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.
Jan
--
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux
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