Thread suspension: Implement for Linux

src/trusted/service_runtime/posix/nacl_signal.c

 /*
  * Copyright (c) 2012 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include <errno.h>
 #include <signal.h>
 #include <stddef.h>
 #include <string.h>
@@ skipping 28 matching lines @@
  * into architecture specific files. Bug #955
  */
 
 /* Use 4K more than the minimum to allow breakpad to run. */
 #define SIGNAL_STACK_SIZE (SIGSTKSZ + 4096)
 #define STACK_GUARD_SIZE NACL_PAGESIZE
 
 static int s_Signals[] = {
 #if NACL_LINUX
   SIGSTKFLT,
+  NACL_THREAD_SUSPEND_SIGNAL,
 #endif
   SIGINT, SIGQUIT, SIGILL, SIGTRAP, SIGBUS, SIGFPE, SIGSEGV
 };
 
 static struct sigaction s_OldActions[NACL_ARRAY_SIZE_UNSAFE(s_Signals)];
 
 int NaClSignalStackAllocate(void **result) {
   /*
    * We use mmap() to allocate the signal stack for two reasons:
    *
@@ skipping 250 matching lines @@
    * Note that we check natp (which is based on %gs) rather than
    * is_untrusted (which is based on %cs) because we need to handle
    * the case where %gs is set to the untrusted-code value but %cs is
    * not.
    */
   if (natp != NULL) {
     NaClSetGs(natp->sys.gs);
   }
 #endif
 
+#if NACL_LINUX
+  if (sig == NACL_THREAD_SUSPEND_SIGNAL) {
+    NaClSuspendSignalHandler();
+    return;
+  }
+#endif
+
   if (is_untrusted && sig == SIGSEGV) {
     if (DispatchToUntrustedHandler(natp, &sigCtx)) {
       NaClSignalContextToHandler(uc, &sigCtx);
       /* Resume untrusted code using the modified register state. */
       return;
     }
   }
 
   FindAndRunHandler(sig, info, uc);
 }
@@ skipping 52 matching lines @@
     }
     if ((sa.sa_flags & SA_SIGINFO) != 0
         ? sa.sa_sigaction != NULL
         : (sa.sa_handler != SIG_DFL && sa.sa_handler != SIG_IGN)) {
       NaClLog(LOG_FATAL, "NaClSignalAssertNoHandlers: "
               "A signal handler is registered for signal %d.  "
               "Did Breakpad register this?\n", signum);
     }
   }
 }