coffgrok access of u.auxent.x_sym.x_tagndx.p

u.auxent.x_sym.x_tagndx is a union.  The p field is only valid when
fix_tag is set.  This patch fixes code in coffgrok.c that accessed the
field without first checking fix_tag, and removes a whole lot of code
validating bogus pointers to prevent segfaults (which no longer
happen, I checked the referenced PR 17512 testcases).  The patch also
documents this in the fix_tag comment, makes is_sym a bitfield, and
sorts the selecter fields a little.

bfd/
	* coffcode.h (combined_entry_type): Make is_sym a bitfield.
	Sort and comment on union selectors.
	* libcoff.h: Regenerate.
binutils/
	* coffgrok.c (do_type): Make aux a combined_entry_type.  Test
	fix_tag before accessing u.auxent.x_sym.x_tagndx.p.  Remove
	now unnecessary pointer bounds checking.

1 files changed, 15 insertions, 15 deletions

diff --git a/bfd/libcoff.h b/bfd/libcoff.h
index b7a4f67..b58ee8a 100644
--- a/bfd/libcoff.h
+++ b/bfd/libcoff.h
@@ -633,27 +633,30 @@ extern bool _bfd_ppc_xcoff_relocate_section
 typedef struct coff_ptr_struct
 {
   /* Remembers the offset from the first symbol in the file for
-     this symbol. Generated by coff_renumber_symbols.  */
+     this symbol.  Generated by coff_renumber_symbols.  */
   unsigned int offset;
 
-  /* Should the value of this symbol be renumbered.  Used for
-     XCOFF C_BSTAT symbols.  Set by coff_slurp_symbol_table.  */
-  unsigned int fix_value : 1;
+  /* Selects between the elements of the union below.  */
+  unsigned int is_sym : 1;
 
-  /* Should the tag field of this symbol be renumbered.
-     Created by coff_pointerize_aux.  */
+  /* Selects between the elements of the x_sym.x_tagndx union.  If set,
+     p is valid and the field will be renumbered.  */
   unsigned int fix_tag : 1;
 
-  /* Should the endidx field of this symbol be renumbered.
-     Created by coff_pointerize_aux.  */
+  /* Selects between the elements of the x_sym.x_fcnary.x_fcn.x_endndx
+     union.  If set, p is valid and the field will be renumbered.  */
   unsigned int fix_end : 1;
 
-  /* Should the x_csect.x_scnlen field be renumbered.
-     Created by coff_pointerize_aux.  */
+  /* Selects between the elements of the x_csect.x_scnlen union.  If set,
+     p is valid and the field will be renumbered.  */
   unsigned int fix_scnlen : 1;
 
-  /* Fix up an XCOFF C_BINCL/C_EINCL symbol.  The value is the
-     index into the line number entries.  Set by coff_slurp_symbol_table.  */
+  /* If set, u.syment.n_value contains a pointer to a symbol.  The final
+     value will be the offset field.  Used for XCOFF C_BSTAT symbols.  */
+  unsigned int fix_value : 1;
+
+  /* If set, u.syment.n_value is an index into the line number entries.
+     Used for XCOFF C_BINCL/C_EINCL symbols.  */
   unsigned int fix_line : 1;
 
   /* The container for the symbol structure as read and translated
@@ -664,9 +667,6 @@ typedef struct coff_ptr_struct
     struct internal_syment syment;
   } u;
 
- /* Selector for the union above.  */
- bool is_sym;
-
  /* An extra pointer which can used by format based on COFF (like XCOFF)
     to provide extra information to their backend.  */
  void *extrap;