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