linux-kernel - Re: [PATCH v3 2/7] lib/hexdump.c: Relax rowsize checks in hex_dump_to

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Date:   Mon, 17 Jun 2019 15:47:03 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Alastair D'Silva <alastair@....ibm.com>, alastair@...ilva.org
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Karsten Keil <isdn@...ux-pingi.de>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Stanislaw Gruszka <sgruszka@...hat.com>,
        Benson Leung <bleung@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        David Laight <David.Laight@...LAB.COM>,
        Andrew Morton <akpm@...ux-foundation.org>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        ath10k@...ts.infradead.org, linux-wireless@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-fbdev@...r.kernel.org,
        devel@...verdev.osuosl.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v3 2/7] lib/hexdump.c: Relax rowsize checks in
 hex_dump_to_buffer

Hi,
Just a comment style nit below...

On 6/16/19 7:04 PM, Alastair D'Silva wrote:
> From: Alastair D'Silva <alastair@...ilva.org>
> 
> This patch removes the hardcoded row limits and allows for
> other lengths. These lengths must still be a multiple of
> groupsize.
> 
> This allows structs that are not 16/32 bytes to display on
> a single line.
> 
> This patch also expands the self-tests to test row sizes
> up to 64 bytes (though they can now be arbitrarily long).
> 
> Signed-off-by: Alastair D'Silva <alastair@...ilva.org>
> ---
>  lib/hexdump.c      | 48 ++++++++++++++++++++++++++++--------------
>  lib/test_hexdump.c | 52 ++++++++++++++++++++++++++++++++++++++--------
>  2 files changed, 75 insertions(+), 25 deletions(-)
> 
> diff --git a/lib/hexdump.c b/lib/hexdump.c
> index 81b70ed37209..3943507bc0e9 100644
> --- a/lib/hexdump.c
> +++ b/lib/hexdump.c

> @@ -246,17 +248,29 @@ void print_hex_dump(const char *level, const char *prefix_str, int prefix_type,
>  {
>  	const u8 *ptr = buf;
>  	int i, linelen, remaining = len;
> -	unsigned char linebuf[32 * 3 + 2 + 32 + 1];
> +	unsigned char *linebuf;
> +	unsigned int linebuf_len;
>  
> -	if (rowsize != 16 && rowsize != 32)
> -		rowsize = 16;
> +	if (rowsize % groupsize)
> +		rowsize -= rowsize % groupsize;
> +
> +	/* Worst case line length:
> +	 * 2 hex chars + space per byte in, 2 spaces, 1 char per byte in, NULL
> +	 */

According to Documentation/process/coding-style.rst:

The preferred style for long (multi-line) comments is:

.. code-block:: c

	/*
	 * This is the preferred style for multi-line
	 * comments in the Linux kernel source code.
	 * Please use it consistently.
	 *
	 * Description:  A column of asterisks on the left side,
	 * with beginning and ending almost-blank lines.
	 */


except in networking software.


> +	linebuf_len = rowsize * 3 + 2 + rowsize + 1;
> +	linebuf = kzalloc(linebuf_len, GFP_KERNEL);
> +	if (!linebuf) {
> +		printk("%s%shexdump: Could not alloc %u bytes for buffer\n",
> +			level, prefix_str, linebuf_len);
> +		return;
> +	}


-- 
~Randy