[Xen-devel] [PATCH] x86/msr: Correct the definition of MSR_IA32_APICBASE_BASE

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

0xfffff << 12 is undefined behaviour, due to shifting into the sign bit of an
integer.

Spotted by the Undefined Behaviour Sanitiser

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>

I appear to have missed this patch from my past UBSAN work.
---
 xen/include/asm-x86/msr-index.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/include/asm-x86/msr-index.h b/xen/include/asm-x86/msr-index.h
index 4e08de6..b99c623 100644
--- a/xen/include/asm-x86/msr-index.h
+++ b/xen/include/asm-x86/msr-index.h
@@ -305,7 +305,7 @@
 #define MSR_IA32_APICBASE_BSP          (1<<8)
 #define MSR_IA32_APICBASE_EXTD         (1<<10)
 #define MSR_IA32_APICBASE_ENABLE       (1<<11)
-#define MSR_IA32_APICBASE_BASE         (0xfffff<<12)
+#define MSR_IA32_APICBASE_BASE         0x000ffffffffff000ul
 #define MSR_IA32_APICBASE_MSR           0x800
 #define MSR_IA32_APICTPR_MSR            0x808
 #define MSR_IA32_APICPPR_MSR            0x80a
-- 
2.1.4


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