x86/cpu: Make alternative_msr_write work for 32-bit code

Cast val and (val >> 32) to (u32), so that they fit in a
general-purpose register in both 32-bit and 64-bit code.

[ tglx: Made it u32 instead of uintptr_t ]

Fixes: c65732e4f721 ("x86/cpu: Restore CPUID_8000_0008_EBX reload")
Signed-off-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
CVE-2018-3639 (x86)

(cherry-picked from commit 5f2b745f5e1304f438f9b2cd03ebc8120b6e0d3b)
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 5ce68e3e5bc94350fd71fdfbafa1e520ec50e26c..ef7d5bf5d0791a100e14871287204b2114592b2d 100644 (file)
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -189,8 +189,8 @@ void alternative_msr_write(unsigned int msr, u64 val, unsigned int feature)
 {
        asm volatile(ALTERNATIVE("", "wrmsr", %c[feature])
                : : "c" (msr),
-                   "a" (val),
-                   "d" (val >> 32),
+                   "a" ((u32)val),
+                   "d" ((u32)(val >> 32)),
                    [feature] "i" (feature)
                : "memory");
 }