Re: [PATCH,gdb,Update5]: ensures that cie ptr of an fda is a cie

[Fawzi Mohamed <fawzi.mohamed@nokia.com>]

Clearly as soon as I sent it away I realized that I did not check if the arguments of
printf were null. Here a new patch reviewed by Andre, hopefully close to ok :)

master is still a bit buggy on mac, and I have found that 10.7 lion uses some more load commands
in mach-o that are not even defined in the mach-o/loader.h, but that is something for another time
(I will switch back to the 7.2 branch for now).

Fawzi

2011-07-07  Fawzi Mohamed  <fawzi.mohamed@nokia.com>

	* dwarf2-frame.c (decode_frame_entry, decode_frame_entry_1): Ensure
	that CIE pointer of an FDE really points to a CIE .

diff --git a/gdb/dwarf2-frame.c b/gdb/dwarf2-frame.c
index b68a773..dcc3682 100644
--- a/gdb/dwarf2-frame.c
+++ b/gdb/dwarf2-frame.c
@@ -1801,17 +1801,30 @@ add_fde (struct dwarf2_fde_table *fde_table, struct dwarf2_fde *fde)
 #define DW64_CIE_ID ~0
 #endif
 
+/* Defines the type of eh_frames that are expected to be decoded: CIE, FDE
+   or any of them.  */
+
+enum eh_frame_type
+{
+  EH_CIE_TYPE_ID = 1 << 0,
+  EH_FDE_TYPE_ID = 1 << 1,
+  EH_CIE_OR_FDE_TYPE_ID = EH_CIE_TYPE_ID | EH_FDE_TYPE_ID
+};
+
 static gdb_byte *decode_frame_entry (struct comp_unit *unit, gdb_byte *start,
 				     int eh_frame_p,
                                      struct dwarf2_cie_table *cie_table,
-                                     struct dwarf2_fde_table *fde_table);
+                                     struct dwarf2_fde_table *fde_table,
+                                     enum eh_frame_type entry_type);
+
+/* Decode the next CIE or FDE, entry_type specifies the expected type.
+   Return NULL if invalid input, otherwise the next byte to be processed.  */
 
-/* Decode the next CIE or FDE.  Return NULL if invalid input, otherwise
-   the next byte to be processed.  */
 static gdb_byte *
 decode_frame_entry_1 (struct comp_unit *unit, gdb_byte *start, int eh_frame_p,
                       struct dwarf2_cie_table *cie_table,
-                      struct dwarf2_fde_table *fde_table)
+                      struct dwarf2_fde_table *fde_table,
+                      enum eh_frame_type entry_type)
 {
   struct gdbarch *gdbarch = get_objfile_arch (unit->objfile);
   gdb_byte *buf, *end;
@@ -1862,6 +1875,10 @@ decode_frame_entry_1 (struct comp_unit *unit, gdb_byte *start, int eh_frame_p,
       char *augmentation;
       unsigned int cie_version;
 
+      /* Check that a CIE was expected.  */
+      if ((entry_type & EH_CIE_TYPE_ID) == 0)
+	error (_("Found a CIE when not expecting it, broken eh_info"));
+
       /* Record the offset into the .debug_frame section of this CIE.  */
       cie_pointer = start - unit->dwarf_frame_buffer;
 
@@ -2027,6 +2044,10 @@ decode_frame_entry_1 (struct comp_unit *unit, gdb_byte *start, int eh_frame_p,
       /* This is a FDE.  */
       struct dwarf2_fde *fde;
 
+      /* Check that an FDE was expected.  */
+      if ((entry_type & EH_FDE_TYPE_ID) == 0)
+	error (_("Found an FDE when not expecting it, broken eh_info."));
+
       /* In an .eh_frame section, the CIE pointer is the delta between the
 	 address within the FDE where the CIE pointer is stored and the
 	 address of the CIE.  Convert it to an offset into the .eh_frame
@@ -2048,7 +2069,8 @@ decode_frame_entry_1 (struct comp_unit *unit, gdb_byte *start, int eh_frame_p,
       if (fde->cie == NULL)
 	{
 	  decode_frame_entry (unit, unit->dwarf_frame_buffer + cie_pointer,
-			      eh_frame_p, cie_table, fde_table);
+			      eh_frame_p, cie_table, fde_table,
+			      EH_CIE_TYPE_ID);
 	  fde->cie = find_cie (cie_table, cie_pointer);
 	}
 
@@ -2089,11 +2111,14 @@ decode_frame_entry_1 (struct comp_unit *unit, gdb_byte *start, int eh_frame_p,
   return end;
 }
 
-/* Read a CIE or FDE in BUF and decode it.  */
+/* Read a CIE or FDE in BUF and decode it. Entry_type specifies whether we
+   expect an FDE or a CIE.  */
+
 static gdb_byte *
 decode_frame_entry (struct comp_unit *unit, gdb_byte *start, int eh_frame_p,
                     struct dwarf2_cie_table *cie_table,
-                    struct dwarf2_fde_table *fde_table)
+                    struct dwarf2_fde_table *fde_table,
+                    enum eh_frame_type entry_type)
 {
   enum { NONE, ALIGN4, ALIGN8, FAIL } workaround = NONE;
   gdb_byte *ret;
@@ -2102,7 +2127,7 @@ decode_frame_entry (struct comp_unit *unit, gdb_byte *start, int eh_frame_p,
   while (1)
     {
       ret = decode_frame_entry_1 (unit, start, eh_frame_p,
-                                  cie_table, fde_table);
+				  cie_table, fde_table, entry_type);
       if (ret != NULL)
 	break;
 
@@ -2212,6 +2237,7 @@ dwarf2_build_frame_info (struct objfile *objfile)
   struct dwarf2_cie_table cie_table;
   struct dwarf2_fde_table fde_table;
   struct dwarf2_fde_table *fde_table2;
+  volatile struct gdb_exception e;
 
   cie_table.num_entries = 0;
   cie_table.entries = NULL;
@@ -2253,10 +2279,29 @@ dwarf2_build_frame_info (struct objfile *objfile)
           if (txt)
             unit->tbase = txt->vma;
 
-          frame_ptr = unit->dwarf_frame_buffer;
-          while (frame_ptr < unit->dwarf_frame_buffer + unit->dwarf_frame_size)
-            frame_ptr = decode_frame_entry (unit, frame_ptr, 1,
-                                            &cie_table, &fde_table);
+	  TRY_CATCH (e, RETURN_MASK_ERROR)
+	    {
+	      frame_ptr = unit->dwarf_frame_buffer;
+	      while (frame_ptr < unit->dwarf_frame_buffer + unit->dwarf_frame_size)
+		frame_ptr = decode_frame_entry (unit, frame_ptr, 1,
+						&cie_table, &fde_table,
+						EH_CIE_OR_FDE_TYPE_ID);
+	    }
+
+	  if (e.reason < 0)
+	    {
+	      warning (_("skipping .eh_frame info of %s: %s"),
+		       (objfile->name ? objfile->name : "*unknown*"),
+		       (e.message ? e.message : ""));
+
+	      if (fde_table.num_entries != 0)
+		{
+		  xfree(fde_table.entries);
+		  fde_table.entries = NULL;
+		  fde_table.num_entries = 0;
+		}
+	      /* The cie_table is discarded by the next if.  */
+	    }
 
           if (cie_table.num_entries != 0)
             {
@@ -2274,10 +2319,39 @@ dwarf2_build_frame_info (struct objfile *objfile)
                            &unit->dwarf_frame_size);
   if (unit->dwarf_frame_size)
     {
-      frame_ptr = unit->dwarf_frame_buffer;
-      while (frame_ptr < unit->dwarf_frame_buffer + unit->dwarf_frame_size)
-	frame_ptr = decode_frame_entry (unit, frame_ptr, 0,
-                                        &cie_table, &fde_table);
+      int num_old_fde_entries = fde_table.num_entries;
+
+      TRY_CATCH (e, RETURN_MASK_ERROR)
+	{
+	  frame_ptr = unit->dwarf_frame_buffer;
+	  while (frame_ptr < unit->dwarf_frame_buffer + unit->dwarf_frame_size)
+	    frame_ptr = decode_frame_entry (unit, frame_ptr, 0,
+					    &cie_table, &fde_table,
+					    EH_CIE_OR_FDE_TYPE_ID);
+	}
+      if (e.reason < 0)
+	{
+	  warning (_("skipping .debug_frame info of %s: %s"),
+		   (objfile->name ? objfile->name : "*unknown*"),
+		   (e.message ? e.message : ""));
+
+	  if (fde_table.num_entries != 0)
+	    {
+	      fde_table.num_entries = num_old_fde_entries;
+	      if (num_old_fde_entries == 0)
+		{
+		  xfree(fde_table.entries);
+		  fde_table.entries = NULL;
+		}
+	      else
+		{
+		    xrealloc (fde_table.entries,
+			      fde_table.num_entries * sizeof (fde_table.entries[0]));
+		}
+	    }
+	  fde_table.num_entries = num_old_fde_entries;
+	  /* The cie_table is discarded by the next if.  */
+	}
     }
 
   /* Discard the cie_table, it is no longer needed.  */