sysdeps/unix/sysv/linux/hppa/makecontext.c

   1 /* Create new context.
   2    Copyright (C) 2008-2020 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Helge Deller <deller@gmx.de>, 2008.
   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 <libintl.h>
  21 #include <stdarg.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <sysdep.h>
  25 #include <ucontext.h>
  26
  27 /* POSIX only supports integer arguments.  */
  28
  29 /* Stack must be 64-byte aligned at all times.  */
  30 #define STACK_ALIGN 64
  31 /* Size of frame marker in unsigned long words.  */
  32 #define FRAME_SIZE_UL 8
  33 /* Size of frame marker in bytes.  */
  34 #define FRAME_SIZE_BYTES (8 * sizeof (unsigned long))
  35 /* Size of X arguments in bytes.  */
  36 #define ARGS(x) (x * sizeof (unsigned long))
  37
  38 void
  39 __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
  40 {
  41   unsigned long *sp, *osp;
  42   va_list ap;
  43   int i;
  44
  45   /* Create a 64-byte aligned frame to store args. Use ss_sp if
  46      it is available, otherwise be robust and use the currently
  47      saved stack pointer.  */
  48   if (ucp->uc_stack.ss_sp && ucp->uc_stack.ss_size)
  49     osp = (unsigned long *)ucp->uc_stack.ss_sp;
  50   else
  51     osp = (unsigned long *)ucp->uc_mcontext.sc_gr[30];
  52
  53   sp = (unsigned long *)((((unsigned long) osp)
  54                            + FRAME_SIZE_BYTES + ARGS(argc) + STACK_ALIGN)
  55                          & ~(STACK_ALIGN - 1));
  56
  57   /* Use new frame.  */
  58   ucp->uc_mcontext.sc_gr[30] = ((unsigned long) sp);
  59
  60   /* Finish frame setup.  */
  61   if (ucp->uc_link)
  62     {
  63       /* Returning to the next context and next frame.  */
  64       sp[-4 / sizeof (unsigned long)] = ucp->uc_link->uc_mcontext.sc_gr[30];
  65       sp[-20 / sizeof (unsigned long)] = ucp->uc_link->uc_mcontext.sc_gr[2];
  66     }
  67   else
  68     {
  69       /* This is the main context. No frame marker, and no return address.  */
  70       sp[-4 / sizeof (unsigned long)] = 0x0;
  71       sp[-20 / sizeof (unsigned long)] = 0x0;
  72     }
  73
  74   /* Store address to jump to.  */
  75   ucp->uc_mcontext.sc_gr[2] = (unsigned long) func;
  76
  77   /* Process arguments.  */
  78   va_start (ap, argc);
  79   for (i = 0; i < argc; ++i)
  80     {
  81       if (i < 4)
  82         {
  83           ucp->uc_mcontext.sc_gr[26-i] = va_arg (ap, int);
  84           continue;
  85         }
  86
  87       if ((i < 8) && (sizeof (unsigned long) == 8))
  88         {
  89           /* 64bit: r19-r22 are arg7-arg4.  */
  90           ucp->uc_mcontext.sc_gr[22+4-i] = va_arg (ap, int);
  91           continue;
  92         }
  93
  94       /* All other arguments go on the stack.  */
  95       sp[-1 * (FRAME_SIZE_UL + 1 + i)] = va_arg (ap, int);
  96     }
  97   va_end (ap);
  98 }
  99 weak_alias(__makecontext, makecontext)