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

   1 /* POSIX.1 `sigaction' call for Linux/i386.
   2    Copyright (C) 1991,1995-2000,2002-2004,2005 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 #if defined HAVE_HIDDEN && defined HAVE_VISIBILITY_ATTRIBUTE \
  50     && !defined HAVE_BROKEN_VISIBILITY_ATTRIBUTE
  51 # ifdef __NR_rt_sigaction
  52 extern void restore_rt (void) asm ("__restore_rt") attribute_hidden;
  53 # endif
  54 extern void restore (void) asm ("__restore") attribute_hidden;
  55 #else
  56 # ifdef __NR_rt_sigaction
  57 static void restore_rt (void) asm ("__restore_rt");
  58 # endif
  59 static void restore (void) asm ("__restore");
  60 #endif
  61
  62
  63 /* If ACT is not NULL, change the action for SIG to *ACT.
  64    If OACT is not NULL, put the old action for SIG in *OACT.  */
  65 int
  66 __libc_sigaction (int sig, const struct sigaction *act, struct sigaction *oact)
  67 {
  68 #if __ASSUME_REALTIME_SIGNALS == 0
  69   struct old_kernel_sigaction k_newact, k_oldact;
  70 #endif
  71   int result;
  72
  73 #ifdef __NR_rt_sigaction
  74
  75   /* First try the RT signals.  */
  76 # if __ASSUME_REALTIME_SIGNALS == 0
  77   if (!__libc_missing_rt_sigs)
  78 # endif
  79     {
  80       struct kernel_sigaction kact, koact;
  81 # if __ASSUME_REALTIME_SIGNALS == 0
  82       int saved_errno = errno;
  83 # endif
  84
  85       if (act)
  86         {
  87           kact.k_sa_handler = act->sa_handler;
  88           kact.sa_flags = act->sa_flags;
  89           memcpy (&kact.sa_mask, &act->sa_mask, sizeof (sigset_t));
  90
  91           if (GLRO(dl_sysinfo_dso) == NULL)
  92             {
  93               kact.sa_flags |= SA_RESTORER;
  94
  95               kact.sa_restorer = ((act->sa_flags & SA_SIGINFO)
  96                                   ? &restore_rt : &restore);
  97             }
  98         }
  99
 100       /* XXX The size argument hopefully will have to be changed to the
 101          real size of the user-level sigset_t.  */
 102       result = INLINE_SYSCALL (rt_sigaction, 4,
 103                                sig, act ? __ptrvalue (&kact) : NULL,
 104                                oact ? __ptrvalue (&koact) : NULL, _NSIG / 8);
 105
 106 # if __ASSUME_REALTIME_SIGNALS == 0
 107       if (result >= 0 || errno != ENOSYS)
 108 # endif
 109         {
 110           if (oact && result >= 0)
 111             {
 112               oact->sa_handler = koact.k_sa_handler;
 113               memcpy (&oact->sa_mask, &koact.sa_mask, sizeof (sigset_t));
 114               oact->sa_flags = koact.sa_flags;
 115               oact->sa_restorer = koact.sa_restorer;
 116             }
 117           return result;
 118         }
 119
 120 # if __ASSUME_REALTIME_SIGNALS == 0
 121       __set_errno (saved_errno);
 122       __libc_missing_rt_sigs = 1;
 123 # endif
 124     }
 125 #endif
 126
 127 #if __ASSUME_REALTIME_SIGNALS == 0
 128   if (act)
 129     {
 130       k_newact.k_sa_handler = act->sa_handler;
 131       k_newact.sa_mask = act->sa_mask.__val[0];
 132       k_newact.sa_flags = act->sa_flags | SA_RESTORER;
 133
 134       k_newact.sa_restorer = &restore;
 135     }
 136
 137   result = INLINE_SYSCALL (sigaction, 3, sig,
 138                            act ? __ptrvalue (&k_newact) : 0,
 139                            oact ? __ptrvalue (&k_oldact) : 0);
 140
 141   if (result < 0)
 142     return -1;
 143
 144   if (oact)
 145     {
 146       oact->sa_handler = k_oldact.k_sa_handler;
 147       oact->sa_mask.__val[0] = k_oldact.sa_mask;
 148       oact->sa_flags = k_oldact.sa_flags;
 149       oact->sa_restorer = k_oldact.sa_restorer;
 150     }
 151
 152   return 0;
 153 #endif
 154 }
 155 libc_hidden_def (__libc_sigaction)
 156
 157 #ifdef WRAPPER_INCLUDE
 158 # include WRAPPER_INCLUDE
 159 #endif
 160
 161 #ifndef LIBC_SIGACTION
 162 weak_alias (__libc_sigaction, __sigaction)
 163 libc_hidden_weak (__sigaction)
 164 weak_alias (__libc_sigaction, sigaction)
 165 #endif
 166
 167 /* NOTE: Please think twice before making any changes to the bits of
 168    code below.  GDB needs some intimate knowledge about it to
 169    recognize them as signal trampolines, and make backtraces through
 170    signal handlers work right.  Important are both the names
 171    (__restore and __restore_rt) and the exact instruction sequence.
 172    If you ever feel the need to make any changes, please notify the
 173    appropriate GDB maintainer.  */
 174
 175 #define RESTORE(name, syscall) RESTORE2 (name, syscall)
 176 #define RESTORE2(name, syscall) \
 177 asm                                             \
 178   (                                             \
 179    ".text\n"                                    \
 180    "    .align 16\n"                            \
 181    "__" #name ":\n"                             \
 182    "    movl $" #syscall ", %eax\n"             \
 183    "    int  $0x80"                             \
 184    );
 185
 186 #ifdef __NR_rt_sigaction
 187 /* The return code for realtime-signals.  */
 188 RESTORE (restore_rt, __NR_rt_sigreturn)
 189 #endif
 190
 191 /* For the boring old signals.  */
 192 #undef RESTORE2
 193 #define RESTORE2(name, syscall) \
 194 asm                                             \
 195   (                                             \
 196    ".text\n"                                    \
 197    "    .align 8\n"                             \
 198    "__" #name ":\n"                             \
 199    "    popl %eax\n"                            \
 200    "    movl $" #syscall ", %eax\n"             \
 201    "    int  $0x80"                             \
 202    );
 203
 204 RESTORE (restore, __NR_sigreturn)