two proposed linuxulator fixes + ptrace

[Konstantin Belousov]

On Thu, Jun 14, 2018 at 02:46:20PM +0300, Yanko Yankulov wrote:
> Hi Konstantin,
> 
> For the ptrace patch, I suggest you to put it on https://reviews.freebsd.org
> > and set at least me (kib), jhb and dchagin as reviewers.  I will handle it.
> >
> > Will do. Just have to figure out how it works.
> 
> 
> > For the patch 1, TracePid, can you explain what is the meaning of the
> > pid reported ?
> >
> > The TracerPid is the PID of the process currently ptrace-ing the process.
> TracerPid 0 means no active tracer. So the patch is not semantically
> correct as it always reports no tracer, but it got the program running.
Ok, but what is the tracer ?  Is it ptrace(2) debugger, or something
else ?

> 
> 
> > For the patch 3, %r10 preservation for linux_rt_sigreturn, shouldn't the
> > same handling applied to non-rt signal return ? And in fact, shouldn't
> > it be done based on the return code instead of the syscall number ? Look
> > at the amd64/amd64/vm_machdep.c:cpu_set_syscall_retval(), where I think
> > EJUSTRETURN case is used by linux sigreturns.
> >
> The linux_rt_sigreturn seems to be the only signall return syscall.
> The no rt_ version seems to be an old pre Linux 2.2 interface.
> 
> The return code observation sounds right. Thanks. New patch. Ran a
> quick check, the issue is still solved.
Committed as r335135, thanks.