include/linux/context_tracking.h

   1 #ifndef _LINUX_CONTEXT_TRACKING_H
   2 #define _LINUX_CONTEXT_TRACKING_H
   3
   4 #include <linux/sched.h>
   5 #include <linux/percpu.h>
   6 #include <asm/ptrace.h>
   7
   8 struct context_tracking {
   9         /*
  10          * When active is false, probes are unset in order
  11          * to minimize overhead: TIF flags are cleared
  12          * and calls to user_enter/exit are ignored. This
  13          * may be further optimized using static keys.
  14          */
  15         bool active;
  16         enum ctx_state {
  17                 IN_KERNEL = 0,
  18                 IN_USER,
  19         } state;
  20 };
  21
  22 #ifdef CONFIG_CONTEXT_TRACKING
  23 DECLARE_PER_CPU(struct context_tracking, context_tracking);
  24
  25 static inline bool context_tracking_in_user(void)
  26 {
  27         return __this_cpu_read(context_tracking.state) == IN_USER;
  28 }
  29
  30 static inline bool context_tracking_active(void)
  31 {
  32         return __this_cpu_read(context_tracking.active);
  33 }
  34
  35 extern void user_enter(void);
  36 extern void user_exit(void);
  37
  38 static inline enum ctx_state exception_enter(void)
  39 {
  40         enum ctx_state prev_ctx;
  41
  42         prev_ctx = this_cpu_read(context_tracking.state);
  43         user_exit();
  44
  45         return prev_ctx;
  46 }
  47
  48 static inline void exception_exit(enum ctx_state prev_ctx)
  49 {
  50         if (prev_ctx == IN_USER)
  51                 user_enter();
  52 }
  53
  54 extern void context_tracking_task_switch(struct task_struct *prev,
  55                                          struct task_struct *next);
  56 #else
  57 static inline bool context_tracking_in_user(void) { return false; }
  58 static inline void user_enter(void) { }
  59 static inline void user_exit(void) { }
  60 static inline enum ctx_state exception_enter(void) { return 0; }
  61 static inline void exception_exit(enum ctx_state prev_ctx) { }
  62 static inline void context_tracking_task_switch(struct task_struct *prev,
  63                                                 struct task_struct *next) { }
  64 #endif /* !CONFIG_CONTEXT_TRACKING */
  65
  66 #endif