linux-kernel - Re: [PATCH tip/core/rcu 02/20] torture: Prepare scripting for shift from %p to %pK

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Message-ID: <CAHp75VcJKYnW2grD6jViNFU3z6+fJoTmqs+ZP3Xm6YB3C8ZH1Q@mail.gmail.com>
Date:   Sun, 10 Dec 2017 14:52:49 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Kees Cook <keescook@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     David Laight <David.Laight@...lab.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "jiangshanlai@...il.com" <jiangshanlai@...il.com>,
        "dipankar@...ibm.com" <dipankar@...ibm.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "mathieu.desnoyers@...icios.com" <mathieu.desnoyers@...icios.com>,
        "josh@...htriplett.org" <josh@...htriplett.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "dhowells@...hat.com" <dhowells@...hat.com>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "fweisbec@...il.com" <fweisbec@...il.com>,
        "oleg@...hat.com" <oleg@...hat.com>
Subject: Re: [PATCH tip/core/rcu 02/20] torture: Prepare scripting for shift
 from %p to %pK

On Mon, Dec 4, 2017 at 6:11 PM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:
> On Mon, Dec 04, 2017 at 02:13:38PM +0000, David Laight wrote:
>> From: Paul E. McKenney
>> > Sent: 04 December 2017 13:42
>> > On Mon, Dec 04, 2017 at 12:32:30PM +0000, David Laight wrote:
>> > > From: Paul E. McKenney
>> > > > Sent: 01 December 2017 20:09
>> > > >
>> > > > Because %p prints "(null)" and %pK prints "0000000000000000" or (on
>> > > > 32-bit systems) "00000000", this commit adjusts torture-test scripting
>> > > > accordingly.
>> > >
>> > > Surely NULL v not-NULL is one bit of info that the message needs to contain?
>> >
>> > Indeed.  So the script needs to check for the strings "00000000",
>> > "0000000000000000", and "(null) in the console output".  The "(null)"
>> > is what "%p" prints for a NULL pointer, and the other two strings are
>> > what "%pK" prints for a NULL pointer.
>> >
>> > Or am I missing your point?
>>
>> I was thinking that even %pK should print "(null)".
>
> That was my expectation, as in the need for this patch came as a
> surprise to me.
>
>> Perhaps it should have printed a fixed, non-zero value for non-zero
>> pointers.
>
> I must leave this to the people who have a dog in that contest.  ;-)

Since there is an ongoing discussion with security people near to %pK
and alike, I added Kees and Linus to Cc list.

The proposed change can be done easily, though I have no knowledge
about possible implications.

-- 
With Best Regards,
Andy Shevchenko