1  /* Create new context.  OpenRISC version.
       2     Copyright (C) 2022-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #include <sysdep.h>
      20  #include <stdarg.h>
      21  #include <stdint.h>
      22  #include <ucontext.h>
      23  
      24  /* makecontext sets up a stack and the registers for the
      25     user context.  The stack looks like this:
      26  
      27  		+-----------------------+
      28  		| padding as required   |
      29  		+-----------------------+
      30      sp ->       | parameters 7 to n     |
      31  		+-----------------------+
      32  
      33     The registers are set up like this:
      34       r3-r8  : parameters 1 to 6
      35       r14    : uc_link
      36       r1     : stack pointer
      37       r2     : frame pointer, set to NULL
      38  */
      39  void
      40  __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
      41  {
      42    extern void __startcontext (void);
      43    unsigned long int *sp;
      44    va_list ap;
      45    int i;
      46  
      47    sp = (unsigned long int *)
      48      ((uintptr_t) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
      49  
      50    /* Allocate stack arguments.  */
      51    sp -= argc < 6 ? 0 : argc - 6;
      52  
      53    /* Keep the stack aligned.  */
      54    sp = (unsigned long int *) (((uintptr_t) sp) & -4L);
      55  
      56    /* Keep uc_link in r14.  */
      57    ucp->uc_mcontext.__gprs[14] = (uintptr_t) ucp->uc_link;
      58    /* Return address points to function __startcontext.  */
      59    ucp->uc_mcontext.__gprs[9] = (uintptr_t) &__startcontext;
      60    /* Frame pointer is null.  */
      61    ucp->uc_mcontext.__gprs[2] = (uintptr_t) 0;
      62    /* Restart in user-space starting at 'func'.  */
      63    ucp->uc_mcontext.__gprs[11] = (uintptr_t) func;
      64    /* Set stack pointer.  */
      65    ucp->uc_mcontext.__gprs[1] = (uintptr_t) sp;
      66  
      67    va_start (ap, argc);
      68    for (i = 0; i < argc; ++i)
      69      if (i < 6)
      70        ucp->uc_mcontext.__gprs[i + 3] = va_arg (ap, unsigned long int);
      71      else
      72        sp[i - 6] = va_arg (ap, unsigned long int);
      73  
      74    va_end (ap);
      75  }
      76  
      77  weak_alias (__makecontext, makecontext)