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(const 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 */
123
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