linux-kernel - [PATCH 38 of 55] xen64: deal with extra words Xen pushes onto exception frames

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Date:	Tue, 08 Jul 2008 15:07:00 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
	Stephen Tweedie <sct@...hat.com>,
	Eduardo Habkost <ehabkost@...hat.com>,
	Mark McLoughlin <markmc@...hat.com>, x86@...nel.org
Subject: [PATCH 38 of 55] xen64: deal with extra words Xen pushes onto
	exception frames

Xen pushes two extra words containing the values of rcx and r11.  This
pvop hook copies the words back into their appropriate registers, and
cleans them off the stack.  This leaves the stack in native form, so
the normal handler can run unchanged.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
---
 arch/x86/xen/enlighten.c  |    2 +-
 arch/x86/xen/xen-asm_64.S |    5 +++++
 arch/x86/xen/xen-ops.h    |    2 ++
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1091,7 +1091,7 @@
 	.safe_halt = xen_safe_halt,
 	.halt = xen_halt,
 #ifdef CONFIG_X86_64
-	.adjust_exception_frame = paravirt_nop,
+	.adjust_exception_frame = xen_adjust_exception_frame,
 #endif
 };
 
diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S
--- a/arch/x86/xen/xen-asm_64.S
+++ b/arch/x86/xen/xen-asm_64.S
@@ -133,6 +133,11 @@
 	ret
 #endif
 
+ENTRY(xen_adjust_exception_frame)
+	mov 8+0(%rsp),%rcx
+	mov 8+8(%rsp),%r11
+	ret $16
+
 ENTRY(xen_iret)
 	pushq $0
 	jmp hypercall_page + __HYPERVISOR_iret * 32
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -67,7 +67,9 @@
 DECL_ASM(unsigned long, xen_save_fl_direct, void);
 DECL_ASM(void, xen_restore_fl_direct, unsigned long);
 
+/* These are not functions, and cannot be called normally */
 void xen_iret(void);
 void xen_sysexit(void);
+void xen_adjust_exception_frame(void);
 
 #endif /* XEN_OPS_H */


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