1  /* Create new context.  C-SKY version.
       2     Copyright (C) 2018-2023 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 <stdarg.h>
      20  #include <ucontext.h>
      21  
      22  /* Number of arguments that go in registers.  */
      23  #define NREG_ARGS  4
      24  
      25  /* Take a context previously prepared via getcontext() and set to
      26     call func() with the given int only args.  */
      27  void
      28  __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
      29  {
      30    extern void __startcontext (void);
      31    unsigned long *funcstack;
      32    va_list vl;
      33    unsigned long *regptr;
      34    unsigned int reg;
      35    int misaligned;
      36  
      37    /* Start at the top of stack.  */
      38    funcstack = (unsigned long *) (ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
      39  
      40    /* Ensure the stack stays eight byte aligned.  */
      41    misaligned = ((unsigned long) funcstack & 4) != 0;
      42  
      43    if ((argc > NREG_ARGS) && (argc & 1) != 0)
      44      misaligned = !misaligned;
      45  
      46    if (misaligned)
      47      funcstack -= 1;
      48  
      49    va_start (vl, argc);
      50  
      51    /* Reserve space for the on-stack arguments.  */
      52    if (argc > NREG_ARGS)
      53      funcstack -= (argc - NREG_ARGS);
      54  
      55    ucp->uc_mcontext.__gregs.__usp = (unsigned long) funcstack;
      56    ucp->uc_mcontext.__gregs.__pc = (unsigned long) func;
      57  
      58    /* Exit to startcontext() with the next context in R9.  */
      59    ucp->uc_mcontext.__gregs.__regs[5] = (unsigned long) ucp->uc_link;
      60    ucp->uc_mcontext.__gregs.__lr = (unsigned long) __startcontext;
      61  
      62    /* The first four arguments go into registers.  */
      63    regptr = &(ucp->uc_mcontext.__gregs.__a0);
      64  
      65    for (reg = 0; (reg < argc) && (reg < NREG_ARGS); reg++)
      66      *regptr++ = va_arg (vl, unsigned long);
      67  
      68    /* And the remainder on the stack.  */
      69    for (; reg < argc; reg++)
      70      *funcstack++ = va_arg (vl, unsigned long);
      71  
      72    va_end (vl);
      73  }
      74  weak_alias (__makecontext, makecontext)