syscall: Export all emitted syscalls, enabling them for extensions

Linkable loadable extensions can only use syscalls if they are exported
via EXPORT_SYSCALL (or EXPORT_SYMBOL). Instead of enabling used syscalls
one by one, this patch exports all of them automatically via
`gen_syscalls.py`. If CONFIG_LLEXT=n, the section where the exported
symbols live is discarded, so it should be a non-op when llext is not
enabled.

This patch also removes the now redundant EXPORT_SYSCALL macro. Note
that EXPORT_SYMBOL is still useful on different situations (and is
indeed used by the code generated by `gen_syscalls.py`).

Signed-off-by: Ederson de Souza <ederson.desouza@intel.com>

include/zephyr/llext/symbol.h

@@ -83,16 +83,6 @@ struct llext_symtable {
 	struct llext_symbol Z_GENERIC_SECTION(".exported_sym") __used		\
 		symbol_##x = {STRINGIFY(x), (void *)&x}
 
-/**
- * @brief Export a system call to a table of symbols
- *
- * Takes a system call name and uses @a EXPORT_SYMBOL() to export the respective
- * function.
- *
- * @param x System call to export
- */
-#define EXPORT_SYSCALL(x) EXPORT_SYMBOL(z_impl_ ## x)
-
 /**
  * @}
  */

kernel/mutex.c

@@ -196,7 +196,6 @@ int z_impl_k_mutex_lock(struct k_mutex *mutex, k_timeout_t timeout)
 
 	return -EAGAIN;
 }
-EXPORT_SYSCALL(k_mutex_lock);
 
 #ifdef CONFIG_USERSPACE
 static inline int z_vrfy_k_mutex_lock(struct k_mutex *mutex,
@@ -282,7 +281,6 @@ k_mutex_unlock_return:
 
 	return 0;
 }
-EXPORT_SYSCALL(k_mutex_unlock);
 
 #ifdef CONFIG_USERSPACE
 static inline int z_vrfy_k_mutex_unlock(struct k_mutex *mutex)

scripts/build/gen_syscalls.py

@@ -52,6 +52,8 @@ noweak = ["z_mrsh_k_object_release",
 
 table_template = """/* auto-generated by gen_syscalls.py, don't edit */
 
+#include <zephyr/llext/symbol.h>
+
 /* Weak handler functions that get replaced by the real ones unless a system
  * call is not implemented due to kernel configuration.
  */
@@ -60,6 +62,8 @@ table_template = """/* auto-generated by gen_syscalls.py, don't edit */
 const _k_syscall_handler_t _k_syscall_table[K_SYSCALL_LIMIT] = {
 \t%s
 };
+/* Export syscalls for extensions */
+%s
 """
 
 list_template = """/* auto-generated by gen_syscalls.py, don't edit */
@@ -460,8 +464,12 @@ def main():
         weak_defines += "\n".join(["extern uintptr_t %s(uintptr_t arg1, uintptr_t arg2, uintptr_t arg3, uintptr_t arg4, uintptr_t arg5, uintptr_t arg6, void *ssf);"
                                    % s for s in noweak])
 
+        # Export symbols for emitted syscalls
+        exported_symbols = "\n".join("EXPORT_SYMBOL(%s);" % e for e in emit_list)
+
         fp.write(table_template % (weak_defines,
-                                   ",\n\t".join(table_entries)))
+                                   ",\n\t".join(table_entries),
+                                   exported_symbols))
 
     # Listing header emitted to stdout
     ids_emit.sort()

subsys/logging/log_msg.c

@@ -329,7 +329,6 @@ void z_impl_z_log_msg_static_create(const void *source,
 
 	z_log_msg_finalize(msg, source, out_desc, data);
 }
-EXPORT_SYSCALL(z_log_msg_static_create);
 
 #ifdef CONFIG_USERSPACE
 static inline void z_vrfy_z_log_msg_static_create(const void *source,