llext: export some symbols

Export some symbols for loadable modules. Also add an
EXPORT_SYSCALL() helper macro for exporting system calls by their
official names.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>

include/zephyr/llext/symbol.h

@@ -78,6 +78,16 @@ struct llext_symtable {
 		.name = STRINGIFY(x), .addr = &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

@@ -37,6 +37,7 @@
 #include <zephyr/tracing/tracing.h>
 #include <zephyr/sys/check.h>
 #include <zephyr/logging/log.h>
+#include <zephyr/llext/symbol.h>
 LOG_MODULE_DECLARE(os, CONFIG_KERNEL_LOG_LEVEL);
 
 /* We use a global spinlock here because some of the synchronization
@@ -195,6 +196,7 @@ 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,
@@ -280,6 +282,7 @@ 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)

kernel/thread.c

@@ -29,6 +29,7 @@
 #include <zephyr/random/random.h>
 #include <zephyr/sys/atomic.h>
 #include <zephyr/logging/log.h>
+#include <zephyr/llext/symbol.h>
 #include <zephyr/sys/iterable_sections.h>
 
 LOG_MODULE_DECLARE(os, CONFIG_KERNEL_LOG_LEVEL);
@@ -141,6 +142,7 @@ bool k_is_in_isr(void)
 {
 	return arch_is_in_isr();
 }
+EXPORT_SYMBOL(k_is_in_isr);
 
 /*
  * This function tags the current thread as essential to system operation.

lib/os/assert.c

@@ -7,7 +7,7 @@
 #include <zephyr/sys/__assert.h>
 #include <zephyr/sys/printk.h>
 #include <zephyr/kernel.h>
-
+#include <zephyr/llext/symbol.h>
 
 /**
  * @brief Assert Action Handler
@@ -42,6 +42,7 @@ __weak void assert_post_action(const char *file, unsigned int line)
 
 	k_panic();
 }
+EXPORT_SYMBOL(assert_post_action);
 
 void assert_print(const char *fmt, ...)
 {
@@ -53,3 +54,4 @@ void assert_print(const char *fmt, ...)
 
 	va_end(ap);
 }
+EXPORT_SYMBOL(assert_print);

subsys/llext/CMakeLists.txt

@@ -1,6 +1,5 @@
 if(CONFIG_LLEXT)
   zephyr_library()
-  zephyr_library_sources(llext.c)
-  zephyr_library_sources(buf_loader.c)
+  zephyr_library_sources(llext.c llext_export.c buf_loader.c)
   zephyr_library_sources_ifdef(CONFIG_LLEXT_SHELL shell.c)
 endif()

subsys/llext/llext_export.c

@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2023 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <string.h>
+#include <zephyr/llext/symbol.h>
+
+EXPORT_SYMBOL(strcpy);
+EXPORT_SYMBOL(strncpy);
+EXPORT_SYMBOL(strlen);
+EXPORT_SYMBOL(strcmp);
+EXPORT_SYMBOL(strncmp);
+EXPORT_SYMBOL(memcmp);
+EXPORT_SYMBOL(memcpy);
+EXPORT_SYMBOL(memset);

subsys/logging/log_msg.c

@@ -10,6 +10,7 @@
 #include <zephyr/logging/log_frontend.h>
 #include <zephyr/logging/log_backend.h>
 #include <zephyr/logging/log.h>
+#include <zephyr/llext/symbol.h>
 LOG_MODULE_DECLARE(log);
 
 BUILD_ASSERT(sizeof(struct log_msg_desc) == sizeof(uint32_t),
@@ -270,6 +271,7 @@ 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,