1  /* Copyright (C) 2012-2023 Free Software Foundation, Inc.
       2     This file is part of the GNU C Library.
       3  
       4     The GNU C Library is free software; you can redistribute it and/or
       5     modify it under the terms of the GNU Lesser General Public
       6     License as published by the Free Software Foundation; either
       7     version 2.1 of the License, or (at your option) any later version.
       8  
       9     The GNU C Library is distributed in the hope that it will be useful,
      10     but WITHOUT ANY WARRANTY; without even the implied warranty of
      11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      12     Lesser General Public License for more details.
      13  
      14     You should have received a copy of the GNU Lesser General Public
      15     License along with the GNU C Library; if not, see
      16     <https://www.gnu.org/licenses/>.  */
      17  
      18  #include <stdarg.h>
      19  #include <ucontext.h>
      20  
      21  /* Number of arguments that go in registers.  */
      22  #define NREG_ARGS  4
      23  
      24  /* Take a context previously prepared via getcontext() and set to
      25     call func() with the given int only args.  */
      26  void
      27  __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
      28  {
      29    extern void __startcontext (void);
      30    unsigned long *funcstack;
      31    va_list vl;
      32    unsigned long *regptr;
      33    unsigned int reg;
      34    int misaligned;
      35  
      36    /* Start at the top of stack.  */
      37    funcstack = (unsigned long *) (ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
      38  
      39    /* Ensure the stack stays eight byte aligned.  */
      40    misaligned = ((unsigned long) funcstack & 4) != 0;
      41  
      42    if ((argc > NREG_ARGS) && (argc & 1) != 0)
      43      misaligned = !misaligned;
      44  
      45    if (misaligned)
      46      funcstack -= 1;
      47  
      48    va_start (vl, argc);
      49  
      50    /* Reserve space for the on-stack arguments.  */
      51    if (argc > NREG_ARGS)
      52      funcstack -= (argc - NREG_ARGS);
      53  
      54    ucp->uc_mcontext.arm_sp = (unsigned long) funcstack;
      55    ucp->uc_mcontext.arm_pc = (unsigned long) func;
      56  
      57    /* Exit to startcontext() with the next context in R4 */
      58    ucp->uc_mcontext.arm_r4 = (unsigned long) ucp->uc_link;
      59    ucp->uc_mcontext.arm_lr = (unsigned long) __startcontext;
      60  
      61    /* The first four arguments go into registers.  */
      62    regptr = &(ucp->uc_mcontext.arm_r0);
      63  
      64    for (reg = 0; (reg < argc) && (reg < NREG_ARGS); reg++)
      65      *regptr++ = va_arg (vl, unsigned long);
      66  
      67    /* And the remainder on the stack.  */
      68    for (; reg < argc; reg++)
      69      *funcstack++ = va_arg (vl, unsigned long);
      70  
      71    va_end (vl);
      72  }
      73  weak_alias (__makecontext, makecontext)