1 /* SPDX-License-Identifier: GPL-2.0 */
8  * Static calls use code patching to hard-code function pointers into direct
17  *   DECLARE_STATIC_CALL(name, func);
18  *   DEFINE_STATIC_CALL(name, func);
19  *   DEFINE_STATIC_CALL_NULL(name, typename);
20  *   DEFINE_STATIC_CALL_RET0(name, typename);
24  *   static_call(name)(args...);
25  *   static_call_cond(name)(args...);
26  *   static_call_update(name, func);
27  *   static_call_query(name);
52  *   This requires some arch-specific code (CONFIG_HAVE_STATIC_CALL).
55  *   Each static_call() site calls into a trampoline associated with the name.
57  *   name will modify the trampoline's branch destination.
84  *   instruction, instead of an immediate tail-call JMP. HAVE_STATIC_CALL_INLINE
97  *     static_call_cond(name)(arg1);
99  *   which will include the required value tests to avoid NULL-pointer
104  *   func = static_call_query(name);
115  *   make things work. In particular it relies on Caller Stack-cleanup and the
146 #define STATIC_CALL_TRAMP_ADDR(name) &STATIC_CALL_TRAMP(name)  argument
149 #define STATIC_CALL_TRAMP_ADDR(name) NULL  argument
152 #define static_call_update(name, func)					\  argument
154 	typeof(&STATIC_CALL_TRAMP(name)) __F = (func);			\
155 	__static_call_update(&STATIC_CALL_KEY(name),			\
156 			     STATIC_CALL_TRAMP_ADDR(name), __F);	\
159 #define static_call_query(name) (READ_ONCE(STATIC_CALL_KEY(name).func))  argument
183 #define DEFINE_STATIC_CALL(name, _func)					\  argument
184 	DECLARE_STATIC_CALL(name, _func);				\
185 	struct static_call_key STATIC_CALL_KEY(name) = {		\
189 	ARCH_DEFINE_STATIC_CALL_TRAMP(name, _func)
191 #define DEFINE_STATIC_CALL_NULL(name, _func)				\  argument
192 	DECLARE_STATIC_CALL(name, _func);				\
193 	struct static_call_key STATIC_CALL_KEY(name) = {		\
197 	ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name)
199 #define DEFINE_STATIC_CALL_RET0(name, _func)				\  argument
200 	DECLARE_STATIC_CALL(name, _func);				\
201 	struct static_call_key STATIC_CALL_KEY(name) = {		\
205 	ARCH_DEFINE_STATIC_CALL_RET0_TRAMP(name)
207 #define static_call_cond(name)	(void)__static_call(name)  argument
209 #define EXPORT_STATIC_CALL(name)					\  argument
210 	EXPORT_SYMBOL(STATIC_CALL_KEY(name));				\
211 	EXPORT_SYMBOL(STATIC_CALL_TRAMP(name))
212 #define EXPORT_STATIC_CALL_GPL(name)					\  argument
213 	EXPORT_SYMBOL_GPL(STATIC_CALL_KEY(name));			\
214 	EXPORT_SYMBOL_GPL(STATIC_CALL_TRAMP(name))
217 #define EXPORT_STATIC_CALL_TRAMP(name)					\  argument
218 	EXPORT_SYMBOL(STATIC_CALL_TRAMP(name));				\
219 	ARCH_ADD_TRAMP_KEY(name)
220 #define EXPORT_STATIC_CALL_TRAMP_GPL(name)				\  argument
221 	EXPORT_SYMBOL_GPL(STATIC_CALL_TRAMP(name));			\
222 	ARCH_ADD_TRAMP_KEY(name)
228 #define DEFINE_STATIC_CALL(name, _func)					\  argument
229 	DECLARE_STATIC_CALL(name, _func);				\
230 	struct static_call_key STATIC_CALL_KEY(name) = {		\
233 	ARCH_DEFINE_STATIC_CALL_TRAMP(name, _func)
235 #define DEFINE_STATIC_CALL_NULL(name, _func)				\  argument
236 	DECLARE_STATIC_CALL(name, _func);				\
237 	struct static_call_key STATIC_CALL_KEY(name) = {		\
240 	ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name)
242 #define DEFINE_STATIC_CALL_RET0(name, _func)				\  argument
243 	DECLARE_STATIC_CALL(name, _func);				\
244 	struct static_call_key STATIC_CALL_KEY(name) = {		\
247 	ARCH_DEFINE_STATIC_CALL_RET0_TRAMP(name)
249 #define static_call_cond(name)	(void)__static_call(name)  argument
255 	WRITE_ONCE(key->func, func);  in __static_call_update()
267 #define EXPORT_STATIC_CALL(name)					\  argument
268 	EXPORT_SYMBOL(STATIC_CALL_KEY(name));				\
269 	EXPORT_SYMBOL(STATIC_CALL_TRAMP(name))
270 #define EXPORT_STATIC_CALL_GPL(name)					\  argument
271 	EXPORT_SYMBOL_GPL(STATIC_CALL_KEY(name));			\
272 	EXPORT_SYMBOL_GPL(STATIC_CALL_TRAMP(name))
275 #define EXPORT_STATIC_CALL_TRAMP(name)					\  argument
276 	EXPORT_SYMBOL(STATIC_CALL_TRAMP(name))
277 #define EXPORT_STATIC_CALL_TRAMP_GPL(name)				\  argument
278 	EXPORT_SYMBOL_GPL(STATIC_CALL_TRAMP(name))
289 #define __DEFINE_STATIC_CALL(name, _func, _func_init)			\  argument
290 	DECLARE_STATIC_CALL(name, _func);				\
291 	struct static_call_key STATIC_CALL_KEY(name) = {		\
295 #define DEFINE_STATIC_CALL(name, _func)					\  argument
296 	__DEFINE_STATIC_CALL(name, _func, _func)
298 #define DEFINE_STATIC_CALL_NULL(name, _func)				\  argument
299 	__DEFINE_STATIC_CALL(name, _func, NULL)
301 #define DEFINE_STATIC_CALL_RET0(name, _func)				\  argument
302 	__DEFINE_STATIC_CALL(name, _func, __static_call_return0)
309  *  - it ensures the compiler will only load the function pointer ONCE,
312  *  - it ensures the argument evaluation is unconditional, similar
316  * and will emit an indirect call for the NULL case :-(
318 #define __static_call_cond(name)					\  argument
320 	void *func = READ_ONCE(STATIC_CALL_KEY(name).func);		\
323 	(typeof(STATIC_CALL_TRAMP(name))*)func;				\
326 #define static_call_cond(name)	(void)__static_call_cond(name)  argument
331 	WRITE_ONCE(key->func, func);  in __static_call_update()
339 #define EXPORT_STATIC_CALL(name)	EXPORT_SYMBOL(STATIC_CALL_KEY(name))  argument
340 #define EXPORT_STATIC_CALL_GPL(name)	EXPORT_SYMBOL_GPL(STATIC_CALL_KEY(name))  argument