Accessing temperature sensors on Android (6+) platforms

[Guru Prasad]

I'm a researcher looking into studying temperature on smartphones. My work requires me to track CPU temperature on Android devices.

I've observed that on newer versions of Android, access to /sys/class/thermal seems to be denied to my app with a message on these lines:

avc: denied { search } for name="thermal" dev="sysfs" ino=17530 scontext=u:r:untrusted_app:s0:c512,c768 tcontext=u:object_r:sysfs_thermal:s0 tclass=dir permissive=0

I understand that this is a SELinux message telling me that my (untrusted) app has been denied access to a file of type sysfs_thermal.

So far, I have tried the following with no luck:

• Attempt to read file via a simple cat-like binary packed along with the app
• Attempt to read file via Runtime.getRuntime().exec("cat ...")
• Attempt to read file via Java APIs (tried both File and RandomAccessFile)

What I find confusing is that other apps such as CPU-Z are able to read various temperature sensors under /sys/class/thermal without difficulty.

For the record, I'm using a Nexus 6P running stock Android 6.0.1 kernel version: 3.10.73-g8c0675f.

How can I read temperature sensor values on these devices and/or android versions?

[Braganza Roberts]

Check this,

https://developer.android.com/guide/topics/sensors/sensors_environment.html

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[Paul Chang]

You should read this node directly,not accessing to the /sys/class/thermal dir:

/sys/class/thermal/thermal_zone0/temp