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

   1 /* POSIX.1 `sigaction' call for Linux/i386.
   2    Copyright (C) 1991,95,96,97,98,99,2000,02 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 /* Using the hidden attribute here does not change the code but it
  50    helps to avoid warnings.  */
  51 #if defined HAVE_HIDDEN && !defined HAVE_BROKEN_VISIBILITY_ATTRIBUTE
  52 # ifdef __NR_rt_sigaction
  53 extern void restore_rt (void) asm ("__restore_rt") attribute_hidden;
  54 # endif
  55 extern void restore (void) asm ("__restore") attribute_hidden;
  56 #else
  57 # ifdef __NR_rt_sigaction
  58 static void restore_rt (void) asm ("__restore_rt");
  59 # endif
  60 static void restore (void) asm ("__restore");
  61 #endif
  62
  63
  64 /* If ACT is not NULL, change the action for SIG to *ACT.
  65    If OACT is not NULL, put the old action for SIG in *OACT.  */
  66 int
  67 __libc_sigaction (int sig, const struct sigaction *act, struct sigaction *oact)
  68 {
  69 #if __ASSUME_REALTIME_SIGNALS == 0
  70   struct old_kernel_sigaction k_newact, k_oldact;
  71 #endif
  72   int result;
  73
  74 #ifdef __NR_rt_sigaction
  75
  76   /* First try the RT signals.  */
  77 # if __ASSUME_REALTIME_SIGNALS == 0
  78   if (!__libc_missing_rt_sigs)
  79 # endif
  80     {
  81       struct kernel_sigaction kact, koact;
  82 # if __ASSUME_REALTIME_SIGNALS == 0
  83       int saved_errno = errno;
  84 # endif
  85
  86       if (act)
  87         {
  88           kact.k_sa_handler = act->sa_handler;
  89           memcpy (&kact.sa_mask, &act->sa_mask, sizeof (sigset_t));
  90           kact.sa_flags = act->sa_flags | SA_RESTORER;
  91
  92           kact.sa_restorer = ((act->sa_flags & SA_SIGINFO)
  93                               ? &restore_rt : &restore);
  94         }
  95
  96       /* XXX The size argument hopefully will have to be changed to the
  97          real size of the user-level sigset_t.  */
  98       result = INLINE_SYSCALL (rt_sigaction, 4,
  99                                sig, act ? __ptrvalue (&kact) : NULL,
 100                                oact ? __ptrvalue (&koact) : NULL, _NSIG / 8);
 101
 102 # if __ASSUME_REALTIME_SIGNALS == 0
 103       if (result >= 0 || errno != ENOSYS)
 104 # endif
 105         {
 106           if (oact && result >= 0)
 107             {
 108               oact->sa_handler = koact.k_sa_handler;
 109               memcpy (&oact->sa_mask, &koact.sa_mask, sizeof (sigset_t));
 110               oact->sa_flags = koact.sa_flags;
 111               oact->sa_restorer = koact.sa_restorer;
 112             }
 113           return result;
 114         }
 115
 116 # if __ASSUME_REALTIME_SIGNALS == 0
 117       __set_errno (saved_errno);
 118       __libc_missing_rt_sigs = 1;
 119 # endif
 120     }
 121 #endif
 122
 123 #if __ASSUME_REALTIME_SIGNALS == 0
 124   if (act)
 125     {
 126       k_newact.k_sa_handler = act->sa_handler;
 127       k_newact.sa_mask = act->sa_mask.__val[0];
 128       k_newact.sa_flags = act->sa_flags | SA_RESTORER;
 129
 130       k_newact.sa_restorer = &restore;
 131     }
 132
 133   asm volatile ("pushl %%ebx\n"
 134                 "movl %2, %%ebx\n"
 135                 "int $0x80\n"
 136                 "popl %%ebx"
 137                 : "=a" (result)
 138                 : "0" (SYS_ify (sigaction)), "mr" (sig),
 139                   "c" (act ? __ptrvalue (&k_newact) : 0),
 140                   "d" (oact ? __ptrvalue (&k_oldact) : 0));
 141
 142   if (result < 0)
 143     {
 144       __set_errno (-result);
 145       return -1;
 146     }
 147
 148   if (oact)
 149     {
 150       oact->sa_handler = k_oldact.k_sa_handler;
 151       oact->sa_mask.__val[0] = k_oldact.sa_mask;
 152       oact->sa_flags = k_oldact.sa_flags;
 153       oact->sa_restorer = k_oldact.sa_restorer;
 154     }
 155
 156   return 0;
 157 #endif
 158 }
 159
 160 weak_alias (__libc_sigaction, __sigaction)
 161 libc_hidden_weak (__sigaction)
 162 weak_alias (__libc_sigaction, sigaction)
 163
 164 /* NOTE: Please think twice before making any changes to the bits of
 165    code below.  GDB needs some intimate knowledge about it to
 166    recognize them as signal trampolines, and make backtraces through
 167    signal handlers work right.  Important are both the names
 168    (__restore and __restore_rt) and the exact instruction sequence.
 169    If you ever feel the need to make any changes, please notify the
 170    appropriate GDB maintainer.  */
 171
 172 #define RESTORE(name, syscall) RESTORE2 (name, syscall)
 173 #define RESTORE2(name, syscall) \
 174 asm                                             \
 175   (                                             \
 176    ".text\n"                                    \
 177    "    .align 16\n"                            \
 178    "__" #name ":\n"                             \
 179    "    movl $" #syscall ", %eax\n"             \
 180    "    int  $0x80"                             \
 181    );
 182
 183 #ifdef __NR_rt_sigaction
 184 /* The return code for realtime-signals.  */
 185 RESTORE (restore_rt, __NR_rt_sigreturn)
 186 #endif
 187
 188 /* For the boring old signals.  */
 189 # undef RESTORE2
 190 # define RESTORE2(name, syscall) \
 191 asm                                             \
 192   (                                             \
 193    ".text\n"                                    \
 194    "    .align 8\n"                             \
 195    "__" #name ":\n"                             \
 196    "    popl %eax\n"                            \
 197    "    movl $" #syscall ", %eax\n"             \
 198    "    int  $0x80"                             \
 199    );
 200
 201 RESTORE (restore, __NR_sigreturn)