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  */
task_stack_page(const struct task_struct * task)19 static __always_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 
end_of_stack(const struct task_struct * task)26 static __always_inline unsigned long *end_of_stack(const struct task_struct *task)
27 {
28 #ifdef CONFIG_STACK_GROWSUP
29 	return (unsigned long *)((unsigned long)task->stack + THREAD_SIZE) - 1;
30 #else
31 	return task->stack;
32 #endif
33 }
34 
35 #elif !defined(__HAVE_THREAD_FUNCTIONS)
36 
37 #define task_stack_page(task)	((void *)(task)->stack)
38 
setup_thread_stack(struct task_struct * p,struct task_struct * org)39 static inline void setup_thread_stack(struct task_struct *p, struct task_struct *org)
40 {
41 	*task_thread_info(p) = *task_thread_info(org);
42 	task_thread_info(p)->task = p;
43 }
44 
45 /*
46  * Return the address of the last usable long on the stack.
47  *
48  * When the stack grows down, this is just above the thread
49  * info struct. Going any lower will corrupt the threadinfo.
50  *
51  * When the stack grows up, this is the highest address.
52  * Beyond that position, we corrupt data on the next page.
53  */
end_of_stack(struct task_struct * p)54 static inline unsigned long *end_of_stack(struct task_struct *p)
55 {
56 #ifdef CONFIG_STACK_GROWSUP
57 	return (unsigned long *)((unsigned long)task_thread_info(p) + THREAD_SIZE) - 1;
58 #else
59 	return (unsigned long *)(task_thread_info(p) + 1);
60 #endif
61 }
62 
63 #endif
64 
65 #ifdef CONFIG_THREAD_INFO_IN_TASK
try_get_task_stack(struct task_struct * tsk)66 static inline void *try_get_task_stack(struct task_struct *tsk)
67 {
68 	return refcount_inc_not_zero(&tsk->stack_refcount) ?
69 		task_stack_page(tsk) : NULL;
70 }
71 
72 extern void put_task_stack(struct task_struct *tsk);
73 #else
try_get_task_stack(struct task_struct * tsk)74 static inline void *try_get_task_stack(struct task_struct *tsk)
75 {
76 	return task_stack_page(tsk);
77 }
78 
put_task_stack(struct task_struct * tsk)79 static inline void put_task_stack(struct task_struct *tsk) {}
80 #endif
81 
82 void exit_task_stack_account(struct task_struct *tsk);
83 
84 #define task_stack_end_corrupted(task) \
85 		(*(end_of_stack(task)) != STACK_END_MAGIC)
86 
object_is_on_stack(const void * obj)87 static inline int object_is_on_stack(const void *obj)
88 {
89 	void *stack = task_stack_page(current);
90 
91 	return (obj >= stack) && (obj < (stack + THREAD_SIZE));
92 }
93 
94 extern void thread_stack_cache_init(void);
95 
96 #ifdef CONFIG_DEBUG_STACK_USAGE
stack_not_used(struct task_struct * p)97 static inline unsigned long stack_not_used(struct task_struct *p)
98 {
99 	unsigned long *n = end_of_stack(p);
100 
101 	do { 	/* Skip over canary */
102 # ifdef CONFIG_STACK_GROWSUP
103 		n--;
104 # else
105 		n++;
106 # endif
107 	} while (!*n);
108 
109 # ifdef CONFIG_STACK_GROWSUP
110 	return (unsigned long)end_of_stack(p) - (unsigned long)n;
111 # else
112 	return (unsigned long)n - (unsigned long)end_of_stack(p);
113 # endif
114 }
115 #endif
116 extern void set_task_stack_end_magic(struct task_struct *tsk);
117 
118 #ifndef __HAVE_ARCH_KSTACK_END
kstack_end(void * addr)119 static inline int kstack_end(void *addr)
120 {
121 	/* Reliable end of stack detection:
122 	 * Some APM bios versions misalign the stack
123 	 */
124 	return !(((unsigned long)addr+sizeof(void*)-1) & (THREAD_SIZE-sizeof(void*)));
125 }
126 #endif
127 
128 #endif /* _LINUX_SCHED_TASK_STACK_H */
129