linuxthreads/signals.c

   1 /* Linuxthreads - a simple clone()-based implementation of Posix        */
   2 /* threads for Linux.                                                   */
   3 /* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr)              */
   4 /*                                                                      */
   5 /* This program is free software; you can redistribute it and/or        */
   6 /* modify it under the terms of the GNU Library General Public License  */
   7 /* as published by the Free Software Foundation; either version 2       */
   8 /* of the License, or (at your option) any later version.               */
   9 /*                                                                      */
  10 /* This program 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        */
  13 /* GNU Library General Public License for more details.                 */
  14
  15 /* Handling of signals */
  16
  17 #include <errno.h>
  18 #include <signal.h>
  19 #include "pthread.h"
  20 #include "internals.h"
  21 #include "spinlock.h"
  22 #include <ucontext.h>
  23 #include <sigcontextinfo.h>
  24
  25 int pthread_sigmask(int how, const sigset_t * newmask, sigset_t * oldmask)
  26 {
  27   sigset_t mask;
  28
  29   if (newmask != NULL) {
  30     mask = *newmask;
  31     /* Don't allow __pthread_sig_restart to be unmasked.
  32        Don't allow __pthread_sig_cancel to be masked. */
  33     switch(how) {
  34     case SIG_SETMASK:
  35       sigaddset(&mask, __pthread_sig_restart);
  36       sigdelset(&mask, __pthread_sig_cancel);
  37       break;
  38     case SIG_BLOCK:
  39       sigdelset(&mask, __pthread_sig_cancel);
  40       break;
  41     case SIG_UNBLOCK:
  42       sigdelset(&mask, __pthread_sig_restart);
  43       break;
  44     }
  45     newmask = &mask;
  46   }
  47   if (sigprocmask(how, newmask, oldmask) == -1)
  48     return errno;
  49   else
  50     return 0;
  51 }
  52
  53 int pthread_kill(pthread_t thread, int signo)
  54 {
  55   pthread_handle handle = thread_handle(thread);
  56   int pid;
  57
  58   __pthread_lock(&handle->h_lock, NULL);
  59   if (invalid_handle(handle, thread)) {
  60     __pthread_unlock(&handle->h_lock);
  61     return ESRCH;
  62   }
  63   pid = handle->h_descr->p_pid;
  64   __pthread_unlock(&handle->h_lock);
  65   if (kill(pid, signo) == -1)
  66     return errno;
  67   else
  68     return 0;
  69 }
  70
  71 /* User-provided signal handlers */
  72 typedef void (*arch_sighandler_t) (int, SIGCONTEXT);
  73 static union
  74 {
  75   arch_sighandler_t old;
  76   void (*rt) (int, struct siginfo *, struct ucontext *);
  77 } sighandler[NSIG];
  78
  79 /* The wrapper around user-provided signal handlers */
  80 static void pthread_sighandler(int signo, SIGCONTEXT ctx)
  81 {
  82   pthread_descr self;
  83   char * in_sighandler;
  84   self = thread_self();
  85   /* If we're in a sigwait operation, just record the signal received
  86      and return without calling the user's handler */
  87   if (THREAD_GETMEM(self, p_sigwaiting)) {
  88     THREAD_SETMEM(self, p_sigwaiting, 0);
  89     THREAD_SETMEM(self, p_signal, signo);
  90     return;
  91   }
  92   /* Record that we're in a signal handler and call the user's
  93      handler function */
  94   in_sighandler = THREAD_GETMEM(self, p_in_sighandler);
  95   if (in_sighandler == NULL)
  96     THREAD_SETMEM(self, p_in_sighandler, CURRENT_STACK_FRAME);
  97   CALL_SIGHANDLER(sighandler[signo].old, signo, ctx);
  98   if (in_sighandler == NULL)
  99     THREAD_SETMEM(self, p_in_sighandler, NULL);
 100 }
 101
 102 /* The same, this time for real-time signals.  */
 103 static void pthread_sighandler_rt(int signo, struct siginfo *si,
 104                                   struct ucontext *uc)
 105 {
 106   pthread_descr self;
 107   char * in_sighandler;
 108   self =  thread_self();
 109   /* If we're in a sigwait operation, just record the signal received
 110      and return without calling the user's handler */
 111   if (THREAD_GETMEM(self, p_sigwaiting)) {
 112     THREAD_SETMEM(self, p_sigwaiting, 0);
 113     THREAD_SETMEM(self, p_signal, signo);
 114     return;
 115   }
 116   /* Record that we're in a signal handler and call the user's
 117      handler function */
 118   in_sighandler = THREAD_GETMEM(self, p_in_sighandler);
 119   if (in_sighandler == NULL)
 120     THREAD_SETMEM(self, p_in_sighandler, CURRENT_STACK_FRAME);
 121   sighandler[signo].rt(signo, si, uc);
 122   if (in_sighandler == NULL)
 123     THREAD_SETMEM(self, p_in_sighandler, NULL);
 124 }
 125
 126 /* The wrapper around sigaction.  Install our own signal handler
 127    around the signal. */
 128 int __sigaction(int sig, const struct sigaction * act,
 129               struct sigaction * oact)
 130 {
 131   struct sigaction newact;
 132   struct sigaction *newactp;
 133
 134   if (sig == __pthread_sig_restart ||
 135       sig == __pthread_sig_cancel ||
 136       (sig == __pthread_sig_debug && __pthread_sig_debug > 0))
 137     {
 138       __set_errno (EINVAL);
 139       return -1;
 140     }
 141   if (act)
 142     {
 143       newact = *act;
 144       if (act->sa_handler != SIG_IGN && act->sa_handler != SIG_DFL
 145           && sig > 0 && sig < NSIG)
 146         {
 147           if (act->sa_flags & SA_SIGINFO)
 148             newact.sa_handler = (__sighandler_t) pthread_sighandler_rt;
 149           else
 150             newact.sa_handler = (__sighandler_t) pthread_sighandler;
 151         }
 152       newactp = &newact;
 153     }
 154   else
 155     newactp = NULL;
 156   if (__libc_sigaction(sig, newactp, oact) == -1)
 157     return -1;
 158   if (sig > 0 && sig < NSIG)
 159     {
 160       if (oact != NULL)
 161         oact->sa_handler = (__sighandler_t) sighandler[sig].old;
 162       if (act)
 163         /* For the assignment is does not matter whether it's a normal
 164            or real-time signal.  */
 165         sighandler[sig].old = (arch_sighandler_t) act->sa_handler;
 166     }
 167   return 0;
 168 }
 169 strong_alias(__sigaction, sigaction)
 170
 171 /* A signal handler that does nothing */
 172 static void pthread_null_sighandler(int sig) { }
 173
 174 /* sigwait -- synchronously wait for a signal */
 175 int sigwait(const sigset_t * set, int * sig)
 176 {
 177   volatile pthread_descr self = thread_self();
 178   sigset_t mask;
 179   int s;
 180   sigjmp_buf jmpbuf;
 181   struct sigaction sa;
 182
 183   /* Get ready to block all signals except those in set
 184      and the cancellation signal.
 185      Also check that handlers are installed on all signals in set,
 186      and if not, install our dummy handler.  This is conformant to
 187      POSIX: "The effect of sigwait() on the signal actions for the
 188      signals in set is unspecified." */
 189   sigfillset(&mask);
 190   sigdelset(&mask, __pthread_sig_cancel);
 191   for (s = 1; s < NSIG; s++) {
 192     if (sigismember(set, s) &&
 193         s != __pthread_sig_restart &&
 194         s != __pthread_sig_cancel &&
 195         s != __pthread_sig_debug) {
 196       sigdelset(&mask, s);
 197       if (sighandler[s].old == NULL ||
 198           sighandler[s].old == (arch_sighandler_t) SIG_DFL ||
 199           sighandler[s].old == (arch_sighandler_t) SIG_IGN) {
 200         sa.sa_handler = pthread_null_sighandler;
 201         sigfillset(&sa.sa_mask);
 202         sa.sa_flags = 0;
 203         sigaction(s, &sa, NULL);
 204       }
 205     }
 206   }
 207   /* Test for cancellation */
 208   if (sigsetjmp(jmpbuf, 1) == 0) {
 209     THREAD_SETMEM(self, p_cancel_jmp, &jmpbuf);
 210     if (! (THREAD_GETMEM(self, p_canceled)
 211            && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE)) {
 212       /* Reset the signal count */
 213       THREAD_SETMEM(self, p_signal, 0);
 214       /* Say we're in sigwait */
 215       THREAD_SETMEM(self, p_sigwaiting, 1);
 216       /* Unblock the signals and wait for them */
 217       sigsuspend(&mask);
 218     }
 219   }
 220   THREAD_SETMEM(self, p_cancel_jmp, NULL);
 221   /* The signals are now reblocked.  Check for cancellation */
 222   pthread_testcancel();
 223   /* We should have self->p_signal != 0 and equal to the signal received */
 224   *sig = THREAD_GETMEM(self, p_signal);
 225   return 0;
 226 }
 227
 228 /* Redefine raise() to send signal to calling thread only,
 229    as per POSIX 1003.1c */
 230 int raise (int sig)
 231 {
 232   int retcode = pthread_kill(pthread_self(), sig);
 233   if (retcode == 0)
 234     return 0;
 235   else {
 236     errno = retcode;
 237     return -1;
 238   }
 239 }