Re: [patch/RFA] multiarch INSTRUCTION_NULLIFIED

[Randolph Chung <randolph at tausq dot org>]

> Anyway, trying modifying gdbarch_read_pc and unwind_pc (I suspect you 
> need to modify both - which is a bug) to read something like:
> 
> 	if (instruction nullified)
> 		return next-pc
> 	else
> 		return this-pc

i did s/next-pc/prev-pc/ instead... still seems a bit hacky to me, but
it does seem to work.

so is this ok?

randolph


2004-12-01  Randolph Chung  <tausq@debian.org>

	* gdbarch.sh (instruction_nullified): Delete.
	* gdbarch.c: Regenerate.
	* gdbarch.h: Regenerate.
	* hppa-tdep.c (hppa_target_read_pc): Adjust pc if instruction is
	nullified.
	(hppa_unwind_pc): Likewise. 
	(hppa_instruction_nullified): Delete.
	(hppa_gdbarch_init): Don't set instruction_nullified method.
	* infrun.c (infwait_states): Remove infwait_nullified_state.
	(handle_inferior_event): Remove handling of infwait_nullified_state.
	Remove handling of nullified instructions.

Index: gdbarch.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbarch.c,v
retrieving revision 1.315
diff -u -p -r1.315 gdbarch.c
--- gdbarch.c	23 Nov 2004 21:05:18 -0000	1.315
+++ gdbarch.c	1 Dec 2004 22:13:12 -0000
@@ -212,7 +212,6 @@ struct gdbarch
   gdbarch_smash_text_address_ftype *smash_text_address;
   gdbarch_software_single_step_ftype *software_single_step;
   gdbarch_single_step_through_delay_ftype *single_step_through_delay;
-  gdbarch_instruction_nullified_ftype *instruction_nullified;
   gdbarch_print_insn_ftype *print_insn;
   gdbarch_skip_trampoline_code_ftype *skip_trampoline_code;
   gdbarch_skip_solib_resolver_ftype *skip_solib_resolver;
@@ -339,7 +338,6 @@ struct gdbarch startup_gdbarch =
   0,  /* smash_text_address */
   0,  /* software_single_step */
   0,  /* single_step_through_delay */
-  generic_instruction_nullified,  /* instruction_nullified */
   0,  /* print_insn */
   0,  /* skip_trampoline_code */
   generic_skip_solib_resolver,  /* skip_solib_resolver */
@@ -437,7 +435,6 @@ gdbarch_alloc (const struct gdbarch_info
   current_gdbarch->convert_from_func_ptr_addr = convert_from_func_ptr_addr_identity;
   current_gdbarch->addr_bits_remove = core_addr_identity;
   current_gdbarch->smash_text_address = core_addr_identity;
-  current_gdbarch->instruction_nullified = generic_instruction_nullified;
   current_gdbarch->skip_trampoline_code = generic_skip_trampoline_code;
   current_gdbarch->skip_solib_resolver = generic_skip_solib_resolver;
   current_gdbarch->in_solib_return_trampoline = generic_in_solib_return_trampoline;
@@ -594,7 +591,6 @@ verify_gdbarch (struct gdbarch *current_
   /* Skip verify of smash_text_address, invalid_p == 0 */
   /* Skip verify of software_single_step, has predicate */
   /* Skip verify of single_step_through_delay, has predicate */
-  /* Skip verify of instruction_nullified, invalid_p == 0 */
   if (current_gdbarch->print_insn == 0)
     fprintf_unfiltered (log, "\n\tprint_insn");
   /* Skip verify of skip_trampoline_code, invalid_p == 0 */
@@ -1199,9 +1195,6 @@ gdbarch_dump (struct gdbarch *current_gd
   fprintf_unfiltered (file,
                       "gdbarch_dump: inner_than = <0x%lx>\n",
                       (long) current_gdbarch->inner_than);
-  fprintf_unfiltered (file,
-                      "gdbarch_dump: instruction_nullified = <0x%lx>\n",
-                      (long) current_gdbarch->instruction_nullified);
 #ifdef TARGET_INT_BIT
   fprintf_unfiltered (file,
                       "gdbarch_dump: TARGET_INT_BIT # %s\n",
@@ -3373,23 +3366,6 @@ set_gdbarch_single_step_through_delay (s
 }
 
 int
-gdbarch_instruction_nullified (struct gdbarch *gdbarch, struct regcache *regcache)
-{
-  gdb_assert (gdbarch != NULL);
-  gdb_assert (gdbarch->instruction_nullified != NULL);
-  if (gdbarch_debug >= 2)
-    fprintf_unfiltered (gdb_stdlog, "gdbarch_instruction_nullified called\n");
-  return gdbarch->instruction_nullified (gdbarch, regcache);
-}
-
-void
-set_gdbarch_instruction_nullified (struct gdbarch *gdbarch,
-                                   gdbarch_instruction_nullified_ftype instruction_nullified)
-{
-  gdbarch->instruction_nullified = instruction_nullified;
-}
-
-int
 gdbarch_print_insn (struct gdbarch *gdbarch, bfd_vma vma, struct disassemble_info *info)
 {
   gdb_assert (gdbarch != NULL);
Index: gdbarch.h
===================================================================
RCS file: /cvs/src/src/gdb/gdbarch.h,v
retrieving revision 1.276
diff -u -p -r1.276 gdbarch.h
--- gdbarch.h	23 Nov 2004 21:05:19 -0000	1.276
+++ gdbarch.h	1 Dec 2004 22:13:12 -0000
@@ -1227,16 +1227,6 @@ typedef int (gdbarch_single_step_through
 extern int gdbarch_single_step_through_delay (struct gdbarch *gdbarch, struct frame_info *frame);
 extern void set_gdbarch_single_step_through_delay (struct gdbarch *gdbarch, gdbarch_single_step_through_delay_ftype *single_step_through_delay);
 
-/* On some systems, the PC may be left pointing at an instruction that won't
-   actually be executed.  This is usually indicated by a bit in the PSW.  If
-   we find ourselves in such a state, then we step the target beyond the
-   nullified instruction before returning control to gdb.
-   Return non-zero if the processor is about to execute a nullified instruction. */
-
-typedef int (gdbarch_instruction_nullified_ftype) (struct gdbarch *gdbarch, struct regcache *regcache);
-extern int gdbarch_instruction_nullified (struct gdbarch *gdbarch, struct regcache *regcache);
-extern void set_gdbarch_instruction_nullified (struct gdbarch *gdbarch, gdbarch_instruction_nullified_ftype *instruction_nullified);
-
 /* FIXME: cagney/2003-08-28: Need to find a better way of selecting the
    disassembler.  Perhaps objdump can handle it? */
 
Index: gdbarch.sh
===================================================================
RCS file: /cvs/src/src/gdb/gdbarch.sh,v
retrieving revision 1.351
diff -u -p -r1.351 gdbarch.sh
--- gdbarch.sh	23 Nov 2004 21:05:20 -0000	1.351
+++ gdbarch.sh	1 Dec 2004 22:13:12 -0000
@@ -614,12 +614,6 @@ F:=:void:software_single_step:enum targe
 # Return non-zero if the processor is executing a delay slot and a
 # further single-step is needed before the instruction finishes.
 M::int:single_step_through_delay:struct frame_info *frame:frame
-# On some systems, the PC may be left pointing at an instruction that won't
-# actually be executed.  This is usually indicated by a bit in the PSW.  If
-# we find ourselves in such a state, then we step the target beyond the
-# nullified instruction before returning control to gdb.
-# Return non-zero if the processor is about to execute a nullified instruction.
-m::int:instruction_nullified:struct regcache *regcache:regcache::generic_instruction_nullified::0
 # FIXME: cagney/2003-08-28: Need to find a better way of selecting the
 # disassembler.  Perhaps objdump can handle it?
 f:TARGET_PRINT_INSN:int:print_insn:bfd_vma vma, struct disassemble_info *info:vma, info::0:
Index: hppa-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/hppa-tdep.c,v
retrieving revision 1.183
diff -u -p -r1.183 hppa-tdep.c
--- hppa-tdep.c	1 Dec 2004 06:54:56 -0000	1.183
+++ hppa-tdep.c	1 Dec 2004 22:13:12 -0000
@@ -1042,6 +1080,8 @@ static CORE_ADDR
 hppa_target_read_pc (ptid_t ptid)
 {
   int flags = read_register_pid (HPPA_FLAGS_REGNUM, ptid);
+  ULONGEST ipsw = read_register_pid (HPPA_IPSW_REGNUM, ptid);
+  CORE_ADDR pc;
 
   /* The following test does not belong here.  It is OS-specific, and belongs
      in native code.  */
@@ -1049,7 +1089,17 @@ hppa_target_read_pc (ptid_t ptid)
   if (flags & 2)
     return read_register_pid (31, ptid) & ~0x3;
 
-  return read_register_pid (HPPA_PCOQ_HEAD_REGNUM, ptid) & ~0x3;
+  pc = read_register_pid (HPPA_PCOQ_HEAD_REGNUM, ptid) & ~0x3;
+
+  /* If the current instruction is nullified, then we are effectively
+     still executing the previous instruction.  Pretend we are still
+     there.  This is needed when single stepping; if the nullified instruction
+     is on a different line, we don't want gdb to think we've stepped onto
+     that line.  */
+  if (ipsw & 0x00200000)
+    pc -= 4;
+
+  return pc;
 }
 
 /* Write out the PC.  If currently in a syscall, then also write the new
@@ -2185,7 +2235,21 @@ hppa_unwind_dummy_id (struct gdbarch *gd
 static CORE_ADDR
 hppa_unwind_pc (struct gdbarch *gdbarch, struct frame_info *next_frame)
 {
-  return frame_unwind_register_signed (next_frame, HPPA_PCOQ_HEAD_REGNUM) & ~3;
+  ULONGEST ipsw;
+  CORE_ADDR pc;
+
+  ipsw = frame_unwind_register_signed (next_frame, HPPA_IPSW_REGNUM);
+  pc = frame_unwind_register_signed (next_frame, HPPA_PCOQ_HEAD_REGNUM) & ~3;
+
+  /* If the current instruction is nullified, then we are effectively
+     still executing the previous instruction.  Pretend we are still
+     there.  This is needed when single stepping; if the nullified instruction
+     is on a different line, we don't want gdb to think we've stepped onto
+     that line.  */
+  if (ipsw & 0x00200000)
+    pc -= 4;
+
+  return pc;
 }
 
 /* Instead of this nasty cast, add a method pvoid() that prints out a
@@ -2291,22 +2355,6 @@ hppa_pc_requires_run_before_use (CORE_AD
   return (!target_has_stack && (pc & 0xFF000000));
 }
 
-static int
-hppa_instruction_nullified (struct gdbarch *gdbarch, struct regcache *regcache)
-{
-  ULONGEST tmp, ipsw, flags;
-
-  regcache_cooked_read (regcache, HPPA_IPSW_REGNUM, &tmp);
-  ipsw = extract_unsigned_integer (&tmp, 
-		  		   register_size (gdbarch, HPPA_IPSW_REGNUM));
-
-  regcache_cooked_read (regcache, HPPA_FLAGS_REGNUM, &tmp);
-  flags = extract_unsigned_integer (&tmp, 
-		  		    register_size (gdbarch, HPPA_FLAGS_REGNUM));
-
-  return ((ipsw & 0x00200000) && !(flags & 0x2));
-}
-
 /* Return the GDB type object for the "standard" data type of data
    in register N.  */
 
@@ -2573,7 +2623,6 @@ hppa_gdbarch_init (struct gdbarch_info i
       
   set_gdbarch_breakpoint_from_pc (gdbarch, hppa_breakpoint_from_pc);
   set_gdbarch_pseudo_register_read (gdbarch, hppa_pseudo_register_read);
-  set_gdbarch_instruction_nullified (gdbarch, hppa_instruction_nullified);
 
   /* Frame unwind methods.  */
   set_gdbarch_unwind_dummy_id (gdbarch, hppa_unwind_dummy_id);
Index: infrun.c
===================================================================
RCS file: /cvs/src/src/gdb/infrun.c,v
retrieving revision 1.183
diff -u -p -r1.183 infrun.c
--- infrun.c	23 Nov 2004 21:05:23 -0000	1.183
+++ infrun.c	1 Dec 2004 22:13:12 -0000
@@ -870,7 +870,6 @@ enum infwait_states
 {
   infwait_normal_state,
   infwait_thread_hop_state,
-  infwait_nullified_state,
   infwait_nonstep_watch_state
 };
 
@@ -1263,12 +1262,6 @@ handle_inferior_event (struct execution_
       stepped_after_stopped_by_watchpoint = 0;
       break;
 
-    case infwait_nullified_state:
-      if (debug_infrun)
-        printf_unfiltered ("infrun: infwait_nullified_state\n");
-      stepped_after_stopped_by_watchpoint = 0;
-      break;
-
     case infwait_nonstep_watch_state:
       if (debug_infrun)
         printf_unfiltered ("infrun: infwait_nonstep_watch_state\n");
@@ -1730,30 +1723,6 @@ handle_inferior_event (struct execution_
       singlestep_breakpoints_inserted_p = 0;
     }
 
-  /* If PC is pointing at a nullified instruction, then step beyond
-     it before deciding what to do.  This is required when we are stepping
-     through a function where the last instruction is a branch with a
-     nullified instruction in the delay slot that belongs to the next
-     line (which may be in a different function altogether).  */
-
-  if (gdbarch_instruction_nullified (current_gdbarch, current_regcache))
-    {
-      if (debug_infrun)
-	printf_unfiltered ("infrun: instruction nullified\n");
-      registers_changed ();
-      target_resume (ecs->ptid, 1, TARGET_SIGNAL_0);
-
-      /* We may have received a signal that we want to pass to
-         the inferior; therefore, we must not clobber the waitstatus
-         in WS. */
-
-      ecs->infwait_state = infwait_nullified_state;
-      ecs->waiton_ptid = ecs->ptid;
-      ecs->wp = &(ecs->tmpstatus);
-      prepare_to_wait (ecs);
-      return;
-    }
-
   /* It may not be necessary to disable the watchpoint to stop over
      it.  For example, the PA can (with some kernel cooperation)
      single step over a watchpoint without disabling the watchpoint.  */

-- 
Randolph Chung
Debian GNU/Linux Developer, hppa/ia64 ports
http://www.tausq.org/