3 files changed, 27 insertions, 3 deletions
diff --git a/arch/x86/include/asm/static_call.h b/arch/x86/include/asm/static_call.h
index 125c407e2abe..41502bd2afd6 100644
--- a/arch/x86/include/asm/static_call.h
+++ b/arch/x86/include/asm/static_call.h
@@ -65,4 +65,19 @@
 
 extern bool __static_call_fixup(void *tramp, u8 op, void *dest);
 
+extern void __static_call_update_early(void *tramp, void *func);
+
+#define static_call_update_early(name, _func)				\
+({									\
+	typeof(&STATIC_CALL_TRAMP(name)) __F = (_func);			\
+	if (static_call_initialized) {					\
+		__static_call_update(&STATIC_CALL_KEY(name),		\
+				     STATIC_CALL_TRAMP_ADDR(name), __F);\
+	} else {							\
+		WRITE_ONCE(STATIC_CALL_KEY(name).func, _func);		\
+		__static_call_update_early(STATIC_CALL_TRAMP_ADDR(name),\
+					   __F);			\
+	}								\
+})
+
 #endif /* _ASM_STATIC_CALL_H */
diff --git a/arch/x86/include/asm/sync_core.h b/arch/x86/include/asm/sync_core.h
index ab7382f92aff..96bda43538ee 100644
--- a/arch/x86/include/asm/sync_core.h
+++ b/arch/x86/include/asm/sync_core.h
@@ -8,7 +8,7 @@
 #include <asm/special_insns.h>
 
 #ifdef CONFIG_X86_32
-static inline void iret_to_self(void)
+static __always_inline void iret_to_self(void)
 {
 	asm volatile (
 		"pushfl\n\t"
@@ -19,7 +19,7 @@ static inline void iret_to_self(void)
 		: ASM_CALL_CONSTRAINT : : "memory");
 }
 #else
-static inline void iret_to_self(void)
+static __always_inline void iret_to_self(void)
 {
 	unsigned int tmp;
 
@@ -55,7 +55,7 @@ static inline void iret_to_self(void)
  * Like all of Linux's memory ordering operations, this is a
  * compiler barrier as well.
  */
-static inline void sync_core(void)
+static __always_inline void sync_core(void)
 {
 	/*
 	 * The SERIALIZE instruction is the most straightforward way to
diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c
index 4eefaac64c6c..9eed0c144dad 100644
--- a/arch/x86/kernel/static_call.c
+++ b/arch/x86/kernel/static_call.c
@@ -172,6 +172,15 @@ void arch_static_call_transform(void *site, void *tramp, void *func, bool tail)
 }
 EXPORT_SYMBOL_GPL(arch_static_call_transform);
 
+noinstr void __static_call_update_early(void *tramp, void *func)
+{
+	BUG_ON(system_state != SYSTEM_BOOTING);
+	BUG_ON(!early_boot_irqs_disabled);
+	BUG_ON(static_call_initialized);
+	__text_gen_insn(tramp, JMP32_INSN_OPCODE, tramp, func, JMP32_INSN_SIZE);
+	sync_core();
+}
+
 #ifdef CONFIG_MITIGATION_RETHUNK
 /*
  * This is called by apply_returns() to fix up static call trampolines,