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

   1 /* POSIX.1 `sigaction' call for Linux/i386.
   2    Copyright (C) 1991-2014 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <sysdep.h>
  20 #include <errno.h>
  21 #include <stddef.h>
  22 #include <signal.h>
  23 #include <string.h>
  24
  25 #include <sysdep.h>
  26 #include <sys/syscall.h>
  27 #include <ldsodefs.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 /* Using the hidden attribute here does not change the code but it
  41    helps to avoid warnings.  */
  42 #ifdef __NR_rt_sigaction
  43 extern void restore_rt (void) asm ("__restore_rt") attribute_hidden;
  44 #endif
  45 extern void restore (void) asm ("__restore") attribute_hidden;
  46
  47
  48 /* If ACT is not NULL, change the action for SIG to *ACT.
  49    If OACT is not NULL, put the old action for SIG in *OACT.  */
  50 int
  51 __libc_sigaction (int sig, const struct sigaction *act, struct sigaction *oact)
  52 {
  53   int result;
  54
  55   struct kernel_sigaction kact, koact;
  56
  57   if (act)
  58     {
  59       kact.k_sa_handler = act->sa_handler;
  60       kact.sa_flags = act->sa_flags;
  61       memcpy (&kact.sa_mask, &act->sa_mask, sizeof (sigset_t));
  62
  63       if (GLRO(dl_sysinfo_dso) == NULL)
  64         {
  65           kact.sa_flags |= SA_RESTORER;
  66
  67           kact.sa_restorer = ((act->sa_flags & SA_SIGINFO)
  68                               ? &restore_rt : &restore);
  69         }
  70     }
  71
  72   /* XXX The size argument hopefully will have to be changed to the
  73      real size of the user-level sigset_t.  */
  74   result = INLINE_SYSCALL (rt_sigaction, 4,
  75                            sig, act ? &kact : NULL,
  76                            oact ? &koact : NULL, _NSIG / 8);
  77
  78   if (oact && result >= 0)
  79     {
  80       oact->sa_handler = koact.k_sa_handler;
  81       memcpy (&oact->sa_mask, &koact.sa_mask, sizeof (sigset_t));
  82       oact->sa_flags = koact.sa_flags;
  83       oact->sa_restorer = koact.sa_restorer;
  84     }
  85   return result;
  86 }
  87 libc_hidden_def (__libc_sigaction)
  88
  89 #ifdef WRAPPER_INCLUDE
  90 # include WRAPPER_INCLUDE
  91 #endif
  92
  93 #ifndef LIBC_SIGACTION
  94 weak_alias (__libc_sigaction, __sigaction)
  95 libc_hidden_weak (__sigaction)
  96 weak_alias (__libc_sigaction, sigaction)
  97 #endif
  98
  99 /* NOTE: Please think twice before making any changes to the bits of
 100    code below.  GDB needs some intimate knowledge about it to
 101    recognize them as signal trampolines, and make backtraces through
 102    signal handlers work right.  Important are both the names
 103    (__restore and __restore_rt) and the exact instruction sequence.
 104    If you ever feel the need to make any changes, please notify the
 105    appropriate GDB maintainer.  */
 106
 107 #define RESTORE(name, syscall) RESTORE2 (name, syscall)
 108 #define RESTORE2(name, syscall) \
 109 asm                                             \
 110   (                                             \
 111    ".text\n"                                    \
 112    "    .align 16\n"                            \
 113    "__" #name ":\n"                             \
 114    "    movl $" #syscall ", %eax\n"             \
 115    "    int  $0x80"                             \
 116    );
 117
 118 #ifdef __NR_rt_sigaction
 119 /* The return code for realtime-signals.  */
 120 RESTORE (restore_rt, __NR_rt_sigreturn)
 121 #endif
 122
 123 /* For the boring old signals.  */
 124 #undef RESTORE2
 125 #define RESTORE2(name, syscall) \
 126 asm                                             \
 127   (                                             \
 128    ".text\n"                                    \
 129    "    .align 8\n"                             \
 130    "__" #name ":\n"                             \
 131    "    popl %eax\n"                            \
 132    "    movl $" #syscall ", %eax\n"             \
 133    "    int  $0x80"                             \
 134    );
 135
 136 RESTORE (restore, __NR_sigreturn)