svn commit: r216255 - in head/sys/amd64: amd64 linux32

[Konstantin Belousov]

Author: kib
Date: Tue Dec  7 12:44:33 2010
New Revision: 216255
URL: http://svn.freebsd.org/changeset/base/216255

Log:
  Update some comments related to use of amd64 full context switch.
  In exec_linux_setregs(), use locally cached pointer to pcb to set
  pcb_full_iret.
  In set_regs(), note that full return is needed when code that sets
  segment registers is enabled.
  
  MFC after:	1 week

Modified:
  head/sys/amd64/amd64/machdep.c
  head/sys/amd64/amd64/vm_machdep.c
  head/sys/amd64/linux32/linux32_sysvec.c

Modified: head/sys/amd64/amd64/machdep.c
==============================================================================
--- head/sys/amd64/amd64/machdep.c	Tue Dec  7 12:25:26 2010	(r216254)
+++ head/sys/amd64/amd64/machdep.c	Tue Dec  7 12:44:33 2010	(r216255)
@@ -1906,6 +1906,7 @@ set_regs(struct thread *td, struct reg *
 		tp->tf_fs = regs->r_fs;
 		tp->tf_gs = regs->r_gs;
 		tp->tf_flags = TF_HASSEGS;
+		td->td_pcb->pcb_full_iret = 1;
 	}
 	return (0);
 }

Modified: head/sys/amd64/amd64/vm_machdep.c
==============================================================================
--- head/sys/amd64/amd64/vm_machdep.c	Tue Dec  7 12:25:26 2010	(r216254)
+++ head/sys/amd64/amd64/vm_machdep.c	Tue Dec  7 12:44:33 2010	(r216255)
@@ -339,10 +339,9 @@ cpu_set_syscall_retval(struct thread *td
 		 * Reconstruct pc, we know that 'syscall' is 2 bytes,
 		 * lcall $X,y is 7 bytes, int 0x80 is 2 bytes.
 		 * We saved this in tf_err.
-		 * We have to do a full context restore so that %r10
-		 * (which was holding the value of %rcx) is restored
+		 * %r10 (which was holding the value of %rcx) is restored
 		 * for the next iteration.
-		 * r10 restore is only required for freebsd/amd64 processes,
+		 * %r10 restore is only required for freebsd/amd64 processes,
 		 * but shall be innocent for any ia32 ABI.
 		 */
 		td->td_frame->tf_rip -= td->td_frame->tf_err;

Modified: head/sys/amd64/linux32/linux32_sysvec.c
==============================================================================
--- head/sys/amd64/linux32/linux32_sysvec.c	Tue Dec  7 12:25:26 2010	(r216254)
+++ head/sys/amd64/linux32/linux32_sysvec.c	Tue Dec  7 12:44:33 2010	(r216255)
@@ -865,13 +865,13 @@ exec_linux_setregs(struct thread *td, st
 	regs->tf_flags = TF_HASSEGS;
 	regs->tf_cs = _ucode32sel;
 	regs->tf_rbx = imgp->ps_strings;
-	td->td_pcb->pcb_full_iret = 1;
 	load_cr0(rcr0() | CR0_MP | CR0_TS);
 	fpstate_drop(td);
 
-	/* Return via doreti so that we can change to a different %cs */
+	/* Do full restore on return so that we can change to a different %cs */
 	pcb->pcb_flags |= PCB_32BIT;
 	pcb->pcb_flags &= ~PCB_GS32BIT;
+	pcb->pcb_full_iret = 1;
 	td->td_retval[1] = 0;
 }