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/* mpscvm.c: MEMORY POOL SYSTEM C INTERFACE LAYER TO CONFIGURA VIRTUAL MACHINE
 *
 * $Id: //info.ravenbrook.com/project/mps/custom/cet/branch/2016-09-13/job004020/code/mpscvm.c#1 $
 * Copyright (c) 2013 Ravenbrook Limited.  See end of file for license.
 *
 * This file implements miscellaneous extensions to the MPS for
 * interfacing to the Configura Virtual Machine. It is not part of the
 * open source MPS.
 */

#include "mpm.h"
#include "mpscvm.h"
#include "mpsavm.h"


SRCID(mpscvm, "$Id: //info.ravenbrook.com/project/mps/custom/cet/branch/2016-09-13/job004020/code/mpscvm.c#1 $");


/* mps_addr_object -- pointer to allocated object from interior pointer
 * See job003589.
 */

mps_res_t mps_addr_object(mps_addr_t *p_o, mps_arena_t arena, mps_addr_t addr)
{
  Res res;
  Addr p;

  AVER(p_o != NULL);

  /* This function cannot be called while walking the heap, unlike
   * mps_arena_has_addr(). This is because it is designed to be called
   * with an active mutator, so takes the arena lock. This is in order
   * that it sees a consistent view of MPS structures and the heap,
   * and can peek behind the barrier.
   */
  ArenaEnter(arena);
  AVERT(Arena, arena);
  res = ArenaAddrObject(&p, arena, (Addr)addr);
  ArenaLeave(arena);
  /* We require the object to be ambiguously referenced (hence pinned)
   * so that p doesn't become invalid before it is written to *p_o.
   * (We can't simply put this write before the ArenaLeave(), because
   * p_o could point to MPS-managed memory that is behind a barrier.)
   */
  if(res == ResOK) {
    *p_o = (mps_addr_t)p;
  }
  return res;
}


/* Extensions transferred from Configura
 *
 * The functions below this line were copied from
 * //depot/project/cet/kernel/internal/version7.5/cvm/lang/gcMPS.c#1 and
 * are Configura-specific hacks added mostly by Göran Rydqvist on advice
 * from Ravenbrook.
 */

#if defined(MPS_OS_W3)

#include "mpswin.h"

/**
 * Remove protection from all MPS mapped pages. This leaves the heap
 * in a possibly inconsistent state and so it is not safe to continue
 * execution. The use case that it's intended to address is to make it
 * possible to print a stack trace from an MPS assertion handler, in a
 * case where some of the stack frames require heap access to decode.
 * (This is the case on 64-bit CVM.) An MPS assertion might be
 * triggered by some innocent action like hitting a breakpoint in a
 * debugger inside a callback from the MPS (because the debugger will
 * try to decode the stack frames and so hit a barrier and re-enter
 * the MPS, which fails). Even decoding the stack trace might fail but
 * this is the best we can do. Here be dragons.
 * 
 *                     .     _///_,
 *                   .      / ` ' '>
 *                     )   o'  __/_'>
 *                    (   /  _/  )_\'>
 *                     ' "__/   /_/\_>
 *                         ____/_/_/_/
 *                        /,---, _/ /
 *                       ""  /_/_/_/
 *                          /_(_(_(_                 \
 *                         (   \_\_\\_               )\
 *                          \'__\_\_\_\__            ).\
 *                          //____|___\__)           )_/
 *                          |  _  \'___'_(           /'
 *                           \_ (-'\'___'_\      __,'_'
 *                           __) \  \\___(_   __/.__,'
 *                        ,((,-,__\  '", __\_/. __,'
 *                                     '"./_._._-'
 */

extern LONG WINAPI ProtSEHfilter(LPEXCEPTION_POINTERS info);

static void mps_unsafe_unprotect_visitor(void *base, size_t size, void *closure)
{
  DWORD old;
  UNUSED(closure);
  VirtualProtect((LPVOID)base, (SIZE_T)size, PAGE_EXECUTE_READWRITE, &old);
}

void mps_unsafe_unprotect(Arena arena) {
    mps_unsafe_arena_vm_pages(arena, mps_unsafe_unprotect_visitor, UNUSED_POINTER);
    if (mps_arena_count() == 1) {
	/* this was the only arena, so the MPS doesn't want to see memory faults any more */
        ProtTeardownUnsafe();
    }
}

/* Returns true if the MPS currently holds the lock for the given
 * arena.  That is, if we are "in the MPS". This should only be true
 * if we are in a callback from the MPS, for example a format scanning
 * method or an MPS assertion failure callback.
 */ 
int mps_is_arena_lock_held(Arena arena) {
  return LockIsHeld(ArenaGlobals(arena)->lock);
}


/**
 * Release all locks when going suicidal (gcFatalMode).
 */
void mps_unsafe_release_arena_locks(Arena arena) {
  while (LockIsHeld(ArenaGlobals(arena)->lock))
    LockReleaseRecursive(ArenaGlobals(arena)->lock);
}


/**
 * Enter fatal gc mode - survive for diagnostic purposes only before exit.
 */
void mps_enter_fatal_mode(Arena arena) {
    mps_unsafe_release_arena_locks(arena);
    //mps_arena_clamp(arena);
    mps_unsafe_unprotect(arena);
}

#endif


/* C. COPYRIGHT AND LICENSE
 *
 * Copyright (C) 2013 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.
 */