Fix sigaction(3) for 64-bit.

Also clean up <signal.h> and revert the hacks that were necessary
for 64-bit in linker/debugger.cpp until now.

Change-Id: I3b0554ca8a49ee1c97cda086ce2c1954ebc11892
diff --git a/libc/bionic/sigaction.cpp b/libc/bionic/sigaction.cpp
new file mode 100644
index 0000000..6468b2d
--- /dev/null
+++ b/libc/bionic/sigaction.cpp
@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <signal.h>
+
+#if __LP64__
+extern "C" void __rt_sigreturn(void);
+extern "C" int __rt_sigaction(int, const struct __kernel_sigaction*, struct __kernel_sigaction*, size_t);
+#else
+extern "C" int __sigaction(int, const struct sigaction*, struct sigaction*);
+#endif
+
+int sigaction(int signal, const struct sigaction* bionic_new_action, struct sigaction* bionic_old_action) {
+#if __LP64__
+  __kernel_sigaction kernel_new_action;
+  if (bionic_new_action != NULL) {
+    kernel_new_action.sa_flags = bionic_new_action->sa_flags;
+    kernel_new_action.sa_handler = bionic_new_action->sa_handler;
+    kernel_new_action.sa_mask = bionic_new_action->sa_mask;
+    kernel_new_action.sa_restorer = bionic_new_action->sa_restorer;
+
+    if (!(kernel_new_action.sa_flags & SA_RESTORER)) {
+      kernel_new_action.sa_flags |= SA_RESTORER;
+      kernel_new_action.sa_restorer = &__rt_sigreturn;
+    }
+  }
+
+  __kernel_sigaction kernel_old_action;
+  int result = __rt_sigaction(signal,
+                              (bionic_new_action != NULL) ? &kernel_new_action : NULL,
+                              (bionic_old_action != NULL) ? &kernel_old_action : NULL,
+                              sizeof(sigset_t));
+
+  if (bionic_old_action != NULL) {
+    bionic_old_action->sa_flags = kernel_old_action.sa_flags;
+    bionic_old_action->sa_handler = kernel_old_action.sa_handler;
+    bionic_old_action->sa_mask = kernel_old_action.sa_mask;
+    bionic_old_action->sa_restorer = kernel_old_action.sa_restorer;
+
+    if (bionic_old_action->sa_restorer == &__rt_sigreturn) {
+      bionic_old_action->sa_flags &= ~SA_RESTORER;
+    }
+  }
+
+  return result;
+#else
+  // The 32-bit ABI is broken. struct sigaction includes a too-small sigset_t.
+  // TODO: if we also had correct struct sigaction definitions available, we could copy in and out.
+  return __sigaction(signal, bionic_new_action, bionic_old_action);
+#endif
+}