9723 provide support for VMM's GDT handling
Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed by: Patrick Mooney <patrick.mooney@joyent.com>

*** 902,914 ****
  }
  
  #ifdef _KMDB
  /* ARGSUSED */
  static int
! crregs_dcmd(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
  {
          ulong_t cr0, cr2, cr3, cr4;
          static const mdb_bitmask_t cr0_flag_bits[] = {
                  { "PE",         CR0_PE,         CR0_PE },
                  { "MP",         CR0_MP,         CR0_MP },
                  { "EM",         CR0_EM,         CR0_EM },
                  { "TS",         CR0_TS,         CR0_TS },
--- 902,916 ----
  }
  
  #ifdef _KMDB
  /* ARGSUSED */
  static int
! sysregs_dcmd(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
  {
          ulong_t cr0, cr2, cr3, cr4;
+         desctbr_t gdtr;
+ 
          static const mdb_bitmask_t cr0_flag_bits[] = {
                  { "PE",         CR0_PE,         CR0_PE },
                  { "MP",         CR0_MP,         CR0_MP },
                  { "EM",         CR0_EM,         CR0_EM },
                  { "TS",         CR0_TS,         CR0_TS },
*** 951,960 ****
--- 953,965 ----
  
          cr0 = kmdb_unix_getcr0();
          cr2 = kmdb_unix_getcr2();
          cr3 = kmdb_unix_getcr3();
          cr4 = kmdb_unix_getcr4();
+ 
+         kmdb_unix_getgdtr(&gdtr);
+ 
          mdb_printf("%%cr0 = 0x%lx <%b>\n", cr0, cr0, cr0_flag_bits);
          mdb_printf("%%cr2 = 0x%lx <%a>\n", cr2, cr2);
  
          if ((cr4 & CR4_PCIDE)) {
                  mdb_printf("%%cr3 = 0x%lx <pfn:0x%lx pcid:%lu>\n", cr3,
*** 964,973 ****
--- 969,981 ----
                      cr3 >> MMU_PAGESHIFT, cr3, cr3_flag_bits);
          }
  
          mdb_printf("%%cr4 = 0x%lx <%b>\n", cr4, cr4, cr4_flag_bits);
  
+         mdb_printf("%%gdtr.base = 0x%lx, %%gdtr.limit = 0x%hx\n",
+             gdtr.dtr_base, gdtr.dtr_limit);
+ 
          return (DCMD_OK);
  }
  #endif
  
  static const mdb_dcmd_t dcmds[] = {
*** 995,1005 ****
          { "scalehrtime", ":",
              "scale an unscaled high-res time", scalehrtime_cmd },
          { "x86_featureset", NULL, "dump the x86_featureset vector",
                  x86_featureset_cmd },
  #ifdef _KMDB
!         { "crregs", NULL, "dump control registers", crregs_dcmd },
  #endif
          { NULL }
  };
  
  static const mdb_walker_t walkers[] = {
--- 1003,1013 ----
          { "scalehrtime", ":",
              "scale an unscaled high-res time", scalehrtime_cmd },
          { "x86_featureset", NULL, "dump the x86_featureset vector",
                  x86_featureset_cmd },
  #ifdef _KMDB
!         { "sysregs", NULL, "dump system registers", sysregs_dcmd },
  #endif
          { NULL }
  };
  
  static const mdb_walker_t walkers[] = {