Troubleshooting of Logging Interpreter on ESP32/QEMU with Zephyr RTOS

[OkannShn]

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I have an ESP32 board and I am interested in running a WebAssembly (WASM) application on the Zephyr RTOS. To understand the process of loading and executing the WASM binary, I would like some guidance on monitoring the workflow. Instead of using a debugger, which can be complex to follow step-by-step, I prefer to track the process through log messages that detail how the interpreter operates. Somehow printf does not work.

Example

While ı am debugging, ı observe that program enters wasm_runtime_invoke_native, but after ı compile and flash the program with printf statement. ı can not see message properly. ı only see a few characters even if program enters here more than once.

Board

Link to board https://docs.espressif.com/projects/esp-idf/en/latest/esp32/hw-reference/esp32/get-started-devkitc.html

 cd wasm-micro-runtime/product-mini/platforms/zephyr/simple
 west build -b esp32_devkitc_wroom . -p always ---DWAMR_BUILD_TARGET=XTENSA
 west flash

I tried whether ı can observe log messages with qemu_cortex_a53. It does not work again.

This might be a very simple question, I'm a newbie to wasm. It would be great to see any help. Thank you

[TianlongLiang]

Hi, could you try replacing printf with os_printf? If that doesn't work, I suspect that it may be due to your board's buffering or console configuration. You can try a Hello World C program to test whether it can print successfully to verify whether it's a configuration issue.

[OkannShn]

Thank you for your response.

west build -b qemu_cortex_a53 . -p always -- -DWAMR_BUILD_TARGET=AARCH64
west build -t run
-- west build: running target run
[0/1] To exit from QEMU enter: 'CTRL+a, x'[QEMU] CPU: cortex-a53
iwasm_main
45--- 54 messages dropped ---
8
buf: 1234
elapsed: 0

I inserted a few os_printf, As far as i understand it does not work after I initialized the working env with wasm_runtime_full_init. However, I observe that not printed messages are seen as dropped messages. The question then becomes how to prevent message drops?

[TianlongLiang]

Maybe try building WAMR with Debug mode using CMake flags cmake -DCMAKE_BUILD_TYPE=Debug, so the west build command should be: west build -b esp32_devkitc_wroom . -p always -- -DWAMR_BUILD_TARGET=XTENSA -DCMAKE_BUILD_TYPE=Debug I think maybe the non-debug mode disables some macro so that it won't print inside the vmcore https://github.com/bytecodealliance/wasm-micro-runtime/blob/4806e4e298c42bee9d35c542d8a7b1ceaef86c1c/core/shared/platform/zephyr/zephyr_platform.c#L135

[OkannShn]

Unfortunately, it did not work for qemu_cortex_a53, I will also try for esp32_devkitc_wroom , but ı expect similar output

[OkannShn]

Hi,

I found the cause of the issue. It looks like the Zephyr logging mechanism causes it. You can check https://github.com/zephyrproject-rtos/zephyr/issues/14903. I have added CONFIG_LOG_BUFFER_SIZE=4096 into wasm-micro-runtime/product-mini/platforms/zephyr/simple, and it works. Indeed, I did not expect to solve the issue by doing this because the log mechanism is different than basic prinft. Does it mean that Wamr redirects all the prints to Zephyr log when Zephyr is selected as a platform?

[wenyongh]

@OkannShn thanks for the reminding, I added CONFIG_LOG_BUFFER_SIZE=4096 in https://github.com/bytecodealliance/wasm-micro-runtime/pull/3370.