fix: Only set stack registers / exit unwind early on 32-bit

While the stack enhancements added in #378 are intended only to be run
on 32-bit devices and gated to the __arm__ build, when 64-bit devices
are running the 32-bit library, the stacktraces for those devices were
unintentionally affected. This is the case when an app is configured to
only run 32-bit binaries (Android cannot run both 64-bit and 32-bit
binaries at once), and many popular libraries (e.g. React Native) only
distribute 32-bit libraries.

To further improve the stack quality on 32-bit, switches the underlying
unwinder from gnu unwind to non-gnu libunwind. Improves frame resolution
and does not have the crash in unwind when setting registers.

Fixes #382

CHANGELOG.md

@@ -1,5 +1,13 @@
 # Changelog
 
+## TBD
+
+### Bug fixes
+
+* [NDK] Fix regression in 4.9.0 which truncated stacktraces on 64-bit devices to
+  a single frame
+  [#383](https://github.com/bugsnag/bugsnag-android/pull/383)
+
 ## 4.9.1 (2018-11-01)
 
 ### Bug fixes

ndk/src/main/CMakeLists.txt

@@ -24,6 +24,7 @@ add_library( # Specifies the name of the library.
 include_directories(
              jni/
              jni/deps
+             jni/external/libunwind/include
              )
 
 target_include_directories(bugsnag-ndk PRIVATE ${BUGSNAG_DIR}/assets/include)
@@ -47,3 +48,9 @@ set_target_properties(bugsnag-ndk
                       COMPILE_OPTIONS
                       -Werror -Wall -pedantic)
 
+if(${ANDROID_ABI} STREQUAL "armeabi" OR ${ANDROID_ABI} STREQUAL "armeabi-v7a")
+    add_library(libunwind STATIC IMPORTED)
+    set_target_properties(libunwind PROPERTIES IMPORTED_LOCATION
+        ${ANDROID_NDK}/sources/cxx-stl/llvm-libc++/libs/${ANDROID_ABI}/libunwind.a)
+    target_link_libraries(bugsnag-ndk libunwind)
+endif()

ndk/src/main/java/com/bugsnag/android/ndk/NativeBridge.java

@@ -32,7 +32,8 @@ public class NativeBridge implements Observer {
     private static final Lock lock = new ReentrantLock();
     private static final AtomicBoolean installed = new AtomicBoolean(false);
 
-    public static native void install(String reportingDirectory, boolean autoNotify, int apiLevel);
+    public static native void install(String reportingDirectory, boolean autoNotify, int apiLevel,
+                                      boolean is32bit);
 
     public static native void deliverReportAtPath(String filePath);
 
@@ -216,7 +217,15 @@ private void handleInstallMessage(Object arg) {
                 return;
             }
             String reportPath = reportDirectory + UUID.randomUUID().toString() + ".crash";
-            install(reportPath, true, Build.VERSION.SDK_INT);
+            String[] abis = (String[])NativeInterface.getDeviceData().get("cpuAbi");
+            boolean is32bit = true;
+            for (String abi : abis) {
+                if (abi.contains("64")) {
+                    is32bit = false;
+                    break;
+                }
+            }
+            install(reportPath, true, Build.VERSION.SDK_INT, is32bit);
             installed.set(true);
         } finally {
             lock.unlock();

ndk/src/main/jni/bugsnag_ndk.c

@@ -43,9 +43,9 @@ bsg_unwinder bsg_configured_unwind_style() {
 
 JNIEXPORT void JNICALL Java_com_bugsnag_android_ndk_NativeBridge_install(
     JNIEnv *env, jobject _this, jstring _report_path, jboolean auto_notify,
-    jint _api_level) {
+    jint _api_level, jboolean is32bit) {
   bsg_environment *bugsnag_env = calloc(1, sizeof(bsg_environment));
-  bugsnag_env->unwind_style = bsg_get_unwind_type((int)_api_level);
+  bugsnag_env->unwind_style = bsg_get_unwind_type((int)_api_level, (bool)is32bit);
   bugsnag_env->report_header.big_endian =
       htonl(47) == 47; // potentially too clever, see man 3 htonl
   bugsnag_env->report_header.version = BUGSNAG_REPORT_VERSION;

ndk/src/main/jni/external/libunwind/include/__libunwind_config.h

@@ -0,0 +1,55 @@
+//===------------------------- __libunwind_config.h -----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#ifndef ____LIBUNWIND_CONFIG_H__
+#define ____LIBUNWIND_CONFIG_H__
+#if defined(__arm__) && !defined(__USING_SJLJ_EXCEPTIONS__) && \
+    !defined(__ARM_DWARF_EH__)
+#define _LIBUNWIND_ARM_EHABI 1
+#else
+#define _LIBUNWIND_ARM_EHABI 0
+#endif
+#if defined(_LIBUNWIND_IS_NATIVE_ONLY)
+# if defined(__i386__)
+#  define _LIBUNWIND_TARGET_I386 1
+#  define _LIBUNWIND_CONTEXT_SIZE 8
+#  define _LIBUNWIND_CURSOR_SIZE 19
+# elif defined(__x86_64__)
+#  define _LIBUNWIND_TARGET_X86_64 1
+#  define _LIBUNWIND_CONTEXT_SIZE 21
+#  define _LIBUNWIND_CURSOR_SIZE 33
+# elif defined(__ppc__)
+#  define _LIBUNWIND_TARGET_PPC 1
+#  define _LIBUNWIND_CONTEXT_SIZE 117
+#  define _LIBUNWIND_CURSOR_SIZE 128
+# elif defined(__aarch64__)
+#  define _LIBUNWIND_TARGET_AARCH64 1
+#  define _LIBUNWIND_CONTEXT_SIZE 66
+#  define _LIBUNWIND_CURSOR_SIZE 78
+# elif defined(__arm__)
+#  define _LIBUNWIND_TARGET_ARM 1
+#  define _LIBUNWIND_CONTEXT_SIZE 60
+#  define _LIBUNWIND_CURSOR_SIZE 67
+# elif defined(__or1k__)
+#  define _LIBUNWIND_TARGET_OR1K 1
+#  define _LIBUNWIND_CONTEXT_SIZE 16
+#  define _LIBUNWIND_CURSOR_SIZE 28
+# else
+#  error "Unsupported architecture."
+# endif
+#else // !_LIBUNWIND_IS_NATIVE_ONLY
+# define _LIBUNWIND_TARGET_I386 1
+# define _LIBUNWIND_TARGET_X86_64 1
+# define _LIBUNWIND_TARGET_PPC 1
+# define _LIBUNWIND_TARGET_AARCH64 1
+# define _LIBUNWIND_TARGET_ARM 1
+# define _LIBUNWIND_TARGET_OR1K 1
+# define _LIBUNWIND_CONTEXT_SIZE 128
+# define _LIBUNWIND_CURSOR_SIZE 140
+#endif // _LIBUNWIND_IS_NATIVE_ONLY
+#endif // ____LIBUNWIND_CONFIG_H__