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 #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
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 */
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
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
74 static inline void *try_get_task_stack(struct task_struct *tsk)
75 {
76 return task_stack_page(tsk);
77 }
78
79 static inline void put_task_stack(struct task_struct *tsk) {}
80 #endif
81
82 #define task_stack_end_corrupted(task) \
83 (*(end_of_stack(task)) != STACK_END_MAGIC)
84
85 static inline int object_is_on_stack(const void *obj)
86 {
87 void *stack = task_stack_page(current);
88
89 return (obj >= stack) && (obj < (stack + THREAD_SIZE));
90 }
91
92 extern void thread_stack_cache_init(void);
93
94 #ifdef CONFIG_DEBUG_STACK_USAGE
95 static inline unsigned long stack_not_used(struct task_struct *p)
96 {
97 unsigned long *n = end_of_stack(p);
98
99 do { /* Skip over canary */
100 # ifdef CONFIG_STACK_GROWSUP
101 n--;
102 # else
103 n++;
104 # endif
105 } while (!*n);
106
107 # ifdef CONFIG_STACK_GROWSUP
108 return (unsigned long)end_of_stack(p) - (unsigned long)n;
109 # else
110 return (unsigned long)n - (unsigned long)end_of_stack(p);
111 # endif
112 }
113 #endif
114 extern void set_task_stack_end_magic(struct task_struct *tsk);
115
116 #ifndef __HAVE_ARCH_KSTACK_END
117 static inline int kstack_end(void *addr)
118 {
119 /* Reliable end of stack detection:
120 * Some APM bios versions misalign the stack
121 */
122 return !(((unsigned long)addr+sizeof(void*)-1) & (THREAD_SIZE-sizeof(void*)));
123 }
124 #endif
125
126 #endif /* _LINUX_SCHED_TASK_STACK_H */
127
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