android user用户版本提高adb权限
有的user用户版本的log 不全，且push/pull某些文件或者属性文件
常常会遇到权限不够的情况，给调试带来很多便：
对于user 版本adb shell 开启的还是shell 权限，而不是root 权限，
如果您需要root 权限，需要再改一下system/core/adb/adb.c 里面的should_drop_privileges()
这个函数，在#ifndef ALLOW_ADBD_ROOT 时return 0; 而不是return 1; 即可。
判断是否降低权限：
static int should_drop_privileges() {#ifndef ALLOW_ADBD_ROOT return 1;#else /* ALLOW_ADBD_ROOT */ int secure = 0; char value[PROPERTY_VALUE_MAX]; /* run adbd in secure mode if ro.secure is set and ** we are not in the emulator */ property_get("ro.kernel.qemu", value, ""); if (strcmp(value, "1") != 0) { property_get("ro.secure", value, "1"); if (strcmp(value, "1") == 0) { // don't run as root if ro.secure is set... secure = 1; // ... except we allow running as root in userdebug builds if the // service.adb.root property has been set by the "adb root" command property_get("ro.debuggable", value, ""); if (strcmp(value, "1") == 0) { property_get("service.adb.root", value, ""); if (strcmp(value, "1") == 0) { secure = 0; } } } } return secure;#endif /* ALLOW_ADBD_ROOT */}
具体怎么降低权限：
if (should_drop_privileges()) { struct __user_cap_header_struct header; struct __user_cap_data_struct cap; if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) != 0) { exit(1); } /* add extra groups: ** AID_ADB to access the USB driver ** AID_LOG to read system logs (adb logcat) ** AID_INPUT to diagnose input issues (getevent) ** AID_INET to diagnose network issues (netcfg, ping) ** AID_GRAPHICS to access the frame buffer ** AID_NET_BT and AID_NET_BT_ADMIN to diagnose bluetooth (hcidump) ** AID_SDCARD_R to allow reading from the SD card ** AID_SDCARD_RW to allow writing to the SD card ** AID_MOUNT to allow unmounting the SD card before rebooting ** AID_NET_BW_STATS to read out qtaguid statistics */ gid_t groups[] = { AID_ADB, AID_LOG, AID_INPUT, AID_INET, AID_GRAPHICS, AID_NET_BT, AID_NET_BT_ADMIN, AID_SDCARD_R, AID_SDCARD_RW, AID_MOUNT, AID_NET_BW_STATS }; if (setgroups(sizeof(groups)/sizeof(groups[0]), groups) != 0) { exit(1); } /* then switch user and group to "shell" */ if (setgid(AID_SHELL) != 0) { exit(1); } if (setuid(AID_SHELL) != 0) { exit(1); } /* set CAP_SYS_BOOT capability, so "adb reboot" will succeed */ header.version = _LINUX_CAPABILITY_VERSION; header.pid = 0; cap.effective = cap.permitted = (1 << CAP_SYS_BOOT); cap.inheritable = 0; capset(&header, &cap); D("Local port disabled\n"); }