GDB realmode to protected mode, on the fly disassamble

Question

I'm trying to debug a piece of MBR code, with some context switch in it. I have the asm layout set up by default with 16bit disassambled instructions.

My problem appears when I make a context to protected mode, in wich case the instructions in the asm window will go nuts / senseless (the processor will still run the correct instructions ofc).

I know about the set architecture i8086/i386 command. But they work only before I connect to the virtual machine. I can't change the architecture "on the fly".

Note: I'd like to make context switches back & forth, so I need to see the correct instructions.

All in all is it possible to switch the architecture & refresh the instructions in the asm windows? (with some strange command? strange workaroud?)

I don't think it matters ... It could be a simple exe file too. But I use vmware workstation for both the mbr & for the ubuntu system. (I debug the mbr code though the ubuntu) — lerosQ, Jan 09 '13 at 14:49

score 3 · Accepted Answer · edited Nov 24 '21 at 10:09

3

Okay, figured out myself at the end.

No magic is needed ...

The architecture needs to be set up first:

set arch i8086 / set arch i386 (...)

then the disassemble command should be used on a specific function/address range:

disassemble 0x7c00, +100

edited Nov 24 '21 at 10:09

zhenguoli

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answered Jan 11 '13 at 14:18

lerosQ

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`layout asm` / `layout reg` should hopefully swap too, at least if you scroll the sub-window to make GDB re-draw. – Peter Cordes Nov 24 '21 at 10:19

GDB realmode to protected mode, on the fly disassamble

1 Answers1