generic, x86: add prctl commands PR_GET_TSC and PR_SET_TSC

This patch adds prctl commands that make it possible
to deny the execution of timestamp counters in userspace.
If this is not implemented on a specific architecture,
prctl will return -EINVAL.
ned-off-by: NErik Bosman <ejbosman@cs.vu.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

include/linux/prctl.h

@@ -67,4 +67,10 @@
 #define PR_CAPBSET_READ 23
 #define PR_CAPBSET_DROP 24
 
+/* Get/set the process' ability to use the timestamp counter instruction */
+#define PR_GET_TSC 25
+#define PR_SET_TSC 26
+# define PR_TSC_ENABLE		1	/* allow the use of the timestamp counter */
+# define PR_TSC_SIGSEGV		2	/* throw a SIGSEGV instead of reading the TSC */
+
 #endif /* _LINUX_PRCTL_H */

kernel/sys.c

@@ -67,6 +67,12 @@
 #ifndef SET_ENDIAN
 # define SET_ENDIAN(a,b)	(-EINVAL)
 #endif
+#ifndef GET_TSC_CTL
+# define GET_TSC_CTL(a)		(-EINVAL)
+#endif
+#ifndef SET_TSC_CTL
+# define SET_TSC_CTL(a)		(-EINVAL)
+#endif
 
 /*
  * this is where the system-wide overflow UID and GID are defined, for
@@ -1737,7 +1743,12 @@ asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
 #else
 			return -EINVAL;
 #endif
-
+		case PR_GET_TSC:
+			error = GET_TSC_CTL(arg2);
+			break;
+		case PR_SET_TSC:
+			error = SET_TSC_CTL(arg2);
+			break;
 		default:
 			error = -EINVAL;
 			break;