APP_ABI := arm64-v8a
APP_PLATFORM := android-21

# Copyright (C) 2009 The Android Open Source Project
#
# 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.
#
LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)
LOCAL_MODULE    := auxv
LOCAL_SRC_FILES := auxv.c
LOCAL_ARM_MODE := arm
include $(BUILD_EXECUTABLE)

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>/** Parsing auxv: if you parse the auxv structure yourself (not relying on the dynamic loader), then there's * a bit of a conundrum: the auxv structure follows the rule of the process it describes, so sizeof(unsigned * long) will be 4 for 32-bit processes and 8 for 64-bit processes. We can make this work for us. In * order for this to work on 32-bit systems, all key codes must be 0xffffffff or less. On a 64-bit system,* the most significant 32 bits will be zero. Intel machines are little endians, so these 32 bits follow* the least significant ones in memory.* As such, all you need to do is:* 1. Read 16 bytes from the `auxv` file.* 2. Is this the end of the file?* 3.   Then it's a 64-bit process.* 4.   Done.* 5. Is buf[4], buf[5], buf[6] or buf[7] non-zero?* 6.   Then it's a 32-bit process.* 7.   Done.* 8. Go to 1.*/int check_auxv(int pid)
{if(pid < 0){printf("invalid process id\n");return -1;}char auxv[256];snprintf(auxv, 256, "/proc/%d/auxv", pid);int fd = open(auxv, O_RDONLY);if(fd < 0){printf("%s does not exist\nprocess %d maybe running in 32 bit elf mode", auxv, pid);return 0;}const int SIZE = 16;char buf[SIZE];do {int nread = read(fd, buf, SIZE);if(nread < SIZE){printf("process %d running in 64 bit elf mode\n", pid);break;}if(buf[4] && buf[5] && buf[6]){printf("process %d running in 32 bit elf mode @ line %d\n", pid, __LINE__);printf("%x, %x, %x, %x\n", buf[4], buf[5], buf[6], buf[7]);break;}else if(buf[7]){printf("process %d running in 32 bit elf mode\n", pid);break;}} while(1);close(fd);return 0;
}int main(int argc, char* argv[])
{if(argc <= 1){printf("usage:auxv pid1 [pid2 pid3 ...]\n");return 0;}int i = 0;for(i = 1; i < argc; ++i){int pid = atoi(argv[i]);check_auxv(pid);}return 0;
}

call ndk-build NDK_PROJECT_PATH=. NDK_APPLICATION_MK=./Application.mk

|---Application.mk
|---build.bat
|---jni
||---Android.mk
||---auxv.c