Re: Fix gdb crash during .debug_line parsing

[Joel Brobecker <brobecker@adacore.com>]

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> 2008-11-05  Andreas Schwab  <schwab@suse.de>
> 
> 	* dwarf2read.c (dwarf_decode_lines): Add checks for corrupted line
> 	number programs.

Funny, we had a very similar problem not very long ago...

> -      if (!decode_for_pst_p && lh->num_file_names >= file)
> +      if (!decode_for_pst_p && file != 0 && lh->num_file_names >= file)

I believe that this hunk is useless, since this check is at the
beginning of the while loop where file is initialized to 1, so
file can never be zero at this point.


> @@ -7102,7 +7109,7 @@ dwarf_decode_lines (struct line_header *
>  	      line += lh->line_base + (adj_opcode % lh->line_range);
>  	      if (lh->num_file_names < file)
>  		dwarf2_debug_line_missing_file_complaint ();
> -	      else
> +	      else if (file != 0)
>  		{
>  		  lh->file_names[file - 1].included_p = 1;
>  		  if (!decode_for_pst_p)

The problem I see with your approach is taht we don't get to
issue a complaint if file is zero.

Attached is the patch that we have checked in our tree. It handles
the incorrect file number as well as a missing end­sequence. Could
you test it on your side to see if it fixes your problem(s)?

2008-11-09  Jerome Guitton  <guitton@adacore.com>


        * dwarf2read.c (dwarf2_debug_line_missing_end_sequence_complaint):
        New function.
        (dwarf_decode_lines): Detect null file numbers. Detect the end of
        the line program sequence when no end sequence is emitted.

If it works for you, then I'll do a round of testing and commit
(I might have to fix some space-vs-tabs issues as well, sigh...).

-- 
Joel

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Index: dwarf2read.c
===================================================================
--- dwarf2read.c	(revision 134708)
+++ dwarf2read.c	(revision 134718)
@@ -695,6 +695,13 @@ dwarf2_debug_line_missing_file_complaint
 }
 
 static void
+dwarf2_debug_line_missing_end_sequence_complaint (void)
+{
+  complaint (&symfile_complaints,
+	     _(".debug_line section has line program sequence without an end"));
+}
+
+static void
 dwarf2_complex_location_expr_complaint (void)
 {
   complaint (&symfile_complaints, _("location expression too complex"));
@@ -7253,6 +7260,11 @@ dwarf_decode_lines (struct line_header *
 	{
 	  op_code = read_1_byte (abfd, line_ptr);
 	  line_ptr += 1;
+          if (line_ptr > line_end)
+            {
+              dwarf2_debug_line_missing_end_sequence_complaint ();
+              break;
+            }
 
 	  if (op_code >= lh->opcode_base)
 	    {		
@@ -7261,7 +7273,7 @@ dwarf_decode_lines (struct line_header *
 	      address += (adj_opcode / lh->line_range)
 		* lh->minimum_instruction_length;
 	      line += lh->line_base + (adj_opcode % lh->line_range);
-	      if (lh->num_file_names < file)
+	      if (lh->num_file_names < file || file == 0)
 		dwarf2_debug_line_missing_file_complaint ();
 	      else
 		{
@@ -7293,15 +7305,6 @@ dwarf_decode_lines (struct line_header *
 		{
 		case DW_LNE_end_sequence:
 		  end_sequence = 1;
-
-		  if (lh->num_file_names < file)
-		    dwarf2_debug_line_missing_file_complaint ();
-		  else
-		    {
-		      lh->file_names[file - 1].included_p = 1;
-		      if (!decode_for_pst_p)
-			record_line (current_subfile, 0, address);
-		    }
 		  break;
 		case DW_LNE_set_address:
 		  address = read_address (abfd, line_ptr, cu, &bytes_read);
@@ -7343,7 +7346,7 @@ dwarf_decode_lines (struct line_header *
 		}
 	      break;
 	    case DW_LNS_copy:
-	      if (lh->num_file_names < file)
+	      if (lh->num_file_names < file || file == 0)
 		dwarf2_debug_line_missing_file_complaint ();
 	      else
 		{
@@ -7381,7 +7384,7 @@ dwarf_decode_lines (struct line_header *
 
                 file = read_unsigned_leb128 (abfd, line_ptr, &bytes_read);
                 line_ptr += bytes_read;
-                if (lh->num_file_names < file)
+                if (lh->num_file_names < file || file == 0)
                   dwarf2_debug_line_missing_file_complaint ();
                 else
                   {
@@ -7432,6 +7435,14 @@ dwarf_decode_lines (struct line_header *
 	      }
 	    }
 	}
+      if (lh->num_file_names < file || file == 0)
+        dwarf2_debug_line_missing_file_complaint ();
+      else
+        {
+          lh->file_names[file - 1].included_p = 1;
+          if (!decode_for_pst_p)
+            record_line (current_subfile, 0, address);
+        }
     }
 
   if (decode_for_pst_p)