base/android/linker/linker_jni.h - chromium/src - Git at Google

 // Copyright 2015 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.

 // This is the Android-specific Chromium dynamic linker (loader of dynamic
 // libraries), a tiny shared library implementing a custom dynamic linker that
 // can be used to load the real Chromium libraries.
 //
 // The purpose of this custom linker is to be able to share the RELRO section of
 // libcontentshell.so (or equivalent) between the browser process and all other
 // processes it asks to create.
 //
 // This source code *cannot* depend on anything from //base or the C++ standard
 // library to keep this DSO small and avoid dependency issues. An exception is
 // made for std::unique_ptr as a risky header-only definition.

 #ifndef BASE_ANDROID_LINKER_LINKER_JNI_H_
 #define BASE_ANDROID_LINKER_LINKER_JNI_H_

 #include <android/log.h>
 #include <jni.h>
 #include <stddef.h>
 #include <stdlib.h>

 #include "build/build_config.h"

 // Set this to 1 to enable debug traces to the Android log.
 // Note that LOG() from "base/logging.h" cannot be used, since it is
 // in base/ which hasn't been loaded yet.
 #define DEBUG 0

 #define TAG "cr_ChromiumAndroidLinker"

 #if DEBUG
 #define LOG_INFO(FORMAT, ...)                                             \
   __android_log_print(ANDROID_LOG_INFO, TAG, "%s: " FORMAT, __FUNCTION__, \
                       ##__VA_ARGS__)
 #else
 #define LOG_INFO(FORMAT, ...) ((void)0)
 #endif
 #define LOG_ERROR(FORMAT, ...)                                             \
   __android_log_print(ANDROID_LOG_ERROR, TAG, "%s: " FORMAT, __FUNCTION__, \
                       ##__VA_ARGS__)
 #define PLOG_ERROR(FORMAT, ...) \
   LOG_ERROR(FORMAT ": %s", ##__VA_ARGS__, strerror(errno))

 #define UNUSED __attribute__((unused))

 #if defined(ARCH_CPU_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. https://crbug.com/655248
 #define JNI_GENERATOR_EXPORT \
   extern "C" __attribute__((visibility("default"), force_align_arg_pointer))
 #else
 #define JNI_GENERATOR_EXPORT extern "C" __attribute__((visibility("default")))
 #endif

 #if defined(__arm__) && defined(__ARM_ARCH_7A__)
 #define CURRENT_ABI "armeabi-v7a"
 #elif defined(__arm__)
 #define CURRENT_ABI "armeabi"
 #elif defined(__i386__)
 #define CURRENT_ABI "x86"
 #elif defined(__mips__)
 #define CURRENT_ABI "mips"
 #elif defined(__x86_64__)
 #define CURRENT_ABI "x86_64"
 #elif defined(__aarch64__)
 #define CURRENT_ABI "arm64-v8a"
 #else
 #error "Unsupported target abi"
 #endif

 #if !defined(PAGE_SIZE)
 #define PAGE_SIZE (1 << 12)
 #define PAGE_MASK (~(PAGE_SIZE - 1))
 #endif

 #define PAGE_START(x) ((x)&PAGE_MASK)
 #define PAGE_END(x) PAGE_START((x) + (PAGE_SIZE - 1))

 // Copied from //base/posix/eintr_wrapper.h to avoid depending on //base.
 #define HANDLE_EINTR(x)                                     \
   ({                                                        \
     decltype(x) eintr_wrapper_result;                       \
     do {                                                    \
       eintr_wrapper_result = (x);                           \
     } while (eintr_wrapper_result == -1 && errno == EINTR); \
     eintr_wrapper_result;                                   \
   })

 namespace chromium_android_linker {

 // Larger than the largest library we might attempt to load.
 static const size_t kAddressSpaceReservationSize = 192 * 1024 * 1024;

 // A simple scoped UTF String class that can be initialized from
 // a Java jstring handle. Modeled like std::string, which cannot
 // be used here.
 class String {
  public:
   String(JNIEnv* env, jstring str);

   inline ~String() { ::free(ptr_); }

   inline const char* c_str() const { return ptr_ ? ptr_ : ""; }
   inline size_t size() const { return size_; }

  private:
   char* ptr_;
   size_t size_;
 };

 // Returns true iff casting a java-side |address| to uintptr_t does not lose
 // bits.
 bool IsValidAddress(jlong address);

 // Find the jclass JNI reference corresponding to a given |class_name|.
 // |env| is the current JNI environment handle.
 // On success, return true and set |*clazz|.
 bool InitClassReference(JNIEnv* env, const char* class_name, jclass* clazz);

 // Finds the region reserved by the WebView zygote if the current process is
 // inherited from the modern enough zygote that has this reservation. If the
 // lookup is successful, returns true and sets |address| and |size|. Otherwise
 // returns false.
 bool FindWebViewReservation(uintptr_t* address, size_t* size);

 // Initialize a jfieldID corresponding to the field of a given |clazz|,
 // with name |field_name| and signature |field_sig|.
 // |env| is the current JNI environment handle.
 // On success, return true and set |*field_id|.
 bool InitFieldId(JNIEnv* env,
                  jclass clazz,
                  const char* field_name,
                  const char* field_sig,
                  jfieldID* field_id);

 // Initialize a jfieldID corresponding to the static field of a given |clazz|,
 // with name |field_name| and signature |field_sig|.
 // |env| is the current JNI environment handle.
 // On success, return true and set |*field_id|.
 bool InitStaticFieldId(JNIEnv* env,
                        jclass clazz,
                        const char* field_name,
                        const char* field_sig,
                        jfieldID* field_id);

 // A class used to model the field IDs of the org.chromium.base.Linker
 // LibInfo inner class, used to communicate data with the Java side
 // of the linker.
 struct LibInfo_class {
   jfieldID load_address_id;
   jfieldID load_size_id;
   jfieldID relro_start_id;
   jfieldID relro_size_id;
   jfieldID relro_fd_id;

   // Initialize an instance.
   bool Init(JNIEnv* env) {
     jclass clazz;
     if (!InitClassReference(
             env, "org/chromium/base/library_loader/Linker$LibInfo", &clazz)) {
       return false;
     }

     return InitFieldId(env, clazz, "mLoadAddress", "J", &load_address_id) &&
            InitFieldId(env, clazz, "mLoadSize", "J", &load_size_id) &&
            InitFieldId(env, clazz, "mRelroStart", "J", &relro_start_id) &&
            InitFieldId(env, clazz, "mRelroSize", "J", &relro_size_id) &&
            InitFieldId(env, clazz, "mRelroFd", "I", &relro_fd_id);
   }

   void SetLoadInfo(JNIEnv* env,
                    jobject library_info_obj,
                    uintptr_t load_address,
                    size_t load_size) {
     env->SetLongField(library_info_obj, load_address_id, load_address);
     env->SetLongField(library_info_obj, load_size_id, load_size);
   }

   void SetRelroInfo(JNIEnv* env,
                     jobject library_info_obj,
                     uintptr_t relro_start,
                     size_t relro_size,
                     int relro_fd) {
     env->SetLongField(library_info_obj, relro_start_id, relro_start);
     env->SetLongField(library_info_obj, relro_size_id, relro_size);
     env->SetIntField(library_info_obj, relro_fd_id, relro_fd);
   }

   bool GetLoadInfo(JNIEnv* env,
                    jobject library_info_obj,
                    uintptr_t* load_address,
                    size_t* load_size) {
     if (load_address) {
       jlong java_address = env->GetLongField(library_info_obj, load_address_id);
       if (!IsValidAddress(java_address))
         return false;
       *load_address = static_cast<uintptr_t>(java_address);
     }
     if (load_size) {
       *load_size = static_cast<uintptr_t>(
           env->GetLongField(library_info_obj, load_size_id));
     }
     return true;
   }

   void GetRelroInfo(JNIEnv* env,
                     jobject library_info_obj,
                     uintptr_t* relro_start,
                     size_t* relro_size,
                     int* relro_fd) {
     if (relro_start) {
       *relro_start = static_cast<uintptr_t>(
           env->GetLongField(library_info_obj, relro_start_id));
     }

     if (relro_size) {
       *relro_size = static_cast<size_t>(
           env->GetLongField(library_info_obj, relro_size_id));
     }

     if (relro_fd) {
       *relro_fd = env->GetIntField(library_info_obj, relro_fd_id);
     }
   }
 };

 // Variable containing LibInfo accessors for the loaded library.
 extern LibInfo_class s_lib_info_fields;

 jint JNI_OnLoad(JavaVM* vm, void* reserved);

 }  // namespace chromium_android_linker

 #endif  // BASE_ANDROID_LINKER_LINKER_JNI_H_
	// Copyright 2015 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.

	// This is the Android-specific Chromium dynamic linker (loader of dynamic
	// libraries), a tiny shared library implementing a custom dynamic linker that
	// can be used to load the real Chromium libraries.
	//
	// The purpose of this custom linker is to be able to share the RELRO section of
	// libcontentshell.so (or equivalent) between the browser process and all other
	// processes it asks to create.
	//
	// This source code cannot depend on anything from //base or the C++ standard
	// library to keep this DSO small and avoid dependency issues. An exception is
	// made for std::unique_ptr as a risky header-only definition.

	#ifndef BASE_ANDROID_LINKER_LINKER_JNI_H_
	#define BASE_ANDROID_LINKER_LINKER_JNI_H_

	#include <android/log.h>
	#include <jni.h>
	#include <stddef.h>
	#include <stdlib.h>

	#include "build/build_config.h"

	// Set this to 1 to enable debug traces to the Android log.
	// Note that LOG() from "base/logging.h" cannot be used, since it is
	// in base/ which hasn't been loaded yet.
	#define DEBUG 0

	#define TAG "cr_ChromiumAndroidLinker"

	#if DEBUG
	#define LOG_INFO(FORMAT, ...) \
	__android_log_print(ANDROID_LOG_INFO, TAG, "%s: " FORMAT, __FUNCTION__, \
	##__VA_ARGS__)
	#else
	#define LOG_INFO(FORMAT, ...) ((void)0)
	#endif
	#define LOG_ERROR(FORMAT, ...) \
	__android_log_print(ANDROID_LOG_ERROR, TAG, "%s: " FORMAT, __FUNCTION__, \
	##__VA_ARGS__)
	#define PLOG_ERROR(FORMAT, ...) \
	LOG_ERROR(FORMAT ": %s", ##__VA_ARGS__, strerror(errno))

	#define UNUSED __attribute__((unused))

	#if defined(ARCH_CPU_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. https://crbug.com/655248
	#define JNI_GENERATOR_EXPORT \
	extern "C" __attribute__((visibility("default"), force_align_arg_pointer))
	#else
	#define JNI_GENERATOR_EXPORT extern "C" __attribute__((visibility("default")))
	#endif

	#if defined(__arm__) && defined(__ARM_ARCH_7A__)
	#define CURRENT_ABI "armeabi-v7a"
	#elif defined(__arm__)
	#define CURRENT_ABI "armeabi"
	#elif defined(__i386__)
	#define CURRENT_ABI "x86"
	#elif defined(__mips__)
	#define CURRENT_ABI "mips"
	#elif defined(__x86_64__)
	#define CURRENT_ABI "x86_64"
	#elif defined(__aarch64__)
	#define CURRENT_ABI "arm64-v8a"
	#else
	#error "Unsupported target abi"
	#endif

	#if !defined(PAGE_SIZE)
	#define PAGE_SIZE (1 << 12)
	#define PAGE_MASK (~(PAGE_SIZE - 1))
	#endif

	#define PAGE_START(x) ((x)&PAGE_MASK)
	#define PAGE_END(x) PAGE_START((x) + (PAGE_SIZE - 1))

	// Copied from //base/posix/eintr_wrapper.h to avoid depending on //base.
	#define HANDLE_EINTR(x) \
	({ \
	decltype(x) eintr_wrapper_result; \
	do { \
	eintr_wrapper_result = (x); \
	} while (eintr_wrapper_result == -1 && errno == EINTR); \
	eintr_wrapper_result; \
	})

	namespace chromium_android_linker {

	// Larger than the largest library we might attempt to load.
	static const size_t kAddressSpaceReservationSize = 192 * 1024 * 1024;

	// A simple scoped UTF String class that can be initialized from
	// a Java jstring handle. Modeled like std::string, which cannot
	// be used here.
	class String {
	public:
	String(JNIEnv* env, jstring str);

	inline ~String() { ::free(ptr_); }

	inline const char* c_str() const { return ptr_ ? ptr_ : ""; }
	inline size_t size() const { return size_; }

	private:
	char* ptr_;
	size_t size_;
	};

	// Returns true iff casting a java-side \|address\| to uintptr_t does not lose
	// bits.
	bool IsValidAddress(jlong address);

	// Find the jclass JNI reference corresponding to a given \|class_name\|.
	// \|env\| is the current JNI environment handle.
	// On success, return true and set \|*clazz\|.
	bool InitClassReference(JNIEnv* env, const char* class_name, jclass* clazz);

	// Finds the region reserved by the WebView zygote if the current process is
	// inherited from the modern enough zygote that has this reservation. If the
	// lookup is successful, returns true and sets \|address\| and \|size\|. Otherwise
	// returns false.
	bool FindWebViewReservation(uintptr_t* address, size_t* size);

	// Initialize a jfieldID corresponding to the field of a given \|clazz\|,
	// with name \|field_name\| and signature \|field_sig\|.
	// \|env\| is the current JNI environment handle.
	// On success, return true and set \|*field_id\|.
	bool InitFieldId(JNIEnv* env,
	jclass clazz,
	const char* field_name,
	const char* field_sig,
	jfieldID* field_id);

	// Initialize a jfieldID corresponding to the static field of a given \|clazz\|,
	// with name \|field_name\| and signature \|field_sig\|.
	// \|env\| is the current JNI environment handle.
	// On success, return true and set \|*field_id\|.
	bool InitStaticFieldId(JNIEnv* env,
	jclass clazz,
	const char* field_name,
	const char* field_sig,
	jfieldID* field_id);

	// A class used to model the field IDs of the org.chromium.base.Linker
	// LibInfo inner class, used to communicate data with the Java side
	// of the linker.
	struct LibInfo_class {
	jfieldID load_address_id;
	jfieldID load_size_id;
	jfieldID relro_start_id;
	jfieldID relro_size_id;
	jfieldID relro_fd_id;

	// Initialize an instance.
	bool Init(JNIEnv* env) {
	jclass clazz;
	if (!InitClassReference(
	env, "org/chromium/base/library_loader/Linker$LibInfo", &clazz)) {
	return false;
	}

	return InitFieldId(env, clazz, "mLoadAddress", "J", &load_address_id) &&
	InitFieldId(env, clazz, "mLoadSize", "J", &load_size_id) &&
	InitFieldId(env, clazz, "mRelroStart", "J", &relro_start_id) &&
	InitFieldId(env, clazz, "mRelroSize", "J", &relro_size_id) &&
	InitFieldId(env, clazz, "mRelroFd", "I", &relro_fd_id);
	}

	void SetLoadInfo(JNIEnv* env,
	jobject library_info_obj,
	uintptr_t load_address,
	size_t load_size) {
	env->SetLongField(library_info_obj, load_address_id, load_address);
	env->SetLongField(library_info_obj, load_size_id, load_size);
	}

	void SetRelroInfo(JNIEnv* env,
	jobject library_info_obj,
	uintptr_t relro_start,
	size_t relro_size,
	int relro_fd) {
	env->SetLongField(library_info_obj, relro_start_id, relro_start);
	env->SetLongField(library_info_obj, relro_size_id, relro_size);
	env->SetIntField(library_info_obj, relro_fd_id, relro_fd);
	}

	bool GetLoadInfo(JNIEnv* env,
	jobject library_info_obj,
	uintptr_t* load_address,
	size_t* load_size) {
	if (load_address) {
	jlong java_address = env->GetLongField(library_info_obj, load_address_id);
	if (!IsValidAddress(java_address))
	return false;
	*load_address = static_cast<uintptr_t>(java_address);
	}
	if (load_size) {
	*load_size = static_cast<uintptr_t>(
	env->GetLongField(library_info_obj, load_size_id));
	}
	return true;
	}

	void GetRelroInfo(JNIEnv* env,
	jobject library_info_obj,
	uintptr_t* relro_start,
	size_t* relro_size,
	int* relro_fd) {
	if (relro_start) {
	*relro_start = static_cast<uintptr_t>(
	env->GetLongField(library_info_obj, relro_start_id));
	}

	if (relro_size) {
	*relro_size = static_cast<size_t>(
	env->GetLongField(library_info_obj, relro_size_id));
	}

	if (relro_fd) {
	*relro_fd = env->GetIntField(library_info_obj, relro_fd_id);
	}
	}
	};

	// Variable containing LibInfo accessors for the loaded library.
	extern LibInfo_class s_lib_info_fields;

	jint JNI_OnLoad(JavaVM* vm, void* reserved);

	} // namespace chromium_android_linker

	#endif // BASE_ANDROID_LINKER_LINKER_JNI_H_