Android: create a generic android_ucontext.h

sandbox/linux/services/android_arm_ucontext.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SANDBOX_LINUX_SERVICES_ANDROID_ARM_UCONTEXT_H_
 #define SANDBOX_LINUX_SERVICES_ANDROID_ARM_UCONTEXT_H_
 
+#if !defined(__BIONIC_HAVE_UCONTEXT_T)
 #include <asm/sigcontext.h>
 
-typedef long int greg_t;
-typedef unsigned long sigset_t;
+// We also need greg_t for the sandbox, include it in this header as well.
+typedef unsigned long greg_t;
+
+// sigset_t from arch/arm/include/asm/signal.h in the Linux kernel.
+typedef struct {
+  unsigned long sig[64 / 8 / sizeof(long)];  // Always 64 bits (yes we assume
+                                             // 8 bits per char).
+} android_header_sigset_t;  // Change name to avoid collissions if sigset_t
+                            // gets defined in newer Android headers.
+
+//typedef unsigned long sigset_t;
 typedef struct ucontext {
   unsigned long   uc_flags;
   struct ucontext  *uc_link;
   stack_t     uc_stack;
   struct sigcontext uc_mcontext;
   sigset_t    uc_sigmask;
   /* Allow for uc_sigmask growth.  Glibc uses a 1024-bit sigset_t.  */
-  int     __not_used[32 - (sizeof (sigset_t) / sizeof (int))];
+  int     __not_used[32 - (sizeof (android_header_sigset_t) / sizeof (int))];
   /* Last for extensibility.  Eight byte aligned because some
      coprocessors require eight byte alignment.  */
   unsigned long   uc_regspace[128] __attribute__((__aligned__(8)));
 } ucontext_t;
+
+#else
+#include <sys/ucontext.h>
+#endif  // __BIONIC_HAVE_UCONTEXT_T
+
 #endif  // SANDBOX_LINUX_SERVICES_ANDROID_ARM_UCONTEXT_H_