linux-kernel - Re: [PATCH tracing 0/3] tracing: support

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Message-Id: <20230425233233.2ad5168c630b4c1349ab3398@kernel.org>
Date:   Tue, 25 Apr 2023 23:32:33 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Alan Maguire <alan.maguire@...cle.com>
Cc:     rostedt@...dmis.org, corbet@....net, shuah@...nel.org,
        linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH tracing 0/3] tracing: support > 8 byte filter predicates

On Tue, 25 Apr 2023 10:16:34 +0100
Alan Maguire <alan.maguire@...cle.com> wrote:

> For cases like IPv6 addresses, having a means to supply tracing
> predicates for fields with more than 8 bytes would be convenient.
> This series provides a simple way to support this by allowing
> simple ==, != memory comparison with the predicate supplied when
> the size of the field exceeds 8 bytes.  For example, to trace
> ::1, the predicate
> 
> 	"dst == 0x00000000000000000000000000000001"
> 
> ..could be used.

Nice!
And I also would like to use something like "dst == ipv6(::1)" because
it seems easy to make a mistake on the number of zeros.

Can we add such type casting feature to the filter?

Thank you,

> 
> Patch 1 provides the support for > 8 byte fields via a memcmp()-style
> predicate. Patch 2 adds tests for filter predicates, and patch 3
> documents the fact that for > 8 bytes. only == and != are supported.
> 
> Changes since RFC [1]:
> 
> - originally a fix was intermixed with the new functionality as
>   patch 1 in series [1]; the fix landed separately
> - small tweaks to how filter predicates are defined via fn_num as
>   opposed to via fn directly
> 
> [1] https://lore.kernel.org/lkml/1659910883-18223-1-git-send-email-alan.maguire@oracle.com/
> 
> Alan Maguire (3):
>   tracing: support > 8 byte array filter predicates
>   selftests/ftrace: add test coverage for filter predicates
>   tracing: document > 8 byte numeric filtering support
> 
>  Documentation/trace/events.rst                |  9 +++
>  kernel/trace/trace_events_filter.c            | 55 +++++++++++++++-
>  .../selftests/ftrace/test.d/event/filter.tc   | 62 +++++++++++++++++++
>  3 files changed, 125 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/ftrace/test.d/event/filter.tc
> 
> -- 
> 2.31.1
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>