h
>>> index a23be89119aa..d08ee1060d82 100644
>>> --- a/include/trace/bpf_probe.h
>>> +++ b/include/trace/bpf_probe.h
>>> @@ -93,8 +93,7 @@ __section("__bpf_raw_tp_map") = { \
>>> #define FIRST(x, ...) x
>>> -#undef DEFINE_EVENT_WRITABLE
>>> -#define DEFINE_EVENT_WRITABLE(template, call, proto, args, size) \
>>> +#define __CHECK_WRITABLE_BUF_SIZE(call, proto, args, size) \
>>> static inline void bpf_test_buffer_##call(void) \
>>> { \
>>> /* BUILD_BUG_ON() is ignored if the code is completely eliminated, but \
>>> @@ -103,8 +102,12 @@ static inline void
>>> bpf_test_buffer_##call(void) \
>>> */ \
>>> FIRST(proto); \
>>> (void)BUILD_BUG_ON_ZERO(size != sizeof(*FIRST(args))); \
>>> -} \
>>> -__DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), size)
>>> +}
>>> +
>>> +#undef DEFINE_EVENT_WRITABLE
>>> +#define DEFINE_EVENT_WRITABLE(template, call, proto, args, size) \
>>> + __CHECK_WRITABLE_BUF_SIZE(call, PARAMS(proto), PARAMS(args), size) \
>>> + __DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), size)
>>> #undef DEFINE_EVENT
>>> #define DEFINE_EVENT(template, call, proto, args) \
>>> @@ -119,10 +122,18 @@ __DEFINE_EVENT(template, call, PARAMS(proto),
>>> PARAMS(args), size)
>>> __BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args)) \
>>> __DEFINE_EVENT(call, call, PARAMS(proto), PARAMS(args), 0)
>>> +#undef DECLARE_TRACE_WRITABLE
>>> +#define DECLARE_TRACE_WRITABLE(call, proto, args, size) \
>>> + __CHECK_WRITABLE_BUF_SIZE(call, PARAMS(proto), PARAMS(args), size) \
>>> + __BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args)) \
>>> + __DEFINE_EVENT(call, call, PARAMS(proto), PARAMS(args), size)
>>> +
>>> #include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
>>> #undef DEFINE_EVENT_WRITABLE
>>> +#undef DECLARE_TRACE_WRITABLE
>>> #undef __DEFINE_EVENT
>>> +#undef __CHECK_WRITABLE_BUF_SIZE
>>
>> Put "#undef __CHECK_WRITABLE_BUF_SIZE" right after "#undef
>> DECLARE_TRACE_WRITABLE" since they are related to each other
>> and also they are in correct reverse order w.r.t. __DEFINE_EVENT?
> If considering __CHECK_WRITABLE_BUF_SIZE is used in both DECLARE_TRACE_WRITABLE and
> DEFINE_EVENT_WRITABLE and the order of definitions, is the following order better ?
>
> #undef DECLARE_TRACE_WRITABLE
> #undef DEFINE_EVENT_WRITABLE
> #undef __CHECK_WRITABLE_BUF_SIZE
This should be okay.
>
>>
>>> #undef FIRST
>>> #endif /* CONFIG_BPF_EVENTS */
>>>
>> .
>
next prev parent reply other threads:[~2021-09-17 14:49 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-16 13:55 [PATCH 0/3] add support for writable bare tracepoint Hou Tao
2021-09-16 13:55 ` [PATCH 1/3] bpf: support writable context for " Hou Tao
2021-09-16 23:16 ` Yonghong Song
2021-09-17 13:45 ` Hou Tao
2021-09-17 14:48 ` Yonghong Song [this message]
2021-09-16 13:55 ` [PATCH 2/3] libbpf: support detecting and attaching of writable tracepoint program Hou Tao
2021-09-16 23:35 ` Yonghong Song
2021-09-16 13:55 ` [PATCH 3/3] bpf/selftests: add test for writable bare tracepoint Hou Tao
2021-09-16 23:46 ` Yonghong Song
2021-09-17 14:03 ` Hou Tao
2021-09-16 22:58 ` [PATCH 0/3] add support " Yonghong Song
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