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