SW4STM32 and SW4Linux fully supports the STM32MP1 asymmetric multicore Cortex/A7+M4 MPUs

   With System Workbench for Linux, Embedded Linux on the STM32MP1 family of MPUs from ST was never as simple to build and maintain, even for newcomers in the Linux world.
And, if you install System Workbench for Linux in System Workbench for STM32 you can seamlessly develop and debug asymmetric applications running partly on Linux, partly on the Cortex-M4.
You can get more information from the ac6-tools website and download two short videos (registration required) highlighting:

System Workbench for STM32

initialise_monitor_handles causes SIGTRAP


Yes, this incomplete configuration is to enable semihosting (not SWO/SWV) :
you have missed the : -lc -lrdimon
the complete linker flags are :

-specs=nano.specs -u _printf_float -specs=rdimon.specs -lc -lrdimon

To use SWO/SWV:
in syscalls.c, add #include “stm32f4xx.h” (depends on your device) & (you should include CMSIS folder)
and modify the _write function :

int _write(int file, char *ptr, int len)
	int DataIdx;

	for (DataIdx = 0; DataIdx < len; DataIdx++)
	   ITM_SendChar( *ptr++ );

	return len;

After that, you can use printf to output message via printf.

To visualize the ITM output, you can use ST-Link Utility (menu : ST-LINK > Printf via SWO Viewer)

Best Regards,