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x86/mce: Fix check for processor context when machine check was taken.

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Linus pointed out that there was no value is checking whether m->ip
was zero - because zero is a legimate value.  If we have a reliable
(or faked in the VM86 case) "m->cs" we can use it to tell whether we
were in user mode or kernelwhen the machine check hit.

Reported-by: Linus Torvalds <torvalds@linuxfoundation.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
This commit is contained in:
Tony Luck 2012-05-23 14:14:22 -07:00
parent a129a7c845
commit 875e26648c
1 changed files with 10 additions and 6 deletions
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16
arch/x86/kernel/cpu/mcheck/mce-severity.c
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@ -165,15 +165,19 @@ static struct severity {
};
/*
* If the EIPV bit is set, it means the saved IP is the
* instruction which caused the MCE.
* If mcgstatus indicated that ip/cs on the stack were
* no good, then "m->cs" will be zero and we will have
* to assume the worst case (IN_KERNEL) as we actually
* have no idea what we were executing when the machine
* check hit.
* If we do have a good "m->cs" (or a faked one in the
* case we were executing in VM86 mode) we can use it to
* distinguish an exception taken in user from from one
* taken in the kernel.
*/
static int error_context(struct mce *m)
{
if (m->mcgstatus & MCG_STATUS_EIPV)
return (m->ip && (m->cs & 3) == 3) ? IN_USER : IN_KERNEL;
/* Unknown, assume kernel */
return IN_KERNEL;
return ((m->cs & 3) == 3) ? IN_USER : IN_KERNEL;
}
int mce_severity(struct mce *m, int tolerant, char **msg)