binutils-gdb/gdb/tramp-frame.c

/* Signal trampoline unwinder, for GDB the GNU Debugger.

   Copyright (C) 2004, 2007, 2008, 2009, 2010, 2011
   Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"
#include "tramp-frame.h"
#include "frame-unwind.h"
#include "gdbcore.h"
#include "symtab.h"
#include "objfiles.h"
#include "target.h"
#include "trad-frame.h"
#include "frame-base.h"
#include "gdb_assert.h"

struct frame_data
{
  const struct tramp_frame *tramp_frame;
};

struct tramp_frame_cache
{
  CORE_ADDR func;
  const struct tramp_frame *tramp_frame;
  struct trad_frame_cache *trad_cache;
};

static struct trad_frame_cache *
tramp_frame_cache (struct frame_info *this_frame,
		   void **this_cache)
{
  struct tramp_frame_cache *tramp_cache = (*this_cache);

  if (tramp_cache->trad_cache == NULL)
    {
      tramp_cache->trad_cache = trad_frame_cache_zalloc (this_frame);
      tramp_cache->tramp_frame->init (tramp_cache->tramp_frame,
				      this_frame,
				      tramp_cache->trad_cache,
				      tramp_cache->func);
    }
  return tramp_cache->trad_cache;
}

static void
tramp_frame_this_id (struct frame_info *this_frame,
		     void **this_cache,
		     struct frame_id *this_id)
{
  struct trad_frame_cache *trad_cache
    = tramp_frame_cache (this_frame, this_cache);

  trad_frame_get_id (trad_cache, this_id);
}

static struct value *
tramp_frame_prev_register (struct frame_info *this_frame,
			   void **this_cache,
			   int prev_regnum)
{
  struct trad_frame_cache *trad_cache
    = tramp_frame_cache (this_frame, this_cache);

  return trad_frame_get_register (trad_cache, this_frame, prev_regnum);
}

static CORE_ADDR
tramp_frame_start (const struct tramp_frame *tramp,
		   struct frame_info *this_frame, CORE_ADDR pc)
{
  struct gdbarch *gdbarch = get_frame_arch (this_frame);
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  int ti;

  /* Search through the trampoline for one that matches the
     instruction sequence around PC.  */
  for (ti = 0; tramp->insn[ti].bytes != TRAMP_SENTINEL_INSN; ti++)
    {
      CORE_ADDR func = pc - tramp->insn_size * ti;
      int i;

      for (i = 0; 1; i++)
	{
	  gdb_byte buf[sizeof (tramp->insn[0])];
	  ULONGEST insn;

	  if (tramp->insn[i].bytes == TRAMP_SENTINEL_INSN)
	    return func;
	  if (!safe_frame_unwind_memory (this_frame,
					 func + i * tramp->insn_size,
					 buf, tramp->insn_size))
	    break;
	  insn = extract_unsigned_integer (buf, tramp->insn_size, byte_order);
	  if (tramp->insn[i].bytes != (insn & tramp->insn[i].mask))
	    break;
	}
    }
  /* Trampoline doesn't match.  */
  return 0;
}

static int
tramp_frame_sniffer (const struct frame_unwind *self,
		     struct frame_info *this_frame,
		     void **this_cache)
{
  const struct tramp_frame *tramp = self->unwind_data->tramp_frame;
  CORE_ADDR pc = get_frame_pc (this_frame);
  CORE_ADDR func;
  struct tramp_frame_cache *tramp_cache;

  /* tausq/2004-12-12: We used to assume if pc has a name or is in a valid 
     section, then this is not a trampoline.  However, this assumption is
     false on HPUX which has a signal trampoline that has a name; it can
     also be false when using an alternative signal stack.  */
  func = tramp_frame_start (tramp, this_frame, pc);
  if (func == 0)
    return 0;
  tramp_cache = FRAME_OBSTACK_ZALLOC (struct tramp_frame_cache);
  tramp_cache->func = func;
  tramp_cache->tramp_frame = tramp;
  (*this_cache) = tramp_cache;
  return 1;
}

void
tramp_frame_prepend_unwinder (struct gdbarch *gdbarch,
			      const struct tramp_frame *tramp_frame)
{
  struct frame_data *data;
  struct frame_unwind *unwinder;
  int i;

  /* Check that the instruction sequence contains a sentinel.  */
  for (i = 0; i < ARRAY_SIZE (tramp_frame->insn); i++)
    {
      if (tramp_frame->insn[i].bytes == TRAMP_SENTINEL_INSN)
	break;
    }
  gdb_assert (i < ARRAY_SIZE (tramp_frame->insn));
  gdb_assert (tramp_frame->insn_size <= sizeof (tramp_frame->insn[0].bytes));

  data = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_data);
  unwinder = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind);

  data->tramp_frame = tramp_frame;
  unwinder->type = tramp_frame->frame_type;
  unwinder->unwind_data = data;
  unwinder->sniffer = tramp_frame_sniffer;
  unwinder->this_id = tramp_frame_this_id;
  unwinder->prev_register = tramp_frame_prev_register;
  frame_unwind_prepend_unwinder (gdbarch, unwinder);
}