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 Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    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    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 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 *,
  41                                    struct kernel_sigaction *, 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, sig, act ? &kact : NULL,
  90                                oact ? &koact : NULL, _NSIG / 8);
  91
  92 # if __ASSUME_REALTIME_SIGNALS == 0
  93       if (result >= 0 || errno != ENOSYS)
  94 # endif
  95         {
  96           if (oact && result >= 0)
  97             {
  98               oact->sa_handler = koact.k_sa_handler;
  99               memcpy (&oact->sa_mask, &koact.sa_mask, sizeof (sigset_t));
 100               oact->sa_flags = koact.sa_flags;
 101               oact->sa_restorer = koact.sa_restorer;
 102             }
 103           return result;
 104         }
 105
 106 # if __ASSUME_REALTIME_SIGNALS == 0
 107       __set_errno (saved_errno);
 108       __libc_missing_rt_sigs = 1;
 109 # endif
 110     }
 111 #endif
 112
 113 #if __ASSUME_REALTIME_SIGNALS == 0
 114   if (act)
 115     {
 116       k_newact.k_sa_handler = act->sa_handler;
 117       k_newact.sa_mask = act->sa_mask.__val[0];
 118       k_newact.sa_flags = act->sa_flags | SA_RESTORER;
 119
 120       k_newact.sa_restorer = &restore;
 121     }
 122
 123   asm volatile ("pushl %%ebx\n"
 124                 "movl %2, %%ebx\n"
 125                 "int $0x80\n"
 126                 "popl %%ebx"
 127                 : "=a" (result)
 128                 : "0" (SYS_ify (sigaction)), "r" (sig),
 129                   "c" (act ? &k_newact : 0), "d" (oact ? &k_oldact : 0));
 130
 131   if (result < 0)
 132     {
 133       __set_errno (-result);
 134       return -1;
 135     }
 136
 137   if (oact)
 138     {
 139       oact->sa_handler = k_oldact.k_sa_handler;
 140       oact->sa_mask.__val[0] = k_oldact.sa_mask;
 141       oact->sa_flags = k_oldact.sa_flags;
 142       oact->sa_restorer = k_oldact.sa_restorer;
 143     }
 144
 145   return 0;
 146 #endif
 147 }
 148
 149 strong_alias (__libc_sigaction, __sigaction)
 150 weak_alias (__libc_sigaction, sigaction)
 151
 152 /* NOTE: Please think twice before making any changes to the bits of
 153    code below.  GDB needs some intimate knowledge about it to
 154    recognize them as signal trampolines, and make backtraces through
 155    signal handlers work right.  Important are both the names
 156    (__restore and __restore_rt) and the exact instruction sequence.
 157    If you ever feel the need to make any changes, please notify the
 158    appropriate GDB maintainer.  */
 159
 160 #define RESTORE(name, syscall) RESTORE2 (name, syscall)
 161 #define RESTORE2(name, syscall) \
 162 asm                                             \
 163   (                                             \
 164    ".align 16\n"                                \
 165    "__" #name ":\n"                             \
 166    "    movl $" #syscall ", %eax\n"             \
 167    "    int  $0x80"                             \
 168    );
 169
 170 #ifdef __NR_rt_sigaction
 171 /* The return code for realtime-signals.  */
 172 RESTORE (restore_rt, __NR_rt_sigreturn)
 173 #endif
 174
 175 /* For the boring old signals.  */
 176 # undef RESTORE2
 177 # define RESTORE2(name, syscall) \
 178 asm                                             \
 179   (                                             \
 180    ".align 8\n"                                 \
 181    "__" #name ":\n"                             \
 182    "    popl %eax\n"                            \
 183    "    movl $" #syscall ", %eax\n"             \
 184    "    int  $0x80"                             \
 185    );
 186
 187 RESTORE (restore, __NR_sigreturn)