kmemcheck: add opcode self-testing at boot

We've had some troubles in the past with weird instructions. This
patch adds a self-test framework which can be used to verify that
a certain set of opcodes are decoded correctly. Of course, the
opcodes which are not tested can still give the wrong results.

In short, this is just a safeguard to catch unintentional changes
in the opcode decoder. It does not mean that errors can't still
occur!

[rebased for mainline inclusion]
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>

1 files changed, 9 insertions, 16 deletions

diff --git a/arch/x86/mm/kmemcheck/kmemcheck.c b/arch/x86/mm/kmemcheck/kmemcheck.c
index 6931e5115bcd..2c55ed098654 100644
--- a/arch/x86/mm/kmemcheck/kmemcheck.c
+++ b/arch/x86/mm/kmemcheck/kmemcheck.c
@@ -29,8 +29,10 @@
 #include "error.h"
 #include "opcode.h"
 #include "pte.h"
+#include "selftest.h"
 #include "shadow.h"
 
+
 #ifdef CONFIG_KMEMCHECK_DISABLED_BY_DEFAULT
 #  define KMEMCHECK_ENABLED 0
 #endif
@@ -47,8 +49,6 @@ int kmemcheck_enabled = KMEMCHECK_ENABLED;
 
 int __init kmemcheck_init(void)
 {
-        printk(KERN_INFO "kmemcheck: Initialized\n");
-
 #ifdef CONFIG_SMP
         /*
          * Limit SMP to use a single CPU. We rely on the fact that this code
@@ -61,25 +61,18 @@ int __init kmemcheck_init(void)
         }
 #endif
 
+        if (!kmemcheck_selftest()) {
+                printk(KERN_INFO "kmemcheck: self-tests failed; disabling\n");
+                kmemcheck_enabled = 0;
+                return -EINVAL;
+        }
+
+        printk(KERN_INFO "kmemcheck: Initialized\n");
         return 0;
 }
 
 early_initcall(kmemcheck_init);
 
-#ifdef CONFIG_KMEMCHECK_DISABLED_BY_DEFAULT
-#  define KMEMCHECK_ENABLED 0
-#endif
-
-#ifdef CONFIG_KMEMCHECK_ENABLED_BY_DEFAULT
-#  define KMEMCHECK_ENABLED 1
-#endif
-
-#ifdef CONFIG_KMEMCHECK_ONESHOT_BY_DEFAULT
-#  define KMEMCHECK_ENABLED 2
-#endif
-
-int kmemcheck_enabled = KMEMCHECK_ENABLED;
-
 /*
  * We need to parse the kmemcheck= option before any memory is allocated.
  */