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

   1 /* POSIX.1 `sigaction' call for Linux/i386.
   2    Copyright (C) 1991, 95, 96, 97, 98, 99, 2000 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
  29 #include <kernel-features.h>
  30
  31 /* The difference here is that the sigaction structure used in the
  32    kernel is not the same as we use in the libc.  Therefore we must
  33    translate it here.  */
  34 #include <kernel_sigaction.h>
  35
  36 /* We do not globally define the SA_RESTORER flag so do it here.  */
  37 #define SA_RESTORER 0x04000000
  38
  39
  40 extern int __syscall_rt_sigaction (int, const struct kernel_sigaction *__unbounded,
  41                                    struct kernel_sigaction *__unbounded, size_t);
  42
  43 #if __ASSUME_REALTIME_SIGNALS == 0
  44 /* The variable is shared between all wrappers around signal handling
  45    functions which have RT equivalents.  */
  46 int __libc_missing_rt_sigs;
  47 #endif
  48
  49 #ifdef __NR_rt_sigaction
  50 static void restore_rt (void) asm ("__restore_rt");
  51 #endif
  52 static void restore (void) asm ("__restore");
  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           memcpy (&kact.sa_mask, &act->sa_mask, sizeof (sigset_t));
  81           kact.sa_flags = act->sa_flags | SA_RESTORER;
  82
  83           kact.sa_restorer = ((act->sa_flags & SA_SIGINFO)
  84                               ? &restore_rt : &restore);
  85         }
  86
  87       /* XXX The size argument hopefully will have to be changed to the
  88          real size of the user-level sigset_t.  */
  89       result = INLINE_SYSCALL (rt_sigaction, 4,
  90                                sig, act ? __ptrvalue (&kact) : NULL,
  91                                oact ? __ptrvalue (&koact) : NULL, _NSIG / 8);
  92
  93 # if __ASSUME_REALTIME_SIGNALS == 0
  94       if (result >= 0 || errno != ENOSYS)
  95 # endif
  96         {
  97           if (oact && result >= 0)
  98             {
  99               oact->sa_handler = koact.k_sa_handler;
 100               memcpy (&oact->sa_mask, &koact.sa_mask, sizeof (sigset_t));
 101               oact->sa_flags = koact.sa_flags;
 102               oact->sa_restorer = koact.sa_restorer;
 103             }
 104           return result;
 105         }
 106
 107 # if __ASSUME_REALTIME_SIGNALS == 0
 108       __set_errno (saved_errno);
 109       __libc_missing_rt_sigs = 1;
 110 # endif
 111     }
 112 #endif
 113
 114 #if __ASSUME_REALTIME_SIGNALS == 0
 115   if (act)
 116     {
 117       k_newact.k_sa_handler = act->sa_handler;
 118       k_newact.sa_mask = act->sa_mask.__val[0];
 119       k_newact.sa_flags = act->sa_flags | SA_RESTORER;
 120
 121       k_newact.sa_restorer = &restore;
 122     }
 123
 124   asm volatile ("pushl %%ebx\n"
 125                 "movl %2, %%ebx\n"
 126                 "int $0x80\n"
 127                 "popl %%ebx"
 128                 : "=a" (result)
 129                 : "0" (SYS_ify (sigaction)), "r" (sig),
 130                   "c" (act ? __ptrvalue (&k_newact) : 0),
 131                   "d" (oact ? __ptrvalue (&k_oldact) : 0));
 132
 133   if (result < 0)
 134     {
 135       __set_errno (-result);
 136       return -1;
 137     }
 138
 139   if (oact)
 140     {
 141       oact->sa_handler = k_oldact.k_sa_handler;
 142       oact->sa_mask.__val[0] = k_oldact.sa_mask;
 143       oact->sa_flags = k_oldact.sa_flags;
 144       oact->sa_restorer = k_oldact.sa_restorer;
 145     }
 146
 147   return 0;
 148 #endif
 149 }
 150
 151 weak_alias (__libc_sigaction, __sigaction)
 152 weak_alias (__libc_sigaction, sigaction)
 153
 154 /* NOTE: Please think twice before making any changes to the bits of
 155    code below.  GDB needs some intimate knowledge about it to
 156    recognize them as signal trampolines, and make backtraces through
 157    signal handlers work right.  Important are both the names
 158    (__restore and __restore_rt) and the exact instruction sequence.
 159    If you ever feel the need to make any changes, please notify the
 160    appropriate GDB maintainer.  */
 161
 162 #define RESTORE(name, syscall) RESTORE2 (name, syscall)
 163 #define RESTORE2(name, syscall) \
 164 asm                                             \
 165   (                                             \
 166    ".align 16\n"                                \
 167    "__" #name ":\n"                             \
 168    "    movl $" #syscall ", %eax\n"             \
 169    "    int  $0x80"                             \
 170    );
 171
 172 #ifdef __NR_rt_sigaction
 173 /* The return code for realtime-signals.  */
 174 RESTORE (restore_rt, __NR_rt_sigreturn)
 175 #endif
 176
 177 /* For the boring old signals.  */
 178 # undef RESTORE2
 179 # define RESTORE2(name, syscall) \
 180 asm                                             \
 181   (                                             \
 182    ".align 8\n"                                 \
 183    "__" #name ":\n"                             \
 184    "    popl %eax\n"                            \
 185    "    movl $" #syscall ", %eax\n"             \
 186    "    int  $0x80"                             \
 187    );
 188
 189 RESTORE (restore, __NR_sigreturn)