On 09/22/2015 01:03 PM, Thomas Gleixner wrote:
> On Wed, 16 Sep 2015, Dave Hansen wrote:
>>
>> +static inline u16 vma_pkey(struct vm_area_struct *vma)
>> +{
>> + u16 pkey = 0;
>> +#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
>> + unsigned long f = vma->vm_flags;
>> + pkey |= (!!(f & VM_HIGH_ARCH_0)) << 0;
>> + pkey |= (!!(f & VM_HIGH_ARCH_1)) << 1;
>> + pkey |= (!!(f & VM_HIGH_ARCH_2)) << 2;
>> + pkey |= (!!(f & VM_HIGH_ARCH_3)) << 3;
>
> Eew. What's wrong with:
>
> pkey = (vma->vm_flags & VM_PKEY_MASK) >> VM_PKEY_SHIFT;
I didn't do that only because we don't have any other need for
VM_PKEY_MASK or VM_PKEY_SHIFT. We could do:
#define VM_PKEY_MASK (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2...)
static inline u16 vma_pkey(struct vm_area_struct *vma)
{
int vm_pkey_shift = __ffs(VM_PKEY_MASK)
return (vma->vm_flags & VM_PKEY_MASK) >> vm_pkey_shift;
}
That's probably the same number of lines of code in the end. The
compiler _probably_ ends up doing the same thing either way.
>> +static u16 fetch_pkey(unsigned long address, struct task_struct *tsk)
>
> So here we get a u16 and assign it to si_pkey
>
>> + if (boot_cpu_has(X86_FEATURE_OSPKE) && si_code == SEGV_PKUERR)
>> + info.si_pkey = fetch_pkey(address, tsk);
>
> which is int.
>
>> + int _pkey; /* FIXME: protection key value??
>
> Inconsistent at least.
So I defined all the kernel-internal types as u16 since I *know* the
size of the hardware.
The user-exposed ones should probably be a bit more generic. I did just
realize that this is an int and my proposed syscall is a long. That I
definitely need to make consistent.
Does anybody care whether it's an int or a long?
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>