gdbserver does not work correctly

[Doug Evans]

On Wed, Jan 21, 2015 at 5:40 PM, fei ding <fdingiit@gmail.com> wrote:
> Hi everyone:
>
> I have a program, which uses LJMP instruction to switch from i386 to
> amd64 (both in Linux), and GDB does not support this architecture
> switch, but we have fixed this problem, and everything goes well, the
> registers' values are correct and 'disas'  command also works well
> after 'set architecture i386:x86_64', but when we compile a gdbserver,
> and use it to debug a remote target(and this target is just the same
> as the program we test early, which we used as a local target), it
> cannot work well. Almost every registers' values are wrong, and all
> the new registers, such as R8-R15, are assigned as 0, RIP is 0 also.
> does anyone familiar with this problem? or does anyone know which
> piece of source code I should see.

The remote protocol doesn't AFAICT support changing the architecture
in a live program.
If you want to try to make this work you'll need to extend the protocol somehow.
The main file on the gdb side is remote.c.