Alexander Graf wrote:
> On 23.10.2009, at 10:41, Jan Kiszka wrote:
>
>> Alexander Graf wrote:
>>> From: Arnd Bergmann <arnd@xxxxxxxx>
>>>
>>> With big endian userspace, we can't quite figure out if a pointer
>>> is 32 bit (shifted >> 32) or 64 bit when we read a 64 bit pointer.
>>>
>>> This is what happens with dirty logging. To get the pointer
>>> interpreted
>>> correctly, we thus need Arnd's patch to implement a compat layer for
>>> the ioctl:
>>>
>>> A better way to do this is to add a separate compat_ioctl() method
>>> that
>>> converts this for you.
>>>
>>> From: Arnd Bergmann <arnd@xxxxxxxx>
>>> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
>>> Acked-by: Alexander Graf <agraf@xxxxxxx>
>>>
>>> ---
>>>
>>> Changes from Arnd's example version:
>>>
>>> - s/log.log/log/ (Avi)
>>> - use sizeof(compat_log) (Avi)
>>> - compile fixes
>>> ---
>>> virt/kvm/kvm_main.c | 49 +++++++++++++++++++++++++++++++++++++++++
>>> +++++++-
>>> 1 files changed, 48 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>>> index cac69c4..54a272f 100644
>>> --- a/virt/kvm/kvm_main.c
>>> +++ b/virt/kvm/kvm_main.c
>>> @@ -43,6 +43,7 @@
>>> #include <linux/swap.h>
>>> #include <linux/bitops.h>
>>> #include <linux/spinlock.h>
>>> +#include <linux/compat.h>
>>>
>>> #include <asm/processor.h>
>>> #include <asm/io.h>
>>> @@ -1542,6 +1543,52 @@ out:
>>> return r;
>>> }
>>>
>>> +#ifdef CONFIG_COMPAT
>>> +struct compat_kvm_dirty_log {
>>> + __u32 slot;
>>> + __u32 padding1;
>>> + union {
>>> + compat_uptr_t dirty_bitmap; /* one bit per page */
>>> + __u64 padding2;
>>> + };
>>> +};
>>> +
>>> +static long kvm_vm_compat_ioctl(struct file *filp,
>>> + unsigned int ioctl, unsigned long arg)
>>> +{
>>> + struct kvm *kvm = filp->private_data;
>>> + int r;
>>> +
>>> + if (kvm->mm != current->mm)
>>> + return -EIO;
>>> + switch (ioctl) {
>>> + case KVM_GET_DIRTY_LOG: {
>>> + struct compat_kvm_dirty_log compat_log;
>>> + struct kvm_dirty_log log;
>>> +
>>> + r = -EFAULT;
>>> + if (copy_from_user(&compat_log, (void __user *)arg,
>>> + sizeof(compat_log)))
>>> + goto out;
>>> + log.slot = compat_log.slot;
>>> + log.padding1 = compat_log.padding1;
>>> + log.padding2 = compat_log.padding2;
>>> + log.dirty_bitmap = compat_ptr(compat_log.dirty_bitmap);
>>> +
>>> + r = kvm_vm_ioctl_get_dirty_log(kvm, &log);
>>> + if (r)
>>> + goto out;
>>> + break;
>>> + }
>>> + default:
>>> + r = kvm_vm_ioctl(filp, ioctl, arg);
>>> + }
>>> +
>>> +out:
>>> + return r;
>>> +}
>>> +#endif
>>> +
>>> static int kvm_vm_fault(struct vm_area_struct *vma, struct vm_fault
>>> *vmf)
>>> {
>>> struct page *page[1];
>>> @@ -1576,7 +1623,7 @@ static int kvm_vm_mmap(struct file *file,
>>> struct vm_area_struct *vma)
>>> static struct file_operations kvm_vm_fops = {
>>> .release = kvm_vm_release,
>>> .unlocked_ioctl = kvm_vm_ioctl,
>>> - .compat_ioctl = kvm_vm_ioctl,
>>> + .compat_ioctl = kvm_vm_compat_ioctl,
>> This fails in the absence of CONFIG_COMPAT.
>
>
> So should it rather be
>
> #ifdef CONFIG_COMPAT
> .compat_ioctl = kvm_vm_compat_ioctl,
> #else
> .compat_ioctl = kvm_vm_ioctl,
> #endif
>
> or
>
> #ifdef CONFIG_COMPAT
> .compat_ioctl = kvm_vm_compat_ioctl,
> #endif
>
> ?
I would say the latter as .compat_ioctl should simply be unused in case
of !CONFIG_COMPAT.
Jan
--
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux
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