[patch/rfa] Handle unwinding through export stubs on hpux

[Randolph Chung <randolph@tausq.org>]

This fixes a problem reported by Dave Anglin; when doing a backtrace
through a function that is called through an export stub, the unwinder
fails. The problem is that the stub unwinder assumes that the return
pointer doesn't change inside the stub, but the export stub changes it.

Possibly something also needs to be changed for an argument relocation
stub. Will investigate and fix that separately if needed.

tested on hppa2.0w-hp-hpux11.11.

ok to apply?

randolph


2004-05-15  Randolph Chung  <tausq@debian.org>

	* hppa-tdep.c (hppa_stub_frame_unwind_cache): For HPUX stub unwinding,
	check to see if we are unwinding an export stub.  Export stubs clobber
	the %rp in the call path and stores the original rp in a stack slot.

Index: hppa-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/hppa-tdep.c,v
retrieving revision 1.156
diff -u -p -u -r1.156 hppa-tdep.c
--- hppa-tdep.c	8 May 2004 03:59:34 -0000	1.156
+++ hppa-tdep.c	15 May 2004 20:54:57 -0000
@@ -2023,6 +2023,7 @@ hppa_stub_frame_unwind_cache (struct fra
 {
   struct gdbarch *gdbarch = get_frame_arch (next_frame);
   struct hppa_stub_unwind_cache *info;
+  struct unwind_table_entry *u;
 
   if (*this_cache)
     return *this_cache;
@@ -2031,8 +2032,19 @@ hppa_stub_frame_unwind_cache (struct fra
   *this_cache = info;
   info->saved_regs = trad_frame_alloc_saved_regs (next_frame);
 
-  info->saved_regs[HPPA_PCOQ_HEAD_REGNUM].realreg = HPPA_RP_REGNUM;
-  info->base = frame_unwind_register_unsigned (next_frame, HPPA_SP_REGNUM);
+  if ((gdbarch_osabi (gdbarch) == GDB_OSABI_HPUX_ELF 
+       || gdbarch_osabi (gdbarch) == GDB_OSABI_HPUX_SOM)
+      && (u = find_unwind_entry (frame_pc_unwind (next_frame)))
+      && (u->stub_unwind.stub_type == EXPORT))
+    {
+      info->base = frame_unwind_register_unsigned (next_frame, HPPA_SP_REGNUM);
+      info->saved_regs[HPPA_PCOQ_HEAD_REGNUM].addr = info->base - 24;
+    }
+  else
+    {
+      info->base = frame_unwind_register_unsigned (next_frame, HPPA_SP_REGNUM);
+      info->saved_regs[HPPA_PCOQ_HEAD_REGNUM].realreg = HPPA_RP_REGNUM;
+    }
 
   return info;
 }

-- 
Randolph Chung
Debian GNU/Linux Developer, hppa/ia64 ports
http://www.tausq.org/