sdk/android/src/jni/jni_generator_helper.h

/*
 *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */
// Do not include this file directly. It's intended to be used only by the JNI
// generation script. We are exporting types in strange namespaces in order to
// be compatible with the generated code targeted for Chromium.

#ifndef SDK_ANDROID_SRC_JNI_JNI_GENERATOR_HELPER_H_
#define SDK_ANDROID_SRC_JNI_JNI_GENERATOR_HELPER_H_

#include <jni.h>
#include <atomic>

#include "rtc_base/checks.h"
#include "sdk/android/native_api/jni/jni_int_wrapper.h"
#include "sdk/android/native_api/jni/scoped_java_ref.h"

#define CHECK_CLAZZ(env, jcaller, clazz, ...) RTC_DCHECK(clazz);
#define CHECK_NATIVE_PTR(env, jcaller, native_ptr, method_name, ...) \
  RTC_DCHECK(native_ptr) << method_name;

#define BASE_EXPORT
#define JNI_REGISTRATION_EXPORT __attribute__((visibility("default")))

#if defined(WEBRTC_ARCH_X86)
// Dalvik JIT generated code doesn't guarantee 16-byte stack alignment on
// x86 - use force_align_arg_pointer to realign the stack at the JNI
// boundary. crbug.com/655248
#define JNI_GENERATOR_EXPORT \
  __attribute__((force_align_arg_pointer)) extern "C" JNIEXPORT JNICALL
#else
#define JNI_GENERATOR_EXPORT extern "C" JNIEXPORT JNICALL
#endif

#define CHECK_EXCEPTION(jni)        \
  RTC_CHECK(!jni->ExceptionCheck()) \
      << (jni->ExceptionDescribe(), jni->ExceptionClear(), "")

namespace webrtc {

// This function will initialize `atomic_class_id` to contain a global ref to
// the given class, and will return that ref on subsequent calls. The caller is
// responsible to zero-initialize `atomic_class_id`. It's fine to
// simultaneously call this on multiple threads referencing the same
// `atomic_method_id`.
jclass LazyGetClass(JNIEnv* env,
                    const char* class_name,
                    std::atomic<jclass>* atomic_class_id);

// This class is a wrapper for JNIEnv Get(Static)MethodID.
class MethodID {
 public:
  enum Type {
    TYPE_STATIC,
    TYPE_INSTANCE,
  };

  // This function will initialize `atomic_method_id` to contain a ref to
  // the given method, and will return that ref on subsequent calls. The caller
  // is responsible to zero-initialize `atomic_method_id`. It's fine to
  // simultaneously call this on multiple threads referencing the same
  // `atomic_method_id`.
  template <Type type>
  static jmethodID LazyGet(JNIEnv* env,
                           jclass clazz,
                           const char* method_name,
                           const char* jni_signature,
                           std::atomic<jmethodID>* atomic_method_id);
};

}  // namespace webrtc

// Re-export relevant classes into the namespaces the script expects.
namespace base {
namespace android {

using webrtc::JavaParamRef;
using webrtc::JavaRef;
using webrtc::ScopedJavaLocalRef;
using webrtc::LazyGetClass;
using webrtc::MethodID;

}  // namespace android
}  // namespace base

namespace jni_generator {
inline void CheckException(JNIEnv* env) {
  CHECK_EXCEPTION(env);
}

// A 32 bit number could be an address on stack. Random 64 bit marker on the
// stack is much less likely to be present on stack.
constexpr uint64_t kJniStackMarkerValue = 0xbdbdef1bebcade1b;

// Context about the JNI call with exception checked to be stored in stack.
struct BASE_EXPORT JniJavaCallContextUnchecked {
  inline JniJavaCallContextUnchecked() {
// TODO(ssid): Implement for other architectures.
#if defined(__arm__) || defined(__aarch64__)
    // This assumes that this method does not increment the stack pointer.
    asm volatile("mov %0, sp" : "=r"(sp));
#else
    sp = 0;
#endif
  }

  // Force no inline to reduce code size.
  template <base::android::MethodID::Type type>
  void Init(JNIEnv* env,
            jclass clazz,
            const char* method_name,
            const char* jni_signature,
            std::atomic<jmethodID>* atomic_method_id) {
    env1 = env;

    // Make sure compiler doesn't optimize out the assignment.
    memcpy(&marker, &kJniStackMarkerValue, sizeof(kJniStackMarkerValue));
    // Gets PC of the calling function.
    pc = reinterpret_cast<uintptr_t>(__builtin_return_address(0));

    method_id = base::android::MethodID::LazyGet<type>(
        env, clazz, method_name, jni_signature, atomic_method_id);
  }

  ~JniJavaCallContextUnchecked() {
    // Reset so that spurious marker finds are avoided.
    memset(&marker, 0, sizeof(marker));
  }

  uint64_t marker;
  uintptr_t sp;
  uintptr_t pc;

  JNIEnv* env1;
  jmethodID method_id;
};

// Context about the JNI call with exception unchecked to be stored in stack.
struct BASE_EXPORT JniJavaCallContextChecked {
  // Force no inline to reduce code size.
  template <base::android::MethodID::Type type>
  void Init(JNIEnv* env,
            jclass clazz,
            const char* method_name,
            const char* jni_signature,
            std::atomic<jmethodID>* atomic_method_id) {
    base.Init<type>(env, clazz, method_name, jni_signature, atomic_method_id);
    // Reset `pc` to correct caller.
    base.pc = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
  }

  ~JniJavaCallContextChecked() { jni_generator::CheckException(base.env1); }

  JniJavaCallContextUnchecked base;
};

static_assert(sizeof(JniJavaCallContextChecked) ==
                  sizeof(JniJavaCallContextUnchecked),
              "Stack unwinder cannot work with structs of different sizes.");
}  // namespace jni_generator

#endif  // SDK_ANDROID_SRC_JNI_JNI_GENERATOR_HELPER_H_