1.. zephyr:code-sample:: llext-shell-loader
2 :name: Linkable loadable extensions shell module
3 :relevant-api: llext_apis
4
5 Manage loadable extensions using shell commands.
6
7Overview
8********
9
10This example provides shell access to the :ref:`llext` system and provides the
11ability to manage loadable code extensions in the shell.
12
13Requirements
14************
15
16A board with a supported LLEXT architecture and shell capable console. The
17following example uses an ARMv7 CPU, but the same instructions can be adapted
18to any LLEXT-supported target.
19
20Building
21********
22
23The following command will build the main shell application:
24
25.. zephyr-app-commands::
26 :zephyr-app: samples/subsys/llext/shell_loader
27 :board: robokit1
28 :goals: build
29 :compact:
30
31.. note::
32
33 You may need to disable memory protection for the sample to work (e.g.
34 ``CONFIG_ARM_MPU=n``). See the full list of similar flags in
35 :zephyr_file:`tests/subsys/llext/no_mem_protection.conf`.
36
37This sample also includes the source for a very basic extension,
38:zephyr_file:`samples/subsys/llext/shell_loader/hello_world.c`, which can be
39used to test the LLEXT features.
40
41It can be compiled to :file:`build/hello_world.llext` using the Zephyr build
42system like this:
43
44.. code-block:: console
45
46 $ ninja -C build -vvv hello_world_ext
47
48On a host machine with the Zephyr SDK and the ``arm-zephyr-eabi`` toolchain in
49``PATH``, you can also obtain the same result directly with ``gcc``:
50
51.. code-block:: console
52
53 $ arm-zephyr-eabi-gcc -mlong-calls -mthumb -c -o build/hello_world.llext samples/subsys/llext/shell/hello_world.c
54
55.. note::
56
57 LLEXT by default only imports symbols that have been explicitly exported by
58 the extension via the :c:macro:`EXPORT_SYMBOL` macro. Compiling with this
59 macro requires using the full Zephyr build system, or at least the
60 :ref:`LLEXT EDK <llext_build_edk>`.
61
62 To avoid this complexity, this sample configures Zephyr to use all global
63 symbols defined in the extension ELF file via the Kconfig option
64 :kconfig:option:`CONFIG_LLEXT_IMPORT_ALL_GLOBALS`. This is not recommended
65 for large extensions as the memory usage increases significantly.
66
67The compiled extension can be inspected with the usual binutils utilities to
68see symbols, sections, and relocations. Then, using additional tools, converted
69to a hex string usable by the ``llext load_hex`` shell command:
70
71.. code-block:: console
72
73 $ arm-zephyr-eabi-objdump -r -d -x build/hello_world.llext
74
75 hello_world.elf: file format elf32-littlearm
76 hello_world.elf
77 architecture: armv4t, flags 0x00000011:
78 HAS_RELOC, HAS_SYMS
79 start address 0x00000000
80 private flags = 0x5000000: [Version5 EABI]
81
82 Sections:
83 Idx Name Size VMA LMA File off Algn
84 0 .text 00000038 00000000 00000000 00000034 2**2
85 CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
86 1 .data 00000000 00000000 00000000 0000006c 2**0
87 CONTENTS, ALLOC, LOAD, DATA
88 2 .bss 00000000 00000000 00000000 0000006c 2**0
89 ALLOC
90 3 .rodata 00000025 00000000 00000000 0000006c 2**2
91 CONTENTS, ALLOC, LOAD, READONLY, DATA
92 4 .comment 00000021 00000000 00000000 00000091 2**0
93 CONTENTS, READONLY
94 5 .ARM.attributes 0000002a 00000000 00000000 000000b2 2**0
95 CONTENTS, READONLY
96 SYMBOL TABLE:
97 00000000 l df *ABS* 00000000 hello_world.c
98 00000000 l d .text 00000000 .text
99 00000000 l d .data 00000000 .data
100 00000000 l d .bss 00000000 .bss
101 00000000 l d .rodata 00000000 .rodata
102 00000000 l O .rodata 00000004 number
103 00000000 l d .comment 00000000 .comment
104 00000000 l d .ARM.attributes 00000000 .ARM.attributes
105 00000000 g F .text 00000034 hello_world
106 00000000 *UND* 00000000 printk
107
108
109
110 Disassembly of section .text:
111
112 00000000 <hello_world>:
113 0: b580 push {r7, lr}
114 2: af00 add r7, sp, #0
115 4: 4b08 ldr r3, [pc, #32] ; (28 <hello_world+0x28>)
116 6: 0018 movs r0, r3
117 8: 4b08 ldr r3, [pc, #32] ; (2c <hello_world+0x2c>)
118 a: f000 f813 bl 34 <hello_world+0x34>
119 e: 222a movs r2, #42 ; 0x2a
120 10: 4b07 ldr r3, [pc, #28] ; (30 <hello_world+0x30>)
121 12: 0011 movs r1, r2
122 14: 0018 movs r0, r3
123 16: 4b05 ldr r3, [pc, #20] ; (2c <hello_world+0x2c>)
124 18: f000 f80c bl 34 <hello_world+0x34>
125 1c: 46c0 nop ; (mov r8, r8)
126 1e: 46bd mov sp, r7
127 20: bc80 pop {r7}
128 22: bc01 pop {r0}
129 24: 4700 bx r0
130 26: 46c0 nop ; (mov r8, r8)
131 28: 00000004 .word 0x00000004
132 28: R_ARM_ABS32 .rodata
133 2c: 00000000 .word 0x00000000
134 2c: R_ARM_ABS32 printk
135 30: 00000014 .word 0x00000014
136 30: R_ARM_ABS32 .rodata
137 34: 4718 bx r3
138 36: 46c0 nop ; (mov r8, r8)
139
140 $ xxd -p build/hello_world.llext | tr -d '\n'
141 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
142
143In this sample there are 3 absolute (``R_ARM_ABS32``) relocations, 2 of which
144are meant to hold addresses into the ``.rodata`` sections where the strings are
145located. A third is an address of where the ``printk`` function (symbol) can be
146found. At load time LLEXT replaces the values in the ``.text`` section with
147real memory addresses so that ``printk`` works as expected with the strings
148included in the hello world sample.
149
150Running
151*******
152
153Once the board has booted, you will be presented with a shell prompt.
154All the LLEXT system related commands are available as sub-commands of
155``llext``, and can be seen with ``llext help``:
156
157.. code-block:: console
158
159 uart:~$ llext help
160 llext - Loadable extension commands
161 Subcommands:
162 list :List loaded extensions and their size in memory
163 load_hex :Load an elf file encoded in hex directly from the shell input.
164 Syntax:
165 <ext_name> <ext_hex_string>
166 unload :Unload an extension by name. Syntax:
167 <ext_name>
168 list_symbols :List extension symbols. Syntax:
169 <ext_name>
170 call_fn :Call extension function with prototype void fn(void). Syntax:
171 <ext_name> <function_name>
172
173The hex string generated above can be used to load the extension:
174
175.. code-block:: console
176
177 uart:~$ llext load_hex hello_world 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
178
179This extension can then be seen in the list of loaded extensions (``list``), its symbols printed
180(``list_symbols``), and the hello_world function which the extension exports can be called and
181run (``call_fn``).
182
183.. code-block:: console
184
185 uart:~$ llext call_fn hello_world hello_world
186 hello world
187
