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Subject: Re: [PATCH 0/2] introduce DUMP_PREFIX_UNHASHED for hex dumps
To:     Vlastimil Babka <vbabka@suse.cz>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Matthew Wilcox <willy@infradead.org>
Cc:     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>
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From:   Timur Tabi <timur@kernel.org>
Message-ID: <cd9e7a31-e4f6-69d3-0648-c6228108b592@kernel.org>
Date:   Tue, 26 Jan 2021 10:59:12 -0600
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On 1/26/21 10:47 AM, Vlastimil Babka wrote:
> Given Linus' current stance later in this thread, could we revive the idea of a
> boot time option, or at least a CONFIG (I assume a runtime toggle would be too
> much, even if limited to !kernel_lockdown:)  , that would disable all hashing?
> It would be really useful for a development/active debugging, as evidenced
> below. Thanks.

So you're saying:

if CONFIG_PRINTK_NEVER_HASH is disabled, then %p prints hashed addresses 
and %px prints unhashed.

If CONFIG_PRINTK_NEVER_HASH is enabled, then %p and %px both print 
unhashed addresses.

I like this idea, and I would accept it as a solution if I had to, but I 
still would also like for an option for print_hex_dump() to print 
unhashed addresses even when CONFIG_PRINTK_NEVER_HASH is disabled.  I 
can't always recompile the entire kernel for my testing purposes.

The only drawback to this idea is: what happens if distros start 
enabling CONFIG_PRINTK_NEVER_HASH by default, just because it makes 
debugging easier?