Re: gdbserver

Daniel Jacobowitz
2002-08-31T02:21:56Z

On Fri, Aug 30, 2002 at 04:34:39PM -0700, Michael Snyder wrote:
> 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.

I think we're ready, but let's wait and see. For any non-threaded
target generic_prepare_to_proceed won't do any harm, since it checks
inferior_ptid != resume_ptid; for threaded targets, some version of
this function must be better than none.

>
>
> > 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. */