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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Return hooking with list-based shadow stack.
*/
#ifndef _LINUX_RETHOOK_H
#define _LINUX_RETHOOK_H
#include <linux/compiler.h>
#include <linux/freelist.h>
#include <linux/kallsyms.h>
#include <linux/llist.h>
#include <linux/rcupdate.h>
#include <linux/refcount.h>
struct rethook_node;
typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long, struct pt_regs *);
/**
* struct rethook - The rethook management data structure.
* @data: The user-defined data storage.
* @handler: The user-defined return hook handler.
* @pool: The pool of struct rethook_node.
* @ref: The reference counter.
* @rcu: The rcu_head for deferred freeing.
*
* Don't embed to another data structure, because this is a self-destructive
* data structure when all rethook_node are freed.
*/
struct rethook {
void *data;
rethook_handler_t handler;
struct freelist_head pool;
refcount_t ref;
struct rcu_head rcu;
};
/**
* struct rethook_node - The rethook shadow-stack entry node.
* @freelist: The freelist, linked to struct rethook::pool.
* @rcu: The rcu_head for deferred freeing.
* @llist: The llist, linked to a struct task_struct::rethooks.
* @rethook: The pointer to the struct rethook.
* @ret_addr: The storage for the real return address.
* @frame: The storage for the frame pointer.
*
* You can embed this to your extended data structure to store any data
* on each entry of the shadow stack.
*/
struct rethook_node {
union {
struct freelist_node freelist;
struct rcu_head rcu;
};
struct llist_node llist;
struct rethook *rethook;
unsigned long ret_addr;
unsigned long frame;
};
struct rethook *rethook_alloc(void *data, rethook_handler_t handler);
void rethook_free(struct rethook *rh);
void rethook_add_node(struct rethook *rh, struct rethook_node *node);
struct rethook_node *rethook_try_get(struct rethook *rh);
void rethook_recycle(struct rethook_node *node);
void rethook_hook(struct rethook_node *node, struct pt_regs *regs, bool mcount);
unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame,
struct llist_node **cur);
/* Arch dependent code must implement arch_* and trampoline code */
void arch_rethook_prepare(struct rethook_node *node, struct pt_regs *regs, bool mcount);
void arch_rethook_trampoline(void);
/**
* is_rethook_trampoline() - Check whether the address is rethook trampoline
* @addr: The address to be checked
*
* Return true if the @addr is the rethook trampoline address.
*/
static inline bool is_rethook_trampoline(unsigned long addr)
{
return addr == (unsigned long)dereference_symbol_descriptor(arch_rethook_trampoline);
}
/* If the architecture needs to fixup the return address, implement it. */
void arch_rethook_fixup_return(struct pt_regs *regs,
unsigned long correct_ret_addr);
/* Generic trampoline handler, arch code must prepare asm stub */
unsigned long rethook_trampoline_handler(struct pt_regs *regs,
unsigned long frame);
#ifdef CONFIG_RETHOOK
void rethook_flush_task(struct task_struct *tk);
#else
#define rethook_flush_task(tsk) do { } while (0)
#endif
#endif
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