Line data    Source code

       1             : /* SPDX-License-Identifier: GPL-2.0 */
       2             : /*
       3             :  * Shadow Call Stack support.
       4             :  *
       5             :  * Copyright (C) 2019 Google LLC
       6             :  */
       7             : 
       8             : #ifndef _LINUX_SCS_H
       9             : #define _LINUX_SCS_H
      10             : 
      11             : #include <linux/gfp.h>
      12             : #include <linux/poison.h>
      13             : #include <linux/sched.h>
      14             : #include <linux/sizes.h>
      15             : 
      16             : #ifdef CONFIG_SHADOW_CALL_STACK
      17             : 
      18             : #define SCS_ORDER               0
      19             : #define SCS_SIZE                (PAGE_SIZE << SCS_ORDER)
      20             : #define GFP_SCS                 (GFP_KERNEL | __GFP_ZERO)
      21             : 
      22             : /* An illegal pointer value to mark the end of the shadow stack. */
      23             : #define SCS_END_MAGIC           (0x5f6UL + POISON_POINTER_DELTA)
      24             : 
      25             : #define task_scs(tsk)           (task_thread_info(tsk)->scs_base)
      26             : #define task_scs_sp(tsk)        (task_thread_info(tsk)->scs_sp)
      27             : 
      28             : void *scs_alloc(int node);
      29             : void scs_free(void *s);
      30             : void scs_init(void);
      31             : int scs_prepare(struct task_struct *tsk, int node);
      32             : void scs_release(struct task_struct *tsk);
      33             : 
      34             : static inline void scs_task_reset(struct task_struct *tsk)
      35             : {
      36             :         /*
      37             :          * Reset the shadow stack to the base address in case the task
      38             :          * is reused.
      39             :          */
      40             :         task_scs_sp(tsk) = task_scs(tsk);
      41             : }
      42             : 
      43             : static inline unsigned long *__scs_magic(void *s)
      44             : {
      45             :         return (unsigned long *)(s + SCS_SIZE) - 1;
      46             : }
      47             : 
      48             : static inline bool task_scs_end_corrupted(struct task_struct *tsk)
      49             : {
      50             :         unsigned long *magic = __scs_magic(task_scs(tsk));
      51             :         unsigned long sz = task_scs_sp(tsk) - task_scs(tsk);
      52             : 
      53             :         return sz >= SCS_SIZE - 1 || READ_ONCE_NOCHECK(*magic) != SCS_END_MAGIC;
      54             : }
      55             : 
      56             : #else /* CONFIG_SHADOW_CALL_STACK */
      57             : 
      58             : static inline void *scs_alloc(int node) { return NULL; }
      59             : static inline void scs_free(void *s) {}
      60           1 : static inline void scs_init(void) {}
      61          10 : static inline void scs_task_reset(struct task_struct *tsk) {}
      62         916 : static inline int scs_prepare(struct task_struct *tsk, int node) { return 0; }
      63         834 : static inline void scs_release(struct task_struct *tsk) {}
      64             : static inline bool task_scs_end_corrupted(struct task_struct *tsk) { return false; }
      65             : 
      66             : #endif /* CONFIG_SHADOW_CALL_STACK */
      67             : 
      68             : #endif /* _LINUX_SCS_H */