[vbox-dev] single stepping VM boot using the VirtualBox debugger

Mike Wood muscletot at gmail.com
Sat Mar 10 17:19:34 PST 2012

Is it possible to single-step through 16-bit real-mode code using the
VirtualBox debugger?

In particular, I would like to be able to step through the boot
process (i.e. from the execution of the guest's Master Boot Record).

However, the 't' single-step command simply continues VM execution, as
described previously in an April 4 2011 post for VBox 4.0.4 (original
text below). Though I have encountered the same issue using the VBox

Previous message for reference:
Elias Bachaalany lallousz-bochs at yahoo.com
Mon Apr 4 11:54:10 CEST 2011

I am using VBox 4.0.4 with --dbg switch passed when I start the VM.
Now in the debug console, I type:
1. stop
The vm stops, I can inspect registers
2. t
To single step
However, I expect VBox to single step and break at the next
instruction, instead
is just resumes execution!

Thanks in advance for any thoughts or advice.

- Mike

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