On Monday, August 25, 2014 6:30:34 pm John-Mark Gurney wrote:
> John Baldwin wrote this message on Mon, Aug 25, 2014 at 13:35 -0400:
> > On Monday, August 25, 2014 07:02:41 PM Mateusz Guzik wrote:
> > > On Mon, Aug 25, 2014 at 10:23:19AM -0400, John Baldwin wrote:
> > > > On Sunday, August 24, 2014 09:04:09 AM Mateusz Guzik wrote:
> > > > > Author: mjg
> > > > > Date: Sun Aug 24 09:04:09 2014
> > > > > New Revision: 270444
> > > > > URL: http://svnweb.freebsd.org/changeset/base/270444
> > > > >
> > > > > Log:
> > > > > Fix getppid for traced processes.
> > > > >
> > > > > Traced processes always have the tracer set as the parent.
> > > > > Utilize proc_realparent to obtain the right process when needed.
> > > >
> > > > Are you sure this won't break things? I know of several applications
> > > > that
> > > > expect a debugger to be the parent when attached and change behavior as
> > > > a
> > > > result (e.g. inserting a breakpoint on an assertion failure rather than
> > > > generating a core).
> > >
> > > Well, this is what linux and solaris do.
> >
> > Interesting.
> >
> > > I don't feel strongly about this change. If you really want I'm happy to
> > > revert.
> >
> > In general I'd like to someday have the debugger-debuggee relationship not
> > override parent-child and this is a step in that direction. However, this
> > will break existing applications, so this needs to be clearly documented in
> > the release notes. In addition, we should probably advertise how a process
> > can correctly determine if it is being run under a debugger (right now you
> > can
> > do 'getppid()' and use strcmp or strstr on the p_comm of that pid so you
> > can
> > do different things for "gdb" vs "gcore", etc. so just checking P_TRACED
> > from
> > kinfo_proc wouldn't be equivalent in functionality)
>
> But what about when you attach gdb to a running process... That
> doesn't magicly make the now debugged process a child of gdb does it?
% cat hello.c
#include <stdio.h>
int
main()
{
printf("hello world\n");
(void)getchar();
return (0);
}
% cc -g hello.c -o hello
% ./hello
hello world
load: 9.81 cmd: hello 42599 [ttyin] 1.67r 0.00u 0.00s 0% 1056k
< different window >
% ps -O ppid -p `pgrep hello`
PID PPID TT STAT TIME COMMAND
42599 5340 16 I+ 0:00.00 ./hello
% gdb hello `pgrep hello`
GNU gdb 6.1.1 [FreeBSD]
...
(gdb) <hit Ctrl-Z>
Suspended
% ps -O ppid -p `pgrep hello`
PID PPID TT STAT TIME COMMAND
42599 45079 16 TX+ 0:00.00 ./hello
--
John Baldwin
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