[coreboot] New patch to review for coreboot: 7f8e685 Load an IDT with NULL limit
Stefan Reinauer (stefan.reinauer@coreboot.org)
gerrit at coreboot.org
Thu Oct 13 00:48:59 CEST 2011
Stefan Reinauer (stefan.reinauer at coreboot.org) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/259
-gerrit
commit 7f8e685996f65f2c67d1113fcfaab33ccc385da7
Author: Stefan Reinauer <reinauer at chromium.org>
Date: Wed Jun 1 14:01:46 2011 -0700
Load an IDT with NULL limit
Load an IDT with NULL limit to prevent the 16bit IDT being used
in protected mode before c_start.S sets up a 32bit IDT when entering
ram stage.
Signed-off-by: Stefan Reinauer <reinauer at google.com>
Change-Id: I8d048c894c863ac4971fcef8f065be6b899e1d3e
---
src/cpu/x86/16bit/entry16.inc | 15 ++++++++++++++-
src/cpu/x86/16bit/entry16.lds | 1 +
2 files changed, 15 insertions(+), 1 deletions(-)
diff --git a/src/cpu/x86/16bit/entry16.inc b/src/cpu/x86/16bit/entry16.inc
index 1eb92c8..9f4c0e3 100644
--- a/src/cpu/x86/16bit/entry16.inc
+++ b/src/cpu/x86/16bit/entry16.inc
@@ -45,7 +45,6 @@ _start:
xorl %eax, %eax
movl %eax, %cr3 /* Invalidate TLB*/
-
/* Invalidating the cache here seems to be a bad idea on
* modern processors. Don't.
* If we are hyperthreaded or we have multiple cores it is bad,
@@ -55,6 +54,13 @@ _start:
* entry16.inc.
*/
+ /* Load an IDT with NULL limit to prevent the 16bit IDT being used
+ * in protected mode before c_start.S sets up a 32bit IDT when entering
+ * ram stage.
+ */
+ movw $nullidt_offset, %bx
+ lidt %cs:(%bx)
+
/* Note: gas handles memory addresses in 16 bit code very poorly.
* In particular it doesn't appear to have a directive allowing you
* associate a section or even an absolute offset with a segment register.
@@ -118,6 +124,13 @@ gdtptr16:
.word gdt_end - gdt -1 /* compute the table limit */
.long gdt /* we know the offset */
+.align 4
+.globl nullidt
+nullidt:
+ .word 0 /* limit */
+ .long 0
+ .word 0
+
.globl _estart
_estart:
.code32
diff --git a/src/cpu/x86/16bit/entry16.lds b/src/cpu/x86/16bit/entry16.lds
index 0580f0e..112d429 100644
--- a/src/cpu/x86/16bit/entry16.lds
+++ b/src/cpu/x86/16bit/entry16.lds
@@ -1 +1,2 @@
gdtptr16_offset = gdtptr16 & 0xffff;
+ nullidt_offset = nullidt & 0xffff;
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