x86: fdiv bug detection fix

commit e0d22d03c06c4e2c194d7010bc1e4a972199f156 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>

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 170d2f5523b2c6e04f4c28aa423077388bb3abce..912a84b89627b24c1927a3a4386f59f90ab7b3e3 100644 (file)
--- 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");
@@ -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");
 }