x86: fdiv bug detection fix

commit e0d22d03 upstream

The fdiv detection code writes s32 integer into
the boot_cpu_data.fdiv_bug.
However, the boot_cpu_data.fdiv_bug is only char (s8)
field so the detection overwrites already set fields for
other bugs, e.g. the f00f bug field.

Use local s32 variable to receive result.

This is a partial fix to Bugzilla #9928  - fixes wrong
information about the f00f bug (tested) and probably
for coma bug (I have no cpu to test this).
Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

arch/x86/kernel/cpu/bugs.c

@@ -50,6 +50,8 @@ static double __initdata y = 3145727.0;
  */
 static void __init check_fpu(void)
 {
+	s32 fdiv_bug;
+
 	if (!boot_cpu_data.hard_math) {
 #ifndef CONFIG_MATH_EMULATION
 		printk(KERN_EMERG "No coprocessor found and no math emulation present.\n");
@@ -70,8 +72,10 @@ static void __init check_fpu(void)
 		"fistpl %0\n\t"
 		"fwait\n\t"
 		"fninit"
-		: "=m" (*&boot_cpu_data.fdiv_bug)
+		: "=m" (*&fdiv_bug)
 		: "m" (*&x), "m" (*&y));
+
+	boot_cpu_data.fdiv_bug = fdiv_bug;
 	if (boot_cpu_data.fdiv_bug)
 		printk("Hmm, FPU with FDIV bug.\n");
 }