property_set() can't get property value when I call it in an native thread

[Yang Liu]

Hello~

Recently, I'm in a project. I need to start a native thread from audioflinger and this thread will call property_get() to monitor some my own property (I create my property in init.my_device.rc at beginning time). But in runtime, I find that in my thread, property_get() can't return actual value.

I checked my property permission, it's AID_MEDIA. my thread's uid is "AID_MEDIA" also. When I looked the kernel log via adb dmesg, it shows "permission denied uid: 1013". Is there any thing that I missed or do I have wrong steps?

Thanks,

[shridutt kothari]

HI Yang Liu,

Please see following link: 

http://androidxref.com/4.4.2_r2/xref/system/core/include/private/android_filesystem_config.h

you can see AID_MEDIA is defined as 1013 uid, but AID_AUDIO has uid value 1005. so in your case you are being assigned  AID_MEDIA instead of AID_AUDIO.

also see the following link: 

http://androidxref.com/4.4.2_r2/xref/frameworks/base/data/etc/platform.xml

for the linking of Linux UID to android permission for further mapping.

So i think you need to modify your init.yourdevice.rc file for getting AID_AUDIO so that you can call property_get() to get 1005. 

I hope you have enough pointers.

Thanks,

Shridutt Kothari

shridut...@gmail.com

Impetus Infotech India Ltd.

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Thanks & Regards,
Shridutt Kothari.