make seccomp zerocost in schedule

This follows a suggestion from Chuck Ebbert on how to make seccomp
absolutely zerocost in schedule too.  The only remaining footprint of
seccomp is in terms of the bzImage size that becomes a few bytes (perhaps
even a few kbytes) larger, measure it if you care in the embedded.

Signed-off-by: Andrea Arcangeli <andrea@cpushare.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 8 insertions, 1 deletions

diff --git a/include/asm-i386/processor.h b/include/asm-i386/processor.h
index 94e0c147c165..422cffef00c9 100644
--- a/include/asm-i386/processor.h
+++ b/include/asm-i386/processor.h
@@ -228,6 +228,10 @@ extern int bootloader_type;
 
 #define HAVE_ARCH_PICK_MMAP_LAYOUT
 
+extern void hard_disable_TSC(void);
+extern void disable_TSC(void);
+extern void hard_enable_TSC(void);
+
 /*
  * Size of io_bitmap.
  */
diff --git a/include/asm-i386/thread_info.h b/include/asm-i386/thread_info.h
index 4cb0f91ae64f..54424e045e01 100644
--- a/include/asm-i386/thread_info.h
+++ b/include/asm-i386/thread_info.h
@@ -137,6 +137,7 @@ static inline struct thread_info *current_thread_info(void)
 #define TIF_DEBUG               17      /* uses debug registers */
 #define TIF_IO_BITMAP           18      /* uses I/O bitmap */
 #define TIF_FREEZE              19      /* is freezing for suspend */
+#define TIF_NOTSC               20      /* TSC is not accessible in userland */
 
 #define _TIF_SYSCALL_TRACE      (1<<TIF_SYSCALL_TRACE)
 #define _TIF_NOTIFY_RESUME      (1<<TIF_NOTIFY_RESUME)
@@ -151,6 +152,7 @@ static inline struct thread_info *current_thread_info(void)
 #define _TIF_DEBUG              (1<<TIF_DEBUG)
 #define _TIF_IO_BITMAP          (1<<TIF_IO_BITMAP)
 #define _TIF_FREEZE             (1<<TIF_FREEZE)
+#define _TIF_NOTSC              (1<<TIF_NOTSC)
 
 /* work to do on interrupt/exception return */
 #define _TIF_WORK_MASK \
@@ -160,7 +162,8 @@ static inline struct thread_info *current_thread_info(void)
 #define _TIF_ALLWORK_MASK       (0x0000FFFF & ~_TIF_SECCOMP)
 
 /* flags to check in __switch_to() */
-#define _TIF_WORK_CTXSW (_TIF_DEBUG|_TIF_IO_BITMAP)
+#define _TIF_WORK_CTXSW_NEXT (_TIF_IO_BITMAP | _TIF_NOTSC | _TIF_DEBUG)
+#define _TIF_WORK_CTXSW_PREV (_TIF_IO_BITMAP | _TIF_NOTSC)
 
 /*
  * Thread-synchronous status.