[src/trunk]: src/sys/arch Improve our segregs model. Pass 3/3.

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/c6269f5d5588
branches:  trunk
changeset: 356926:c6269f5d5588
user:      maxv <maxv%NetBSD.org@localhost>
date:      Sat Oct 21 06:55:54 2017 +0000

description:
Improve our segregs model. Pass 3/3.

Treat %gs the same way we treat %ds/%es/%fs: restore it in INTRFASTEXIT
on 32bit LWPs.

On Xen however, its behavior does not change, because we need to do an
hypercall before INTR_RESTORE_GPRS, and that's too complicated for now.

As a side effect, this change fixes a bug in the ACPI wakeup code; %fs/%gs
were not restored on 32bit LWPs, and chances are they would segfault
shortly afterwards.

Support for USER_LDT on amd64 is almost complete now.

diffstat:

 sys/arch/amd64/acpi/acpi_wakeup_low.S |  8 ++++----
 sys/arch/amd64/amd64/locore.S         |  9 ++++++---
 sys/arch/amd64/amd64/machdep.c        |  8 ++++++--
 sys/arch/x86/x86/sys_machdep.c        |  6 +++---
 4 files changed, 19 insertions(+), 12 deletions(-)

diffs (116 lines):

diff -r bfd2cb13e85f -r c6269f5d5588 sys/arch/amd64/acpi/acpi_wakeup_low.S
--- a/sys/arch/amd64/acpi/acpi_wakeup_low.S     Sat Oct 21 05:30:48 2017 +0000
+++ b/sys/arch/amd64/acpi/acpi_wakeup_low.S     Sat Oct 21 06:55:54 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: acpi_wakeup_low.S,v 1.7 2017/10/19 18:36:31 maxv Exp $ */
+/*     $NetBSD: acpi_wakeup_low.S,v 1.8 2017/10/21 06:55:54 maxv Exp $ */
 
 /*-
  * Copyright (c) 2007 Joerg Sonnenberger <joerg%netbsd.org@localhost>
@@ -47,9 +47,9 @@
        movw    %ax,%ss
 
        /*
-        * FS and GS are driven by MSRs, so use NULL for them.
-        * XXX XXX XXX That's not the case if we're returning to a 32bit
-        * LWP!
+        * FS and GS are driven by MSRs, so use NULL for them. If we're
+        * returning to a 32bit LWP, %fs/%gs will be restored in
+        * INTRFASTEXIT.
         */
        xorw    %ax,%ax
        movw    %ax,%fs
diff -r bfd2cb13e85f -r c6269f5d5588 sys/arch/amd64/amd64/locore.S
--- a/sys/arch/amd64/amd64/locore.S     Sat Oct 21 05:30:48 2017 +0000
+++ b/sys/arch/amd64/amd64/locore.S     Sat Oct 21 06:55:54 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: locore.S,v 1.136 2017/10/19 20:27:12 maxv Exp $        */
+/*     $NetBSD: locore.S,v 1.137 2017/10/21 06:55:54 maxv Exp $        */
 
 /*
  * Copyright-o-rama!
@@ -1196,7 +1196,7 @@
        movq    PCB_GS(%r14),%rax
        movq    %rax,(GUGS_SEL*8)(%rcx)
 
-       /* Set default 32bit values in %ds, %es and %fs. %gs is special. */
+       /* Set default 32bit values in %ds, %es, %fs and %gs. */
        movq    L_MD_REGS(%r12),%rbx
        movq    $GSEL(GUDATA32_SEL, SEL_UPL),%rax
        movw    %ax,%ds
@@ -1204,7 +1204,7 @@
        movw    %ax,%fs
        CLI(ax)
        SWAPGS
-       movw    TF_GS(%rbx),%gs
+       movw    %ax,%gs
        SWAPGS
        STI(ax)
 #else
@@ -1486,6 +1486,9 @@
        movw    TF_DS(%rsp),%ds
        movw    TF_FS(%rsp),%fs
        SWAPGS
+#ifndef XEN
+       movw    TF_GS(%rsp),%gs
+#endif
        jmp     .Lkexit
 
 .Luexit64:
diff -r bfd2cb13e85f -r c6269f5d5588 sys/arch/amd64/amd64/machdep.c
--- a/sys/arch/amd64/amd64/machdep.c    Sat Oct 21 05:30:48 2017 +0000
+++ b/sys/arch/amd64/amd64/machdep.c    Sat Oct 21 06:55:54 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: machdep.c,v 1.271 2017/10/19 19:05:53 maxv Exp $       */
+/*     $NetBSD: machdep.c,v 1.272 2017/10/21 06:55:54 maxv Exp $       */
 
 /*
  * Copyright (c) 1996, 1997, 1998, 2000, 2006, 2007, 2008, 2011
@@ -110,7 +110,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.271 2017/10/19 19:05:53 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.272 2017/10/21 06:55:54 maxv Exp $");
 
 /* #define XENDEBUG_LOW  */
 
@@ -2138,7 +2138,11 @@
        kpreempt_disable();
        update_descriptor(&curcpu()->ci_gdt[GUFS_SEL], &pcb->pcb_fs);
        update_descriptor(&curcpu()->ci_gdt[GUGS_SEL], &pcb->pcb_gs);
+
+#ifdef XEN
        setusergs(gssel);
+#endif
+
        tf->tf_fs = fssel;
        tf->tf_gs = gssel;
        kpreempt_enable();
diff -r bfd2cb13e85f -r c6269f5d5588 sys/arch/x86/x86/sys_machdep.c
--- a/sys/arch/x86/x86/sys_machdep.c    Sat Oct 21 05:30:48 2017 +0000
+++ b/sys/arch/x86/x86/sys_machdep.c    Sat Oct 21 06:55:54 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sys_machdep.c,v 1.41 2017/10/19 19:05:53 maxv Exp $    */
+/*     $NetBSD: sys_machdep.c,v 1.42 2017/10/21 06:55:54 maxv Exp $    */
 
 /*
  * Copyright (c) 1998, 2007, 2009, 2017 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sys_machdep.c,v 1.41 2017/10/19 19:05:53 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_machdep.c,v 1.42 2017/10/21 06:55:54 maxv Exp $");
 
 #include "opt_mtrr.h"
 #include "opt_pmc.h"
@@ -608,7 +608,7 @@
                    sizeof(struct segment_descriptor));
                if (l == curlwp) {
                        update_descriptor(&curcpu()->ci_gdt[GUGS_SEL], &usd);
-#ifdef __x86_64__
+#if defined(__x86_64__) && defined(XEN)
                        setusergs(GSEL(GUGS_SEL, SEL_UPL));
 #endif
                }