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Message-ID: <20240119105243.05082e5b@gandalf.local.home>
Date: Fri, 19 Jan 2024 10:52:43 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc: Ye Bin <yebin10@...wei.com>, <mathieu.desnoyers@...icios.com>,
<linux-trace-kernel@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] support '%pd' and '%pD' for print file name
On Fri, 19 Jan 2024 23:43:56 +0900
Masami Hiramatsu (Google) <mhiramat@...nel.org> wrote:
> Thanks for your proposal!
>
> Generically, I think this type of hack is not good for the tracing
> because there are already some ways to do that. e.g.
> - Use perf probe to specify dentry->name:string or file->name:string
> - Use BTF to specify in the same way (but only for function entry)
> And those are more obvious what it does.
>
> However, if this is implemented in more generic syntax, it will be
> acceptable.
> For example, type specifying with "arg1:printfmt(%pD)" will be
> more generic because it is apparently one of the printfmt and output
> string. Or, maybe we can just allow to use ":%pD" as a fetch type
> (start with '%' means the printfmt)
Yes, I like this idea a lot. Please add the '%' keyword/token to change how
to display this in the print format.
We may need to add more than one token though. Is that supported?
$arg1:u32:%08x
or that could also be:
$arg1:%08x:u32
That is, the order should not be important.
Thoughts?
-- Steve
>
> Also, could you update readme_msg[] in kernel/trace/trace.c if
> you add a type, and add a testcase of selftests/ftrace, for this
> feature? Documentation should also be updated with more syntax
> information.
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