linux-kernel - Re: [PATCH v2 2/2] tracing: Use seq_buf_hex

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Date:   Tue, 26 Nov 2019 15:53:26 +0100
From:   Piotr Maziarz <piotrx.maziarz@...ux.intel.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, mingo@...hat.com,
        andriy.shevchenko@...el.com, cezary.rojewski@...el.com,
        gustaw.lewandowski@...el.com
Subject: Re: [PATCH v2 2/2] tracing: Use seq_buf_hex_dump() to dump buffers

On 2019-11-13 22:09, Steven Rostedt wrote:
> OK, so the __print_hex_dump() will be exported to the format files.
> 
> Would you be willing to add a function to handle __print_hex_dump() in
> tools/lib/traceevent/event-parse.c, like __print_flags(),
> __print_symbolic(), and other __print_*() functions are handled. This
> will allow trace-cmd and perf to be able to parse the data when you
> used it via the userspace tools.
> 
> This can be a separate patch, but ideally before any trace events start
> using this.
> 
> Thanks,
> 
> -- Steve
> 

Hello Steven,

I'm writing handle in event-parse and I came across some technical 
problems. I have an event which print function looks like that:
TP_printk("%s",
	  __print_hex_dump("", DUMP_PREFIX_OFFSET, 16, 4,
			   __get_dynamic_array(buf),
			   __get_dynamic_array_len(buf), false))
It works properly when printing events to debugfs.
I'm testing my implementation with trace-cmd and it has problem with 
parsing DUMP_PREFIX_OFFSET and false (I'm using 
alloc_and_process_delim()). Instead of having numerical values 
tep_print_args are of type TEP_PRINT_ATOM and have char array 
"DUMP_PREFIX_OFFSET" or "true".
Am I doing something incorrect? Parsing it this way is problematic 
because instead of false someone may use 0 or logic expression. And 
writing it to support all possible scenarios may be tedious and prone to 
errors.

Best regards,
Piotr Maziarz