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.c b/kernel/futex.c
>> index b687cb22301c..c5ff9850952f 100644
>> --- a/kernel/futex.c
>> +++ b/kernel/futex.c
>> @@ -1457,6 +1457,42 @@ futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset)
>> return ret;
>> }
>>
>> +static int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
>> +{
>> + int op = (encoded_op >> 28) & 7;
>> + int cmp = (encoded_op >> 24) & 15;
>> + int oparg = (encoded_op << 8) >> 20;
>> + int cmparg = (encoded_op << 20) >> 20;
>
> Hmm. 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".
I thought Linux depended on the LP64 standard for all architectures?
Standard: http://www.unix.org/whitepapers/64bit.html
Rationale: http://www.unix.org/version2/whatsnew/lp64_wp.html
So int has a defined bit width (32) on linux?
Rob
