static_call: Add inline static call infrastructure

Add infrastructure for an arch-specific CONFIG_HAVE_STATIC_CALL_INLINE
option, which is a faster version of CONFIG_HAVE_STATIC_CALL.  At
runtime, the static call sites are patched directly, rather than using
the out-of-line trampolines.

Compared to out-of-line static calls, the performance benefits are more
modest, but still measurable.  Steven Rostedt did some tracepoint
measurements:

  https://lkml.kernel.org/r/20181126155405.72b4f718@gandalf.local.home

This code is heavily inspired by the jump label code (aka "static
jumps"), as some of the concepts are very similar.

For more details, see the comments in include/linux/static_call.h.

[peterz: simplified interface; merged trampolines]

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20200818135804.684334440@infradead.org

1 files changed, 35 insertions, 1 deletions

diff --git a/include/linux/static_call.h b/include/linux/static_call.h
index d8892dff2e91..0d7f9efaa3b2 100644
--- a/include/linux/static_call.h
+++ b/include/linux/static_call.h
@@ -95,7 +95,41 @@ extern void arch_static_call_transform(void *site, void *tramp, void *func);
 			     STATIC_CALL_TRAMP_ADDR(name), func);	\
 })
 
-#if defined(CONFIG_HAVE_STATIC_CALL)
+#ifdef CONFIG_HAVE_STATIC_CALL_INLINE
+
+struct static_call_mod {
+	struct static_call_mod *next;
+	struct module *mod; /* for vmlinux, mod == NULL */
+	struct static_call_site *sites;
+};
+
+struct static_call_key {
+	void *func;
+	struct static_call_mod *mods;
+};
+
+extern void __static_call_update(struct static_call_key *key, void *tramp, void *func);
+extern int static_call_mod_init(struct module *mod);
+
+#define DEFINE_STATIC_CALL(name, _func)					\
+	DECLARE_STATIC_CALL(name, _func);				\
+	struct static_call_key STATIC_CALL_KEY(name) = {		\
+		.func = _func,						\
+		.mods = NULL,						\
+	};								\
+	ARCH_DEFINE_STATIC_CALL_TRAMP(name, _func)
+
+#define static_call(name)	__static_call(name)
+
+#define EXPORT_STATIC_CALL(name)					\
+	EXPORT_SYMBOL(STATIC_CALL_KEY(name));				\
+	EXPORT_SYMBOL(STATIC_CALL_TRAMP(name))
+
+#define EXPORT_STATIC_CALL_GPL(name)					\
+	EXPORT_SYMBOL_GPL(STATIC_CALL_KEY(name));			\
+	EXPORT_SYMBOL_GPL(STATIC_CALL_TRAMP(name))
+
+#elif defined(CONFIG_HAVE_STATIC_CALL)
 
 struct static_call_key {
 	void *func;