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Date: Thu, 26 Oct 2017 01:05:39 -0700
From: Joe Perches <>
To: "Tobin C. Harding" <>
Cc:, "Jason A. Donenfeld"
 <>,  Theodore Ts'o <>, Linus Torvalds
 <>, Kees Cook <>, Paolo
 Bonzini <>, Tycho Andersen <>, "Roberts,
 William C" <>,  Tejun Heo <>,
 Jordan Glover <>, Greg KH
 <>, Petr Mladek <>, Ian Campbell
 <>, Sergey Senozhatsky <>, 
 Catalin Marinas <>, Will Deacon
 <>, Steven Rostedt <>,  Chris Fries
 <>, Dave Weinstein <>, Daniel Micay
 <>,  Djalal Harouni <>,
Subject: Re: [PATCH V8 1/2] printk: remove tabular output for NULL pointer

On Thu, 2017-10-26 at 17:27 +1100, Tobin C. Harding wrote:
> Hi Joe,
> thanks for your review.
> On Wed, Oct 25, 2017 at 09:57:23PM -0700, Joe Perches wrote:
> > On Thu, 2017-10-26 at 13:53 +1100, Tobin C. Harding wrote:
> > > Currently pointer() checks for a NULL pointer argument and then if so
> > > attempts to print "(null)" with _some_ standard width. This width cannot
> > > correctly be ascertained here because many of the printk specifiers
> > > print pointers of varying widths.
> > 
> > I believe this is not a good change.
> > Only pointers without a <foo> extension call pointer()
> Sorry, I don't understand what you mean here. All the %p<foo> specifier code is
> handled by pointer()?

Sorry, I was imprecise/wrong.

None of the %p<foo> extensions except %pK and %p<invalid_foo>
actually use this bit of the pointer() call.

All of the other valid %p<foo> extension uses do not end up
at this block being executed so it's effectively only regular
pointers being output by number()

> > > Remove the attempt to print NULL pointers with a correct width.
> > 
> > the correct width for a %p is the default width.
> It is the default width if we are printing addresses. Once we hash 64
> bit address to a 32 bit identifier then we don't have a default width.

Perhaps that 32 bit identifier should use leading 0's for
the default width.


Why hash 64 bits to 32?
Why shouldn't the hash width be 64 bits on 64 bit systems?

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