include/linux/sched/task_stack.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_SCHED_TASK_STACK_H
   3 #define _LINUX_SCHED_TASK_STACK_H
   4
   5 /*
   6  * task->stack (kernel stack) handling interfaces:
   7  */
   8
   9 #include <linux/sched.h>
  10 #include <linux/magic.h>
  11
  12 #ifdef CONFIG_THREAD_INFO_IN_TASK
  13
  14 /*
  15  * When accessing the stack of a non-current task that might exit, use
  16  * try_get_task_stack() instead.  task_stack_page will return a pointer
  17  * that could get freed out from under you.
  18  */
  19 static inline void *task_stack_page(const struct task_struct *task)
  20 {
  21         return task->stack;
  22 }
  23
  24 #define setup_thread_stack(new,old)     do { } while(0)
  25
  26 static inline unsigned long *end_of_stack(const struct task_struct *task)
  27 {
  28         return task->stack;
  29 }
  30
  31 #elif !defined(__HAVE_THREAD_FUNCTIONS)
  32
  33 #define task_stack_page(task)   ((void *)(task)->stack)
  34
  35 static inline void setup_thread_stack(struct task_struct *p, struct task_struct *org)
  36 {
  37         *task_thread_info(p) = *task_thread_info(org);
  38         task_thread_info(p)->task = p;
  39 }
  40
  41 /*
  42  * Return the address of the last usable long on the stack.
  43  *
  44  * When the stack grows down, this is just above the thread
  45  * info struct. Going any lower will corrupt the threadinfo.
  46  *
  47  * When the stack grows up, this is the highest address.
  48  * Beyond that position, we corrupt data on the next page.
  49  */
  50 static inline unsigned long *end_of_stack(struct task_struct *p)
  51 {
  52 #ifdef CONFIG_STACK_GROWSUP
  53         return (unsigned long *)((unsigned long)task_thread_info(p) + THREAD_SIZE) - 1;
  54 #else
  55         return (unsigned long *)(task_thread_info(p) + 1);
  56 #endif
  57 }
  58
  59 #endif
  60
  61 #ifdef CONFIG_THREAD_INFO_IN_TASK
  62 static inline void *try_get_task_stack(struct task_struct *tsk)
  63 {
  64         return atomic_inc_not_zero(&tsk->stack_refcount) ?
  65                 task_stack_page(tsk) : NULL;
  66 }
  67
  68 extern void put_task_stack(struct task_struct *tsk);
  69 #else
  70 static inline void *try_get_task_stack(struct task_struct *tsk)
  71 {
  72         return task_stack_page(tsk);
  73 }
  74
  75 static inline void put_task_stack(struct task_struct *tsk) {}
  76 #endif
  77
  78 #define task_stack_end_corrupted(task) \
  79                 (*(end_of_stack(task)) != STACK_END_MAGIC)
  80
  81 static inline int object_is_on_stack(void *obj)
  82 {
  83         void *stack = task_stack_page(current);
  84
  85         return (obj >= stack) && (obj < (stack + THREAD_SIZE));
  86 }
  87
  88 extern void thread_stack_cache_init(void);
  89
  90 #ifdef CONFIG_DEBUG_STACK_USAGE
  91 static inline unsigned long stack_not_used(struct task_struct *p)
  92 {
  93         unsigned long *n = end_of_stack(p);
  94
  95         do {    /* Skip over canary */
  96 # ifdef CONFIG_STACK_GROWSUP
  97                 n--;
  98 # else
  99                 n++;
 100 # endif
 101         } while (!*n);
 102
 103 # ifdef CONFIG_STACK_GROWSUP
 104         return (unsigned long)end_of_stack(p) - (unsigned long)n;
 105 # else
 106         return (unsigned long)n - (unsigned long)end_of_stack(p);
 107 # endif
 108 }
 109 #endif
 110 extern void set_task_stack_end_magic(struct task_struct *tsk);
 111
 112 #ifndef __HAVE_ARCH_KSTACK_END
 113 static inline int kstack_end(void *addr)
 114 {
 115         /* Reliable end of stack detection:
 116          * Some APM bios versions misalign the stack
 117          */
 118         return !(((unsigned long)addr+sizeof(void*)-1) & (THREAD_SIZE-sizeof(void*)));
 119 }
 120 #endif
 121
 122 #endif /* _LINUX_SCHED_TASK_STACK_H */