[ping] [PATCH] Fix for PR gdb/14808, vfork/exec inferior problem

["Breazeal, Don" <donb at codesourcery dot com>]

Ping.

On 5/27/2014 10:01 AM, Breazeal, Don wrote:
> On 5/23/2014 5:57 PM, Yao Qi wrote:
>> A nit on changelog entry:
>>
>> On 05/16/2014 04:43 AM, Don Breazeal wrote:
>>> gdb/
>>> 2014-05-15  Don Breazeal  <donb@codesourcery.com>
>>>
>> 	PR gdb/14808
>>> 	* infrun.c (handle_vfork_child_exec_or_exit): For the case
>>> 	of a vfork where we follow the child and detach the parent,
>>> 	and the child execs, create a new pspace for the parent
>>> 	inferior.
>>
>> With this, the magic script can connect this commit to the right PR.
>>
>> The patch looks good to me, but I can't approve it.
>>
> Thanks for checking this.  An updated ChangeLog and (unchanged) patch
> follow.
> --Don
> 
> gdb/
> 2014-05-12  Don Breazeal  <donb@codesourcery.com>
> 
> 	PR gdb/14808
> 	* infrun.c (handle_vfork_child_exec_or_exit): For the case
> 	of a vfork where we follow the child and detach the parent,
> 	and the child execs, create a new pspace and aspace for the
> 	parent inferior.
> 
> gdb/testsuite
> 2014-05-12  Don Breazeal  <donb@codesourcery.com>
> 
> 	* gdb.base/foll-vfork.exp (vfork_relations_in_info_inferiors):
> 	Test that after a vfork and child exec, the parent's exec file
> 	name has not been changed.
> 
> ---
>  gdb/infrun.c                          |   42
> ++++++++++++++++++++++-----------
>  gdb/testsuite/gdb.base/foll-vfork.exp |   11 ++++++++
>  2 files changed, 39 insertions(+), 14 deletions(-)
> 
> diff --git a/gdb/infrun.c b/gdb/infrun.c
> index ab39b6e..82a67d5 100644
> --- a/gdb/infrun.c
> +++ b/gdb/infrun.c
> @@ -649,6 +649,7 @@ handle_vfork_child_exec_or_exit (int exec)
>  	  struct cleanup *old_chain;
>  	  struct program_space *pspace;
>  	  struct address_space *aspace;
> +	  struct inferior *parent_inf;
> 
>  	  /* follow-fork child, detach-on-fork on.  */
> 
> @@ -665,27 +666,39 @@ handle_vfork_child_exec_or_exit (int exec)
>  	  else
>  	    old_chain = save_current_space_and_thread ();
> 
> -	  /* We're letting loose of the parent.  */
> +	  /* Make the parent the current inferior for target_detach.  */
>  	  tp = any_live_thread_of_process (inf->vfork_parent->pid);
>  	  switch_to_thread (tp->ptid);
> 
> -	  /* We're about to detach from the parent, which implicitly
> -	     removes breakpoints from its address space.  There's a
> -	     catch here: we want to reuse the spaces for the child,
> -	     but, parent/child are still sharing the pspace at this
> -	     point, although the exec in reality makes the kernel give
> -	     the child a fresh set of new pages.  The problem here is
> -	     that the breakpoints module being unaware of this, would
> -	     likely chose the child process to write to the parent
> -	     address space.  Swapping the child temporarily away from
> -	     the spaces has the desired effect.  Yes, this is "sort
> -	     of" a hack.  */
> -
> +	  /* The child inferior INF may be dead, so avoid giving the
> +	     breakpoints module the option to write through to it
> +	     by swapping the child temporarily away from the spaces
> +	     (cloning a program space resets breakpoints).  */
>  	  pspace = inf->pspace;
>  	  aspace = inf->aspace;
>  	  inf->aspace = NULL;
>  	  inf->pspace = NULL;
> 
> +	  if (exec)
> +	    {
> +	      /* The parent and child inferiors have been sharing
> +		 program and address space structures from the point
> +		 where the parent called vfork.  Now that the child has
> +		 called exec and we are detaching from the parent, the
> +		 parent inferior needs to have its own pspace and aspace
> +		 so that changes in the child don't affect it.  We have
> +		 to give the new spaces to the parent since we saved the
> +		 child's spaces as the current spaces above.  Even though
> +		 we are detaching the parent, we want to keep the
> +		 corresponding entry in the inferiors list intact.  */
> +	      parent_inf = current_inferior ();
> +	      parent_inf->aspace = new_address_space ();
> +	      parent_inf->pspace = add_program_space (parent_inf->aspace);
> +	      parent_inf->removable = inf->removable;
> +	      set_current_program_space (parent_inf->pspace);
> +	      clone_program_space (parent_inf->pspace, pspace);
> +	    }
> +
>  	  if (debug_infrun || info_verbose)
>  	    {
>  	      target_terminal_ours ();
> @@ -702,9 +715,10 @@ handle_vfork_child_exec_or_exit (int exec)
>  				  inf->vfork_parent->pid);
>  	    }
> 
> +	  /* Detach the parent.  */
>  	  target_detach (NULL, 0);
> 
> -	  /* Put it back.  */
> +	  /* Put the child spaces back.  */
>  	  inf->pspace = pspace;
>  	  inf->aspace = aspace;
> 
> diff --git a/gdb/testsuite/gdb.base/foll-vfork.exp
> b/gdb/testsuite/gdb.base/foll-vfork.exp
> index fe3663c..e9b0110 100644
> --- a/gdb/testsuite/gdb.base/foll-vfork.exp
> +++ b/gdb/testsuite/gdb.base/foll-vfork.exp
> @@ -442,6 +442,17 @@ proc vfork_relations_in_info_inferiors { variant } {
>  	   pass $test
>         }
>     }
> +
> +   # Make sure the exec file name of the vfork parent is not
> +   # changed when the child's is changed.
> +   if { $variant == "exec" } {
> +       set test "exec file name change"
> +       gdb_test_multiple "info inferiors" $test {
> +	   -re " 2 .*vforked-prog.*  1 .*foll-vfork.*$gdb_prompt " {
> +	       pass $test
> +	   }
> +       }
> +   }
>  }}
> 
>  proc do_vfork_and_follow_parent_tests {} {
>