arch/um/os-Linux/signal.c

   1 /*
   2  * Copyright (C) 2004 PathScale, Inc
   3  * Licensed under the GPL
   4  */
   5
   6 #include <signal.h>
   7 #include <stdio.h>
   8 #include <unistd.h>
   9 #include <stdlib.h>
  10 #include <errno.h>
  11 #include <stdarg.h>
  12 #include <string.h>
  13 #include <sys/mman.h>
  14 #include "user_util.h"
  15 #include "user.h"
  16 #include "signal_kern.h"
  17 #include "sysdep/sigcontext.h"
  18 #include "sysdep/barrier.h"
  19 #include "sigcontext.h"
  20 #include "mode.h"
  21 #include "os.h"
  22
  23 /* These are the asynchronous signals.  SIGVTALRM and SIGARLM are handled
  24  * together under SIGVTALRM_BIT.  SIGPROF is excluded because we want to
  25  * be able to profile all of UML, not just the non-critical sections.  If
  26  * profiling is not thread-safe, then that is not my problem.  We can disable
  27  * profiling when SMP is enabled in that case.
  28  */
  29 #define SIGIO_BIT 0
  30 #define SIGIO_MASK (1 << SIGIO_BIT)
  31
  32 #define SIGVTALRM_BIT 1
  33 #define SIGVTALRM_MASK (1 << SIGVTALRM_BIT)
  34
  35 #define SIGALRM_BIT 2
  36 #define SIGALRM_MASK (1 << SIGALRM_BIT)
  37
  38 /* These are used by both the signal handlers and
  39  * block/unblock_signals.  I don't want modifications cached in a
  40  * register - they must go straight to memory.
  41  */
  42 static volatile int signals_enabled = 1;
  43 static volatile int pending = 0;
  44
  45 void sig_handler(int sig, struct sigcontext *sc)
  46 {
  47         int enabled;
  48
  49         enabled = signals_enabled;
  50         if(!enabled && (sig == SIGIO)){
  51                 pending |= SIGIO_MASK;
  52                 return;
  53         }
  54
  55         block_signals();
  56
  57         CHOOSE_MODE_PROC(sig_handler_common_tt, sig_handler_common_skas,
  58                          sig, sc);
  59
  60         set_signals(enabled);
  61 }
  62
  63 static void real_alarm_handler(int sig, struct sigcontext *sc)
  64 {
  65         if(sig == SIGALRM)
  66                 switch_timers(0);
  67
  68         CHOOSE_MODE_PROC(sig_handler_common_tt, sig_handler_common_skas,
  69                          sig, sc);
  70
  71         if(sig == SIGALRM)
  72                 switch_timers(1);
  73
  74 }
  75
  76 void alarm_handler(int sig, struct sigcontext *sc)
  77 {
  78         int enabled;
  79
  80         enabled = signals_enabled;
  81         if(!signals_enabled){
  82                 if(sig == SIGVTALRM)
  83                         pending |= SIGVTALRM_MASK;
  84                 else pending |= SIGALRM_MASK;
  85
  86                 return;
  87         }
  88
  89         block_signals();
  90
  91         real_alarm_handler(sig, sc);
  92         set_signals(enabled);
  93 }
  94
  95 void set_sigstack(void *sig_stack, int size)
  96 {
  97         stack_t stack = ((stack_t) { .ss_flags  = 0,
  98                                      .ss_sp     = (__ptr_t) sig_stack,
  99                                      .ss_size   = size - sizeof(void *) });
 100
 101         if(sigaltstack(&stack, NULL) != 0)
 102                 panic("enabling signal stack failed, errno = %d\n", errno);
 103 }
 104
 105 void remove_sigstack(void)
 106 {
 107         stack_t stack = ((stack_t) { .ss_flags  = SS_DISABLE,
 108                                      .ss_sp     = NULL,
 109                                      .ss_size   = 0 });
 110
 111         if(sigaltstack(&stack, NULL) != 0)
 112                 panic("disabling signal stack failed, errno = %d\n", errno);
 113 }
 114
 115 void (*handlers[_NSIG])(int sig, struct sigcontext *sc);
 116
 117 extern void hard_handler(int sig);
 118
 119 void set_handler(int sig, void (*handler)(int), int flags, ...)
 120 {
 121         struct sigaction action;
 122         va_list ap;
 123         sigset_t sig_mask;
 124         int mask;
 125
 126         handlers[sig] = (void (*)(int, struct sigcontext *)) handler;
 127         action.sa_handler = hard_handler;
 128
 129         sigemptyset(&action.sa_mask);
 130
 131         va_start(ap, flags);
 132         while((mask = va_arg(ap, int)) != -1)
 133                 sigaddset(&action.sa_mask, mask);
 134         va_end(ap);
 135
 136         action.sa_flags = flags;
 137         action.sa_restorer = NULL;
 138         if(sigaction(sig, &action, NULL) < 0)
 139                 panic("sigaction failed - errno = %d\n", errno);
 140
 141         sigemptyset(&sig_mask);
 142         sigaddset(&sig_mask, sig);
 143         if(sigprocmask(SIG_UNBLOCK, &sig_mask, NULL) < 0)
 144                 panic("sigprocmask failed - errno = %d\n", errno);
 145 }
 146
 147 int change_sig(int signal, int on)
 148 {
 149         sigset_t sigset, old;
 150
 151         sigemptyset(&sigset);
 152         sigaddset(&sigset, signal);
 153         sigprocmask(on ? SIG_UNBLOCK : SIG_BLOCK, &sigset, &old);
 154         return(!sigismember(&old, signal));
 155 }
 156
 157 void block_signals(void)
 158 {
 159         signals_enabled = 0;
 160         /* This must return with signals disabled, so this barrier
 161          * ensures that writes are flushed out before the return.
 162          * This might matter if gcc figures out how to inline this and
 163          * decides to shuffle this code into the caller.
 164          */
 165         mb();
 166 }
 167
 168 void unblock_signals(void)
 169 {
 170         int save_pending;
 171
 172         if(signals_enabled == 1)
 173                 return;
 174
 175         /* We loop because the IRQ handler returns with interrupts off.  So,
 176          * interrupts may have arrived and we need to re-enable them and
 177          * recheck pending.
 178          */
 179         while(1){
 180                 /* Save and reset save_pending after enabling signals.  This
 181                  * way, pending won't be changed while we're reading it.
 182                  */
 183                 signals_enabled = 1;
 184
 185                 /* Setting signals_enabled and reading pending must
 186                  * happen in this order.
 187                  */
 188                 mb();
 189
 190                 save_pending = pending;
 191                 if(save_pending == 0){
 192                         /* This must return with signals enabled, so
 193                          * this barrier ensures that writes are
 194                          * flushed out before the return.  This might
 195                          * matter if gcc figures out how to inline
 196                          * this (unlikely, given its size) and decides
 197                          * to shuffle this code into the caller.
 198                          */
 199                         mb();
 200                         return;
 201                 }
 202
 203                 pending = 0;
 204
 205                 /* We have pending interrupts, so disable signals, as the
 206                  * handlers expect them off when they are called.  They will
 207                  * be enabled again above.
 208                  */
 209
 210                 signals_enabled = 0;
 211
 212                 /* Deal with SIGIO first because the alarm handler might
 213                  * schedule, leaving the pending SIGIO stranded until we come
 214                  * back here.
 215                  */
 216                 if(save_pending & SIGIO_MASK)
 217                         CHOOSE_MODE_PROC(sig_handler_common_tt,
 218                                          sig_handler_common_skas, SIGIO, NULL);
 219
 220                 if(save_pending & SIGALRM_MASK)
 221                         real_alarm_handler(SIGALRM, NULL);
 222
 223                 if(save_pending & SIGVTALRM_MASK)
 224                         real_alarm_handler(SIGVTALRM, NULL);
 225         }
 226 }
 227
 228 int get_signals(void)
 229 {
 230         return signals_enabled;
 231 }
 232
 233 int set_signals(int enable)
 234 {
 235         int ret;
 236         if(signals_enabled == enable)
 237                 return enable;
 238
 239         ret = signals_enabled;
 240         if(enable)
 241                 unblock_signals();
 242         else block_signals();
 243
 244         return ret;
 245 }
 246
 247 void os_usr1_signal(int on)
 248 {
 249         change_sig(SIGUSR1, on);
 250 }