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

*** 21,31 ****
  
  /*
   * Copyright (c) 1992, 2010, Oracle and/or its affiliates. All rights reserved.
   */
  /*
!  * Copyright (c) 2016, Joyent, Inc. All rights reserved.
   */
  
  /*      Copyright (c) 1990, 1991 UNIX System Laboratories, Inc. */
  /*      Copyright (c) 1984, 1986, 1987, 1988, 1989, 1990 AT&T   */
  /*        All Rights Reserved                                   */
--- 21,31 ----
  
  /*
   * Copyright (c) 1992, 2010, Oracle and/or its affiliates. All rights reserved.
   */
  /*
!  * Copyright (c) 2018 Joyent, Inc.
   */
  
  /*      Copyright (c) 1990, 1991 UNIX System Laboratories, Inc. */
  /*      Copyright (c) 1984, 1986, 1987, 1988, 1989, 1990 AT&T   */
  /*        All Rights Reserved                                   */
*** 1184,1194 ****
          movq    %rdi, %r12
          call    dtrace_instr_size
          addq    %rax, %r12
          movq    %r12, REGOFF_RIP(%rbp)
          INTR_POP
!         IRET
          /*NOTREACHED*/
  3:
          leaq    dtrace_badflags(%rip), %rdi
          xorl    %eax, %eax
          call    panic
--- 1184,1194 ----
          movq    %rdi, %r12
          call    dtrace_instr_size
          addq    %rax, %r12
          movq    %r12, REGOFF_RIP(%rbp)
          INTR_POP
!         jmp     tr_iret_auto
          /*NOTREACHED*/
  3:
          leaq    dtrace_badflags(%rip), %rdi
          xorl    %eax, %eax
          call    panic
*** 1597,1616 ****
          /*
           * Return to 32-bit userland
           */
          ALTENTRY(sys_rtt_syscall32)
          USER32_POP
!         IRET
          /*NOTREACHED*/
  
          ALTENTRY(sys_rtt_syscall)
          /*
           * Return to 64-bit userland
           */
          USER_POP
          ALTENTRY(nopop_sys_rtt_syscall)
!         IRET
          /*NOTREACHED*/
          SET_SIZE(nopop_sys_rtt_syscall)
  
          /*
           * Return to supervisor
--- 1597,1616 ----
          /*
           * Return to 32-bit userland
           */
          ALTENTRY(sys_rtt_syscall32)
          USER32_POP
!         jmp     tr_iret_user
          /*NOTREACHED*/
  
          ALTENTRY(sys_rtt_syscall)
          /*
           * Return to 64-bit userland
           */
          USER_POP
          ALTENTRY(nopop_sys_rtt_syscall)
!         jmp     tr_iret_user
          /*NOTREACHED*/
          SET_SIZE(nopop_sys_rtt_syscall)
  
          /*
           * Return to supervisor
*** 1621,1631 ****
          ALTENTRY(sr_sup)
          /*
           * Restore regs before doing iretq to kernel mode
           */
          INTR_POP
!         IRET
          .globl  _sys_rtt_end
  _sys_rtt_end:
          /*NOTREACHED*/
          SET_SIZE(sr_sup)
          SET_SIZE(_sys_rtt_end)
--- 1621,1631 ----
          ALTENTRY(sr_sup)
          /*
           * Restore regs before doing iretq to kernel mode
           */
          INTR_POP
!         jmp     tr_iret_kernel
          .globl  _sys_rtt_end
  _sys_rtt_end:
          /*NOTREACHED*/
          SET_SIZE(sr_sup)
          SET_SIZE(_sys_rtt_end)