11844 add rdmsr utility
Reviewed by: Dan McDonald <danmcd@joyent.com>

*** 20,30 ****
   */
  /*
   * Copyright (c) 2004, 2010, Oracle and/or its affiliates. All rights reserved.
   */
  /*
!  * Copyright (c) 2012, Joyent, Inc.  All rights reserved.
   */
  
  
  #include <sys/types.h>
  #include <sys/file.h>
--- 20,30 ----
   */
  /*
   * Copyright (c) 2004, 2010, Oracle and/or its affiliates. All rights reserved.
   */
  /*
!  * Copyright 2019 Joyent, Inc.
   */
  
  
  #include <sys/types.h>
  #include <sys/file.h>
*** 37,46 ****
--- 37,47 ----
  #include <sys/cpuvar.h>
  #include <sys/kmem.h>
  #include <sys/modctl.h>
  #include <sys/ddi.h>
  #include <sys/sunddi.h>
+ #include <sys/policy.h>
  
  #include <sys/auxv.h>
  #include <sys/cpuid_drv.h>
  #include <sys/systeminfo.h>
  
*** 181,190 ****
--- 182,220 ----
                      (void *)arg, STRUCT_SIZE(h), mode))
                          return (EFAULT);
                  return (0);
          }
  
+ #ifdef __x86
+         case CPUID_RDMSR: {
+                 struct cpuid_rdmsr crm = { 0, };
+                 label_t label;
+ 
+                 if (secpolicy_sys_config(cr, B_FALSE) != 0)
+                         return (EPERM);
+ 
+                 if (ddi_copyin((void *)arg, &crm, sizeof (crm), mode))
+                         return (EFAULT);
+ 
+                 kpreempt_disable();
+ 
+                 if (on_fault(&label)) {
+                         kpreempt_enable();
+                         return (ENOENT);
+                 }
+ 
+                 crm.cr_msr_val = rdmsr(crm.cr_msr_nr);
+ 
+                 no_fault();
+                 kpreempt_enable();
+ 
+                 if (ddi_copyout(&crm, (void *)arg, sizeof (crm), mode))
+                         return (EFAULT);
+                 return (0);
+         }
+ #endif
+ 
          default:
                  return (ENOTTY);
          }
  }