1  /* Create new context.
       2     Copyright (C) 2022-2023 Free Software Foundation, Inc.
       3  
       4     This file is part of the GNU C Library.
       5  
       6     The GNU C Library is free software; you can redistribute it and/or
       7     modify it under the terms of the GNU Lesser General Public
       8     License as published by the Free Software Foundation; either
       9     version 2.1 of the License, or (at your option) any later version.
      10  
      11     The GNU C Library is distributed in the hope that it will be useful,
      12     but WITHOUT ANY WARRANTY; without even the implied warranty of
      13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      14     Lesser General Public License for more details.
      15  
      16     You should have received a copy of the GNU Lesser General Public
      17     License along with the GNU C Library.  If not, see
      18     <https://www.gnu.org/licenses/>.  */
      19  
      20  #include <sysdep.h>
      21  #include <sys/asm.h>
      22  #include <sys/ucontext.h>
      23  #include <stdarg.h>
      24  #include <assert.h>
      25  
      26  void
      27  __makecontext (ucontext_t *ucp, void (*func) (void), int argc, long int a0,
      28  	       long int a1, long int a2, long int a3, long int a4, ...)
      29  {
      30    extern void __start_context (void) attribute_hidden;
      31    unsigned long int *sp;
      32  
      33    _Static_assert(LARCH_REG_NARGS == 8,
      34  		 "__makecontext assumes 8 argument registers");
      35  
      36    /* Set up the stack.  */
      37    sp = (unsigned long int *)
      38         (((uintptr_t) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size) & ALMASK);
      39  
      40    /* Set up the register context.
      41       ra = s0 = 0, terminating the stack for backtracing purposes.
      42       s1 = the function we must call.
      43       s2 = the subsequent context to run.  */
      44    ucp->uc_mcontext.__gregs[LARCH_REG_RA] = (uintptr_t) 0;
      45    ucp->uc_mcontext.__gregs[LARCH_REG_S0] = (uintptr_t) 0;
      46    ucp->uc_mcontext.__gregs[LARCH_REG_S1] = (uintptr_t) func;
      47    ucp->uc_mcontext.__gregs[LARCH_REG_S2] = (uintptr_t) ucp->uc_link;
      48    ucp->uc_mcontext.__gregs[LARCH_REG_SP] = (uintptr_t) sp;
      49    ucp->uc_mcontext.__pc = (uintptr_t) &__start_context;
      50  
      51    /* Put args in a0-a7, then put any remaining args on the stack.  */
      52    ucp->uc_mcontext.__gregs[LARCH_REG_A0 + 0] = (uintptr_t) a0;
      53    ucp->uc_mcontext.__gregs[LARCH_REG_A0 + 1] = (uintptr_t) a1;
      54    ucp->uc_mcontext.__gregs[LARCH_REG_A0 + 2] = (uintptr_t) a2;
      55    ucp->uc_mcontext.__gregs[LARCH_REG_A0 + 3] = (uintptr_t) a3;
      56    ucp->uc_mcontext.__gregs[LARCH_REG_A0 + 4] = (uintptr_t) a4;
      57  
      58    if (__glibc_unlikely (argc > 5))
      59      {
      60        va_list vl;
      61        va_start (vl, a4);
      62  
      63        long int reg_args = argc < LARCH_REG_NARGS ? argc : LARCH_REG_NARGS;
      64        for (long int i = 5; i < reg_args; i++)
      65  	ucp->uc_mcontext.__gregs[LARCH_REG_A0 + i] = va_arg (vl, unsigned long int);
      66  
      67        long int stack_args = argc - reg_args;
      68        if (stack_args > 0)
      69  	{
      70  	  sp = (unsigned long int *)
      71  	       (((uintptr_t) sp - stack_args * sizeof (long int)) & ALMASK);
      72  	  ucp->uc_mcontext.__gregs[LARCH_REG_SP] = (uintptr_t) sp;
      73  	  for (long int i = 0; i < stack_args; i++)
      74  	    sp[i] = va_arg (vl, unsigned long int);
      75  	}
      76  
      77        va_end (vl);
      78      }
      79  }
      80  
      81  weak_alias (__makecontext, makecontext)