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/************************************************************************* * I.MX6 su.c 测试 * 说明： * 今天突然想分析一下su的源代码，看一下其工作机制。 * * 2016-8-10 深圳 南山平山村 曾剑锋 ************************************************************************/一、su源代码修改： /* ** ** Copyright 2008, 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. */ #define LOG_TAG "su" #include#include #include #include #include #include #include #include #include #include /* * SU can be given a specific command to exec. UID _must_ be * specified for this (ie argc => 3). * * Usage: * su 1000 * su 1000 ls -l */ int main(int argc, char **argv) { struct passwd *pw; int uid, gid, myuid; /* Until we have something better, only root and the shell can use su. */ myuid = getuid(); // if (myuid != AID_ROOT && myuid != AID_SHELL) { // fprintf(stderr,"su: uid %d not allowed to su\n", myuid); // // return 1; // } if(argc < 2) { uid = gid = 0; } else { pw = getpwnam(argv[1]); if(pw == 0) { uid = gid = atoi(argv[1]); } else { uid = pw->pw_uid; gid = pw->pw_gid; } } // if(setgid(gid) || setuid(uid)) { // fprintf(stderr,"su: permission denied\n"); // return 1; // } /* User specified command for exec. */ if (argc == 3 ) { if (execlp(argv[2], argv[2], NULL) < 0) { fprintf(stderr, "su: exec failed for %s Error:%s\n", argv[2], strerror(errno)); return -errno; } } else if (argc > 3) { /* Copy the rest of the args from main. */ char *exec_args[argc - 1]; memset(exec_args, 0, sizeof(exec_args)); memcpy(exec_args, &argv[2], sizeof(exec_args)); if (execvp(argv[2], exec_args) < 0) { fprintf(stderr, "su: exec failed for %s Error:%s\n", argv[2], strerror(errno)); return -errno; } } /* Default exec shell. */ execlp("/system/bin/sh", "sh", NULL); fprintf(stderr, "su: exec failed\n"); return 1; }二、权限： chmod 4775 /system/xbin/su 三、调用： private static String cmdList[] = { "su 0 netcfg can0 down", "su 0 ip link set can0 type can bitrate 1000000 triple-sampling on", "su 0 netcfg can0 up", };
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