[07/27] nVMX: Decoding memory operands of VMX instructions

Commit Message

Nadav Har'El Oct. 17, 2010, 10:07 a.m. UTC

None

Patch

--- .before/arch/x86/kvm/x86.c	2010-10-17 11:52:00.000000000 +0200
+++ .after/arch/x86/kvm/x86.c	2010-10-17 11:52:00.000000000 +0200
@@ -3636,13 +3636,14 @@  static int kvm_fetch_guest_virt(gva_t ad
 					  access | PFERR_FETCH_MASK, error);
 }
 
-static int kvm_read_guest_virt(gva_t addr, void *val, unsigned int bytes,
+int kvm_read_guest_virt(gva_t addr, void *val, unsigned int bytes,
 			       struct kvm_vcpu *vcpu, u32 *error)
 {
 	u32 access = (kvm_x86_ops->get_cpl(vcpu) == 3) ? PFERR_USER_MASK : 0;
 	return kvm_read_guest_virt_helper(addr, val, bytes, vcpu, access,
 					  error);
 }
+EXPORT_SYMBOL_GPL(kvm_read_guest_virt);
 
 static int kvm_read_guest_virt_system(gva_t addr, void *val, unsigned int bytes,
 			       struct kvm_vcpu *vcpu, u32 *error)
--- .before/arch/x86/kvm/x86.h	2010-10-17 11:52:00.000000000 +0200
+++ .after/arch/x86/kvm/x86.h	2010-10-17 11:52:00.000000000 +0200
@@ -74,6 +74,9 @@  void kvm_before_handle_nmi(struct kvm_vc
 void kvm_after_handle_nmi(struct kvm_vcpu *vcpu);
 int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq);
 
+int kvm_read_guest_virt(gva_t addr, void *val, unsigned int bytes,
+		struct kvm_vcpu *vcpu, u32 *error);
+
 void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data);
 
 #endif
--- .before/arch/x86/kvm/vmx.c	2010-10-17 11:52:00.000000000 +0200
+++ .after/arch/x86/kvm/vmx.c	2010-10-17 11:52:00.000000000 +0200
@@ -3647,6 +3647,65 @@  static int handle_vmoff(struct kvm_vcpu 
 	return 1;
 }
 
+/*
+ * Decode the memory-address operand of a vmx instruction, as recorded on an
+ * exit caused by such an instruction (run by a guest hypervisor).
+ * On success, returns 0. When the operand is invalid, returns 1 and throws
+ * #UD or #GP.
+ */
+static int get_vmx_mem_address(struct kvm_vcpu *vcpu,
+				 unsigned long exit_qualification,
+				 u32 vmx_instruction_info, gva_t *ret)
+{
+	/*
+	 * According to Vol. 3B, "Information for VM Exits Due to Instruction
+	 * Execution", on an exit, vmx_instruction_info holds most of the
+	 * addressing components of the operand. Only the displacement part
+	 * is put in exit_qualification (see 3B, "Basic VM-Exit Information").
+	 * For how an actual address is calculated from all these components,
+	 * refer to Vol. 1, "Operand Addressing".
+	 */
+	int  scaling = vmx_instruction_info & 3;
+	int  addr_size = (vmx_instruction_info >> 7) & 7;
+	bool is_reg = vmx_instruction_info & (1u << 10);
+	int  seg_reg = (vmx_instruction_info >> 15) & 7;
+	int  index_reg = (vmx_instruction_info >> 18) & 0xf;
+	bool index_is_valid = !(vmx_instruction_info & (1u << 22));
+	int  base_reg       = (vmx_instruction_info >> 23) & 0xf;
+	bool base_is_valid  = !(vmx_instruction_info & (1u << 27));
+
+	if (is_reg) {
+		kvm_queue_exception(vcpu, UD_VECTOR);
+		return 1;
+	}
+
+	switch (addr_size) {
+	case 1: /* 32 bit. high bits are undefined according to the spec: */
+		exit_qualification &= 0xffffffff;
+		break;
+	case 2: /* 64 bit */
+		break;
+	default: /* 16 bit */
+		return 1;
+	}
+
+	/* Addr = segment_base + offset */
+	/* offset = base + [index * scale] + displacement */
+	*ret = vmx_get_segment_base(vcpu, seg_reg);
+	if (base_is_valid)
+		*ret += kvm_register_read(vcpu, base_reg);
+	if (index_is_valid)
+		*ret += kvm_register_read(vcpu, index_reg)<<scaling;
+	*ret += exit_qualification; /* holds the displacement */
+	/*
+	 * TODO: throw #GP (and return 1) in various cases that the VM*
+	 * instructions require it - e.g., offset beyond segment limit,
+	 * unusable or unreadable/unwritable segment, non-canonical 64-bit
+	 * address, and so on. Currently these are not checked.
+	 */
+	return 0;
+}
+
 static int handle_invlpg(struct kvm_vcpu *vcpu)
 {
 	unsigned long exit_qualification = vmcs_readl(EXIT_QUALIFICATION);