[PATCH 16/35] KVM: Enable 32bit dirty log pointers on 64bit host

Avi Kivity
2009-11-19T13:35:08Z

From: Arnd Bergmann <arnd@arndb.de>

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.

Based on initial patch from Arnd Bergmann.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
virt/kvm/kvm_main.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 50 insertions(+), 1 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index cac69c4..bd44fb4 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 +1623,9 @@ 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,
+#ifdef CONFIG_COMPAT
+ .compat_ioctl = kvm_vm_compat_ioctl,
+#endif
.mmap = kvm_vm_mmap,
};

--
1.6.5.2