From: "H. Peter Anvin" <hpa@zytor.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: hans.rosenfeld@amd.com, torvalds@linux-foundation.org,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Arjan van de Ven <arjan@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: bisected boot regression post 2.6.25-rc3.. please revert
Date: Mon, 03 Mar 2008 14:55:30 -0800 [thread overview]
Message-ID: <47CC81E2.5090205@zytor.com> (raw)
In-Reply-To: <a9af8424f96a9118c6b097d9b2df79b2@kernel.crashing.org>
Segher Boessenkool wrote:
>>> so (on 32-bit) ~_PAGE_PSE is ~0x80L is 0xffffff7f, which when cast to
>>> 64-bit is 0x00000000ffffff7f,
>>
>> Actually, it is signed, so this isn't true. Comments about unsafeness
>> still apply.
>
> It turns out that PAGE_SIZE is unsigned. So this gives us for
>
> (~PAGE_MASK & ~_PAGE_USER & ~_PAGE_PSE & ~_PAGE_NX)
>
> the types UL, L, L, ULL resp.
>
> The associativity of & is left-to-right, so this in turn becomes
>
> UL, L, ULL
>
> UL, ULL
>
> ULL
>
> and that cast from UL to ULL doesn't sign-extend.
>
All the masks either need to be the proper size or signed.
-hpa
next prev parent reply other threads:[~2008-03-03 22:59 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-01 18:56 bisected boot regression post 2.6.25-rc3.. please revert Arjan van de Ven
2008-03-03 7:46 ` Ingo Molnar
2008-03-03 9:13 ` Ingo Molnar
2008-03-03 16:41 ` Arjan van de Ven
2008-03-03 17:40 ` Ingo Molnar
2008-03-03 17:51 ` Nish Aravamudan
2008-03-03 17:55 ` Ingo Molnar
2008-03-03 17:58 ` H. Peter Anvin
2008-03-03 18:36 ` Arjan van de Ven
2008-03-03 18:44 ` Linus Torvalds
2008-03-03 22:00 ` Arjan van de Ven
2008-03-04 1:05 ` Arjan van de Ven
2008-03-04 6:53 ` Ingo Molnar
2008-03-05 15:35 ` Arjan van de Ven
2008-03-09 11:56 ` Ingo Molnar
2008-03-09 17:27 ` Linus Torvalds
2008-03-09 18:57 ` Ingo Molnar
2008-03-10 2:45 ` Jeremy Fitzhardinge
2008-03-10 4:35 ` Paul Mackerras
2008-03-03 21:13 ` Segher Boessenkool
2008-03-03 21:22 ` Segher Boessenkool
2008-03-03 22:33 ` Segher Boessenkool
2008-03-03 22:55 ` H. Peter Anvin [this message]
2008-03-03 22:56 ` Jeremy Fitzhardinge
2008-03-03 23:04 ` H. Peter Anvin
2008-03-04 6:58 ` Ingo Molnar
2008-03-03 17:15 ` Nish Aravamudan
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