8956 Implement KPTI
Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>

*** 18,27 ****
--- 18,28 ----
   *
   * CDDL HEADER END
   */
  /*
   * Copyright (c) 1992, 2010, Oracle and/or its affiliates. All rights reserved.
+  * Copyright 2018 Joyent, Inc.
   */
  
  /*      Copyright (c) 1990, 1991 UNIX System Laboratories, Inc. */
  /*      Copyright (c) 1984, 1986, 1987, 1988, 1989, 1990 AT&T   */
  /*        All Rights Reserved   */
*** 58,67 ****
--- 59,69 ----
  #include <vm/faultcode.h>
  #include <sys/fp.h>
  #include <sys/cmn_err.h>
  #include <sys/segments.h>
  #include <sys/clock.h>
+ #include <vm/hat_i86.h>
  #if defined(__xpv)
  #include <sys/hypervisor.h>
  #include <sys/note.h>
  #endif
  
*** 344,354 ****
  {
  #if defined(__xpv)
          xen_set_ldt(get_ssd_base(&curproc->p_ldt_desc),
              curproc->p_ldtlimit + 1);
  #else
!         *((system_desc_t *)&CPU->cpu_gdt[GDT_LDT]) = curproc->p_ldt_desc;
          wr_ldtr(ULDT_SEL);
  #endif
  }
  
  /*
--- 346,368 ----
  {
  #if defined(__xpv)
          xen_set_ldt(get_ssd_base(&curproc->p_ldt_desc),
              curproc->p_ldtlimit + 1);
  #else
!         size_t len;
!         system_desc_t desc;
! 
!         /*
!          * Before we can use the LDT on this CPU, we must install the LDT in the
!          * user mapping table.
!          */
!         len = (curproc->p_ldtlimit + 1) * sizeof (user_desc_t);
!         bcopy(curproc->p_ldt, CPU->cpu_m.mcpu_ldt, len);
!         CPU->cpu_m.mcpu_ldt_len = len;
!         set_syssegd(&desc, CPU->cpu_m.mcpu_ldt, len - 1, SDT_SYSLDT, SEL_KPL);
!         *((system_desc_t *)&CPU->cpu_gdt[GDT_LDT]) = desc;
! 
          wr_ldtr(ULDT_SEL);
  #endif
  }
  
  /*
*** 361,370 ****
--- 375,387 ----
  #if defined(__xpv)
          xen_set_ldt(NULL, 0);
  #else
          *((system_desc_t *)&CPU->cpu_gdt[GDT_LDT]) = null_sdesc;
          wr_ldtr(0);
+ 
+         bzero(CPU->cpu_m.mcpu_ldt, CPU->cpu_m.mcpu_ldt_len);
+         CPU->cpu_m.mcpu_ldt_len = 0;
  #endif
  }
  
  /*ARGSUSED*/
  static void
*** 712,722 ****
          ASSERT(MUTEX_HELD(&pp->p_ldtlock));
          ASSERT(pp->p_ldt == NULL);
          ASSERT(pp->p_ldtlimit == 0);
  
          /*
!          * Allocate new LDT just large enough to contain seli.
           */
          ldtsz = P2ROUNDUP((seli + 1) * sizeof (user_desc_t), PAGESIZE);
          nsels = ldtsz / sizeof (user_desc_t);
          ASSERT(nsels >= MINNLDT && nsels <= MAXNLDT);
  
--- 729,740 ----
          ASSERT(MUTEX_HELD(&pp->p_ldtlock));
          ASSERT(pp->p_ldt == NULL);
          ASSERT(pp->p_ldtlimit == 0);
  
          /*
!          * Allocate new LDT just large enough to contain seli. The LDT must
!          * always be allocated in units of pages for KPTI.
           */
          ldtsz = P2ROUNDUP((seli + 1) * sizeof (user_desc_t), PAGESIZE);
          nsels = ldtsz / sizeof (user_desc_t);
          ASSERT(nsels >= MINNLDT && nsels <= MAXNLDT);
  
*** 830,840 ****
          ASSERT(MUTEX_HELD(&pp->p_ldtlock));
          ASSERT(pp->p_ldt != NULL);
          ASSERT(pp->p_ldtlimit != 0);
  
          /*
!          * Allocate larger LDT just large enough to contain seli.
           */
          nldtsz = P2ROUNDUP((seli + 1) * sizeof (user_desc_t), PAGESIZE);
          nsels = nldtsz / sizeof (user_desc_t);
          ASSERT(nsels >= MINNLDT && nsels <= MAXNLDT);
          ASSERT(nsels > pp->p_ldtlimit);
--- 848,859 ----
          ASSERT(MUTEX_HELD(&pp->p_ldtlock));
          ASSERT(pp->p_ldt != NULL);
          ASSERT(pp->p_ldtlimit != 0);
  
          /*
!          * Allocate larger LDT just large enough to contain seli. The LDT must
!          * always be allocated in units of pages for KPTI.
           */
          nldtsz = P2ROUNDUP((seli + 1) * sizeof (user_desc_t), PAGESIZE);
          nsels = nldtsz / sizeof (user_desc_t);
          ASSERT(nsels >= MINNLDT && nsels <= MAXNLDT);
          ASSERT(nsels > pp->p_ldtlimit);