[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, 24 insertions, 0 deletions

diff --git a/gdb/ia64-hpux-nat.c b/gdb/ia64-hpux-nat.c
index ca1c278..fd58bba 100644
--- a/gdb/ia64-hpux-nat.c
+++ b/gdb/ia64-hpux-nat.c
@@ -568,6 +568,28 @@ ia64_hpux_xfer_memory (struct target_ops *ops, const char *annex,
   return len;
 }
 
+/* Handle the transfer of TARGET_OBJECT_HPUX_UREGS objects on ia64-hpux.
+   ANNEX is currently ignored.
+
+   The current implementation does not support write transfers (because
+   we do not currently do not need these transfers), and will raise
+   a failed assertion if WRITEBUF is not NULL.  */
+
+static LONGEST
+ia64_hpux_xfer_uregs (struct target_ops *ops, const char *annex,
+		      gdb_byte *readbuf, const gdb_byte *writebuf,
+		      ULONGEST offset, LONGEST len)
+{
+  int status;
+
+  gdb_assert (writebuf == NULL);
+
+  status = ia64_hpux_read_register_from_save_state_t (offset, readbuf, len);
+  if (status < 0)
+    return -1;
+  return len;
+}
+
 /* The "to_xfer_partial" target_ops routine for ia64-hpux.  */
 
 static LONGEST
@@ -579,6 +601,8 @@ ia64_hpux_xfer_partial (struct target_ops *ops, enum target_object object,
 
   if (object == TARGET_OBJECT_MEMORY)
     val = ia64_hpux_xfer_memory (ops, annex, readbuf, writebuf, offset, len);
+  else if (object == TARGET_OBJECT_HPUX_UREGS)
+    val = ia64_hpux_xfer_uregs (ops, annex, readbuf, writebuf, offset, len);
   else
     val = super_xfer_partial (ops, object, annex, readbuf, writebuf, offset,
 			      len);