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.h"
  15 #include "signal_kern.h"
  16 #include "sysdep/sigcontext.h"
  17 #include "sysdep/barrier.h"
  18 #include "sigcontext.h"
  19 #include "mode.h"
  20 #include "os.h"
  21
  22 /* These are the asynchronous signals.  SIGVTALRM and SIGARLM are handled
  23  * together under SIGVTALRM_BIT.  SIGPROF is excluded because we want to
  24  * be able to profile all of UML, not just the non-critical sections.  If
  25  * profiling is not thread-safe, then that is not my problem.  We can disable
  26  * profiling when SMP is enabled in that case.
  27  */
  28 #define SIGIO_BIT 0
  29 #define SIGIO_MASK (1 << SIGIO_BIT)
  30
  31 #define SIGVTALRM_BIT 1
  32 #define SIGVTALRM_MASK (1 << SIGVTALRM_BIT)
  33
  34 #define SIGALRM_BIT 2
  35 #define SIGALRM_MASK (1 << SIGALRM_BIT)
  36
  37 /* These are used by both the signal handlers and
  38  * block/unblock_signals.  I don't want modifications cached in a
  39  * register - they must go straight to memory.
  40  */
  41 static volatile int signals_enabled = 1;
  42 static volatile int pending = 0;
  43
  44 void sig_handler(int sig, struct sigcontext *sc)
  45 {
  46         int enabled;
  47
  48         enabled = signals_enabled;
  49         if(!enabled && (sig == SIGIO)){
  50                 pending |= SIGIO_MASK;
  51                 return;
  52         }
  53
  54         block_signals();
  55
  56         CHOOSE_MODE_PROC(sig_handler_common_tt, sig_handler_common_skas,
  57                          sig, sc);
  58
  59         set_signals(enabled);
  60 }
  61
  62 static void real_alarm_handler(int sig, struct sigcontext *sc)
  63 {
  64         union uml_pt_regs regs;
  65
  66         if(sig == SIGALRM)
  67                 switch_timers(0);
  68
  69         if(sc != NULL)
  70                 copy_sc(&regs, sc);
  71         regs.skas.is_user = 0;
  72         unblock_signals();
  73         timer_handler(sig, &regs);
  74
  75         if(sig == SIGALRM)
  76                 switch_timers(1);
  77 }
  78
  79 void alarm_handler(int sig, struct sigcontext *sc)
  80 {
  81         int enabled;
  82
  83         enabled = signals_enabled;
  84         if(!signals_enabled){
  85                 if(sig == SIGVTALRM)
  86                         pending |= SIGVTALRM_MASK;
  87                 else pending |= SIGALRM_MASK;
  88
  89                 return;
  90         }
  91
  92         block_signals();
  93
  94         real_alarm_handler(sig, sc);
  95         set_signals(enabled);
  96 }
  97
  98 void set_sigstack(void *sig_stack, int size)
  99 {
 100         stack_t stack = ((stack_t) { .ss_flags  = 0,
 101                                      .ss_sp     = (__ptr_t) sig_stack,
 102                                      .ss_size   = size - sizeof(void *) });
 103
 104         if(sigaltstack(&stack, NULL) != 0)
 105                 panic("enabling signal stack failed, errno = %d\n", errno);
 106 }
 107
 108 void remove_sigstack(void)
 109 {
 110         stack_t stack = ((stack_t) { .ss_flags  = SS_DISABLE,
 111                                      .ss_sp     = NULL,
 112                                      .ss_size   = 0 });
 113
 114         if(sigaltstack(&stack, NULL) != 0)
 115                 panic("disabling signal stack failed, errno = %d\n", errno);
 116 }
 117
 118 void (*handlers[_NSIG])(int sig, struct sigcontext *sc);
 119
 120 void handle_signal(int sig, struct sigcontext *sc)
 121 {
 122         unsigned long pending = 0;
 123
 124         do {
 125                 int nested, bail;
 126
 127                 /*
 128                  * pending comes back with one bit set for each
 129                  * interrupt that arrived while setting up the stack,
 130                  * plus a bit for this interrupt, plus the zero bit is
 131                  * set if this is a nested interrupt.
 132                  * If bail is true, then we interrupted another
 133                  * handler setting up the stack.  In this case, we
 134                  * have to return, and the upper handler will deal
 135                  * with this interrupt.
 136                  */
 137                 bail = to_irq_stack(sig, &pending);
 138                 if(bail)
 139                         return;
 140
 141                 nested = pending & 1;
 142                 pending &= ~1;
 143
 144                 while((sig = ffs(pending)) != 0){
 145                         sig--;
 146                         pending &= ~(1 << sig);
 147                         (*handlers[sig])(sig, sc);
 148                 }
 149
 150                 /* Again, pending comes back with a mask of signals
 151                  * that arrived while tearing down the stack.  If this
 152                  * is non-zero, we just go back, set up the stack
 153                  * again, and handle the new interrupts.
 154                  */
 155                 if(!nested)
 156                         pending = from_irq_stack(nested);
 157         } while(pending);
 158 }
 159
 160 extern void hard_handler(int sig);
 161
 162 void set_handler(int sig, void (*handler)(int), int flags, ...)
 163 {
 164         struct sigaction action;
 165         va_list ap;
 166         sigset_t sig_mask;
 167         int mask;
 168
 169         handlers[sig] = (void (*)(int, struct sigcontext *)) handler;
 170         action.sa_handler = hard_handler;
 171
 172         sigemptyset(&action.sa_mask);
 173
 174         va_start(ap, flags);
 175         while((mask = va_arg(ap, int)) != -1)
 176                 sigaddset(&action.sa_mask, mask);
 177         va_end(ap);
 178
 179         action.sa_flags = flags;
 180         action.sa_restorer = NULL;
 181         if(sigaction(sig, &action, NULL) < 0)
 182                 panic("sigaction failed - errno = %d\n", errno);
 183
 184         sigemptyset(&sig_mask);
 185         sigaddset(&sig_mask, sig);
 186         if(sigprocmask(SIG_UNBLOCK, &sig_mask, NULL) < 0)
 187                 panic("sigprocmask failed - errno = %d\n", errno);
 188 }
 189
 190 int change_sig(int signal, int on)
 191 {
 192         sigset_t sigset, old;
 193
 194         sigemptyset(&sigset);
 195         sigaddset(&sigset, signal);
 196         sigprocmask(on ? SIG_UNBLOCK : SIG_BLOCK, &sigset, &old);
 197         return(!sigismember(&old, signal));
 198 }
 199
 200 void block_signals(void)
 201 {
 202         signals_enabled = 0;
 203         /* This must return with signals disabled, so this barrier
 204          * ensures that writes are flushed out before the return.
 205          * This might matter if gcc figures out how to inline this and
 206          * decides to shuffle this code into the caller.
 207          */
 208         mb();
 209 }
 210
 211 void unblock_signals(void)
 212 {
 213         int save_pending;
 214
 215         if(signals_enabled == 1)
 216                 return;
 217
 218         /* We loop because the IRQ handler returns with interrupts off.  So,
 219          * interrupts may have arrived and we need to re-enable them and
 220          * recheck pending.
 221          */
 222         while(1){
 223                 /* Save and reset save_pending after enabling signals.  This
 224                  * way, pending won't be changed while we're reading it.
 225                  */
 226                 signals_enabled = 1;
 227
 228                 /* Setting signals_enabled and reading pending must
 229                  * happen in this order.
 230                  */
 231                 mb();
 232
 233                 save_pending = pending;
 234                 if(save_pending == 0){
 235                         /* This must return with signals enabled, so
 236                          * this barrier ensures that writes are
 237                          * flushed out before the return.  This might
 238                          * matter if gcc figures out how to inline
 239                          * this (unlikely, given its size) and decides
 240                          * to shuffle this code into the caller.
 241                          */
 242                         mb();
 243                         return;
 244                 }
 245
 246                 pending = 0;
 247
 248                 /* We have pending interrupts, so disable signals, as the
 249                  * handlers expect them off when they are called.  They will
 250                  * be enabled again above.
 251                  */
 252
 253                 signals_enabled = 0;
 254
 255                 /* Deal with SIGIO first because the alarm handler might
 256                  * schedule, leaving the pending SIGIO stranded until we come
 257                  * back here.
 258                  */
 259                 if(save_pending & SIGIO_MASK)
 260                         CHOOSE_MODE_PROC(sig_handler_common_tt,
 261                                          sig_handler_common_skas, SIGIO, NULL);
 262
 263                 if(save_pending & SIGALRM_MASK)
 264                         real_alarm_handler(SIGALRM, NULL);
 265
 266                 if(save_pending & SIGVTALRM_MASK)
 267                         real_alarm_handler(SIGVTALRM, NULL);
 268         }
 269 }
 270
 271 int get_signals(void)
 272 {
 273         return signals_enabled;
 274 }
 275
 276 int set_signals(int enable)
 277 {
 278         int ret;
 279         if(signals_enabled == enable)
 280                 return enable;
 281
 282         ret = signals_enabled;
 283         if(enable)
 284                 unblock_signals();
 285         else block_signals();
 286
 287         return ret;
 288 }