can target code change architecture setting?

Doug Evans
Thu Nov 3 19:47:00 GMT 2016

On Tue, Oct 11, 2016 at 7:29 AM, Duane Ellis <> wrote:
>>> Question #2 - How should the remote debugger respond to GDB?
>>>      I don't think there is an "architecture change" packet.
>> Such packet is not needed, because GDB has to determine the gdbarch
>> of each when unwinding.
> I think you are making the assumption that GDB always has access to full debug (i.e.: dwarf) information.
> In bare metal - You don’t always have this, you might have *labels* only (function name vrs address) but no source, no dwarf information.
> The only solution is to *ask* the target “what is your *current* arch.
> Or the target needs to send a “target-arch-change-indication” in some way.


Consider booting some x86 kernel on qemu (e.g., passing -s -S to qemu).
At the start $pc is at the x86 reset location and the architecture is 16-bit.

(gdb) tar ext :1234
Remote debugging using :1234
0x000000000000fff0 in ?? ()

At some later point the o/s will switch to 32 or 64-bit mode but until
then gdb isn't as useful as one might want it to be.

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