Please find below an extract from openocd documentation >> 16.5.5 Cortex-M specific commands
Command: cortex_m maskisr (auto|on|off)
Control masking (disabling) interrupts during target step/resume.
The auto option handles interrupts during stepping a way they get served but don’t disturb the program flow. The step command first allows pending interrupt handlers to execute, then disables interrupts and steps over the next instruction where the core was halted. After the step interrupts are enabled again. If the interrupt handlers don’t complete within 500ms, the step command leaves with the core running.
Note that a free breakpoint is required for the auto option. If no breakpoint is available at the time of the step, then the step is taken with interrupts enabled, i.e. the same way the off option does.
Default is auto.