lkml.org 
[lkml]   [2015]   [Sep]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH 10/26] x86, pkeys: notify userspace about protection key faults
    From
    Date
    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?


    \
     
     \ /
      Last update: 2015-09-22 22:41    [W:4.700 / U:0.040 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site