[pushed][Cell/B.E.] Make parse_spufs_run more robust

["Ulrich Weigand" <uweigand at de dot ibm dot com>]

Hello,

with recent changes to inferior handling, parse_spufs_run needs to be
more careful in assumptions it makes.  In particular, this patch:

- Bails out early if the current inferior has not yet been registered
  (e.g. during fork procession) to avoid assertion failures in register
  cache code.

- Sets inferior_ptid to the current ptid while calling target_read_memory
  to make sure the correct process is accessed if parse_spufs_run is
  called early when inferior_ptid has not yet been switched by the caller.

Tested on Cell/B.E., pushed to mainline.

Bye,
Ulrich

ChangeLog:

	* spu-multiarch.c (parse_spufs_run): Bail out if inferior is not
	registered yet.  Set inferior_ptid while calling target_read_memory.

Index: binutils-gdb/gdb/spu-multiarch.c
===================================================================
--- binutils-gdb.orig/gdb/spu-multiarch.c
+++ binutils-gdb/gdb/spu-multiarch.c
@@ -56,6 +56,7 @@ static int
 parse_spufs_run (ptid_t ptid, int *fd, CORE_ADDR *addr)
 {
   enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch ());
+  struct cleanup *old_chain;
   struct gdbarch_tdep *tdep;
   struct regcache *regcache;
   gdb_byte buf[4];
@@ -65,12 +66,21 @@ parse_spufs_run (ptid_t ptid, int *fd, C
   if (gdbarch_bfd_arch_info (target_gdbarch ())->arch != bfd_arch_powerpc)
     return 0;
 
+  /* If we're called too early (e.g. after fork), we cannot
+     access the inferior yet.  */
+  if (find_inferior_ptid (ptid) == NULL)
+    return 0;
+
   /* Get PPU-side registers.  */
   regcache = get_thread_arch_regcache (ptid, target_gdbarch ());
   tdep = gdbarch_tdep (target_gdbarch ());
 
   /* Fetch instruction preceding current NIP.  */
-  if (target_read_memory (regcache_read_pc (regcache) - 4, buf, 4) != 0)
+  old_chain = save_inferior_ptid ();
+  inferior_ptid = ptid;
+  regval = target_read_memory (regcache_read_pc (regcache) - 4, buf, 4);
+  do_cleanups (old_chain);
+  if (regval != 0)
     return 0;
   /* It should be a "sc" instruction.  */
   if (extract_unsigned_integer (buf, 4, byte_order) != INSTR_SC)
-- 
  Dr. Ulrich Weigand
  GNU/Linux compilers and toolchain
  Ulrich.Weigand@de.ibm.com