how to continue from a breakpoint in GNU/Hurd

[Hui Zhu]

On Wed, Jul 17, 2013 at 12:45 AM, Yue Lu <hacklu.newborn@gmail.com> wrote:
> Hi.
>
> I am writing a debugger demo under GNU/Hurd when I study the gdb
> source code. And I have met a big problem that when I set a breakpoint
> in the inferior, my code can't resume inferior from it.
>
> I can get the exception message from the mach kernel when the inferior
> hit the breakpoint. As soon as I got the exception message, I removed
> the int3, and set the EIP to the previous values,

I am not sure but I think you need care about this part is:
In x86, after the inferior is broken by int3, it will point to the
address after int3. So the right address to continue inferior is
eip-1.

Thanks,
Hui

then post a signal
> zero to the inferior by msg_sig_post_untraced_request(). at last I
> called thread_resume() to resume it. But thing goes wrong, the
> inferior is always stops at the breakpoint. and seems never to
> continue.
>
> I don't know how to fix this, could any of you give me a suggestion?
> thanks very much.
>
> --
> Yue Lu (陆岳)