hurd/catch-signal.c

   1 /* Convenience function to catch expected signals during an operation.
   2    Copyright (C) 1996-2020 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    <https://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 strong_alias (__hurd_catch_signal, hurd_catch_signal)
  77
  78
  79 error_t
  80 hurd_safe_memset (void *dest, int byte, size_t nbytes)
  81 {
  82   error_t operate (struct hurd_signal_preemptor *preemptor)
  83     {
  84       memset (dest, byte, nbytes);
  85       return 0;
  86     }
  87   return __hurd_catch_signal (sigmask (SIGBUS) | sigmask (SIGSEGV),
  88                               (vm_address_t) dest, (vm_address_t) dest + nbytes,
  89                               &operate, SIG_ERR);
  90 }
  91
  92
  93 error_t
  94 hurd_safe_copyout (void *dest, const void *src, size_t nbytes)
  95 {
  96   error_t operate (struct hurd_signal_preemptor *preemptor)
  97     {
  98       memcpy (dest, src, nbytes);
  99       return 0;
 100     }
 101   return __hurd_catch_signal (sigmask (SIGBUS) | sigmask (SIGSEGV),
 102                               (vm_address_t) dest, (vm_address_t) dest + nbytes,
 103                               &operate, SIG_ERR);
 104 }
 105
 106 error_t
 107 hurd_safe_copyin (void *dest, const void *src, size_t nbytes)
 108 {
 109   error_t operate (struct hurd_signal_preemptor *preemptor)
 110     {
 111       memcpy (dest, src, nbytes);
 112       return 0;
 113     }
 114   return __hurd_catch_signal (sigmask (SIGBUS) | sigmask (SIGSEGV),
 115                               (vm_address_t) src, (vm_address_t) src + nbytes,
 116                               &operate, SIG_ERR);
 117 }
 118
 119 error_t
 120 hurd_safe_memmove (void *dest, const void *src, size_t nbytes)
 121 {
 122   jmp_buf buf;
 123   void throw (int signo, long int sigcode, struct sigcontext *scp)
 124     { longjmp (buf, scp->sc_error ?: EGRATUITOUS); }
 125
 126   struct hurd_signal_preemptor src_preemptor =
 127     {
 128       sigmask (SIGBUS) | sigmask (SIGSEGV),
 129       (vm_address_t) src, (vm_address_t) src + nbytes,
 130       NULL, (sighandler_t) &throw,
 131     };
 132   struct hurd_signal_preemptor dest_preemptor =
 133     {
 134       sigmask (SIGBUS) | sigmask (SIGSEGV),
 135       (vm_address_t) dest, (vm_address_t) dest + nbytes,
 136       NULL, (sighandler_t) &throw,
 137       &src_preemptor
 138     };
 139
 140   struct hurd_sigstate *const ss = _hurd_self_sigstate ();
 141   error_t error;
 142
 143   /* This returns again with nonzero value when we preempt a signal.  */
 144   error = setjmp (buf);
 145
 146   if (error == 0)
 147     {
 148       /* Install a signal preemptor for the thread.  */
 149       __spin_lock (&ss->lock);
 150       src_preemptor.next = ss->preemptors;
 151       ss->preemptors = &dest_preemptor;
 152       __spin_unlock (&ss->lock);
 153
 154       /* Do the copy; it might fault.  */
 155       memmove (dest, src, nbytes);
 156     }
 157
 158   /* Either memmove completed happily and ERROR is still zero, or it hit
 159      an expected signal and `throw' made setjmp return the signal error
 160      code in ERROR.  Now we can remove the preemptor and return.  */
 161
 162   __spin_lock (&ss->lock);
 163   assert (ss->preemptors == &dest_preemptor);
 164   ss->preemptors = src_preemptor.next;
 165   __spin_unlock (&ss->lock);
 166
 167   return error;
 168 }