Date: Thu, 26 Oct 2017 01:05:39 -0700 From: Joe Perches <joe@...ches.com> To: "Tobin C. Harding" <me@...in.cc> Cc: kernel-hardening@...ts.openwall.com, "Jason A. Donenfeld" <Jason@...c4.com>, Theodore Ts'o <tytso@....edu>, Linus Torvalds <torvalds@...ux-foundation.org>, Kees Cook <keescook@...omium.org>, Paolo Bonzini <pbonzini@...hat.com>, Tycho Andersen <tycho@...ker.com>, "Roberts, William C" <william.c.roberts@...el.com>, Tejun Heo <tj@...nel.org>, Jordan Glover <Golden_Miller83@...tonmail.ch>, Greg KH <gregkh@...uxfoundation.org>, Petr Mladek <pmladek@...e.com>, Ian Campbell <ijc@...lion.org.uk>, Sergey Senozhatsky <sergey.senozhatsky@...il.com>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <wilal.deacon@....com>, Steven Rostedt <rostedt@...dmis.org>, Chris Fries <cfries@...gle.com>, Dave Weinstein <olorin@...gle.com>, Daniel Micay <danielmicay@...il.com>, Djalal Harouni <tixxdz@...il.com>, linux-kernel@...r.kernel.org 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. aside: Why hash 64 bits to 32? Why shouldn't the hash width be 64 bits on 64 bit systems?
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