Re: [PATCH 1/3] futex: remove duplicated code

["H. Peter Anvin" <hpa@zytor.com>]

<cmetcalf@mellanox.com>,Thomas Gleixner <tglx@linutronix.de>,Ingo Molnar <mingo@redhat.com>,Chris Zankel <chris@zankel.net>,Max Filippov <jcmvbkbc@gmail.com>,Arnd Bergmann <arnd@arndb.de>,x86@kernel.org,linux-alpha@vger.kernel.org,linux-snps-arc@lists.infradead.org,linux-arm-kernel@lists.infradead.org,linux-hexagon@vger.kernel.org,linux-ia64@vger.kernel.org,linux-mips@linux-mips.org,openrisc@lists.librecores.org,linux-parisc@vger.kernel.org,linuxppc-dev@lists.ozlabs.org,linux-s390@vger.kernel.org,linux-sh@vger.kernel.org,sparclinux@vger.kernel.org,linux-xtensa@linux-xtensa.org,linux-arch@vger.kernel.org
From: hpa@zytor.com
Message-ID: <83324528-AAA1-4BED-B0C7-48426ECBA261@zytor.com>

On March 8, 2017 8:16:49 PM PST, Rob Landley <rob@landley=2Enet> wrote:
>On 03/04/2017 07:05 AM, Russell King - ARM Linux wrote:
>> On Fri, Mar 03, 2017 at 01:27:10PM +0100, Jiri Slaby wrote:
>>> diff --git a/kernel/futex=2Ec b/kernel/futex=2Ec
>>> index b687cb22301c=2E=2Ec5ff9850952f 100644
>>> --- a/kernel/futex=2Ec
>>> +++ b/kernel/futex=2Ec
>>> @@ -1457,6 +1457,42 @@ futex_wake(u32 __user *uaddr, unsigned int
>flags, int nr_wake, u32 bitset)
>>>  	return ret;
>>>  }
>>> =20
>>> +static int futex_atomic_op_inuser(int encoded_op, u32 __user
>*uaddr)
>>> +{
>>> +	int op =3D (encoded_op >> 28) & 7;
>>> +	int cmp =3D (encoded_op >> 24) & 15;
>>> +	int oparg =3D (encoded_op << 8) >> 20;
>>> +	int cmparg =3D (encoded_op << 20) >> 20;
>>=20
>> Hmm=2E  oparg and cmparg look like they're doing these shifts to get
>sign
>> extension of the 12-bit values by assuming that "int" is 32-bit -
>> probably worth a comment, or for safety, they should be "s32" so it's
>> not dependent on the bit-width of "int"=2E
>
>I thought Linux depended on the LP64 standard for all architectures?
>
>Standard: http://www=2Eunix=2Eorg/whitepapers/64bit=2Ehtml
>Rationale: http://www=2Eunix=2Eorg/version2/whatsnew/lp64_wp=2Ehtml
>
>So int has a defined bit width (32) on linux?
>
>Rob

Linux is ILP32 on 32-bit architectures and LP64 on 64-bit architectures, b=
ut that doesn't inherently make this stuff clear=2E
--=20
Sent from my Android device with K-9 Mail=2E Please excuse my brevity=2E