Re: [patch] nto target: fix null pointer dereference

[Aleksandar Ristovski <aristovski at qnx dot com>]

Ulrich Weigand wrote:
> It seems the main problem is that NTO at some time copied some of
> the logic from solib-svr4.c, but has not adapted to the changes that
> were added to that file later on.  Not even the definition of struct
> lm_info matches any more!
>
> Maybe a more correct fix would be to mimic the new solib-svr4.c logic
> and use the l_addr field to cache the load address?

You are right. This is what I did in the new patch (attached).

Thanks,

Aleksandar
2008-08-13  Aleksandar Ristovski  <aristovski@qnx.com>

	* nto-tdep.c (lm_info): Updated struct lm_info definition from
	solib-svr4.c
	(LM_ADDR): Use l_addr if available; if not, use link map.

Index: gdb/nto-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/nto-tdep.c,v
retrieving revision 1.25
diff -u -p -r1.25 nto-tdep.c
--- gdb/nto-tdep.c	23 Jul 2008 13:36:00 -0000	1.25
+++ gdb/nto-tdep.c	13 Aug 2008 15:21:20 -0000
@@ -253,21 +253,39 @@ nto_parse_redirection (char *pargv[], co
    solib-svr4.c to support nto_relocate_section_addresses
    which is different from the svr4 version.  */
 
+/* Link map info to include in an allocated so_list entry */
+
 struct lm_info
-{
-  /* Pointer to copy of link map from inferior.  The type is char *
-     rather than void *, so that we may use byte offsets to find the
-     various fields without the need for a cast.  */
-  char *lm;
-};
+  {
+    /* Pointer to copy of link map from inferior.  The type is char *
+       rather than void *, so that we may use byte offsets to find the
+       various fields without the need for a cast.  */
+    gdb_byte *lm;
+
+    /* Amount by which addresses in the binary should be relocated to
+       match the inferior.  This could most often be taken directly
+       from lm, but when prelinking is involved and the prelink base
+       address changes, we may need a different offset, we want to
+       warn about the difference and compute it only once.  */
+    CORE_ADDR l_addr;
+
+    /* The target location of lm.  */
+    CORE_ADDR lm_addr;
+  };
+
 
 static CORE_ADDR
 LM_ADDR (struct so_list *so)
 {
-  struct link_map_offsets *lmo = nto_fetch_link_map_offsets ();
+  if (so->lm_info->l_addr == (CORE_ADDR)-1)
+    {
+      struct link_map_offsets *lmo = nto_fetch_link_map_offsets ();
 
-  return extract_typed_address (so->lm_info->lm + lmo->l_addr_offset,
-                                builtin_type_void_data_ptr);
+      return extract_typed_address (so->lm_info->lm + lmo->l_addr_offset,
+				    builtin_type_void_data_ptr);
+    }
+  else
+    return so->lm_info->l_addr;
 }
 
 static CORE_ADDR