linux-kernel - [PATCH 2/7] cleanup: Initialize esp0 properly all the time

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Message-Id: <1171251185.10409.4.camel@localhost.localdomain>
Date:	Mon, 12 Feb 2007 14:33:05 +1100
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>,
	virtualization <virtualization@...ts.osdl.org>,
	Andi Kleen <ak@....de>
Subject: [PATCH 2/7] cleanup: Initialize esp0 properly all the time

Whenever we schedule, __switch_to calls load_esp0 which does:

	tss->esp0 = thread->esp0;

This is never initialized for the initial thread (ie "swapper"), so
when we're scheduling that, we end up setting esp0 to 0.  This is
fine: the swapper never leaves ring 0, so this field is never used.

lguest, however, gets upset that we're trying to used an unmapped page
as our kernel stack.  Rather than work around it there, let's
initialize it.

Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>

===================================================================
--- a/include/asm-i386/processor.h
+++ b/include/asm-i386/processor.h
@@ -421,6 +421,7 @@ struct thread_struct {
 };
 
 #define INIT_THREAD  {							\
+	.esp0 = sizeof(init_stack) + (long)&init_stack,			\
 	.vm86_info = NULL,						\
 	.sysenter_cs = __KERNEL_CS,					\
 	.io_bitmap_ptr = NULL,						\


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