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: Erik Bosman <ejbosman@cs.vu.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 18 insertions, 1 deletions

diff --git a/include/linux/prctl.h b/include/linux/prctl.h
index 3800639775ae..5c80b1939636 100644
--- a/include/linux/prctl.h
+++ b/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 */
diff --git a/kernel/sys.c b/kernel/sys.c
index a626116af5db..6a0cc71ee88d 100644
--- a/kernel/sys.c
+++ b/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;