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glibc  2.9
fe_nomask.c
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00001 /* Procedure definition for FE_NOMASK_ENV for Linux/ppc.
00002    Copyright (C) 2000, 2006, 2008 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
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 <fenv_libc.h>
00021 #include <errno.h>
00022 #include <signal.h>
00023 #include <unistd.h>
00024 #include <sysdep.h>
00025 #include <sys/prctl.h>
00026 #include <kernel-features.h>
00027 
00028 #if __ASSUME_NEW_PRCTL_SYSCALL == 0
00029 /* This is rather fiddly under Linux.  We don't have direct access,
00030    and there is no system call, but we can change the bits
00031    in a signal handler's context...  */
00032 
00033 static struct sigaction oact;
00034 
00035 static void
00036 fe_nomask_handler (int signum, struct sigcontext *sc)
00037 {
00038   sc->regs->msr |= 0x900ul;  /* FE0 | FE1 */
00039   sigaction (SIGUSR1, &oact, NULL);
00040 }
00041 #endif
00042 
00043 const fenv_t *
00044 __fe_nomask_env (void)
00045 {
00046 #if __ASSUME_NEW_PRCTL_SYSCALL == 0
00047 # if defined PR_SET_FPEXC && defined PR_FP_EXC_PRECISE
00048   int result = INLINE_SYSCALL (prctl, 2, PR_SET_FPEXC, PR_FP_EXC_PRECISE);
00049 
00050   if (result == -1 && errno == EINVAL)
00051 # endif
00052     {
00053       struct sigaction act;
00054 
00055       act.sa_handler = (sighandler_t) fe_nomask_handler;
00056       sigemptyset (&act.sa_mask);
00057       act.sa_flags = 0;
00058 
00059       sigaction (SIGUSR1, &act, &oact);
00060       raise (SIGUSR1);
00061     }
00062 #else
00063   INTERNAL_SYSCALL_DECL (err);
00064   INTERNAL_SYSCALL (prctl, err, 2, PR_SET_FPEXC, PR_FP_EXC_PRECISE);
00065 #endif
00066 
00067   return FE_ENABLED_ENV;
00068 }
00069 libm_hidden_def (__fe_nomask_env)