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properly handle extensions to DWARF 2 line number information

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The forthcoming DWARF 3 standard extends the DWARF 2 line number
information in a backwards-compatible way, by increasing opcode_base
and defining new standard opcodes.

That is, it's backwards-compatible if the DWARF 2 reader properly
ignores unknown standard opcodes.  Unfortunately, the ones in BFD,
GDB, and binutils don't; they expect that any opcodes they don't know
about must be special opcodes.

It would be good to get this patch into the next GDB release (5.1?),
because I hope soon to implement one of the extensions in GAS, the
DW_LNS_set_isa opcode, and the effect of this bug is that GDB can't
understand any files in which this opcode is used.

This has been tested on x86-linux using target 'unix/-gdwarf-2'.  It
has also been tested with a file with the DW_LNS_set_isa included (the
file was generated by hand).

OK to commit?  I think I need approval from both GDB and binutils
maintainers.

-- 
Geoff Keating <geoffk@redhat.com>

===File ~/patches/gdb-lineextend.patch======================
Index: bfd/ChangeLog
2001-11-11  Geoffrey Keating  <geoffk@redhat.com>

	* dwarf2.c (decode_line_info): Properly deal with unknown standard
	opcodes.

Index: binutils/ChangeLog
2001-11-11  Geoffrey Keating  <geoffk@redhat.com>

	* readelf.c (display_debug_lines): Deal with unknown standard
	opcodes.  Handle DW_LNS_set_prologue_end, DW_LNS_set_epilogue_begin,
	DW_LNS_set_isa.

Index: gdb/ChangeLog
2001-11-11  Geoffrey Keating  <geoffk@redhat.com>

	* dwarf2read.c (dwarf_decode_lines): Properly deal with
	unknown standard opcodes.

Index: include/elf/ChangeLog
2001-11-11  Geoffrey Keating  <geoffk@redhat.com>

	* dwarf2.h (dwarf_line_number_ops): Add DWARF 3 opcodes.

Index: bfd/dwarf2.c
===================================================================
RCS file: /cvs/src/src/bfd/dwarf2.c,v
retrieving revision 1.24
diff -p -u -p -r1.24 dwarf2.c
--- dwarf2.c	2001/10/06 10:01:09	1.24
+++ dwarf2.c	2001/11/11 11:42:13
@@ -979,7 +979,22 @@ decode_line_info (unit, stash)
 	  op_code = read_1_byte (abfd, line_ptr);
 	  line_ptr += 1;
 
-	  switch (op_code)
+	  if (op_code >= lh.opcode_base)
+	    {		/* Special operand.  */
+	      adj_opcode = op_code - lh.opcode_base;
+	      address += (adj_opcode / lh.line_range)
+		* lh.minimum_instruction_length;
+	      line += lh.line_base + (adj_opcode % lh.line_range);
+	      /* Append row to matrix using current values.  */
+	      add_line_info (table, address, filename, line, column, 0);
+	      basic_block = 1;
+	      if (need_low_pc)
+		{
+		  need_low_pc = 0;
+		  low_pc = address;
+		}
+	    }
+	  else switch (op_code)
 	    {
 	    case DW_LNS_extended_op:
 	      line_ptr += 1;	/* Ignore length.  */
@@ -1079,19 +1094,15 @@ decode_line_info (unit, stash)
 	      address += read_2_bytes (abfd, line_ptr);
 	      line_ptr += 2;
 	      break;
-	    default:		/* Special operand.  */
-	      adj_opcode = op_code - lh.opcode_base;
-	      address += (adj_opcode / lh.line_range)
-		* lh.minimum_instruction_length;
-	      line += lh.line_base + (adj_opcode % lh.line_range);
-	      /* Append row to matrix using current values.  */
-	      add_line_info (table, address, filename, line, column, 0);
-	      basic_block = 1;
-	      if (need_low_pc)
-		{
-		  need_low_pc = 0;
-		  low_pc = address;
-		}
+	    default:
+	      {  /* Unknown standard opcode, ignore it.  */
+		int i;
+		for (i = 0; i < lh.standard_opcode_lengths[op_code]; i++)
+		  {
+		    (void) read_unsigned_leb128 (abfd, line_ptr, &bytes_read);
+		    line_ptr += bytes_read;
+		  }
+	      }
 	    }
 	}
     }
Index: binutils/readelf.c
===================================================================
RCS file: /cvs/src/src/binutils/readelf.c,v
retrieving revision 1.131
diff -p -u -p -r1.131 readelf.c
--- readelf.c	2001/11/10 00:55:48	1.131
+++ readelf.c	2001/11/11 11:42:14
@@ -5888,8 +5888,20 @@ display_debug_lines (section, start, fil
 
 	  op_code = * data ++;
 
-	  switch (op_code)
+	  if (op_code >= info.li_opcode_base)
 	    {
+	      op_code -= info.li_opcode_base;
+	      adv      = (op_code / info.li_line_range) * info.li_min_insn_length;
+	      state_machine_regs.address += adv;
+	      printf (_("  Special opcode %d: advance Address by %d to 0x%lx"),
+		      op_code, adv, state_machine_regs.address);
+	      adv = (op_code % info.li_line_range) + info.li_line_base;
+	      state_machine_regs.line += adv;
+	      printf (_(" and Line by %d to %d\n"),
+		      adv, state_machine_regs.line);
+	    } 
+	  else switch (op_code) 
+	    {
 	    case DW_LNS_extended_op:
 	      data += process_extended_line_op (data, info.li_default_is_stmt,
                                                 debug_line_pointer_size);
@@ -5958,20 +5970,36 @@ display_debug_lines (section, start, fil
 		      adv, state_machine_regs.address);
 	      break;
 
+	    case DW_LNS_set_prologue_end:
+	      printf (_("  Set prologue_end to true\n"));
+	      break;
+	      
+	    case DW_LNS_set_epilogue_begin:
+	      printf (_("  Set epilogue_begin to true\n"));
+	      break;
+	      
+	    case DW_LNS_set_isa:
+	      adv = read_leb128 (data, & bytes_read, 0);
+	      data += bytes_read;
+	      printf (_("  Set ISA to %d\n"), adv);
+	      break;
+	      
 	    default:
-	      op_code -= info.li_opcode_base;
-	      adv      = (op_code / info.li_line_range) * info.li_min_insn_length;
-	      state_machine_regs.address += adv;
-	      printf (_("  Special opcode %d: advance Address by %d to 0x%lx"),
-		      op_code, adv, state_machine_regs.address);
-	      adv = (op_code % info.li_line_range) + info.li_line_base;
-	      state_machine_regs.line += adv;
-	      printf (_(" and Line by %d to %d\n"),
-		      adv, state_machine_regs.line);
+	      printf (_("  Unknown opcode %d with operands: "), op_code);
+	      {
+		int i;
+		for (i = standard_opcodes[op_code - 1]; i > 0 ; --i)
+		  {
+		    printf ("0x%lx%s", read_leb128 (data, &bytes_read, 0),
+			    i == 1 ? "" : ", ");
+		    data += bytes_read;
+		  }
+		putchar ('\n');
+	      }
 	      break;
 	    }
 	}
-      printf ("\n");
+      putchar ('\n');
     }
 
   return 1;
Index: gdb/dwarf2read.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2read.c,v
retrieving revision 1.33
diff -p -u -p -r1.33 dwarf2read.c
--- dwarf2read.c	2001/11/06 23:38:14	1.33
+++ dwarf2read.c	2001/11/11 11:42:16
@@ -3963,7 +3963,18 @@ dwarf_decode_lines (unsigned int offset,
 	{
 	  op_code = read_1_byte (abfd, line_ptr);
 	  line_ptr += 1;
-	  switch (op_code)
+
+	  if (op_code >= lh.opcode_base)
+	    {		/* Special operand.  */
+	      adj_opcode = op_code - lh.opcode_base;
+	      address += (adj_opcode / lh.line_range)
+		* lh.minimum_instruction_length;
+	      line += lh.line_base + (adj_opcode % lh.line_range);
+	      /* append row to matrix using current values */
+	      record_line (current_subfile, line, address);
+	      basic_block = 1;
+	    }
+	  else switch (op_code)
 	    {
 	    case DW_LNS_extended_op:
 	      line_ptr += 1;	/* ignore length */
@@ -4061,14 +4072,15 @@ dwarf_decode_lines (unsigned int offset,
 	      address += read_2_bytes (abfd, line_ptr);
 	      line_ptr += 2;
 	      break;
-	    default:		/* special operand */
-	      adj_opcode = op_code - lh.opcode_base;
-	      address += (adj_opcode / lh.line_range)
-		* lh.minimum_instruction_length;
-	      line += lh.line_base + (adj_opcode % lh.line_range);
-	      /* append row to matrix using current values */
-	      record_line (current_subfile, line, address);
-	      basic_block = 1;
+	    default:
+	      {  /* Unknown standard opcode, ignore it.  */
+		int i;
+		for (i = 0; i < lh.standard_opcode_lengths[op_code]; i++)
+		  {
+		    (void) read_unsigned_leb128 (abfd, line_ptr, &bytes_read);
+		    line_ptr += bytes_read;
+		  }
+	      }
 	    }
 	}
     }
Index: include/elf/dwarf2.h
===================================================================
RCS file: /cvs/src/src/include/elf/dwarf2.h,v
retrieving revision 1.6
diff -p -u -p -r1.6 dwarf2.h
--- dwarf2.h	2001/06/30 08:58:10	1.6
+++ dwarf2.h	2001/11/11 11:42:18
@@ -588,7 +588,11 @@ enum dwarf_line_number_ops
     DW_LNS_negate_stmt = 6,
     DW_LNS_set_basic_block = 7,
     DW_LNS_const_add_pc = 8,
-    DW_LNS_fixed_advance_pc = 9
+    DW_LNS_fixed_advance_pc = 9,
+    /* DWARF 3 */
+    DW_LNS_set_prologue_end = 10,
+    DW_LNS_set_epilogue_begin = 11,
+    DW_LNS_set_isa = 12
   };
 
 /* Line number extended opcodes.  */
============================================================


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