linux-kernel - Re: [RESEND PATCH v2 1/2] tracing: Add array printing helpers

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Message-ID: <20150115212202.7939072a@grimm.local.home>
Date:	Thu, 15 Jan 2015 21:22:02 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Javi Merino <javi.merino@....com>
Cc:	linux-kernel@...r.kernel.org, Dave Martin <Dave.Martin@....com>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [RESEND PATCH v2 1/2] tracing: Add array printing helpers

On Thu, 15 Jan 2015 16:50:58 +0000
Javi Merino <javi.merino@....com> wrote:
 
> +const char *
> +ftrace_print_array_seq(struct trace_seq *p, const void *buf, int
> buf_len,
> +		       size_t el_size)
> +{
> +	const char *ret = trace_seq_buffer_ptr(p);
> +	const char *prefix = "";
> +	void *ptr = (void *)buf;
> +
> +	trace_seq_putc(p, '{');
> +
> +	while (ptr < buf + buf_len) {
> +		switch (el_size) {
> +		case 8:
> +			trace_seq_printf(p, "%s0x%x", prefix,
> +					 *(u8 *)ptr);
> +			break;
> +		case 16:
> +			trace_seq_printf(p, "%s0x%x", prefix,
> +					 *(u16 *)ptr);
> +			break;
> +		case 32:
> +			trace_seq_printf(p, "%s0x%x", prefix,
> +					 *(u32 *)ptr);
> +			break;
> +		case 64:
> +			trace_seq_printf(p, "%s0x%llx", prefix,
> +					 *(u64 *)ptr);
> +			break;
> +		default:
> +			BUG();

BUG() is a bit extreme don't you think? I'm not sure it even deserves a
WARN_ON().

I would suggest doing:

			trace_seq_printf(p, "BAD SIZE:%d 0x%x", el_size,
					*(u8 *)ptr);
			el_size = 8;

No need to go crashing the kernel or even messing with dmesg over
somebody's tracepoint mistake.

The rest looks fine.

> +		}
> +		prefix = ",";
> +		ptr += el_size / 8;
> +	}
> +
> +	trace_seq_putc(p, '}');
> +	trace_seq_putc(p, 0);

I need to add a trace_seq_terminate() for this.

-- Steve

> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(ftrace_print_array_seq);
> +
>  int ftrace_raw_output_prep(struct trace_iterator *iter,
>  			   struct trace_event *trace_event)
>  {

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