x86: fdiv bug detection fix

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>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index c9b58a806e85..c8e315f1aa83 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/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");
@@ -74,8 +76,10 @@ 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");
 }