linux-kernel - Re: [PATCH] libtraceevent: add __print_hex

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Date:   Mon, 9 Dec 2019 13:15:33 +0200
From:   Andy Shevchenko <andriy.shevchenko@...el.com>
To:     Piotr Maziarz <piotrx.maziarz@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, rostedt@...dmis.org, acme@...hat.com,
        tstoyanov@...are.com, cezary.rojewski@...el.com,
        gustaw.lewandowski@...el.com
Subject: Re: [PATCH] libtraceevent: add __print_hex_dump support

On Fri, Dec 06, 2019 at 10:00:51AM +0100, Piotr Maziarz wrote:
> This allows using parsing __print_hex_dump in user space tools. Print
> format is aligned with debugfs tracing interface.

> +int hex_dump_line(const unsigned char *buf, size_t len, int rowsize,
> +		  int groupsize, struct trace_seq *s, bool ascii)
> +{
> +	unsigned long long val;
> +	int i, ret, pos = 0;
> +	const char *format;
> +	int ascii_pos = rowsize * 2 + rowsize / groupsize + 1;
> +
> +	len = min(len, (size_t)rowsize);

> +	if ((groupsize != 2 && groupsize != 4 && groupsize != 8)
> +	    || (len % groupsize) != 0) {

Tools have an implemented is_power_of_2().
I guess you may go thru tools headers and check what else can be un-open-coded
here, in this change.

> +		groupsize = 1;
> +	}
> +
> +	for (i = 0; i < len / groupsize; i++) {
> +		if (groupsize == 8) {
> +			const unsigned long long *ptr8 = (void *)buf;
> +
> +			val = *(ptr8 + i);
> +			format = "%s%16.16llx";
> +		} else if (groupsize == 4) {
> +			const unsigned int *ptr4 = (void *)buf;
> +
> +			val = *(ptr4 + i);
> +			format = "%s%8.8x";
> +		} else if (groupsize == 2) {
> +			const unsigned short *ptr2 = (void *)buf;
> +
> +			val = *(ptr2 + i);
> +			format = "%s%4.4x";
> +		} else {
> +			const unsigned char *ptr1 = (void *)buf;
> +
> +			val = *(ptr1 + i);
> +			format = "%s%2.2x";
> +		}
> +		ret = trace_seq_printf(s,
> +			       format, i ? " " : "",
> +			       val);
> +		if (ret <= 0)
> +			return ret;
> +		pos += ret;
> +	}
> +	if (!ascii)
> +		return 0;
> +	ret = trace_seq_printf(s, "%*s", ascii_pos - pos, "");
> +	if (ret <= 0)
> +		return ret;
> +	for (i = 0; i < len; i++)
> +		trace_seq_putc(s, (isprint(buf[i])) ? buf[i] : '.');
> +	return 0;
> +}
> +
> +int trace_seq_hex_dump(struct trace_seq *s, const char *prefix_str,
> +		       int prefix_type, int rowsize, int groupsize,
> +		       const void *buf, size_t len, int ascii)
> +{
> +	const unsigned char *ptr = buf;
> +	int i, linelen, remaining = len;
> +	int ret;
> +
> +	if (rowsize != 16 && rowsize != 32)
> +		rowsize = 16;
> +
> +	for (i = 0; i < len; i += rowsize) {
> +		linelen = min(remaining, rowsize);
> +		remaining -= linelen;
> +
> +		if (prefix_type == DUMP_PREFIX_ADDRESS)
> +			ret = trace_seq_printf(s, "%s%p: ",
> +					       prefix_str, ptr + i);
> +		else if (prefix_type == DUMP_PREFIX_OFFSET)
> +			ret = trace_seq_printf(s, "%s%.8x: ",
> +					       prefix_str, i);
> +		else
> +			ret = trace_seq_printf(s, "%s",
> +					       prefix_str);
> +		if (ret <= 0)
> +			return ret;
> +		hex_dump_line(ptr + i, linelen, rowsize, groupsize,
> +			      s, ascii);
> +		trace_seq_putc(s, '\n');
> +	}
> +	return 0;
> +}

-- 
With Best Regards,
Andy Shevchenko