NCS v3.0.2: Zephyr's fuzzing sample not working

[jwitowski]

Hello, I have discovered that Zephyr's fuzzing sample: https://docs.zephyrproject.org/latest/samples/subsys/debug/fuzz/README.html is not working with NCS v3.0.2.

Reproduction path:

(btp2_ncs) t14@ThinkPad ~/Desktop/GCX/BT_PLATFORM/btplatform2/test $ export ZEPHYR_TOOLCHAIN_VARIANT=llvm

(btp2_ncs) t14@ThinkPad ~/Desktop/GCX/BT_PLATFORM/btplatform2/test $ west build --no-sysbuild -b native_sim/native/64 zephyr/samples/subsys/debug/fuzz
-- west build: generating a build system
Loading Zephyr default modules (Zephyr base).
-- Application: /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/zephyr/samples/subsys/debug/fuzz
-- CMake version: 3.30.2
-- Found Python3: /home/t14/.virtualenvs/btp2_ncs/bin/python (found suitable version "3.12.3", minimum required is "3.10") found components: Interpreter
-- Cache files will be written to: /home/t14/.cache/zephyr
-- Zephyr version: 4.0.99 (/home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/zephyr)
-- Found west (found suitable version "1.4.0", minimum required is "0.14.0")
-- Board: native_sim, qualifiers: native/64
-- Found host-tools: zephyr 0.17.0 (/home/t14/zephyr-sdk-0.17.0)
-- Found toolchain: llvm (clang/ld)
-- Found Dtc: /home/t14/zephyr-sdk-0.17.0/sysroots/x86_64-pokysdk-linux/usr/bin/dtc (found suitable version "1.6.0", minimum required is "1.4.6")
-- Found BOARD.dts: /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/zephyr/boards/native/native_sim/native_sim_64.dts
-- Generated zephyr.dts: /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build/zephyr/zephyr.dts
-- Generated pickled edt: /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build/zephyr/edt.pickle
-- Generated zephyr.dts: /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build/zephyr/zephyr.dts
-- Generated devicetree_generated.h: /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build/zephyr/include/generated/zephyr/devicetree_generated.h
-- Including generated dts.cmake file: /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build/zephyr/dts.cmake
Parsing /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/zephyr/samples/subsys/debug/fuzz/Kconfig
Loaded configuration '/home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/zephyr/boards/native/native_sim/native_sim_64_defconfig'
Merged configuration '/home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/zephyr/samples/subsys/debug/fuzz/prj.conf'
Configuration saved to '/home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build/zephyr/.config'
Kconfig header saved to '/home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build/zephyr/include/generated/zephyr/autoconf.h'
-- Found LlvmLld: /usr/lib/llvm-14/bin/ld.lld (found suitable version "14.0.6", minimum required is "14.0.0")
-- The C compiler identification is Clang 14.0.6
-- The CXX compiler identification is GNU 13.3.0
-- The ASM compiler identification is Clang with GNU-like command-line
-- Found assembler: /home/t14/.local/bin/clang
-- Configuring done (5.1s)
-- Generating done (0.1s)
-- Build files have been written to: /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build
-- west build: building application
[1/96] Preparing syscall dependency handling

[5/96] Generating include/generated/zephyr/version.h
-- Zephyr version: 4.0.99 (/home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/zephyr), build: v4.0.99-ncs1-2
[94/96] Linking C executable zephyr/zephyr.elf
Generating files from /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build/zephyr/zephyr.elf for board: native_sim
[95/96] Building native simulator runner, and linking final executable
FAILED: zephyr/CMakeFiles/native_runner_executable zephyr/zephyr.exe /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build/zephyr/CMakeFiles/native_runner_executable /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build/zephyr/zephyr.exe
cd /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build/zephyr && /usr/bin/make -f /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/zephyr/scripts/native_simulator/Makefile all --warn-undefined-variables -r NSI_CONFIG_FILE=/home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build/zephyr/NSI/nsi_config
/home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build/zephyr/NSI/home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build/zephyr/zephyr.elf.loc_cpusw.o: file not recognized: file format not recognized
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [/home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/zephyr/scripts/native_simulator/Makefile:131: /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build/zephyr/zephyr.exe] Error 1
ninja: build stopped: subcommand failed.
FATAL ERROR: command exited with status 1: /usr/bin/cmake --build /home/t14/Desktop/GCX/BT_PLATFORM/btplatform2/test/build

I'd like to mention it is still working with mainline Zephyr.

BR,

Jakub

[Alberto Escolar]

The issue is due to NCS defaulting to use the lld linker when selecting llvm. Things would also break in upstream Zephyr if you would select that linker.
If you set CONFIG_LLVM_USE_LD=y it should work like upstream in this regard.

[jwitowski]

It haven't worked either:

$west build -t run -b native_sim/native/64 zephyr/samples/subsys/debug/fuzz -- -DCONFIG_LLVM_USE_LD=y


-- west build: generating a build system
Loading Zephyr module(s) (Zephyr base): sysbuild_default
-- Found Python3: /home/t14/.virtualenvs/btp2_ncs/bin/python (found suitable version "3.12.3", minimum required is "3.10") found components: Interpreter
-- Cache files will be written to: /home/t14/.cache/zephyr
-- Found west (found suitable version "1.4.0", minimum required is "0.14.0")
-- Board: native_sim, qualifiers: native/64
Parsing /home/t14/Desktop/GCX/prj/zephyr/share/sysbuild/Kconfig
Loaded configuration '/home/t14/Desktop/GCX/prj/build/_sysbuild/empty.conf'
Merged configuration '/home/t14/Desktop/GCX/prj/build/_sysbuild/empty.conf'
Configuration saved to '/home/t14/Desktop/GCX/prj/build/zephyr/.config'
Kconfig header saved to '/home/t14/Desktop/GCX/prj/build/_sysbuild/autoconf.h'
--
   **************************
   * Running CMake for fuzz *
   **************************

Loading Zephyr default modules (Zephyr base).
-- Application: /home/t14/Desktop/GCX/prj/zephyr/samples/subsys/debug/fuzz
-- CMake version: 3.30.2
-- Found Python3: /home/t14/.virtualenvs/btp2_ncs/bin/python (found suitable version "3.12.3", minimum required is "3.10") found components: Interpreter
-- Cache files will be written to: /home/t14/.cache/zephyr
-- Zephyr version: 4.0.99 (/home/t14/Desktop/GCX/prj/zephyr)
-- Found west (found suitable version "1.4.0", minimum required is "0.14.0")
-- Board: native_sim, qualifiers: native/64
-- Found host-tools: zephyr 0.17.0 (/home/t14/zephyr-sdk-0.17.0)
-- Found toolchain: llvm (clang/ld)
-- Found Dtc: /home/t14/zephyr-sdk-0.17.0/sysroots/x86_64-pokysdk-linux/usr/bin/dtc (found suitable version "1.6.0", minimum required is "1.4.6")
-- Found BOARD.dts: /home/t14/Desktop/GCX/prj/zephyr/boards/native/native_sim/native_sim_64.dts
-- Generated zephyr.dts: /home/t14/Desktop/GCX/prj/build/fuzz/zephyr/zephyr.dts
-- Generated pickled edt: /home/t14/Desktop/GCX/prj/build/fuzz/zephyr/edt.pickle
-- Generated zephyr.dts: /home/t14/Desktop/GCX/prj/build/fuzz/zephyr/zephyr.dts
-- Generated devicetree_generated.h: /home/t14/Desktop/GCX/prj/build/fuzz/zephyr/include/generated/zephyr/devicetree_generated.h
-- Including generated dts.cmake file: /home/t14/Desktop/GCX/prj/build/fuzz/zephyr/dts.cmake
Parsing /home/t14/Desktop/GCX/prj/zephyr/samples/subsys/debug/fuzz/Kconfig
Loaded configuration '/home/t14/Desktop/GCX/prj/zephyr/boards/native/native_sim/native_sim_64_defconfig'
Merged configuration '/home/t14/Desktop/GCX/prj/zephyr/samples/subsys/debug/fuzz/prj.conf'
Merged configuration '/home/t14/Desktop/GCX/prj/build/fuzz/zephyr/misc/generated/extra_kconfig_options.conf'
Merged configuration '/home/t14/Desktop/GCX/prj/build/fuzz/zephyr/.config.sysbuild'
Configuration saved to '/home/t14/Desktop/GCX/prj/build/fuzz/zephyr/.config'
Kconfig header saved to '/home/t14/Desktop/GCX/prj/build/fuzz/zephyr/include/generated/zephyr/autoconf.h'
-- Found GnuLd: /usr/bin/ld.bfd (found version "2.42")
-- The C compiler identification is Clang 14.0.6
-- The CXX compiler identification is GNU 13.3.0
-- The ASM compiler identification is Clang with GNU-like command-line
-- Found assembler: /home/t14/.local/bin/clang
-- Configuring done (12.4s)
-- Generating done (0.2s)
-- Build files have been written to: /home/t14/Desktop/GCX/prj/build/fuzz
-- Configuring done (15.2s)
-- Generating done (0.0s)
-- Build files have been written to: /home/t14/Desktop/GCX/prj/build
-- west build: running target run
ninja: error: unknown target 'run', did you mean 'fuzz'?
FATAL ERROR: command exited with status 1: /usr/bin/cmake --build /home/t14/Desktop/GCX/prj/build --target run

[jwitowski]

Actually calling the build command with --no-sysbuild fixed the problem after adding CONFIG_LLVM_USE_LD=y
. Thanks a lot !