System permission program cannot access SD card

stay android There is system Permission applications are inaccessible sd Card , This is because vold Hang up sd Card assignment mask Why , Probably for safety reasons . If you have android Source code , This limitation can be removed ：

about android2.2 It's in system/vold/fat.cpp in Fat::doMount To realize . If changed fmask and dmask You can modify the corresponding access permissions . For example, you can adjust the file ：system/vold/Volume.cpp in if (Fat::doMount(devicePath, "/mnt/secure/staging", false, false, 1000, 1015, 0702, true), take 0702 Change to 0. be system Permissions can also access sd card . Specific attributes need to be carefully considered .