llext: Add filesystem based extension loader

Added loader allowing to load extensions stored in a filesystem.

Signed-off-by: Adam Wojasinski <awojasinski@baylibre.com>

include/zephyr/llext/fs_loader.h

@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2024 BayLibre SAS
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_LLEXT_FS_LOADER_H
+#define ZEPHYR_LLEXT_FS_LOADER_H
+
+#include <zephyr/llext/loader.h>
+#include <zephyr/fs/fs.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @file
+ * @brief LLEXT filesystem loader implementation.
+ *
+ * @addtogroup llext_loader_apis
+ * @{
+ */
+
+/**
+ * @brief Implementation of @ref llext_loader that reads from a filesystem.
+ */
+struct llext_fs_loader {
+	/** Extension loader */
+	struct llext_loader loader;
+
+	/** @cond ignore */
+	bool is_open;
+	const char *name;
+	struct fs_file_t file;
+	/** @endcond */
+};
+
+/** @cond ignore */
+int llext_fs_prepare(struct llext_loader *ldr);
+int llext_fs_read(struct llext_loader *ldr, void *buf, size_t len);
+int llext_fs_seek(struct llext_loader *ldr, size_t pos);
+void llext_fs_finalize(struct llext_loader *ldr);
+/** @endcond */
+
+/**
+ * @brief Initializer for an llext_fs_loader structure
+ *
+ * @param _filename Absolute path to the extension file.
+ */
+#define LLEXT_FS_LOADER(_filename)                                                                 \
+	{                                                                                          \
+		.loader =                                                                          \
+			{                                                                          \
+				.prepare = llext_fs_prepare,                                       \
+				.read = llext_fs_read,                                             \
+				.seek = llext_fs_seek,                                             \
+				.peek = NULL,                                                      \
+				.finalize = llext_fs_finalize,                                     \
+			},                                                                         \
+		.is_open = false,                                                                  \
+		.name = (_filename),                                                               \
+	}
+
+/**
+ * @}
+ */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ZEPHYR_LLEXT_FS_LOADER_H */

subsys/llext/CMakeLists.txt

@@ -11,6 +11,7 @@ if(CONFIG_LLEXT)
 		llext_link.c
 		llext_export.c
 		buf_loader.c
+    fs_loader.c
 	)
   zephyr_library_sources_ifdef(CONFIG_LLEXT_SHELL shell.c)
 endif()

subsys/llext/fs_loader.c

@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2024 BayLibre SAS
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ */
+
+#include <zephyr/llext/fs_loader.h>
+#include <zephyr/sys/util.h>
+#include <string.h>
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_REGISTER(llext_fs_loader, CONFIG_LLEXT_LOG_LEVEL);
+
+int llext_fs_prepare(struct llext_loader *l)
+{
+	int ret = 0;
+	struct llext_fs_loader *fs_l = CONTAINER_OF(l, struct llext_fs_loader, loader);
+
+	fs_file_t_init(&fs_l->file);
+
+	ret = fs_open(&fs_l->file, fs_l->name, FS_O_READ);
+	if (ret != 0) {
+		LOG_DBG("Failed opening a file: %d", ret);
+		return ret;
+	}
+
+	fs_l->is_open = true;
+	return 0;
+}
+
+int llext_fs_read(struct llext_loader *l, void *buf, size_t len)
+{
+	int ret = 0;
+	struct llext_fs_loader *fs_l = CONTAINER_OF(l, struct llext_fs_loader, loader);
+
+	if (fs_l->is_open) {
+		ret = fs_read(&fs_l->file, buf, len);
+	} else {
+		ret = -EINVAL;
+	}
+
+	return ret == len ? 0 : -EINVAL;
+}
+
+int llext_fs_seek(struct llext_loader *l, size_t pos)
+{
+	struct llext_fs_loader *fs_l = CONTAINER_OF(l, struct llext_fs_loader, loader);
+
+	if (fs_l->is_open) {
+		return fs_seek(&fs_l->file, pos, FS_SEEK_SET);
+	} else {
+		return -EINVAL;
+	}
+}
+
+void llext_fs_finalize(struct llext_loader *l)
+{
+	struct llext_fs_loader *fs_l = CONTAINER_OF(l, struct llext_fs_loader, loader);
+
+	if (fs_l->is_open) {
+		fs_close(&fs_l->file);
+		fs_l->is_open = false;
+	}
+}