From 1bb939a836b92258aa6af8700448bd1ae95c0f84 Mon Sep 17 00:00:00 2001
From: Luca Burelli <l.burelli@arduino.cc>
Date: Thu, 9 Jan 2025 10:41:44 +0100
Subject: [PATCH] llext: add custom name variant to symbol export macros

Add a new set of macros that allow customizing the symbol name when
exporting symbols. This is useful when the symbol name that extensions
need to look up is different from the identifier used in the base image.

Signed-off-by: Luca Burelli <l.burelli@arduino.cc>
---
 include/zephyr/llext/symbol.h | 62 +++++++++++++++++++++++++----------
 1 file changed, 45 insertions(+), 17 deletions(-)

diff --git a/include/zephyr/llext/symbol.h b/include/zephyr/llext/symbol.h
index 9eb847b97fc..c0b7004ed17 100644
--- a/include/zephyr/llext/symbol.h
+++ b/include/zephyr/llext/symbol.h
@@ -90,18 +90,30 @@ struct llext_symtable {
 /** @cond ignore */
 #ifdef LL_EXTENSION_BUILD
 /* Extension build: add exported symbols to llext table */
-#define Z_LL_EXTENSION_SYMBOL(x)						\
+#define Z_LL_EXTENSION_SYMBOL_NAMED(sym_ident, sym_name)			\
 	static const struct llext_const_symbol					\
 			Z_GENERIC_SECTION(".exported_sym") __used		\
-			__llext_sym_ ## x = {					\
-		.name = STRINGIFY(x), .addr = (const void *)&x,			\
+			__llext_sym_ ## sym_name = {				\
+		.name = STRINGIFY(sym_name), .addr = (const void *)&sym_ident,	\
 	}
 #else
 /* No-op when not building an extension */
-#define Z_LL_EXTENSION_SYMBOL(x)
+#define Z_LL_EXTENSION_SYMBOL_NAMED(sym_ident, sym_name)
 #endif
 /** @endcond */
 
+/**
+ * @brief Exports a symbol from an extension to the base image with a custom name
+ *
+ * Version of @ref LL_EXTENSION_SYMBOL that allows the user to specify a custom
+ * name for the exported symbol.
+ *
+ * @param sym_ident Extension symbol to export to the base image
+ * @param sym_name Name associated with the symbol
+ */
+#define LL_EXTENSION_SYMBOL_NAMED(sym_ident, sym_name)				\
+	Z_LL_EXTENSION_SYMBOL_NAMED(sym_ident, sym_name)
+
 /**
  * @brief Exports a symbol from an extension to the base image
  *
@@ -113,34 +125,50 @@ struct llext_symtable {
  *
  * @param x Extension symbol to export to the base image
  */
-#define LL_EXTENSION_SYMBOL(x) Z_LL_EXTENSION_SYMBOL(x)
+#define LL_EXTENSION_SYMBOL(x) Z_LL_EXTENSION_SYMBOL_NAMED(x, x)
 
 /** @cond ignore */
 #if defined(LL_EXTENSION_BUILD)
 /* Extension build: EXPORT_SYMBOL maps to LL_EXTENSION_SYMBOL */
-#define Z_EXPORT_SYMBOL(x) Z_LL_EXTENSION_SYMBOL(x)
+#define Z_EXPORT_SYMBOL_NAMED(sym_ident, sym_name)				\
+	Z_LL_EXTENSION_SYMBOL_NAMED(sym_ident, sym_name)
 #elif defined(CONFIG_LLEXT_EXPORT_BUILTINS_BY_SLID)
 /* SLID-enabled LLEXT application: export symbols, names in separate section */
-#define Z_EXPORT_SYMBOL(x)							\
+#define Z_EXPORT_SYMBOL_NAMED(sym_ident, sym_name)				\
 	static const char Z_GENERIC_SECTION("llext_exports_strtab") __used	\
-		__llext_sym_name_ ## x[] = STRINGIFY(x);				\
-	static const STRUCT_SECTION_ITERABLE(llext_const_symbol,                \
-					     __llext_sym_ ## x) = {	        \
-		.name = __llext_sym_name_ ## x, .addr = (const void *)&x,		\
+		__llext_sym_name_ ## sym_name[] = STRINGIFY(sym_name);		\
+	static const STRUCT_SECTION_ITERABLE(llext_const_symbol,		\
+					     __llext_sym_ ## sym_name) = {	\
+		.name = __llext_sym_name_ ## sym_name,				\
+		.addr = (const void *)&sym_ident,				\
 	}
 #elif defined(CONFIG_LLEXT)
 /* LLEXT application: export symbols */
-#define Z_EXPORT_SYMBOL(x)							\
-	static const STRUCT_SECTION_ITERABLE(llext_const_symbol,                \
-					     __llext_sym_ ## x) = {	        \
-		.name = STRINGIFY(x), .addr = (const void *)&x,			\
+#define Z_EXPORT_SYMBOL_NAMED(sym_ident, sym_name)				\
+	static const STRUCT_SECTION_ITERABLE(llext_const_symbol,		\
+					     __llext_sym_ ## sym_name) = {	\
+		.name = STRINGIFY(sym_name), .addr = (const void *)&sym_ident,	\
 	}
 #else
 /* No extension support in this build */
-#define Z_EXPORT_SYMBOL(x)
+#define Z_EXPORT_SYMBOL_NAMED(sym_ident, sym_name)
 #endif
 /** @endcond */
 
+/**
+ * @brief Export a constant symbol from the current build with a custom name
+ *
+ * Version of @ref EXPORT_SYMBOL that allows the user to specify a custom name
+ * for the exported symbol.
+ *
+ * When @c CONFIG_LLEXT is not enabled, this macro is a no-op.
+ *
+ * @param sym_ident Symbol to export
+ * @param sym_name Name associated with the symbol
+ */
+#define EXPORT_SYMBOL_NAMED(sym_ident, sym_name)				\
+	Z_EXPORT_SYMBOL_NAMED(sym_ident, sym_name)
+
 /**
  * @brief Export a constant symbol from the current build
  *
@@ -152,7 +180,7 @@ struct llext_symtable {
  *
  * @param x Symbol to export
  */
-#define EXPORT_SYMBOL(x) Z_EXPORT_SYMBOL(x)
+#define EXPORT_SYMBOL(x) EXPORT_SYMBOL_NAMED(x, x)
 
 /**
  * @}