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 */ 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