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

   1 /* Create new context.
   2    Copyright (C) 2008-2024 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 <libintl.h>
  20 #include <stdarg.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <sysdep.h>
  24 #include <ucontext.h>
  25
  26 /* POSIX only supports integer arguments.  */
  27
  28 /* Stack must be 64-byte aligned at all times.  */
  29 #define STACK_ALIGN 64
  30 /* Size of frame marker in unsigned long words.  */
  31 #define FRAME_SIZE_UL 8
  32 /* Size of frame marker in bytes.  */
  33 #define FRAME_SIZE_BYTES (8 * sizeof (unsigned long))
  34 /* Size of X arguments in bytes.  */
  35 #define ARGS(x) (x * sizeof (unsigned long))
  36
  37 void
  38 __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
  39 {
  40   unsigned long *sp, *osp;
  41   va_list ap;
  42   int i;
  43
  44   /* Create a 64-byte aligned frame to store args. Use ss_sp if
  45      it is available, otherwise be robust and use the currently
  46      saved stack pointer.  */
  47   if (ucp->uc_stack.ss_sp && ucp->uc_stack.ss_size)
  48     osp = (unsigned long *)ucp->uc_stack.ss_sp;
  49   else
  50     osp = (unsigned long *)ucp->uc_mcontext.sc_gr[30];
  51
  52   sp = (unsigned long *)((((unsigned long) osp)
  53                            + FRAME_SIZE_BYTES + ARGS(argc) + STACK_ALIGN)
  54                          & ~(STACK_ALIGN - 1));
  55
  56   /* Use new frame.  */
  57   ucp->uc_mcontext.sc_gr[30] = ((unsigned long) sp);
  58
  59   /* Finish frame setup.  */
  60   if (ucp->uc_link)
  61     {
  62       /* Returning to the next context and next frame.  */
  63       sp[-4 / sizeof (unsigned long)] = ucp->uc_link->uc_mcontext.sc_gr[30];
  64       sp[-20 / sizeof (unsigned long)] = ucp->uc_link->uc_mcontext.sc_gr[2];
  65     }
  66   else
  67     {
  68       /* This is the main context. No frame marker, and no return address.  */
  69       sp[-4 / sizeof (unsigned long)] = 0x0;
  70       sp[-20 / sizeof (unsigned long)] = 0x0;
  71     }
  72
  73   /* Store address to jump to.  */
  74   ucp->uc_mcontext.sc_gr[2] = (unsigned long) func;
  75
  76   /* Process arguments.  */
  77   va_start (ap, argc);
  78   for (i = 0; i < argc; ++i)
  79     {
  80       if (i < 4)
  81         {
  82           ucp->uc_mcontext.sc_gr[26-i] = va_arg (ap, int);
  83           continue;
  84         }
  85
  86       if ((i < 8) && (sizeof (unsigned long) == 8))
  87         {
  88           /* 64bit: r19-r22 are arg7-arg4.  */
  89           ucp->uc_mcontext.sc_gr[22+4-i] = va_arg (ap, int);
  90           continue;
  91         }
  92
  93       /* All other arguments go on the stack.  */
  94       sp[-1 * (FRAME_SIZE_UL + 1 + i)] = va_arg (ap, int);
  95     }
  96   va_end (ap);
  97 }
  98 weak_alias(__makecontext, makecontext)