/* Create new context.

   Copyright (C) 2002-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library 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

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <sysdep.h>

#include <stdarg.h>

#include <stdint.h>

#include <ucontext.h>

/* makecontext sets up a stack and the registers for the

   user context.  The stack looks like this:

               +-----------------------+

	       | padding as required   |

               +-----------------------+

    sp ->      | parameter 7-n         |

               +-----------------------+

   The registers are set up like this:

     %x0 .. %x7: parameter 1 to 8

     %x19   : uc_link

     %sp    : stack pointer.

*/

void

__makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)

{

  extern void __startcontext (void);

  uint64_t *sp;

  va_list ap;

  int i;

  sp = (uint64_t *)

    ((uintptr_t) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);

  /* Allocate stack arguments.  */

  sp -= argc < 8 ? 0 : argc - 8;

  /* Keep the stack aligned.  */

  sp = (uint64_t *) (((uintptr_t) sp) & -16L);

  ucp->uc_mcontext.regs[19] = (uintptr_t) ucp->uc_link;

  ucp->uc_mcontext.sp = (uintptr_t) sp;

  ucp->uc_mcontext.pc = (uintptr_t) func;

  ucp->uc_mcontext.regs[29] = (uintptr_t) 0;

  ucp->uc_mcontext.regs[30] = (uintptr_t) &__startcontext;

  va_start (ap, argc);

  for (i = 0; i < argc; ++i)

    if (i < 8)

      ucp->uc_mcontext.regs[i] = va_arg (ap, uint64_t);

    else

      sp[i - 8] = va_arg (ap, uint64_t);

  va_end (ap);

}

weak_alias (__makecontext, makecontext)