sysdeps/unix/sysv/linux/i386/sigaction.c

   1 /* POSIX.1 `sigaction' call for Linux/i386.
   2    Copyright (C) 1991,1995-2000,2002-2005,2006 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <sysdep.h>
  21 #include <errno.h>
  22 #include <stddef.h>
  23 #include <signal.h>
  24 #include <string.h>
  25
  26 #include <sysdep.h>
  27 #include <sys/syscall.h>
  28 #include <ldsodefs.h>
  29
  30 #include <kernel-features.h>
  31
  32 /* The difference here is that the sigaction structure used in the
  33    kernel is not the same as we use in the libc.  Therefore we must
  34    translate it here.  */
  35 #include <kernel_sigaction.h>
  36
  37 /* We do not globally define the SA_RESTORER flag so do it here.  */
  38 #define SA_RESTORER 0x04000000
  39
  40
  41 #if __ASSUME_REALTIME_SIGNALS == 0
  42 /* The variable is shared between all wrappers around signal handling
  43    functions which have RT equivalents.  */
  44 int __libc_missing_rt_sigs;
  45 #endif
  46
  47 /* Using the hidden attribute here does not change the code but it
  48    helps to avoid warnings.  */
  49 #ifdef __NR_rt_sigaction
  50 extern void restore_rt (void) asm ("__restore_rt") attribute_hidden;
  51 #endif
  52 extern void restore (void) asm ("__restore") attribute_hidden;
  53
  54
  55 /* If ACT is not NULL, change the action for SIG to *ACT.
  56    If OACT is not NULL, put the old action for SIG in *OACT.  */
  57 int
  58 __libc_sigaction (int sig, const struct sigaction *act, struct sigaction *oact)
  59 {
  60 #if __ASSUME_REALTIME_SIGNALS == 0
  61   struct old_kernel_sigaction k_newact, k_oldact;
  62 #endif
  63   int result;
  64
  65 #ifdef __NR_rt_sigaction
  66
  67   /* First try the RT signals.  */
  68 # if __ASSUME_REALTIME_SIGNALS == 0
  69   if (!__libc_missing_rt_sigs)
  70 # endif
  71     {
  72       struct kernel_sigaction kact, koact;
  73 # if __ASSUME_REALTIME_SIGNALS == 0
  74       int saved_errno = errno;
  75 # endif
  76
  77       if (act)
  78         {
  79           kact.k_sa_handler = act->sa_handler;
  80           kact.sa_flags = act->sa_flags;
  81           memcpy (&kact.sa_mask, &act->sa_mask, sizeof (sigset_t));
  82
  83           if (GLRO(dl_sysinfo_dso) == NULL)
  84             {
  85               kact.sa_flags |= SA_RESTORER;
  86
  87               kact.sa_restorer = ((act->sa_flags & SA_SIGINFO)
  88                                   ? &restore_rt : &restore);
  89             }
  90         }
  91
  92       /* XXX The size argument hopefully will have to be changed to the
  93          real size of the user-level sigset_t.  */
  94       result = INLINE_SYSCALL (rt_sigaction, 4,
  95                                sig, act ? __ptrvalue (&kact) : NULL,
  96                                oact ? __ptrvalue (&koact) : NULL, _NSIG / 8);
  97
  98 # if __ASSUME_REALTIME_SIGNALS == 0
  99       if (result >= 0 || errno != ENOSYS)
 100 # endif
 101         {
 102           if (oact && result >= 0)
 103             {
 104               oact->sa_handler = koact.k_sa_handler;
 105               memcpy (&oact->sa_mask, &koact.sa_mask, sizeof (sigset_t));
 106               oact->sa_flags = koact.sa_flags;
 107               oact->sa_restorer = koact.sa_restorer;
 108             }
 109           return result;
 110         }
 111
 112 # if __ASSUME_REALTIME_SIGNALS == 0
 113       __set_errno (saved_errno);
 114       __libc_missing_rt_sigs = 1;
 115 # endif
 116     }
 117 #endif
 118
 119 #if __ASSUME_REALTIME_SIGNALS == 0
 120   if (act)
 121     {
 122       k_newact.k_sa_handler = act->sa_handler;
 123       k_newact.sa_mask = act->sa_mask.__val[0];
 124       k_newact.sa_flags = act->sa_flags | SA_RESTORER;
 125
 126       k_newact.sa_restorer = &restore;
 127     }
 128
 129   result = INLINE_SYSCALL (sigaction, 3, sig,
 130                            act ? __ptrvalue (&k_newact) : 0,
 131                            oact ? __ptrvalue (&k_oldact) : 0);
 132
 133   if (result < 0)
 134     return -1;
 135
 136   if (oact)
 137     {
 138       oact->sa_handler = k_oldact.k_sa_handler;
 139       oact->sa_mask.__val[0] = k_oldact.sa_mask;
 140       oact->sa_flags = k_oldact.sa_flags;
 141       oact->sa_restorer = k_oldact.sa_restorer;
 142     }
 143
 144   return 0;
 145 #endif
 146 }
 147 libc_hidden_def (__libc_sigaction)
 148
 149 #ifdef WRAPPER_INCLUDE
 150 # include WRAPPER_INCLUDE
 151 #endif
 152
 153 #ifndef LIBC_SIGACTION
 154 weak_alias (__libc_sigaction, __sigaction)
 155 libc_hidden_weak (__sigaction)
 156 weak_alias (__libc_sigaction, sigaction)
 157 #endif
 158
 159 /* NOTE: Please think twice before making any changes to the bits of
 160    code below.  GDB needs some intimate knowledge about it to
 161    recognize them as signal trampolines, and make backtraces through
 162    signal handlers work right.  Important are both the names
 163    (__restore and __restore_rt) and the exact instruction sequence.
 164    If you ever feel the need to make any changes, please notify the
 165    appropriate GDB maintainer.  */
 166
 167 #define RESTORE(name, syscall) RESTORE2 (name, syscall)
 168 #define RESTORE2(name, syscall) \
 169 asm                                             \
 170   (                                             \
 171    ".text\n"                                    \
 172    "    .align 16\n"                            \
 173    "__" #name ":\n"                             \
 174    "    movl $" #syscall ", %eax\n"             \
 175    "    int  $0x80"                             \
 176    );
 177
 178 #ifdef __NR_rt_sigaction
 179 /* The return code for realtime-signals.  */
 180 RESTORE (restore_rt, __NR_rt_sigreturn)
 181 #endif
 182
 183 /* For the boring old signals.  */
 184 #undef RESTORE2
 185 #define RESTORE2(name, syscall) \
 186 asm                                             \
 187   (                                             \
 188    ".text\n"                                    \
 189    "    .align 8\n"                             \
 190    "__" #name ":\n"                             \
 191    "    popl %eax\n"                            \
 192    "    movl $" #syscall ", %eax\n"             \
 193    "    int  $0x80"                             \
 194    );
 195
 196 RESTORE (restore, __NR_sigreturn)