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Date: Mon, 24 Mar 2025 09:40:05 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Douglas Raillard <douglas.raillard@arm.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@efficios.com>, linux-kernel@vger.kernel.org,
 linux-trace-kernel@vger.kernel.org
Subject: Re: [PATCH] tracing: Fix synth event printk format for str fields
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On Mon, 24 Mar 2025 10:18:50 +0000
Douglas Raillard <douglas.raillard@arm.com> wrote:

> > https://lore.kernel.org/all/b6bdb34e70d970e8026daa3503db6b8e5cdad524.1601848695.git.zanussi@kernel.org/T/#u
> > 
> > So, I think it should always print the STR_VAR_LEN_MAX value.  
> 
> That makes sense. It's tempting to keep the actual length value though as native Rust strings are not null-terminated, so
> it could make it nicer to emit events from Rust code. From a cursory look, the in-tree Rust code seems to be using both
> &str and &CStr (the latter being null-terminated for FFI needs) so I'm not sure what's the plan around those
> and what's the established convention if any.
> 
> > Steve, can you check it?

So I did take this patch, but thinking about this more, I may remove it.

The __get_str() doesn't expect a string end. The parser should limit it, as
the length of the string is saved in the ring buffer. Just like other trace
events where dynamically size strings only use "%s" and __get_str().

I think the real fix is to replace the "%.*s" with "%s".

-- Steve