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