native FUSE FS access: Support any libC and fix random crashes

Split the fuse FS driver into 2 parts: A top built in the embedded side,
with the embedded libC, and a bottom built in the runner side with the
host libC.
The error returns are converted to match the host libC.

Also, before the host FUSE thread, which is asynchronous to Zephyr was
calling directly into the Zephyr filesystem code, which resulted quite
often if catastrophic failures or corruption of the Zephyr state.
This is now fixed by having the FUSE thread queue requests to a Zephyr
thread, which will be handled in the embedded side in a coherent way.
This adds a slightly noticeable overhead, but the performance is still
acceptable.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>

Author: aescolar

subsys/fs/CMakeLists.txt

@@ -36,9 +36,12 @@ if(CONFIG_FUSE_FS_ACCESS)
   zephyr_include_directories(${FUSE_INCLUDE_DIRS})
   if (CONFIG_NATIVE_LIBRARY)
     target_link_options(native_simulator INTERFACE "-l${FUSE_LIBRARIES}")
+    target_sources(native_simulator INTERFACE fuse_fs_access_bottom.c)
+    target_compile_options(native_simulator INTERFACE "-D_FILE_OFFSET_BITS=64")
   else()
     zephyr_link_libraries(${FUSE_LIBRARIES})
+    zephyr_library_sources(fuse_fs_access_bottom.c)
+    zephyr_library_compile_definitions(_FILE_OFFSET_BITS=64)
   endif()
-  zephyr_library_compile_definitions(_FILE_OFFSET_BITS=64)
   zephyr_library_sources(fuse_fs_access.c)
 endif()

subsys/fs/Kconfig

@@ -95,6 +95,7 @@ config FILE_SYSTEM_MKFS
 config FUSE_FS_ACCESS
 	bool "FUSE based access to file system partitions"
 	depends on ARCH_POSIX
+	select NATIVE_USE_NSI_ERRNO
 	help
 	  Expose file system partitions to the host system through FUSE.