.. zephyr:code-sample:: llext-modules
:name: Linkable loadable extensions "module" sample
:relevant-api: llext_apis
Call a function in a loadable extension module,
either built-in or loaded at runtime.
Overview
********
This sample demonstrates the use of the :ref:`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 :zephyr_file:`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
:zephyr_file:`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
:zephyr_file:`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 :zephyr:board:`qemu_xtensa <qemu_xtensa>` or
:zephyr:board:`qemu_cortex_r5 <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:
.. zephyr-app-commands::
:zephyr-app: samples/subsys/llext/modules
:board: qemu_xtensa/dc233c
:goals: build run
:compact:
- 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:
.. zephyr-app-commands::
:zephyr-app: samples/subsys/llext/modules
:board: qemu_xtensa/dc233c
:goals: build run
:west-args: -T sample.llext.modules.module_build
:compact:
.. important::
Take a look at :zephyr_file:`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.
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