Re: gdbserver

[Michael Snyder <msnyder at redhat dot com>]

Daniel Jacobowitz wrote:
> 
> [Bart, please try this patch.]
> 
> List folks,
> 
> I think the time has come for generic_prepare_to_proceed to actually be
> used.  The problem addressed by this patch is that PREPARE_TO_PROCEED
> is not a native-only macro (and not part of the target stack).  So
> lin_lwp_prepare_to_proceed would be called when using gdbserver, and of
> course trap_ptid would be null_ptid or stale.
> generic_prepare_to_proceed works correctly for lin-lwp native
> debugging, and for remote debugging.  This patch fixes an incorrect
> breakpoint hit after manually switching threads; i.e. the same
> breakpoint would be hit a second time.  I'll try to write an
> independent test case.
> 
> Patch look OK?

Of course, a simpler and less intrusive fix would be to simply
define PREPARE_TO_PROCEED as generic_prepare_to_proceed, and 
remove lin_lwp_prepare_to_proceed.  

I'm not necessarily objecting to this patch -- just pointing
out an alternative.  If people think we're ready for this step, 
it's fine with me.


> On Fri, Aug 23, 2002 at 08:35:17AM +0200, Van Assche, Bart wrote:
> > Hello Dan,
> >
> >    Thanks for your response. I tried with the latest snapshot, and debugging
> > threads has indeed improved. However, I still get a SIGSEGV reported when I
> > use remote debugging (that I do not get with native debugging -- see also
> > below).
> 
> --
> Daniel Jacobowitz
> MontaVista Software                         Debian GNU/Linux Developer
> 
> 2002-08-30  Daniel Jacobowitz  <drow@mvista.com>
> 
>         * arch-utils.c (default_prepare_to_proceed): Remove.
>         * arch-utils.h (default_prepare_to_proceed): Remove prototype.
>         * gdbarch.sh (PREPARE_TO_PROCEED): Change default to
>         generic_prepare_to_proceed.
>         * gdbarch.c: Regenerated.
>         * gdbarch.h: Regenerated.
>         * lin-lwp.c (lin_lwp_prepare_to_proceed): Remove.
>         * config/nm-linux.h (PREPARE_TO_PROCEED): Don't define.
>         (lin_lwp_prepare_to_proceed): Remove prototype.
> 
> Index: arch-utils.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/arch-utils.c,v
> retrieving revision 1.67
> diff -u -p -r1.67 arch-utils.c
> --- arch-utils.c        24 Aug 2002 00:21:34 -0000      1.67
> +++ arch-utils.c        30 Aug 2002 22:13:11 -0000
> @@ -320,13 +320,6 @@ default_frame_address (struct frame_info
>    return fi->frame;
>  }
> 
> -/* Default prepare_to_procced().  */
> -int
> -default_prepare_to_proceed (int select_it)
> -{
> -  return 0;
> -}
> -
>  /* Generic prepare_to_proceed().  This one should be suitable for most
>     targets that support threads. */
>  int
> Index: gdbarch.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/gdbarch.c,v
> retrieving revision 1.146
> diff -u -p -r1.146 gdbarch.c
> --- gdbarch.c   24 Aug 2002 00:21:34 -0000      1.146
> +++ gdbarch.c   30 Aug 2002 22:13:12 -0000
> @@ -530,7 +530,7 @@ gdbarch_alloc (const struct gdbarch_info
>    current_gdbarch->memory_insert_breakpoint = default_memory_insert_breakpoint;
>    current_gdbarch->memory_remove_breakpoint = default_memory_remove_breakpoint;
>    current_gdbarch->decr_pc_after_break = -1;
> -  current_gdbarch->prepare_to_proceed = default_prepare_to_proceed;
> +  current_gdbarch->prepare_to_proceed = generic_prepare_to_proceed;
>    current_gdbarch->function_start_offset = -1;
>    current_gdbarch->remote_translate_xfer_address = generic_remote_translate_xfer_address;
>    current_gdbarch->frame_args_skip = -1;
> Index: gdbarch.h
> ===================================================================
> RCS file: /cvs/src/src/gdb/gdbarch.h,v
> retrieving revision 1.114
> diff -u -p -r1.114 gdbarch.h
> --- gdbarch.h   24 Aug 2002 00:21:34 -0000      1.114
> +++ gdbarch.h   30 Aug 2002 22:13:13 -0000
> @@ -1809,7 +1809,7 @@ extern void set_gdbarch_decr_pc_after_br
> 
>  /* Default (function) for non- multi-arch platforms. */
>  #if (!GDB_MULTI_ARCH) && !defined (PREPARE_TO_PROCEED)
> -#define PREPARE_TO_PROCEED(select_it) (default_prepare_to_proceed (select_it))
> +#define PREPARE_TO_PROCEED(select_it) (generic_prepare_to_proceed (select_it))
>  #endif
> 
>  typedef int (gdbarch_prepare_to_proceed_ftype) (int select_it);
> Index: gdbarch.sh
> ===================================================================
> RCS file: /cvs/src/src/gdb/gdbarch.sh,v
> retrieving revision 1.158
> diff -u -p -r1.158 gdbarch.sh
> --- gdbarch.sh  24 Aug 2002 00:21:34 -0000      1.158
> +++ gdbarch.sh  30 Aug 2002 22:13:14 -0000
> @@ -549,7 +549,7 @@ f:2:BREAKPOINT_FROM_PC:const unsigned ch
>  f:2:MEMORY_INSERT_BREAKPOINT:int:memory_insert_breakpoint:CORE_ADDR addr, char *contents_cache:addr, contents_cache::0:default_memory_insert_breakpoint::0
>  f:2:MEMORY_REMOVE_BREAKPOINT:int:memory_remove_breakpoint:CORE_ADDR addr, char *contents_cache:addr, contents_cache::0:default_memory_remove_breakpoint::0
>  v:2:DECR_PC_AFTER_BREAK:CORE_ADDR:decr_pc_after_break::::0:-1
> -f::PREPARE_TO_PROCEED:int:prepare_to_proceed:int select_it:select_it::0:default_prepare_to_proceed::0
> +f::PREPARE_TO_PROCEED:int:prepare_to_proceed:int select_it:select_it::0:generic_prepare_to_proceed::0
>  v:2:FUNCTION_START_OFFSET:CORE_ADDR:function_start_offset::::0:-1
>  #
>  f:2:REMOTE_TRANSLATE_XFER_ADDRESS:void:remote_translate_xfer_address:CORE_ADDR gdb_addr, int gdb_len, CORE_ADDR *rem_addr, int *rem_len:gdb_addr, gdb_len, rem_addr, rem_len:::generic_remote_translate_xfer_address::0
> Index: lin-lwp.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/lin-lwp.c,v
> retrieving revision 1.35
> diff -u -p -r1.35 lin-lwp.c
> --- lin-lwp.c   27 Aug 2002 22:37:06 -0000      1.35
> +++ lin-lwp.c   30 Aug 2002 22:13:14 -0000
> @@ -294,46 +294,6 @@ iterate_over_lwps (int (*callback) (stru
>  }
> 
> 
> -/* Implementation of the PREPARE_TO_PROCEED hook for the GNU/Linux LWP
> -   layer.
> -
> -   Note that this implementation is potentially redundant now that
> -   default_prepare_to_proceed() has been added.
> -
> -   FIXME This may not support switching threads after Ctrl-C
> -   correctly. The default implementation does support this. */
> -
> -int
> -lin_lwp_prepare_to_proceed (void)
> -{
> -  if (! ptid_equal (trap_ptid, null_ptid)
> -      && ! ptid_equal (inferior_ptid, trap_ptid))
> -    {
> -      /* Switched over from TRAP_PID.  */
> -      CORE_ADDR stop_pc = read_pc ();
> -      CORE_ADDR trap_pc;
> -
> -      /* Avoid switching where it wouldn't do any good, i.e. if both
> -         threads are at the same breakpoint.  */
> -      trap_pc = read_pc_pid (trap_ptid);
> -      if (trap_pc != stop_pc && breakpoint_here_p (trap_pc))
> -       {
> -         /* User hasn't deleted the breakpoint.  Return non-zero, and
> -             switch back to TRAP_PID.  */
> -         inferior_ptid = trap_ptid;
> -
> -         /* FIXME: Is this stuff really necessary?  */
> -         flush_cached_frames ();
> -         registers_changed ();
> -
> -         return 1;
> -       }
> -    }
> -
> -  return 0;
> -}
> -
> -
>  #if 0
>  static void
>  lin_lwp_open (char *args, int from_tty)
> Index: config/nm-linux.h
> ===================================================================
> RCS file: /cvs/src/src/gdb/config/nm-linux.h,v
> retrieving revision 1.12
> diff -u -p -r1.12 nm-linux.h
> --- config/nm-linux.h   24 Feb 2002 22:56:04 -0000      1.12
> +++ config/nm-linux.h   30 Aug 2002 22:13:14 -0000
> @@ -49,9 +49,6 @@ struct target_waitstatus;
>  extern ptid_t child_wait (ptid_t ptid, struct target_waitstatus *ourstatus);
>  #define CHILD_WAIT
> 
> -extern int lin_lwp_prepare_to_proceed (void);
> -#define PREPARE_TO_PROCEED(select_it) lin_lwp_prepare_to_proceed ()
> -
>  extern void lin_lwp_attach_lwp (ptid_t ptid, int verbose);
>  #define ATTACH_LWP(ptid, verbose) lin_lwp_attach_lwp ((ptid), (verbose))
> 
> Index: arch-utils.h
> ===================================================================
> RCS file: /cvs/src/src/gdb/arch-utils.h,v
> retrieving revision 1.41
> diff -u -p -r1.41 arch-utils.h
> --- arch-utils.h        24 Aug 2002 00:21:34 -0000      1.41
> +++ arch-utils.h        30 Aug 2002 22:15:25 -0000
> @@ -115,8 +115,6 @@ extern CORE_ADDR default_frame_address (
> 
>  /* Default prepare_to_procced. */
> 
> -extern int default_prepare_to_proceed (int select_it);
> -
>  extern int generic_prepare_to_proceed (int select_it);
> 
>  /* Versions of init_frame_pc().  Do nothing; do the default. */