hurd/catch-signal.c

   1 /* Convenience function to catch expected signals during an operation.
   2    Copyright (C) 1996-2017 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 <hurd/signal.h>
  20 #include <hurd/sigpreempt.h>
  21 #include <string.h>
  22 #include <assert.h>
  23
  24 error_t
  25 hurd_catch_signal (sigset_t sigset,
  26                    unsigned long int first, unsigned long int last,
  27                    error_t (*operate) (struct hurd_signal_preemptor *),
  28                    sighandler_t handler)
  29 {
  30   /* We need to restore the signal mask, because otherwise the
  31      signal-handling code will have blocked the caught signal and for
  32      instance calling hurd_catch_signal again would then dump core.  */
  33   sigjmp_buf buf;
  34   void throw (int signo, long int sigcode, struct sigcontext *scp)
  35     { siglongjmp (buf, scp->sc_error ?: EGRATUITOUS); }
  36
  37   struct hurd_signal_preemptor preemptor =
  38     {
  39       sigset, first, last,
  40       NULL, handler == SIG_ERR ? (sighandler_t) &throw : handler,
  41     };
  42
  43   struct hurd_sigstate *const ss = _hurd_self_sigstate ();
  44   error_t error;
  45
  46   if (handler != SIG_ERR)
  47     /* Not our handler; don't bother saving state.  */
  48     error = 0;
  49   else
  50     /* This returns again with nonzero value when we preempt a signal.  */
  51     error = sigsetjmp (buf, 1);
  52
  53   if (error == 0)
  54     {
  55       /* Install a signal preemptor for the thread.  */
  56       __spin_lock (&ss->lock);
  57       preemptor.next = ss->preemptors;
  58       ss->preemptors = &preemptor;
  59       __spin_unlock (&ss->lock);
  60
  61       /* Try the operation that might crash.  */
  62       (*operate) (&preemptor);
  63     }
  64
  65   /* Either FUNCTION completed happily and ERROR is still zero, or it hit
  66      an expected signal and `throw' made setjmp return the signal error
  67      code in ERROR.  Now we can remove the preemptor and return.  */
  68
  69   __spin_lock (&ss->lock);
  70   assert (ss->preemptors == &preemptor);
  71   ss->preemptors = preemptor.next;
  72   __spin_unlock (&ss->lock);
  73
  74   return error;
  75 }
  76
  77
  78 error_t
  79 hurd_safe_memset (void *dest, int byte, size_t nbytes)
  80 {
  81   error_t operate (struct hurd_signal_preemptor *preemptor)
  82     {
  83       memset (dest, byte, nbytes);
  84       return 0;
  85     }
  86   return hurd_catch_signal (sigmask (SIGBUS) | sigmask (SIGSEGV),
  87                             (vm_address_t) dest, (vm_address_t) dest + nbytes,
  88                             &operate, SIG_ERR);
  89 }
  90
  91
  92 error_t
  93 hurd_safe_copyout (void *dest, const void *src, size_t nbytes)
  94 {
  95   error_t operate (struct hurd_signal_preemptor *preemptor)
  96     {
  97       memcpy (dest, src, nbytes);
  98       return 0;
  99     }
 100   return hurd_catch_signal (sigmask (SIGBUS) | sigmask (SIGSEGV),
 101                             (vm_address_t) dest, (vm_address_t) dest + nbytes,
 102                             &operate, SIG_ERR);
 103 }
 104
 105 error_t
 106 hurd_safe_copyin (void *dest, const void *src, size_t nbytes)
 107 {
 108   error_t operate (struct hurd_signal_preemptor *preemptor)
 109     {
 110       memcpy (dest, src, nbytes);
 111       return 0;
 112     }
 113   return hurd_catch_signal (sigmask (SIGBUS) | sigmask (SIGSEGV),
 114                             (vm_address_t) src, (vm_address_t) src + nbytes,
 115                             &operate, SIG_ERR);
 116 }
 117
 118 error_t
 119 hurd_safe_memmove (void *dest, const void *src, size_t nbytes)
 120 {
 121   jmp_buf buf;
 122   void throw (int signo, long int sigcode, struct sigcontext *scp)
 123     { longjmp (buf, scp->sc_error ?: EGRATUITOUS); }
 124
 125   struct hurd_signal_preemptor src_preemptor =
 126     {
 127       sigmask (SIGBUS) | sigmask (SIGSEGV),
 128       (vm_address_t) src, (vm_address_t) src + nbytes,
 129       NULL, (sighandler_t) &throw,
 130     };
 131   struct hurd_signal_preemptor dest_preemptor =
 132     {
 133       sigmask (SIGBUS) | sigmask (SIGSEGV),
 134       (vm_address_t) dest, (vm_address_t) dest + nbytes,
 135       NULL, (sighandler_t) &throw,
 136       &src_preemptor
 137     };
 138
 139   struct hurd_sigstate *const ss = _hurd_self_sigstate ();
 140   error_t error;
 141
 142   /* This returns again with nonzero value when we preempt a signal.  */
 143   error = setjmp (buf);
 144
 145   if (error == 0)
 146     {
 147       /* Install a signal preemptor for the thread.  */
 148       __spin_lock (&ss->lock);
 149       src_preemptor.next = ss->preemptors;
 150       ss->preemptors = &dest_preemptor;
 151       __spin_unlock (&ss->lock);
 152
 153       /* Do the copy; it might fault.  */
 154       memmove (dest, src, nbytes);
 155     }
 156
 157   /* Either memmove completed happily and ERROR is still zero, or it hit
 158      an expected signal and `throw' made setjmp return the signal error
 159      code in ERROR.  Now we can remove the preemptor and return.  */
 160
 161   __spin_lock (&ss->lock);
 162   assert (ss->preemptors == &dest_preemptor);
 163   ss->preemptors = src_preemptor.next;
 164   __spin_unlock (&ss->lock);
 165
 166   return error;
 167 }