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

   1 /* POSIX.1 `sigaction' call for Linux/i386.
   2    Copyright (C) 1991-2015 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 /* The difference here is that the sigaction structure used in the
  30    kernel is not the same as we use in the libc.  Therefore we must
  31    translate it here.  */
  32 #include <kernel_sigaction.h>
  33
  34 /* We do not globally define the SA_RESTORER flag so do it here.  */
  35 #define SA_RESTORER 0x04000000
  36
  37
  38 /* Using the hidden attribute here does not change the code but it
  39    helps to avoid warnings.  */
  40 #ifdef __NR_rt_sigaction
  41 extern void restore_rt (void) asm ("__restore_rt") attribute_hidden;
  42 #endif
  43 extern void restore (void) asm ("__restore") attribute_hidden;
  44
  45
  46 /* If ACT is not NULL, change the action for SIG to *ACT.
  47    If OACT is not NULL, put the old action for SIG in *OACT.  */
  48 int
  49 __libc_sigaction (int sig, const struct sigaction *act, struct sigaction *oact)
  50 {
  51   int result;
  52
  53   struct kernel_sigaction kact, koact;
  54
  55   if (act)
  56     {
  57       kact.k_sa_handler = act->sa_handler;
  58       kact.sa_flags = act->sa_flags;
  59       memcpy (&kact.sa_mask, &act->sa_mask, sizeof (sigset_t));
  60
  61       if (GLRO(dl_sysinfo_dso) == NULL)
  62         {
  63           kact.sa_flags |= SA_RESTORER;
  64
  65           kact.sa_restorer = ((act->sa_flags & SA_SIGINFO)
  66                               ? &restore_rt : &restore);
  67         }
  68     }
  69
  70   /* XXX The size argument hopefully will have to be changed to the
  71      real size of the user-level sigset_t.  */
  72   result = INLINE_SYSCALL (rt_sigaction, 4,
  73                            sig, act ? &kact : NULL,
  74                            oact ? &koact : NULL, _NSIG / 8);
  75
  76   if (oact && result >= 0)
  77     {
  78       oact->sa_handler = koact.k_sa_handler;
  79       memcpy (&oact->sa_mask, &koact.sa_mask, sizeof (sigset_t));
  80       oact->sa_flags = koact.sa_flags;
  81       oact->sa_restorer = koact.sa_restorer;
  82     }
  83   return result;
  84 }
  85 libc_hidden_def (__libc_sigaction)
  86
  87 #include <nptl/sigaction.c>
  88
  89 /* NOTE: Please think twice before making any changes to the bits of
  90    code below.  GDB needs some intimate knowledge about it to
  91    recognize them as signal trampolines, and make backtraces through
  92    signal handlers work right.  Important are both the names
  93    (__restore and __restore_rt) and the exact instruction sequence.
  94    If you ever feel the need to make any changes, please notify the
  95    appropriate GDB maintainer.  */
  96
  97 #define RESTORE(name, syscall) RESTORE2 (name, syscall)
  98 #define RESTORE2(name, syscall) \
  99 asm                                             \
 100   (                                             \
 101    ".text\n"                                    \
 102    "    .align 16\n"                            \
 103    "__" #name ":\n"                             \
 104    "    movl $" #syscall ", %eax\n"             \
 105    "    int  $0x80"                             \
 106    );
 107
 108 #ifdef __NR_rt_sigaction
 109 /* The return code for realtime-signals.  */
 110 RESTORE (restore_rt, __NR_rt_sigreturn)
 111 #endif
 112
 113 /* For the boring old signals.  */
 114 #undef RESTORE2
 115 #define RESTORE2(name, syscall) \
 116 asm                                             \
 117   (                                             \
 118    ".text\n"                                    \
 119    "    .align 8\n"                             \
 120    "__" #name ":\n"                             \
 121    "    popl %eax\n"                            \
 122    "    movl $" #syscall ", %eax\n"             \
 123    "    int  $0x80"                             \
 124    );
 125
 126 RESTORE (restore, __NR_sigreturn)