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From: hpa@zytor.com
Message-ID: [off-list ref]

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:

quoted

On Fri, Mar 03, 2017 at 01:27:10PM +0100, Jiri Slaby wrote:

quoted

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)

quoted

quoted

 	return ret;
 }
=20
+static int futex_atomic_op_inuser(int encoded_op, u32 __user

*uaddr)

quoted

quoted

+{
+	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

quoted

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