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Date:      Wed, 15 Dec 2010 15:25:57 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-8@freebsd.org
Subject:   svn commit: r216458 - in stable/8/sys/amd64: amd64 linux32
Message-ID:  <201012151525.oBFFPv2q056362@svn.freebsd.org>
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Author: kib
Date: Wed Dec 15 15:25:56 2010
New Revision: 216458
URL: http://svn.freebsd.org/changeset/base/216458

Log:
  MFC r216255:
  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.
  
  Approved by:	re (bz)

Modified:
  stable/8/sys/amd64/amd64/machdep.c
  stable/8/sys/amd64/amd64/vm_machdep.c
  stable/8/sys/amd64/linux32/linux32_sysvec.c
Directory Properties:
  stable/8/sys/   (props changed)
  stable/8/sys/amd64/include/xen/   (props changed)
  stable/8/sys/cddl/contrib/opensolaris/   (props changed)
  stable/8/sys/contrib/dev/acpica/   (props changed)
  stable/8/sys/contrib/pf/   (props changed)

Modified: stable/8/sys/amd64/amd64/machdep.c
==============================================================================
--- stable/8/sys/amd64/amd64/machdep.c	Wed Dec 15 15:23:25 2010	(r216457)
+++ stable/8/sys/amd64/amd64/machdep.c	Wed Dec 15 15:25:56 2010	(r216458)
@@ -1895,6 +1895,7 @@ 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: stable/8/sys/amd64/amd64/vm_machdep.c
==============================================================================
--- stable/8/sys/amd64/amd64/vm_machdep.c	Wed Dec 15 15:23:25 2010	(r216457)
+++ stable/8/sys/amd64/amd64/vm_machdep.c	Wed Dec 15 15:25:56 2010	(r216458)
@@ -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: stable/8/sys/amd64/linux32/linux32_sysvec.c
==============================================================================
--- stable/8/sys/amd64/linux32/linux32_sysvec.c	Wed Dec 15 15:23:25 2010	(r216457)
+++ stable/8/sys/amd64/linux32/linux32_sysvec.c	Wed Dec 15 15:25:56 2010	(r216458)
@@ -875,13 +875,13 @@ exec_linux_setregs(td, entry, stack, ps_
 	regs->tf_flags = TF_HASSEGS;
 	regs->tf_cs = _ucode32sel;
 	regs->tf_rbx = 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;
 }

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