linux-kernel - Re: [PATCH v6 7/9] vsprintf: Consolidate handling of unknown pointer specifiers

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Date:   Fri, 8 Feb 2019 19:25:18 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Tobin C . Harding" <me@...in.cc>, Joe Perches <joe@...ches.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.cz>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 7/9] vsprintf: Consolidate handling of unknown pointer
 specifiers

On Fri, Feb 08, 2019 at 04:23:08PM +0100, Petr Mladek wrote:
> There are few printk formats that make sense only with two or more
> specifiers. Also some specifiers make sense only when a kernel feature
> is enabled.
> 
> The handling of unknown specifiers is inconsistent and not helpful.
> Using WARN() looks like an overkill for this type of error. pr_warn()
> is not good either. It would by handled via printk_safe buffer and
> it might be hard to match it with the problematic string.
> 
> A reasonable compromise seems to be writing the unknown format specifier
> into the original string with a question mark, for example (%pC?).
> It should be self-explaining enough. Note that it is in brackets
> to follow the (null) style.
> 

> Note that the changes in test_printf.c revert many changes made
> by the commit 4d42c44727a062e233 ("lib/vsprintf: Print time and
> date in human readable format via %pt\n"). The format %pt does
> not longer produce a hashed pointer.

It seems in further patch you partially restore back what was brought by that patch.
I would suggest not to touch at least changes for plain_pointer_to_buffer().

Also it would be nice to have a coverage for hashed pointers.

-- 
With Best Regards,
Andy Shevchenko