[ia64-hpux] unwinding bsp value from system call

This fixes unwinding from a thread that is stopped inside a system call.
This can be seen when switching to a thread that is stopped doing a
pthread_cond_wait, for instance...

The comments inside the code should explain what is happening in our
case (the HP-UX exception in the case of system calls): Under certain
circumstances (program stopped inside syscall), the offset to apply to
the current BSP in order to compute the previous BSP is not the usual
CFM & 0x7f.

We parts in this patch:

  1. Figuring out that we are stopped inside a syscal: This requires
     a TT_LWP_RUREGS ttrace call, which is not directly possible from
     ia64-tdep.c.  So use defined a new TARGET_OBJECT_HPUX_UREGS object
     to request it from the -nat side.

  2. Add a gdbarch_tdep method that allows us to change the default
     behavior on ia64-hpux, permitting us to have a different "size of
     register frame" in that one particular case.

gdb/ChangeLog:

        * target.h (enum target_object): Add TARGET_OBJECT_HPUX_UREGS.
        * ia64-tdep.h (struct frame_info): forward declaration.
        (struct gdbarch_tdep): Add field size_of_register_frame.
        * ia64-tdep.c (ia64_access_reg): Use tdep->size_of_register_frame
        to determine the size of the register frame.
        (ia64_size_of_register_frame): New function.
        (ia64_gdbarch_init): Set tdep->size_of_register_frame.
        * ia64-hpux-tdep.c: Include "target.h" and "frame.h".
        (IA64_HPUX_UREG_REASON): New macro.
        (ia64_hpux_stopped_in_syscall, ia64_hpux_size_of_register_frame):
        New functions.
        (ia64_hpux_init_abi): Set tdep->size_of_register_frame.
        * ia64-hpux-nat.c (ia64_hpux_xfer_uregs): New function.
        (ia64_hpux_xfer_partial): Add handling of TARGET_OBJECT_HPUX_UREGS
        objects.

1 files changed, 12 insertions, 2 deletions

diff --git a/gdb/ia64-tdep.c b/gdb/ia64-tdep.c
index 05ca3a1..2529897 100644
--- a/gdb/ia64-tdep.c
+++ b/gdb/ia64-tdep.c
@@ -2452,7 +2452,7 @@ ia64_is_fpreg (int uw_regnum)
 {
   return unw_is_fpreg (uw_regnum);
 }
-  
+
 /* Libunwind callback accessor function for general registers.  */
 static int
 ia64_access_reg (unw_addr_space_t as, unw_regnum_t uw_regnum, unw_word_t *val, 
@@ -2490,7 +2490,7 @@ ia64_access_reg (unw_addr_space_t as, unw_regnum_t uw_regnum, unw_word_t *val,
 	bsp = extract_unsigned_integer (buf, 8, byte_order);
 	get_frame_register (this_frame, IA64_CFM_REGNUM, buf);
 	cfm = extract_unsigned_integer (buf, 8, byte_order);
-	sof = (cfm & 0x7f);
+	sof = gdbarch_tdep (gdbarch)->size_of_register_frame (this_frame, cfm);
 	*val = ia64_rse_skip_regs (bsp, -sof);
 	break;
 
@@ -3848,6 +3848,14 @@ ia64_print_insn (bfd_vma memaddr, struct disassemble_info *info)
   return print_insn_ia64 (memaddr, info);
 }
 
+/* The default "size_of_register_frame" gdbarch_tdep routine for ia64.  */
+
+static int
+ia64_size_of_register_frame (struct frame_info *this_frame, ULONGEST cfm)
+{
+  return (cfm & 0x7f);
+}
+
 static struct gdbarch *
 ia64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
 {
@@ -3862,6 +3870,8 @@ ia64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   tdep = xzalloc (sizeof (struct gdbarch_tdep));
   gdbarch = gdbarch_alloc (&info, tdep);
 
+  tdep->size_of_register_frame = ia64_size_of_register_frame;
+
   /* According to the ia64 specs, instructions that store long double
      floats in memory use a long-double format different than that
      used in the floating registers.  The memory format matches the