added safety checks to cpuid field registration

diff --git a/palacios/src/palacios/vmm_cpuid.c b/palacios/src/palacios/vmm_cpuid.c
index ce7c244..ca7ef86 100644 (file)
--- a/palacios/src/palacios/vmm_cpuid.c
+++ b/palacios/src/palacios/vmm_cpuid.c
@@ -135,20 +135,27 @@ static int mask_hook(struct guest_info * core, uint32_t cpuid,
     v3_cpuid(cpuid, eax, ebx, ecx, edx);
 
     *eax &= ~(mask->rax_mask);
-    *eax |= mask->rax;
+    *eax |= (mask->rax & mask->rax_mask);
 
     *ebx &= ~(mask->rbx_mask);
-    *ebx |= mask->rbx;
+    *ebx |= (mask->rbx & mask->rbx_mask);
 
     *ecx &= ~(mask->rcx_mask);
-    *ecx |= mask->rcx;
+    *ecx |= (mask->rcx & mask->rcx_mask);
 
     *edx &= ~(mask->rdx_mask);
-    *edx |= mask->rdx;
+    *edx |= (mask->rdx & mask->rdx_mask);
 
     return 0;
 }
 
+
+
+/* This function allows you to reserve a set of bits in a given cpuid value 
+ * For each cpuid return register you specify which bits you want to reserve in the mask.
+ * The value of those bits is set in the reg param.
+ * The values of the reserved bits are  returned to the guest, when it reads the cpuid
+ */ 
 int v3_cpuid_add_fields(struct v3_vm_info * vm, uint32_t cpuid, 
                        uint32_t rax_mask, uint32_t rax,
                        uint32_t rbx_mask, uint32_t rbx, 
@@ -156,6 +163,14 @@ int v3_cpuid_add_fields(struct v3_vm_info * vm, uint32_t cpuid,
                        uint32_t rdx_mask, uint32_t rdx) {
     struct v3_cpuid_hook * hook = get_cpuid_hook(vm, cpuid);
 
+
+    if ((~rax_mask & rax) || (~rbx_mask & rbx) ||
+       (~rcx_mask & rcx) || (~rdx_mask & rdx)) {
+       PrintError("Invalid cpuid reg value (mask overrun)\n");
+       return -1;
+    }
+
+
     if (hook == NULL) {
        struct masked_cpuid * mask = V3_Malloc(sizeof(struct masked_cpuid));
        memset(mask, 0, sizeof(struct masked_cpuid));
@@ -192,12 +207,6 @@ int v3_cpuid_add_fields(struct v3_vm_info * vm, uint32_t cpuid,
            return -1;
        }
 
-       if ((~rax_mask & rax) || (~rbx_mask & rbx) ||
-           (~rcx_mask & rcx) || (~rdx_mask & rdx)) {
-           PrintError("Invalid cpuid reg value (mask overrun)\n");
-           return -1;
-       }
-
        mask->rax_mask |= rax_mask;
        mask->rbx_mask |= rbx_mask;
        mask->rcx_mask |= rcx_mask;