linux-kernel - Re: [PATCH v3 1/5] seq_file: provide an analogue of print_hex

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Date:	Mon, 01 Sep 2014 11:36:46 +0300
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Tadeusz Struk <tadeusz.struk@...el.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Mauro Carvalho Chehab <m.chehab@...sung.com>,
	Helge Deller <deller@....de>,
	Ingo Tuchscherer <ingo.tuchscherer@...ibm.com>,
	linux-kernel@...r.kernel.org, Joe Perches <joe@...ches.com>,
	Marek Vasut <marex@...x.de>
Subject: Re: [PATCH v3 1/5] seq_file: provide an analogue of print_hex_dump()

On Sat, 2014-08-30 at 23:54 +0100, Al Viro wrote:
> On Mon, Aug 25, 2014 at 12:03:11PM +0300, Andy Shevchenko wrote:
> > The new seq_hex_dump() is a complete analogue of print_hex_dump().
> > 
> > We have few users of this functionality already. It allows to reduce their
> > codebase.
> 
> I really don't like the stack footprint.
> 
> > +	unsigned char linebuf[32 * 3 + 2 + 32 + 1];
> 
> ... and extra copying for no good reason.  Why not check that we have
> enough space in buffer and generate directly into it?  See what e.g.
> seq_escape() is doing...

What about this variant?


@@ -794,6 +795,47 @@ void seq_pad(struct seq_file *m, char c)
 }
 EXPORT_SYMBOL(seq_pad);
 
+/* Analogue of print_hex_dump() */
+void seq_hex_dump(struct seq_file *m, const char *prefix_str, int prefix_type,
+                 int rowsize, int groupsize, const void *buf, size_t len,
+                 bool ascii)
+{
+       const u8 *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 -= rowsize;
+
+               ret = seq_printf(m, "%s", prefix_str);
+               if (ret < 0)
+                       break;
+
+               if (prefix_type == DUMP_PREFIX_ADDRESS)
+                       ret = seq_printf(m, "%p: ", ptr + i);
+               else if (prefix_type == DUMP_PREFIX_OFFSET)
+                       ret = seq_printf(m, "%.8x: ", i);
+               if (ret < 0)
+                       break;
+
+               if (m->size < m->count + groupsize * 2 + 1)
+                       break;
+
+               hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize,
+                                  m->buf + m->count, m->size - m->count,
+                                  ascii);
+
+               ret = seq_putc(m, '\n');
+               if (ret < 0)
+                       break;
+       }
+}
+EXPORT_SYMBOL(seq_hex_dump);



-- 
Andy Shevchenko <andriy.shevchenko@...el.com>
Intel Finland Oy

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