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4706c5bc GKH |
1 | From 875e26648cf9b6db9d8dc07b7959d7c61fb3f49c Mon Sep 17 00:00:00 2001 |
2 | From: Tony Luck <tony.luck@intel.com> | |
3 | Date: Wed, 23 May 2012 14:14:22 -0700 | |
4 | Subject: x86/mce: Fix check for processor context when machine check was taken. | |
5 | ||
6 | From: Tony Luck <tony.luck@intel.com> | |
7 | ||
8 | commit 875e26648cf9b6db9d8dc07b7959d7c61fb3f49c upstream. | |
9 | ||
10 | Linus pointed out that there was no value is checking whether m->ip | |
11 | was zero - because zero is a legimate value. If we have a reliable | |
12 | (or faked in the VM86 case) "m->cs" we can use it to tell whether we | |
13 | were in user mode or kernelwhen the machine check hit. | |
14 | ||
15 | Reported-by: Linus Torvalds <torvalds@linuxfoundation.org> | |
16 | Signed-off-by: Tony Luck <tony.luck@intel.com> | |
17 | Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> | |
18 | ||
19 | --- | |
20 | arch/x86/kernel/cpu/mcheck/mce-severity.c | 16 ++++++++++------ | |
21 | 1 file changed, 10 insertions(+), 6 deletions(-) | |
22 | ||
23 | --- a/arch/x86/kernel/cpu/mcheck/mce-severity.c | |
24 | +++ b/arch/x86/kernel/cpu/mcheck/mce-severity.c | |
25 | @@ -145,15 +145,19 @@ static struct severity { | |
26 | }; | |
27 | ||
28 | /* | |
29 | - * If the EIPV bit is set, it means the saved IP is the | |
30 | - * instruction which caused the MCE. | |
31 | + * If mcgstatus indicated that ip/cs on the stack were | |
32 | + * no good, then "m->cs" will be zero and we will have | |
33 | + * to assume the worst case (IN_KERNEL) as we actually | |
34 | + * have no idea what we were executing when the machine | |
35 | + * check hit. | |
36 | + * If we do have a good "m->cs" (or a faked one in the | |
37 | + * case we were executing in VM86 mode) we can use it to | |
38 | + * distinguish an exception taken in user from from one | |
39 | + * taken in the kernel. | |
40 | */ | |
41 | static int error_context(struct mce *m) | |
42 | { | |
43 | - if (m->mcgstatus & MCG_STATUS_EIPV) | |
44 | - return (m->ip && (m->cs & 3) == 3) ? IN_USER : IN_KERNEL; | |
45 | - /* Unknown, assume kernel */ | |
46 | - return IN_KERNEL; | |
47 | + return ((m->cs & 3) == 3) ? IN_USER : IN_KERNEL; | |
48 | } | |
49 | ||
50 | int mce_severity(struct mce *m, int tolerant, char **msg) |