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From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Timur Tabi <timur@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
	Petr Mladek <pmladek@suse.com>,
	roman.fietze@magna.com, keescook@chromium.org,
	Steven Rostedt <rostedt@goodmis.org>,
	John Ogness <john.ogness@linutronix.de>,
	linux-mm@kvack.org, Akinobu Mita <akinobu.mita@gmail.com>
Subject: Re: [PATCH 0/2] introduce DUMP_PREFIX_UNHASHED for hex dumps
Date: Tue, 19 Jan 2021 19:38:24 +0900	[thread overview]
Message-ID: <YAa2oCNWjExWlQTu@jagdpanzerIV.localdomain> (raw)
In-Reply-To: <20210119014725.GH2260413@casper.infradead.org>

On (21/01/19 01:47), Matthew Wilcox wrote:
[..]
> 
> > So maybe DUMP_PREFIX_UNHASHED can do the unhashed dump only when
> > CONFIG_DEBUG_KERNEL=y and fallback to DUMP_PREFIX_ADDRESS otherwise?
> 
> Distros enable CONFIG_DEBUG_KERNEL.

Oh, I see.

> If you want to add CONFIG_DEBUG_LEAK_ADDRESSES, then that's great,
> and you won't even have to change users, you can just change how %p
> behaves.

I like the name. config dependent behaviour of %p wouldn't be new,
well, to some extent, e.g. XFS does something similar (see below).
I don't think Linus will be sold on this, however.


fs/xfs/xfs_linux.h:

/*
 * Starting in Linux 4.15, the %p (raw pointer value) printk modifier
 * prints a hashed version of the pointer to avoid leaking kernel
 * pointers into dmesg.  If we're trying to debug the kernel we want the
 * raw values, so override this behavior as best we can.
 */
#ifdef DEBUG
# define PTR_FMT "%px"
#else
# define PTR_FMT "%p"
#endif

And then they just use it as

	xfs_alert(mp, "%s: bad inode magic number, dip = "ptr_fmt",
		  dino bp = "ptr_fmt", ino = %ld",
		  __func__, dip, bp, in_f->ilf_ino);

	-ss

  reply	other threads:[~2021-01-19 10:57 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-16 22:09 [PATCH 0/2] introduce DUMP_PREFIX_UNHASHED for hex dumps Timur Tabi
2021-01-16 22:09 ` [PATCH 1/2] [v2] lib/hexdump: introduce DUMP_PREFIX_UNHASHED for unhashed addresses Timur Tabi
2021-01-18 10:03   ` Andy Shevchenko
2021-01-18 15:57     ` Timur Tabi
2021-01-18 17:14       ` Andy Shevchenko
2021-01-18 17:53         ` Timur Tabi
2021-01-16 22:09 ` [PATCH 2/2] mm/page_poison: use unhashed address in hexdump for check_poison_mem() Timur Tabi
2021-01-18 18:26 ` [PATCH 0/2] introduce DUMP_PREFIX_UNHASHED for hex dumps Matthew Wilcox
2021-01-18 19:03   ` Timur Tabi
2021-01-19  0:53     ` Sergey Senozhatsky
2021-01-19  1:47       ` Matthew Wilcox
2021-01-19 10:38         ` Sergey Senozhatsky [this message]
2021-01-19 19:45           ` Kees Cook
2021-01-26 16:47           ` Vlastimil Babka
2021-01-26 16:59             ` Timur Tabi
2021-01-26 17:14               ` Steven Rostedt
2021-01-26 17:14               ` Vlastimil Babka
2021-01-26 17:30                 ` Timur Tabi
2021-01-26 17:39                   ` Steven Rostedt
2021-01-26 17:40                     ` Steven Rostedt
2021-01-26 19:23                       ` John Ogness
2021-01-27  2:11                         ` Sergey Senozhatsky
2021-01-27  3:22                           ` Timur Tabi
2021-01-27 10:11                       ` Petr Mladek
2021-01-27 10:38                         ` Vlastimil Babka
2021-01-19 19:45         ` Kees Cook
2021-01-19 19:55           ` Timur Tabi
2021-01-19 20:10             ` Steven Rostedt
2021-01-19 20:49               ` Timur Tabi
2021-01-19 21:15                 ` Steven Rostedt
2021-01-19 21:25                   ` Timur Tabi
2021-01-20  9:19             ` Petr Mladek
2021-01-20 12:17               ` Matthew Wilcox
2021-01-20 19:39               ` Linus Torvalds
2021-01-19 20:18           ` Randy Dunlap
2021-01-20 20:28             ` Kees Cook
2021-01-19  2:30       ` Timur Tabi

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