Re: [patch] fix kvm_arch_vcpu_ioctl_[gs]et_regs()

[Jes Sorensen <jes@sgi.com>]

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Zhang, Xiantao wrote:
> Jes
>    Good work!  I ever talked about the issue with Avi and wanted to enable the logic with the following patch, and Avi thought it may lead to security issues, so deferred to now :) 
> 
> One comment:  We still need the logic to save and restore the vcpu's stack for vcpu resuming to the guest in the same environment.  Maybe you can allocate one buf to save it in kvm_reg structure.
> Xiantao

Xiantao,

I have come up with a patch for this. Before we push it, would you mind
taking a look at it and let me know if it looks right? I don't have any
way of really testing this.

Cheers,
Jes


[-- Attachment #2: 6001-kvm-ia64-restore-stack-ioctl.patch --]
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---
 arch/ia64/include/asm/kvm.h      |    8 +++
 arch/ia64/include/asm/kvm_host.h |    2 
 arch/ia64/kvm/kvm-ia64.c         |   92 +++++++++++++++++++++++++++++++++++++--
 include/linux/kvm.h              |    3 +
 4 files changed, 101 insertions(+), 4 deletions(-)

Index: linux-2.6.git/arch/ia64/include/asm/kvm.h
===================================================================
--- linux-2.6.git.orig/arch/ia64/include/asm/kvm.h
+++ linux-2.6.git/arch/ia64/include/asm/kvm.h
@@ -242,4 +242,12 @@
 
 struct kvm_fpu {
 };
+
+#define KVM_IA64_VCPU_STACK_SHIFT	16
+#define KVM_IA64_VCPU_STACK_SIZE	(1UL << KVM_IA64_VCPU_STACK_SHIFT)
+
+struct kvm_ia64_vcpu_stack {
+	unsigned char stack[KVM_IA64_VCPU_STACK_SIZE];
+};
+
 #endif
Index: linux-2.6.git/arch/ia64/include/asm/kvm_host.h
===================================================================
--- linux-2.6.git.orig/arch/ia64/include/asm/kvm_host.h
+++ linux-2.6.git/arch/ia64/include/asm/kvm_host.h
@@ -112,7 +112,7 @@
 #define VCPU_STRUCT_SHIFT	16
 #define VCPU_STRUCT_SIZE	(__IA64_UL_CONST(1)<< VCPU_STRUCT_SHIFT)
 
-#define KVM_STK_OFFSET		VCPU_STRUCT_SIZE
+#define KVM_STK_OFFSET		KVM_IA64_VCPU_STACK_SIZE
 
 #define KVM_VM_STRUCT_SHIFT	19
 #define KVM_VM_STRUCT_SIZE	(__IA64_UL_CONST(1) << KVM_VM_STRUCT_SHIFT)
Index: linux-2.6.git/arch/ia64/kvm/kvm-ia64.c
===================================================================
--- linux-2.6.git.orig/arch/ia64/kvm/kvm-ia64.c
+++ linux-2.6.git/arch/ia64/kvm/kvm-ia64.c
@@ -1456,6 +1456,23 @@
 	return 0;
 }
 
+int kvm_arch_vcpu_ioctl_get_stack(struct kvm_vcpu *vcpu,
+				  struct kvm_ia64_vcpu_stack *stack)
+{
+	memcpy(stack, vcpu, KVM_IA64_VCPU_STACK_SIZE);
+	return 0;
+}
+
+int kvm_arch_vcpu_ioctl_set_stack(struct kvm_vcpu *vcpu,
+				  struct kvm_ia64_vcpu_stack *stack)
+{
+	memcpy(vcpu + 1, &stack->stack[0] + sizeof(struct kvm_vcpu),
+	       KVM_IA64_VCPU_STACK_SIZE - sizeof(struct kvm_vcpu));
+
+	vcpu->arch.exit_data = ((struct kvm_vcpu *)stack)->arch.exit_data;
+	return 0;
+}
+
 void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu)
 {
 
@@ -1465,9 +1482,78 @@
 
 
 long kvm_arch_vcpu_ioctl(struct file *filp,
-		unsigned int ioctl, unsigned long arg)
+			 unsigned int ioctl, unsigned long arg)
 {
-	return -EINVAL;
+	struct kvm_vcpu *vcpu = filp->private_data;
+	void __user *argp = (void __user *)arg;
+	struct kvm_ia64_vcpu_stack *stack = NULL;
+	long r;
+
+	switch (ioctl) {
+	case KVM_IA64_VCPU_GET_STACK: {
+		struct kvm_ia64_vcpu_stack __user *user_stack;
+	        void __user *first_p = argp;
+
+		r = -EFAULT;
+		if (copy_from_user(&user_stack, first_p, sizeof(void *)))
+			goto out;
+
+		if (!access_ok(VERIFY_WRITE, user_stack,
+			       sizeof(struct kvm_ia64_vcpu_stack))) {
+			printk(KERN_INFO "KVM_IA64_VCPU_GET_STACK: "
+			       "Illegal user destination address for stack\n");
+			goto out;
+		}
+		stack = kzalloc(sizeof(struct kvm_ia64_vcpu_stack), GFP_KERNEL);
+		if (!stack) {
+			r = -ENOMEM;
+			goto out;
+		}
+
+		r = kvm_arch_vcpu_ioctl_get_stack(vcpu, stack);
+		if (r)
+			goto out;
+
+		if (copy_to_user(user_stack, stack,
+				 sizeof(struct kvm_ia64_vcpu_stack)))
+			goto out;
+
+		break;
+	}
+	case KVM_IA64_VCPU_SET_STACK: {
+		struct kvm_ia64_vcpu_stack __user *user_stack;
+	        void __user *first_p = argp;
+
+		r = -EFAULT;
+		if (copy_from_user(&user_stack, first_p, sizeof(void *)))
+			goto out;
+
+		if (!access_ok(VERIFY_READ, user_stack,
+			    sizeof(struct kvm_ia64_vcpu_stack))) {
+			printk(KERN_INFO "KVM_IA64_VCPU_SET_STACK: "
+			       "Illegal user address for stack\n");
+			goto out;
+		}
+		stack = kmalloc(sizeof(struct kvm_ia64_vcpu_stack), GFP_KERNEL);
+		if (!stack) {
+			r = -ENOMEM;
+			goto out;
+		}
+		if (copy_from_user(stack, user_stack,
+				   sizeof(struct kvm_ia64_vcpu_stack)))
+			goto out;
+
+		r = kvm_arch_vcpu_ioctl_set_stack(vcpu, stack);
+		break;
+	}
+
+	default:
+		r = -EINVAL;
+	}
+
+out:
+	kfree(stack);
+	return r;
 }
 
 int kvm_arch_set_memory_region(struct kvm *kvm,
@@ -1502,7 +1588,7 @@
 }
 
 long kvm_arch_dev_ioctl(struct file *filp,
-		unsigned int ioctl, unsigned long arg)
+			unsigned int ioctl, unsigned long arg)
 {
 	return -EINVAL;
 }
Index: linux-2.6.git/include/linux/kvm.h
===================================================================
--- linux-2.6.git.orig/include/linux/kvm.h
+++ linux-2.6.git/include/linux/kvm.h
@@ -459,6 +459,9 @@
 #define KVM_GET_MP_STATE          _IOR(KVMIO,  0x98, struct kvm_mp_state)
 #define KVM_SET_MP_STATE          _IOW(KVMIO,  0x99, struct kvm_mp_state)
 
+#define KVM_IA64_VCPU_GET_STACK   _IOR(KVMIO,  0x9a, void *)
+#define KVM_IA64_VCPU_SET_STACK   _IOW(KVMIO,  0x9b, void *)
+
 #define KVM_TRC_INJ_VIRQ         (KVM_TRC_HANDLER + 0x02)
 #define KVM_TRC_REDELIVER_EVT    (KVM_TRC_HANDLER + 0x03)
 #define KVM_TRC_PEND_INTR        (KVM_TRC_HANDLER + 0x04)