1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * Return hooking with list-based shadow stack.
4 */
5 #ifndef _LINUX_RETHOOK_H
6 #define _LINUX_RETHOOK_H
7
8 #include <linux/compiler.h>
9 #include <linux/freelist.h>
10 #include <linux/kallsyms.h>
11 #include <linux/llist.h>
12 #include <linux/rcupdate.h>
13 #include <linux/refcount.h>
14
15 struct rethook_node;
16
17 typedef void (*rethook_handler_t) (struct rethook_node *, void *, struct pt_regs *);
18
19 /**
20 * struct rethook - The rethook management data structure.
21 * @data: The user-defined data storage.
22 * @handler: The user-defined return hook handler.
23 * @pool: The pool of struct rethook_node.
24 * @ref: The reference counter.
25 * @rcu: The rcu_head for deferred freeing.
26 *
27 * Don't embed to another data structure, because this is a self-destructive
28 * data structure when all rethook_node are freed.
29 */
30 struct rethook {
31 void *data;
32 rethook_handler_t handler;
33 struct freelist_head pool;
34 refcount_t ref;
35 struct rcu_head rcu;
36 };
37
38 /**
39 * struct rethook_node - The rethook shadow-stack entry node.
40 * @freelist: The freelist, linked to struct rethook::pool.
41 * @rcu: The rcu_head for deferred freeing.
42 * @llist: The llist, linked to a struct task_struct::rethooks.
43 * @rethook: The pointer to the struct rethook.
44 * @ret_addr: The storage for the real return address.
45 * @frame: The storage for the frame pointer.
46 *
47 * You can embed this to your extended data structure to store any data
48 * on each entry of the shadow stack.
49 */
50 struct rethook_node {
51 union {
52 struct freelist_node freelist;
53 struct rcu_head rcu;
54 };
55 struct llist_node llist;
56 struct rethook *rethook;
57 unsigned long ret_addr;
58 unsigned long frame;
59 };
60
61 struct rethook *rethook_alloc(void *data, rethook_handler_t handler);
62 void rethook_free(struct rethook *rh);
63 void rethook_add_node(struct rethook *rh, struct rethook_node *node);
64 struct rethook_node *rethook_try_get(struct rethook *rh);
65 void rethook_recycle(struct rethook_node *node);
66 void rethook_hook(struct rethook_node *node, struct pt_regs *regs, bool mcount);
67 unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame,
68 struct llist_node **cur);
69
70 /* Arch dependent code must implement arch_* and trampoline code */
71 void arch_rethook_prepare(struct rethook_node *node, struct pt_regs *regs, bool mcount);
72 void arch_rethook_trampoline(void);
73
74 /**
75 * is_rethook_trampoline() - Check whether the address is rethook trampoline
76 * @addr: The address to be checked
77 *
78 * Return true if the @addr is the rethook trampoline address.
79 */
is_rethook_trampoline(unsigned long addr)80 static inline bool is_rethook_trampoline(unsigned long addr)
81 {
82 return addr == (unsigned long)dereference_symbol_descriptor(arch_rethook_trampoline);
83 }
84
85 /* If the architecture needs to fixup the return address, implement it. */
86 void arch_rethook_fixup_return(struct pt_regs *regs,
87 unsigned long correct_ret_addr);
88
89 /* Generic trampoline handler, arch code must prepare asm stub */
90 unsigned long rethook_trampoline_handler(struct pt_regs *regs,
91 unsigned long frame);
92
93 #ifdef CONFIG_RETHOOK
94 void rethook_flush_task(struct task_struct *tk);
95 #else
96 #define rethook_flush_task(tsk) do { } while (0)
97 #endif
98
99 #endif
100
101