From 3c1b270160abc24fed0925767ef6feed230ca76b Mon Sep 17 00:00:00 2001
From: Stefan Lankes <lankes@lfbs.rwth-aachen.de>
Date: Sat, 14 Jul 2012 11:16:29 +0200
Subject: [PATCH] fix bug in the calculation of esp0

---
 arch/x86/kernel/entry32.asm | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/entry32.asm b/arch/x86/kernel/entry32.asm
index 7443ff7f..c5096863 100644
--- a/arch/x86/kernel/entry32.asm
+++ b/arch/x86/kernel/entry32.asm
@@ -799,8 +799,14 @@ common_switch:
     xor eax, eax
 %endif
     add eax, task_state_segments
-    ; set esp0 in TSS
-    mov [eax+4], esp
+ 
+    ; determine and set esp0 in TSS
+    mov ebx, esp
+    mov ecx, KERNEL_STACK_SIZE-1
+    not ecx
+    and ebx, ecx
+    add ebx, KERNEL_STACK_SIZE-16
+    mov [eax+4], ebx
 
     ; call cleanup code
     call finish_task_switch