RFA: [symfile.c} Fix to symbol_file_add()

[Fernando Nasser <fnasser@redhat.com>]

Paul N. Hilfinger has pointed out to me that a few operations should be
done every time a new symbol file is read.  This was an oversight in a
patch I wrote in January.  The small patch attached fixes that.

ChangeLog:

	* symfile.c (symbol_file_command): Move cleanup operations
	from here...
	(symbol_file_add): ...to here, so they are run every time a new
	symbol file is read.

-- 
Fernando Nasser
Red Hat Canada Ltd.                     E-Mail:  fnasser@redhat.com
2323 Yonge Street, Suite #300
Toronto, Ontario   M4P 2C9
Index: symfile.c
===================================================================
RCS file: /cvs/src/src/gdb/symfile.c,v
retrieving revision 1.31
diff -c -p -r1.31 symfile.c
*** symfile.c	2001/04/05 02:02:13	1.31
--- symfile.c	2001/04/29 16:13:12
*************** symbol_file_add (char *name, int from_tt
*** 893,898 ****
--- 893,907 ----
    if (target_new_objfile_hook)
      target_new_objfile_hook (objfile);
  
+ #ifdef HPUXHPPA
+   RESET_HP_UX_GLOBALS ();
+ #endif
+   /* Getting new symbols may change our opinion about
+      what is frameless.  */
+   reinit_frame_cache ();
+ 
+   set_initial_language ();
+ 
    return (objfile);
  }
  
*************** symbol_file_command (char *args, int fro
*** 980,993 ****
  		{
                    name = *argv;
  		  symbol_file_add (name, from_tty, NULL, 1, flags);
- #ifdef HPUXHPPA
- 		  RESET_HP_UX_GLOBALS ();
- #endif
- 		  /* Getting new symbols may change our opinion about
- 		     what is frameless.  */
- 		  reinit_frame_cache ();
- 
- 		  set_initial_language ();
  		}
  	  argv++;
  	}
--- 989,994 ----
From nsd@redhat.com Mon Apr 30 09:32:00 2001
From: Nicholas Duffek <nsd@redhat.com>
To: gdb-patches@sourceware.cygnus.com
Cc: ezannoni@cygnus.com, phdm@macqel.be, kevinb@cygnus.com, Peter.Schauer@regent.e-technik.tu-muenchen.de, jimb@cygnus.com
Subject: [RFA] patch to skip bigtoc fixup code
Date: Mon, 30 Apr 2001 09:32:00 -0000
Message-id: <200104301626.MAA00208@nog.bosbc.com>
X-SW-Source: 2001-04/msg00274.html
Content-length: 8515

This patch is an improvement over the one I committed a couple of weeks
ago.  With the new patch, GDB works similarly to dbx:

  1. "step" silently steps through bigtoc fixup code.

  2. Numeric fixup code addresses resolve to symbols @FIX*.  For example,
     when debugging a cc1plus binary containing bigtoc fixup section @FIX1
     in address range 0x1001b614 through 0x1001bfc8, "x/i 0x1001b6fc"
     displays "<@FIX1+232>: addis r3,r2,1".

Without the patch, "step" stops at bigtoc fixup code because GDB detects
that it has stepped outside the current function into the middle of
another function.  A subsequent "step" would return to the original
function.

The patch uses some of the trampoline hooks in handle_inferior_event() to
tell GDB to skip bigtoc fixup code.  The hooks detect bigtoc fixup code by
looking for "@FIX" in the first 4 bytes of the code's function name.  "@"
symbols are no longer ignored by xcoffread.c; instead, they introduduce
new symbol tables and generate function minimal_symbols via the
misc_func_recorded mechanism.

ChangeLog:

	* config/rs6000/tm-rs6000.h (IN_SOLIB_RETURN_TRAMPOLINE): Define.
	(rs6000_in_solib_return_trampoline): Declare.
	* rs6000-tdep.c (rs6000_in_solib_return_trampoline): New
	function.
	(rs6000_skip_trampoline_code): Skip bigtoc fixup code.
	* xcoffread.c (read_xcoff_symtab): Perform the ISFCN function
	check after the CSECT check rather than before it.  Allocate
	separate symtabs for CSECTs whose names begin with '@'.
	(scan_xcoff_symtab): Don't ignore symbols beginning with '@'.
	Activate the misc_func_recorded mechanism for whose names begin
	with '@'.

Tested on powerpc-ibm-aix4.3.3.0.  Okay to apply?

Nicholas Duffek
<nsd@redhat.com>

[patch follows]

Index: gdb/config/rs6000/tm-rs6000.h
===================================================================
diff -up gdb/config/rs6000/tm-rs6000.h gdb/config/rs6000/tm-rs6000.h
--- gdb/config/rs6000/tm-rs6000.h	Fri Apr 27 13:41:03 2001
+++ gdb/config/rs6000/tm-rs6000.h	Fri Apr 27 12:09:00 2001
@@ -36,6 +36,13 @@ extern char *pc_load_segment_name (CORE_
 #undef CPLUS_MARKER
 #define CPLUS_MARKER '.'
 
+/* Return whether PC in function NAME is in code that should be skipped when
+   single-stepping.  */
+
+#define IN_SOLIB_RETURN_TRAMPOLINE(pc, name) \
+  rs6000_in_solib_return_trampoline (pc, name)
+extern int rs6000_in_solib_return_trampoline (CORE_ADDR, char *);
+
 /* If PC is in some function-call trampoline code, return the PC
    where the function itself actually starts.  If not, return NULL.  */
 
Index: gdb/rs6000-tdep.c
===================================================================
diff -up gdb/rs6000-tdep.c gdb/rs6000-tdep.c
--- gdb/rs6000-tdep.c	Fri Apr 27 13:41:08 2001
+++ gdb/rs6000-tdep.c	Fri Apr 27 13:40:52 2001
@@ -1045,19 +1045,55 @@ rs6000_extract_return_value (struct type
 
 static CORE_ADDR rs6000_struct_return_address;
 
-/* Indirect function calls use a piece of trampoline code to do context
-   switching, i.e. to set the new TOC table. Skip such code if we are on
-   its first instruction (as when we have single-stepped to here). 
-   Also skip shared library trampoline code (which is different from
+/* Return whether handle_inferior_event() should proceed through code
+   starting at PC in function NAME when stepping.
+
+   The AIX -bbigtoc linker option generates functions @FIX0, @FIX1, etc. to
+   handle memory references that are too distant to fit in instructions
+   generated by the compiler.  For example, if 'foo' in the following
+   instruction:
+
+     lwz r9,foo(r2)
+
+   is greater than 32767, the linker might replace the lwz with a branch to
+   somewhere in @FIX1 that does the load in 2 instructions and then branches
+   back to where execution should continue.
+
+   GDB should silently step over @FIX code, just like AIX dbx does.
+   Unfortunately, the linker uses the "b" instruction for the branches,
+   meaning that the link register doesn't get set.  Therefore, GDB's usual
+   step_over_function() mechanism won't work.
+
+   Instead, use the IN_SOLIB_RETURN_TRAMPOLINE and SKIP_TRAMPOLINE_CODE hooks
+   in handle_inferior_event() to skip past @FIX code.  */
+
+int
+rs6000_in_solib_return_trampoline (CORE_ADDR pc, char *name)
+{
+  return name && !strncmp (name, "@FIX", 4);
+}
+
+/* Skip code that the user doesn't want to see when stepping:
+
+   1. Indirect function calls use a piece of trampoline code to do context
+   switching, i.e. to set the new TOC table.  Skip such code if we are on
+   its first instruction (as when we have single-stepped to here).
+
+   2. Skip shared library trampoline code (which is different from
    indirect function call trampolines).
+
+   3. Skip bigtoc fixup code.
+
    Result is desired PC to step until, or NULL if we are not in
-   trampoline code.  */
+   code that should be skipped.  */
 
 CORE_ADDR
 rs6000_skip_trampoline_code (CORE_ADDR pc)
 {
   register unsigned int ii, op;
+  int rel;
   CORE_ADDR solib_target_pc;
+  struct minimal_symbol *msymbol;
 
   static unsigned trampoline_code[] =
   {
@@ -1070,6 +1106,21 @@ rs6000_skip_trampoline_code (CORE_ADDR p
     0x4e800020,			/*    br                */
     0
   };
+
+  /* Check for bigtoc fixup code.  */
+  msymbol = lookup_minimal_symbol_by_pc (pc);
+  if (msymbol && rs6000_in_solib_return_trampoline (pc, SYMBOL_NAME (msymbol)))
+    {
+      /* Double-check that the third instruction from PC is relative "b".  */
+      op = read_memory_integer (pc + 8, 4);
+      if ((op & 0xfc000003) == 0x48000000)
+	{
+	  /* Extract bits 6-29 as a signed 24-bit relative word address and
+	     add it to the containing PC.  */
+	  rel = ((int)(op << 6) >> 6);
+	  return pc + 8 + rel;
+	}
+    }
 
   /* If pc is in a shared library trampoline, return its target.  */
   solib_target_pc = find_solib_trampoline_target (pc);
Index: gdb/xcoffread.c
===================================================================
diff -up gdb/xcoffread.c gdb/xcoffread.c
--- gdb/xcoffread.c	Fri Apr 27 13:41:13 2001
+++ gdb/xcoffread.c	Fri Apr 27 12:52:10 2001
@@ -1100,14 +1100,6 @@ read_xcoff_symtab (pst)
 	  /* done with all files, everything from here on is globals */
 	}
 
-      /* if explicitly specified as a function, treat is as one. */
-      if (ISFCN (cs->c_type) && cs->c_sclass != C_TPDEF)
-	{
-	  bfd_coff_swap_aux_in (abfd, raw_auxptr, cs->c_type, cs->c_sclass,
-				0, cs->c_naux, &main_aux);
-	  goto function_entry_point;
-	}
-
       if ((cs->c_sclass == C_EXT || cs->c_sclass == C_HIDEXT)
 	  && cs->c_naux == 1)
 	{
@@ -1177,7 +1169,8 @@ read_xcoff_symtab (pst)
 						SECT_OFF_TEXT (objfile));
 		      file_end_addr = file_start_addr + CSECT_LEN (&main_aux);
 
-		      if (cs->c_name && cs->c_name[0] == '.')
+		      if (cs->c_name && (cs->c_name[0] == '.'
+					 || cs->c_name[0] == '@'))
 			{
 			  last_csect_name = cs->c_name;
 			  last_csect_val = cs->c_value;
@@ -1251,6 +1244,16 @@ read_xcoff_symtab (pst)
 	    }
 	}
 
+      /* If explicitly specified as a function, treat is as one.  This check
+	 evaluates to true for @FIX* bigtoc CSECT symbols, so it must occur
+	 after the above CSECT check.  */
+      if (ISFCN (cs->c_type) && cs->c_sclass != C_TPDEF)
+	{
+	  bfd_coff_swap_aux_in (abfd, raw_auxptr, cs->c_type, cs->c_sclass,
+				0, cs->c_naux, &main_aux);
+	  goto function_entry_point;
+	}
+
       switch (cs->c_sclass)
 	{
 
@@ -2295,14 +2298,8 @@ scan_xcoff_symtab (objfile)
 	    else
 	      csect_aux = main_aux[0];
 
-	    /* If symbol name starts with ".$" or "$", ignore it. 
-
-	       A symbol like "@FIX1" introduces a section for -bbigtoc jump
-	       tables, which contain anonymous linker-generated code. 
-	       Ignore those sections to avoid "pc 0x... in read in psymtab,
-	       but not in symtab" warnings from find_pc_sect_symtab.  */
-
-	    if (namestring[0] == '$' || namestring[0] == '@'
+	    /* If symbol name starts with ".$" or "$", ignore it.  */
+	    if (namestring[0] == '$'
 		|| (namestring[0] == '.' && namestring[1] == '$'))
 	      break;
 
@@ -2348,7 +2345,11 @@ scan_xcoff_symtab (objfile)
 			       objfile->static_psymbols.next);
 			  }
 		      }
-		    if (namestring && namestring[0] == '.')
+		    /* Activate the misc_func_recorded mechanism for
+		       compiler- and linker-generated CSECTs like ".strcmp"
+		       and "@FIX1".  */ 
+		    if (namestring && (namestring[0] == '.'
+				       || namestring[0] == '@'))
 		      {
 			last_csect_name = namestring;
 			last_csect_val = symbol.n_value;