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glibc  2.9
swapcontext.c
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00001 /* Copyright (C) 2001 Free Software Foundation, Inc.
00002    This file is part of the GNU C Library.
00003    Contributed by Jakub Jelinek <jakub@redhat.com>.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #include <ucontext.h>
00021 
00022 extern int __getcontext (ucontext_t *ucp);
00023 extern int __setcontext (const ucontext_t *ucp, int restoremask);
00024 
00025 int
00026 __swapcontext (ucontext_t *oucp, const ucontext_t *ucp)
00027 {
00028   extern void __swapcontext_ret (void);
00029   /* Save the current machine context to oucp.  */
00030   __getcontext (oucp);
00031   /* Modify oucp to skip the __setcontext call on reactivation.  */
00032   oucp->uc_mcontext.mc_gregs[MC_PC] = (long) __swapcontext_ret;
00033   oucp->uc_mcontext.mc_gregs[MC_NPC] = ((long) __swapcontext_ret) + 4;
00034   /* Restore the machine context in ucp.  */
00035   __setcontext (ucp, 1);
00036   return 0;
00037 }
00038 
00039 asm ("                                           \n\
00040        .text                                     \n\
00041        .type  __swapcontext_ret, #function              \n\
00042 __swapcontext_ret:                               \n\
00043        return %i7 + 8                                   \n\
00044         clr   %o0                                \n\
00045        .size  __swapcontext_ret, .-__swapcontext_ret    \n\
00046      ");
00047 
00048 weak_alias (__swapcontext, swapcontext)