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 #ifdef __i386__
  85   asm volatile ("movw %w0,%%gs" : : "r" (ctx.gs));
  86 #endif
  87   self = thread_self();
  88   /* If we're in a sigwait operation, just record the signal received
  89      and return without calling the user's handler */
  90   if (THREAD_GETMEM(self, p_sigwaiting)) {
  91     THREAD_SETMEM(self, p_sigwaiting, 0);
  92     THREAD_SETMEM(self, p_signal, signo);
  93     return;
  94   }
  95   /* Record that we're in a signal handler and call the user's
  96      handler function */
  97   in_sighandler = THREAD_GETMEM(self, p_in_sighandler);
  98   if (in_sighandler == NULL)
  99     THREAD_SETMEM(self, p_in_sighandler, CURRENT_STACK_FRAME);
 100   sighandler[signo].old(signo, SIGCONTEXT_EXTRA_ARGS ctx);
 101   if (in_sighandler == NULL)
 102     THREAD_SETMEM(self, p_in_sighandler, NULL);
 103 }
 104
 105 /* The same, this time for real-time signals.  */
 106 static void pthread_sighandler_rt(int signo, struct siginfo *si,
 107                                   struct ucontext *uc)
 108 {
 109   pthread_descr self;
 110   char * in_sighandler;
 111 #ifdef __i386__
 112   asm volatile ("movw %w0,%%gs" : : "r" (uc->uc_mcontext.gregs[REG_GS]));
 113 #endif
 114   self =  thread_self();
 115   /* If we're in a sigwait operation, just record the signal received
 116      and return without calling the user's handler */
 117   if (THREAD_GETMEM(self, p_sigwaiting)) {
 118     THREAD_SETMEM(self, p_sigwaiting, 0);
 119     THREAD_SETMEM(self, p_signal, signo);
 120     return;
 121   }
 122   /* Record that we're in a signal handler and call the user's
 123      handler function */
 124   in_sighandler = THREAD_GETMEM(self, p_in_sighandler);
 125   if (in_sighandler == NULL)
 126     THREAD_SETMEM(self, p_in_sighandler, CURRENT_STACK_FRAME);
 127   sighandler[signo].rt(signo, si, uc);
 128   if (in_sighandler == NULL)
 129     THREAD_SETMEM(self, p_in_sighandler, NULL);
 130 }
 131
 132 /* The wrapper around sigaction.  Install our own signal handler
 133    around the signal. */
 134 int sigaction(int sig, const struct sigaction * act,
 135               struct sigaction * oact)
 136 {
 137   struct sigaction newact;
 138   struct sigaction *newactp;
 139
 140   if (sig == __pthread_sig_restart ||
 141       sig == __pthread_sig_cancel ||
 142       (sig == __pthread_sig_debug && __pthread_sig_debug > 0))
 143     {
 144       __set_errno (EINVAL);
 145       return -1;
 146     }
 147   if (act)
 148     {
 149       newact = *act;
 150       if (act->sa_handler != SIG_IGN && act->sa_handler != SIG_DFL
 151           && sig > 0 && sig < NSIG)
 152         {
 153           if (act->sa_flags & SA_SIGINFO)
 154             newact.sa_handler = (__sighandler_t) pthread_sighandler_rt;
 155           else
 156             newact.sa_handler = (__sighandler_t) pthread_sighandler;
 157         }
 158       newactp = &newact;
 159     }
 160   else
 161     newactp = NULL;
 162   if (__sigaction(sig, newactp, oact) == -1)
 163     return -1;
 164   if (sig > 0 && sig < NSIG)
 165     {
 166       if (oact != NULL)
 167         oact->sa_handler = (__sighandler_t) sighandler[sig].old;
 168       if (act)
 169         /* For the assignment is does not matter whether it's a normal
 170            or real-time signal.  */
 171         sighandler[sig].old = (arch_sighandler_t) act->sa_handler;
 172     }
 173   return 0;
 174 }
 175
 176 /* A signal handler that does nothing */
 177 static void pthread_null_sighandler(int sig) { }
 178
 179 /* sigwait -- synchronously wait for a signal */
 180 int sigwait(const sigset_t * set, int * sig)
 181 {
 182   volatile pthread_descr self = thread_self();
 183   sigset_t mask;
 184   int s;
 185   sigjmp_buf jmpbuf;
 186   struct sigaction sa;
 187
 188   /* Get ready to block all signals except those in set
 189      and the cancellation signal.
 190      Also check that handlers are installed on all signals in set,
 191      and if not, install our dummy handler.  This is conformant to
 192      POSIX: "The effect of sigwait() on the signal actions for the
 193      signals in set is unspecified." */
 194   sigfillset(&mask);
 195   sigdelset(&mask, __pthread_sig_cancel);
 196   for (s = 1; s <= NSIG; s++) {
 197     if (sigismember(set, s) &&
 198         s != __pthread_sig_restart &&
 199         s != __pthread_sig_cancel &&
 200         s != __pthread_sig_debug) {
 201       sigdelset(&mask, s);
 202       if (sighandler[s].old == NULL ||
 203           sighandler[s].old == (arch_sighandler_t) SIG_DFL ||
 204           sighandler[s].old == (arch_sighandler_t) SIG_IGN) {
 205         sa.sa_handler = pthread_null_sighandler;
 206         sigemptyset(&sa.sa_mask);
 207         sa.sa_flags = 0;
 208         sigaction(s, &sa, NULL);
 209       }
 210     }
 211   }
 212   /* Test for cancellation */
 213   if (sigsetjmp(jmpbuf, 1) == 0) {
 214     THREAD_SETMEM(self, p_cancel_jmp, &jmpbuf);
 215     if (! (THREAD_GETMEM(self, p_canceled)
 216            && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE)) {
 217       /* Reset the signal count */
 218       THREAD_SETMEM(self, p_signal, 0);
 219       /* Say we're in sigwait */
 220       THREAD_SETMEM(self, p_sigwaiting, 1);
 221       /* Unblock the signals and wait for them */
 222       sigsuspend(&mask);
 223     }
 224   }
 225   THREAD_SETMEM(self, p_cancel_jmp, NULL);
 226   /* The signals are now reblocked.  Check for cancellation */
 227   pthread_testcancel();
 228   /* We should have self->p_signal != 0 and equal to the signal received */
 229   *sig = THREAD_GETMEM(self, p_signal);
 230   return 0;
 231 }
 232
 233 /* Redefine raise() to send signal to calling thread only,
 234    as per POSIX 1003.1c */
 235 int raise (int sig)
 236 {
 237   int retcode = pthread_kill(pthread_self(), sig);
 238   if (retcode == 0)
 239     return 0;
 240   else {
 241     errno = retcode;
 242     return -1;
 243   }
 244 }