Alias user regs structs for glibc ARM64 pre 2.20

Change-Id: Ie8e4ce8df34c4d14e874884db50d748d03af9592
Reviewed-on: https://chromium-review.googlesource.com/1117644
Reviewed-by: Scott Graham <scottmg@chromium.org>
Commit-Queue: Joshua Peraza <jperaza@chromium.org>

compat/BUILD.gn

@@ -69,6 +69,7 @@ compat_target("compat") {
     sources += [
       "linux/signal.h",
       "linux/sys/ptrace.h",
+      "linux/sys/user.h",
     ]
   }
 

compat/compat.gyp

@@ -36,6 +36,7 @@
         'android/sys/user.h',
         'linux/signal.h',
         'linux/sys/ptrace.h',
+        'linux/sys/user.h',
         'mac/AvailabilityMacros.h',
         'mac/kern/exc_resource.h',
         'mac/mach/i386/thread_state.h',

compat/linux/sys/user.h

@@ -0,0 +1,28 @@
+// Copyright 2018 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CRASHPAD_COMPAT_LINUX_SYS_USER_H_
+#define CRASHPAD_COMPAT_LINUX_SYS_USER_H_
+
+#include_next <sys/user.h>
+
+#include <features.h>
+
+// glibc for 64-bit ARM uses different names for these structs prior to 2.20.
+#if defined(__arm64__) && defined(__GLIBC__) && !__GLIBC_PREREQ(2, 20)
+using user_regs_struct = user_pt_regs;
+using user_fpsimd_struct = user_fpsimd_state;
+#endif
+
+#endif  // CRASHPAD_COMPAT_LINUX_SYS_USER_H_