netdev - RE: [PATCH V11 3/5] printk: hash addresses printed with %p

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Date:   Wed, 6 Dec 2017 10:31:15 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'David Miller' <davem@...emloft.net>,
        "geert@...ux-m68k.org" <geert@...ux-m68k.org>
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Subject: RE: [PATCH V11 3/5] printk: hash addresses printed with %p

From: David Miller
> Sent: 05 December 2017 20:31
...
> > Would it make sense to keep the 3 lowest bits of the address?
> >
> > Currently printed pointers no longer have any correlation with the actual
> > alignment in memory of the object, which is a typical cause of a class of bugs.
> 
> Yeah, this is driving people nuts who wonder why pointers are aligned
> all weird now.

I can also image issues where you want to know whether 2 pointers point
into the same structure (like an skb).
Useful if you suspect that code is using a stale pointer because the
skb got reallocated by some internal function.
I'm not sure such pointers are printed by default though.

I know I have debugged things that required hexdumps of memory areas
referenced by traced pointers.
I won't have done that for anything written with the kernel printf because
getting any more info for a linux kernel oops is actually quite hard.

	David