[tip:x86/urgent] x86: fix HYPERVISOR_update_descriptor()

[Jan Beulich]

Commit-ID:  6a5c05f002c3e4f24887a5fe8e7df757d339d368
Gitweb:     http://git.kernel.org/tip/6a5c05f002c3e4f24887a5fe8e7df757d339d368
Author:     "Jan Beulich" <jbeulich@xxxxxxxxxx>
AuthorDate: Thu, 12 Mar 2009 11:54:54 +0000
Commit:     Ingo Molnar <mingo@xxxxxxx>
CommitDate: Thu, 12 Mar 2009 12:56:21 +0100

x86: fix HYPERVISOR_update_descriptor()

Impact: fix potential oops during app-initiated LDT manipulation

The underlying hypercall has differing argument requirements on 32-
and 64-bit.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
LKML-Reference: <49B9061E.76E4.0078.0@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>


---
 arch/x86/include/asm/xen/hypercall.h |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
index 5e79ca6..9c371e4 100644
--- a/arch/x86/include/asm/xen/hypercall.h
+++ b/arch/x86/include/asm/xen/hypercall.h
@@ -296,6 +296,8 @@ HYPERVISOR_get_debugreg(int reg)
 static inline int
 HYPERVISOR_update_descriptor(u64 ma, u64 desc)
 {
+	if (sizeof(u64) == sizeof(long))
+		return _hypercall2(int, update_descriptor, ma, desc);
 	return _hypercall4(int, update_descriptor, ma, ma>>32, desc, desc>>32);
 }
 
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