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/* ssixi6.c: UNIX/x64 STACK SCANNING
 *
 * $Id: //info.ravenbrook.com/project/mps/custom/cet/branch/2016-09-13/job004020/code/ssixi6.c#1 $
 * Copyright (c) 2001-2014 Ravenbrook Limited.  See end of file for license.
 *
 *  This scans the stack and fixes the registers which may contain
 *  roots.  See <design/thread-manager/>
 *
 *  This code was branched from ssixi3.c (32-bit Intel) initially for the
 *  port to XCI6LL (Mac OS X on x86_64 with Clang).
 *
 *  This code is common to more than one Unix implementation on
 *  Intel hardware (but is not portable Unix code).  According to Wikipedia,
 *  all the non-Windows platforms use the System V AMD64 ABI.  See
 *  .sources.callees.saves.
 *
 * SOURCES
 *
 * .sources.callees.saves:
 *  "Registers %rbp, %rbx and %r12 through %r15 "belong" to the calling
 *   function and the called function is required to preserve their values.
 *   In other words, a called function must preserve these registers’ values
 *   for its caller." -- System V AMD64 ABI
 *  <http://x86-64.org/documentation/abi.pdf>
 *
 * ASSUMPTIONS
 *
 * .assume.align: The stack pointer is assumed to be aligned on a word
 * boundary.
 *
 * .assume.asm.stack: The compiler must not do wacky things with the
 * stack pointer around a call since we need to ensure that the
 * callee-save regs are visible during TraceScanArea.
 *
 * .assume.asm.order: The volatile modifier should prevent movement
 * of code, which might break .assume.asm.stack.
 *
 */


#include "mpm.h"

SRCID(ssixi6, "$Id: //info.ravenbrook.com/project/mps/custom/cet/branch/2016-09-13/job004020/code/ssixi6.c#1 $");


/* .assume.asm.order */
#define ASMV(x) __asm__ volatile (x)


Res StackScan(ScanState ss, Word *stackCold,
              mps_area_scan_t scan_area,
              void *closure)
{
  Word calleeSaveRegs[6];
  
  /* .assume.asm.stack */
  /* Store the callee save registers on the stack so they get scanned
   * as they may contain roots.
   */
  ASMV("mov %%rbp, %0" : "=m" (calleeSaveRegs[0]));
  ASMV("mov %%rbx, %0" : "=m" (calleeSaveRegs[1]));
  ASMV("mov %%r12, %0" : "=m" (calleeSaveRegs[2]));
  ASMV("mov %%r13, %0" : "=m" (calleeSaveRegs[3]));
  ASMV("mov %%r14, %0" : "=m" (calleeSaveRegs[4]));
  ASMV("mov %%r15, %0" : "=m" (calleeSaveRegs[5]));
  
  return StackScanInner(ss, stackCold, calleeSaveRegs, NELEMS(calleeSaveRegs),
                        scan_area, closure);
}


/* 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.
 */