/* ss.c: STACK SCANNING
 *
 * $Id$
 * Copyright (c) 2001-2014 Ravenbrook Limited.  See end of file for license.
 *
 * This scans the mutator's stack and fixes the registers that may
 * contain roots. See <design/ss/>.
 *
 * This is a generic implementation, but it makes assumptions that,
 * while true on all the platforms we currently (version 1.115)
 * support, may not be true on all platforms.
 * 
 * .assume.down: The stack grows downwards.
 *
 * .assume.bottom: There is no need to scan the word pointed to by
 * stackBot.
 *
 * .assume.align: Addresses on the stack are aligned to sizeof(Addr).
 */

#include "mpm.h"

SRCID(ss, "$Id$");


/* StackScan -- scan the mutator's stack and registers */

static Res stackScanInner(Arena arena, ScanState ss, Addr *stackBot,
                          StackContext sc)
{
  Addr *stackTop;
  Res res;

  AVERT(Arena, arena);
  AVERT(ScanState, ss);

  stackTop = StackContextStackTop(sc);
  AVER(stackTop < stackBot);                          /* .assume.down */
  AVER(AddrIsAligned((Addr)stackTop, sizeof(Addr)));  /* .assume.align */

  res = TraceScanAreaTagged(ss, stackTop, stackBot);  /* .assume.bottom */
  if (res != ResOK)
    return res;

  res = StackContextScan(ss, sc);
  if (res != ResOK)
    return res;

  return ResOK;
}

Res StackScan(ScanState ss, Addr *stackBot)
{
  Arena arena;
  Res res;

  AVERT(ScanState, ss);
  arena = ss->arena;

  /* See <design/ss/#sol.entry-points.fragile> */
  AVER(arena->scAtArenaEnter);
  if (arena->scAtArenaEnter) {
    res = stackScanInner(arena, ss, stackBot, arena->scAtArenaEnter);
  } else {
    /* Somehow missed saving the context at the entry point: do it now. */
    StackContextStruct sc;
    STACK_CONTEXT_SAVE(&sc);
    res = stackScanInner(arena, ss, stackBot, &sc);
  }
  return res;
}


/* C. COPYRIGHT AND LICENSE
 *
 * Copyright (C) 2001-2014 Ravenbrook Limited <http://www.ravenbrook.com/>.
 * All rights reserved.  This is an open source license.  Contact
 * Ravenbrook for commercial licensing options.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 * 
 * 3. Redistributions in any form must be accompanied by information on how
 * to obtain complete source code for this software and any accompanying
 * software that uses this software.  The source code must either be
 * included in the distribution or be available for no more than the cost
 * of distribution plus a nominal fee, and must be freely redistributable
 * under reasonable conditions.  For an executable file, complete source
 * code means the source code for all modules it contains. It does not
 * include source code for modules or files that typically accompany the
 * major components of the operating system on which the executable file
 * runs.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT, ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS AND CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */