[src/trunk]: src/sys/arch/amd64/amd64 When kernel remaps to high memory in am...

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

details:   https://anonhg.NetBSD.org/src/rev/12df84d3a04b
branches:  trunk
changeset: 754065:12df84d3a04b
user:      jym <jym%NetBSD.org@localhost>
date:      Sun Apr 18 15:24:54 2010 +0000

description:
When kernel remaps to high memory in amd64 locore, the GDT used before
becomes invalid. As such, split it in two parts, one for use when system
boots in low memory, and one for use when it jumps to high memory.

diffstat:

 sys/arch/amd64/amd64/locore.S |  32 ++++++++++++++++++++++++++------
 1 files changed, 26 insertions(+), 6 deletions(-)

diffs (66 lines):

diff -r 8b6de01da708 -r 12df84d3a04b sys/arch/amd64/amd64/locore.S
--- a/sys/arch/amd64/amd64/locore.S     Sun Apr 18 15:19:17 2010 +0000
+++ b/sys/arch/amd64/amd64/locore.S     Sun Apr 18 15:24:54 2010 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: locore.S,v 1.55 2009/11/27 03:23:04 rmind Exp $        */
+/*     $NetBSD: locore.S,v 1.56 2010/04/18 15:24:54 jym Exp $  */
 
 /*
  * Copyright-o-rama!
@@ -269,13 +269,25 @@
 #define        RELOC(x)        _RELOC(_C_LABEL(x))
 
 #ifndef XEN
-       .globl  gdt64
+       .globl  gdt64_lo
+       .globl  gdt64_hi
 
-gdt64:
-       .word   gdt64_end-gdt64_start
+#define GDT64_LIMIT gdt64_end-gdt64_start-1
+
+/* Temporary gdt64, with base address in low memory */
+gdt64_lo:
+       .word   GDT64_LIMIT
        .quad   _RELOC(gdt64_start)
 .align 64
 
+/* Temporary gdt64, with base address in high memory */
+gdt64_hi:
+       .word   GDT64_LIMIT
+       .quad   gdt64_start
+.align 64
+
+#undef GDT64_LIMIT
+
 gdt64_start:
        .quad 0x0000000000000000        /* always empty */
        .quad 0x00af9a000000ffff        /* kernel CS */
@@ -638,7 +650,7 @@
         * in it to do that.
         */
 
-       movl    $RELOC(gdt64),%eax
+       movl    $RELOC(gdt64_lo),%eax
        lgdt    (%eax)
        movl    $RELOC(farjmp64),%eax
        ljmp    *(%eax)
@@ -654,9 +666,17 @@
         */
        movabsq $longmode_hi,%rax
        jmp     *%rax
+
 longmode_hi:
+
        /*
-        * We have arrived.
+        * We left the identity mapped area. Base address of
+        * the temporary gdt64 should now be in high memory.
+        */
+       movq    $RELOC(gdt64_hi),%rax
+       lgdt    (%rax)
+
+       /*
         * There's no need anymore for the identity mapping in low
         * memory, remove it.
         */