linux-kernel - Re: [PATCH 0/2] introduce DUMP_PREFIX

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Message-ID: <cd9e7a31-e4f6-69d3-0648-c6228108b592@kernel.org>
Date:   Tue, 26 Jan 2021 10:59:12 -0600
From:   Timur Tabi <timur@...nel.org>
To:     Vlastimil Babka <vbabka@...e.cz>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Matthew Wilcox <willy@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        Petr Mladek <pmladek@...e.com>, roman.fietze@...na.com,
        keescook@...omium.org, Steven Rostedt <rostedt@...dmis.org>,
        John Ogness <john.ogness@...utronix.de>, linux-mm@...ck.org,
        Akinobu Mita <akinobu.mita@...il.com>
Subject: Re: [PATCH 0/2] introduce DUMP_PREFIX_UNHASHED for hex dumps

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?