Linkable loadable extensions “module” sample
Overview
This sample demonstrates the use of the Linkable Loadable Extensions (LLEXT) subsystem in Zephyr. The llext subsystem allows for the loading of relocatable ELF files at runtime; their symbols can be accessed and functions called.
Specifically, this shows how to call a simple “hello world” function,
implemented in samples/subsys/llext/modules/src/hello_world_ext.c.
This is achieved in two different ways, depending on the value of the Kconfig
symbol CONFIG_HELLO_WORLD_MODE:
if it is
y, the function is directly compiled and called by the Zephyr application. The caller code used in this case is in samples/subsys/llext/modules/src/main_builtin.c.if it is
m, the function is compiled as an llext and it is included in the application as a binary blob. At runtime, the llext subsystem is used to load the extension and call the function. The caller code is in samples/subsys/llext/modules/src/main_module.c.
Requirements
A board with a supported llext architecture and console. This can also be executed in QEMU emulation on the qemu_xtensa or qemu_cortex_r5 virtual boards.
Building and running
By default, the sample will compile the function along with the rest of Zephyr in the same binary. This can be verified via the following commands:
west build -b qemu_xtensa/dc233c samples/subsys/llext/modules west build -t run
The following commands build and run the sample so that the extension code is compiled separately and included in the Zephyr image as a binary blob:
west build -b qemu_xtensa/dc233c -T sample.llext.modules.module_build samples/subsys/llext/modules west build -t run
Important
Take a look at samples/subsys/llext/modules/sample.yaml for the additional architecture-specific configurations required in this case.
To build for a different board, replace qemu_xtensa in the commands above
with the desired board name.