sysdeps/unix/sysv/linux/s390/s390-64/makecontext.c

   1 /* Copyright (C) 2001 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com).
   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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <libintl.h>
  21 #include <stdarg.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <ucontext.h>
  25
  26 /* This implementation can handle any ARGC value but only
  27    normal integer type parameters. Parameters of type float,
  28    double, complex and structure with sizes 0, 2, 4 or 8
  29    won't work.
  30    makecontext sets up a stack and the registers for the
  31    user context. The stack looks like this:
  32            size                         offset
  33     %r15 ->    +-----------------------+
  34              8 | back chain (zero)     |  0
  35              8 | reserved              |  8
  36            144 | save area for (*func) | 16
  37                +-----------------------+
  38              n | overflow parameters   | 160
  39                +-----------------------+
  40    The registers are set up like this:
  41      %r2-%r6: parameters 1 to 5
  42      %r7    : (*func) pointer
  43      %r8    : uc_link from ucontext structure
  44      %r9    : address of setcontext
  45      %r14   : return address to uc_link trampoline
  46      %r15   : stack pointer.
  47
  48    The trampoline looks like this:
  49      basr  %r14,%r7
  50      lgr   %r2,%r8
  51      br    %r9.  */
  52
  53 void
  54 __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
  55 {
  56   extern void __makecontext_ret (void);
  57   unsigned long *sp;
  58   va_list ap;
  59   int i;
  60
  61   sp = (unsigned long *) (((unsigned long) ucp->uc_stack.ss_sp
  62                            + ucp->uc_stack.ss_size) & -8L);
  63
  64   /* Set the return address to trampoline.  */
  65   ucp->uc_mcontext.gregs[14] = (long) __makecontext_ret;
  66
  67   /* Set register parameters.  */
  68   va_start (ap, argc);
  69   for (i = 0; (i < argc) && (i < 5); i++)
  70     ucp->uc_mcontext.gregs[2+i] = va_arg (ap, long);
  71
  72   /* The remaining arguments go to the overflow area.  */
  73   if (argc > 5) {
  74     sp -= argc - 5;
  75     for (i = 5; i < argc; i++)
  76       sp[i] = va_arg(ap, long);
  77   }
  78   va_end (ap);
  79
  80   /* Make room for the save area and set the backchain.  */
  81   sp -= 20;
  82   *sp = 0;
  83
  84   /* Pass (*func) to __start_context in %r7.  */
  85   ucp->uc_mcontext.gregs[7] = (long) func;
  86
  87   /* Pass ucp->uc_link to __start_context in %r8.  */
  88   ucp->uc_mcontext.gregs[8] = (long) ucp->uc_link;
  89
  90   /* Pass address of setcontext in %r9.  */
  91   ucp->uc_mcontext.gregs[9] = (long) &setcontext;
  92
  93   /* Set stack pointer.  */
  94   ucp->uc_mcontext.gregs[15] = (long) sp;
  95 }
  96
  97 asm(".text\n"
  98     ".type __makecontext_ret,@function\n"
  99     "__makecontext_ret:\n"
 100     "      basr  %r14,%r7\n"
 101     "      lgr   %r2,%r8\n"
 102     "      br    %r9\n"
 103     ".size __makecontext_ret, .-__makecontext_ret");
 104
 105 weak_alias (__makecontext, makecontext)