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d08b9f0c ST |
1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | /* | |
3 | * Shadow Call Stack support. | |
4 | * | |
5 | * Copyright (C) 2019 Google LLC | |
6 | */ | |
7 | ||
8 | #ifndef _LINUX_SCS_H | |
9 | #define _LINUX_SCS_H | |
10 | ||
11 | #include <linux/gfp.h> | |
12 | #include <linux/poison.h> | |
13 | #include <linux/sched.h> | |
14 | #include <linux/sizes.h> | |
15 | ||
16 | #ifdef CONFIG_SHADOW_CALL_STACK | |
17 | ||
a2abe7cb ST |
18 | #define SCS_ORDER 0 |
19 | #define SCS_SIZE (PAGE_SIZE << SCS_ORDER) | |
d08b9f0c ST |
20 | #define GFP_SCS (GFP_KERNEL | __GFP_ZERO) |
21 | ||
22 | /* An illegal pointer value to mark the end of the shadow stack. */ | |
23 | #define SCS_END_MAGIC (0x5f6UL + POISON_POINTER_DELTA) | |
24 | ||
25 | #define task_scs(tsk) (task_thread_info(tsk)->scs_base) | |
51189c7a | 26 | #define task_scs_sp(tsk) (task_thread_info(tsk)->scs_sp) |
d08b9f0c | 27 | |
a2abe7cb ST |
28 | void *scs_alloc(int node); |
29 | void scs_free(void *s); | |
d08b9f0c ST |
30 | void scs_init(void); |
31 | int scs_prepare(struct task_struct *tsk, int node); | |
32 | void scs_release(struct task_struct *tsk); | |
33 | ||
34 | static inline void scs_task_reset(struct task_struct *tsk) | |
35 | { | |
36 | /* | |
37 | * Reset the shadow stack to the base address in case the task | |
38 | * is reused. | |
39 | */ | |
51189c7a | 40 | task_scs_sp(tsk) = task_scs(tsk); |
d08b9f0c ST |
41 | } |
42 | ||
43 | static inline unsigned long *__scs_magic(void *s) | |
44 | { | |
45 | return (unsigned long *)(s + SCS_SIZE) - 1; | |
46 | } | |
47 | ||
88485be5 | 48 | static inline bool task_scs_end_corrupted(struct task_struct *tsk) |
d08b9f0c ST |
49 | { |
50 | unsigned long *magic = __scs_magic(task_scs(tsk)); | |
51189c7a | 51 | unsigned long sz = task_scs_sp(tsk) - task_scs(tsk); |
d08b9f0c | 52 | |
51189c7a | 53 | return sz >= SCS_SIZE - 1 || READ_ONCE_NOCHECK(*magic) != SCS_END_MAGIC; |
d08b9f0c ST |
54 | } |
55 | ||
56 | #else /* CONFIG_SHADOW_CALL_STACK */ | |
57 | ||
a2abe7cb ST |
58 | static inline void *scs_alloc(int node) { return NULL; } |
59 | static inline void scs_free(void *s) {} | |
d08b9f0c ST |
60 | static inline void scs_init(void) {} |
61 | static inline void scs_task_reset(struct task_struct *tsk) {} | |
62 | static inline int scs_prepare(struct task_struct *tsk, int node) { return 0; } | |
d08b9f0c | 63 | static inline void scs_release(struct task_struct *tsk) {} |
88485be5 | 64 | static inline bool task_scs_end_corrupted(struct task_struct *tsk) { return false; } |
d08b9f0c ST |
65 | |
66 | #endif /* CONFIG_SHADOW_CALL_STACK */ | |
67 | ||
68 | #endif /* _LINUX_SCS_H */ |