5.0 SELinux And GPIO

lifusong — Tue, 20 Oct 2015 05:07:13 GMT

Dear sir.

we want access gpio pin from android app.

Android 5.0 has a function SELinux. and default is enable

we use function gpio_export To generate gpio device file

in the os the file patch look like as

/sys/devices/soc0/soc.1/2000000.aips-bus/20a0000.gpio/gpio/gpio35/value

/sys/devices/soc0/soc.1/2000000.aips-bus/20a0000.gpio/gpio/gpio35/direction

and have symlink file

/sys/class/gpio/gpio35/value

/sys/class/gpio/gpio35/direction

our android app will read and write /sys/class/gpio/gpio35/value

but The android app only can read the file,can't wirte ,it refuse by SELinux policy

so we want change this policy.

file_contexts add

/sys/devices/soc0/soc.1/2000000.aips-bus/20a0000.gpio/gpio/gpio35/value u:object_r:gpio_control:s0

/sys/devices/soc0/soc.1/2000000.aips-bus/20a0000.gpio/gpio/gpio35/direction u:object_r:gpio_control:s0

file.te add

type gpio_control, fs_type, sysfs_type;

build image and boot .

question one.

the mainboard haven't plug into USB disk \sdcard\sata _hdd

the system will normal boot into os , and check the /sys/class/gpio/gpio35/value attributes

it display the selinux attributes changed from default sysfs to gpio_control

root@sabresd_6dq:/sys/class/gpio/gpio35 # ls -Z

-rw-r--r-- root root u:object_r:sysfs:s0 active_low

lrwxrwxrwx root root u:object_r:sysfs:s0 device -> ../../../20a0000.gpio

-rw-rw-rw- root system u:object_r:gpio_control:s0 direction

-rw-r--r-- root root u:object_r:sysfs:s0 edge

drwxr-xr-x root root u:object_r:sysfs:s0 power

lrwxrwxrwx root root u:object_r:sysfs:s0 subsystem -> ../../../../../../../class/gpio

-rw-r--r-- root root u:object_r:sysfs:s0 uevent

-rw-rw-rw- root system u:object_r:gpio_control:s0 value

root@sabresd_6dq:/sys/class/gpio/gpio35 #

but the file_contexts File content format as a regular expression,the character "." must be escape,

look like as

/sys/devices/soc0/soc\.1/2000000\.aips-bus/20a0000\.gpio/gpio/gpio35/value u:object_r:gpio_control:s0

build and boot ,the kernel can't boot into os,please see append file escape_file.txt

why can't use escape character "."?

question tow.

plug usb disk \sdcard \sata_hdd into mainboard

file_contexts file add below code

/sys/devices/soc0/soc.1/2000000.aips-bus/20a0000.gpio/gpio/gpio35/value u:object_r:gpio_control:s0

the kernel can't boot into os .the error log look like as append escape_file.txt

file_contexts file add below code

/sys/devices/soc0/soc\.1/2000000\.aips-bus/20a0000\.gpio/gpio/gpio35/value u:object_r:gpio_control:s0

the kernel can boot into os ,but the gpio device file can't change anything.The SELinux attributes still is sysfs ,not gpio_control

help please.

Original Attachment has been moved to: Escape_file.txt.zip

Re: 5.0 SELinux And GPIO

weidong_sun — Fri, 06 Nov 2015 05:49:09 GMT

Hi Fusong,

Your questions are on how to use devices based on android 5.0 in APP, so it belongs to system application, I only give you some advice on it, you can get corresponding experience from internet, such as :

http://blog.csdn.net/wh_19910525/article/details/45170755

SELinux on Android（三） - Hack Blog | 黑客博客

Regards,

Weidong

Re: 5.0 SELinux And GPIO

lifusong — Mon, 09 Nov 2015 00:39:32 GMT

The question is add below context

/sys/devices/soc0/soc.1/2000000.aips-bus/20a0000.gpio/gpio/gpio35/direction u:object_r:gpio_control:s0

when plug into harddisk or u-disk,can't boot into os.

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