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How to capture process id and multi-thread for application from ARM hardware

Note: This was originally posted on 5th September 2011 at http://forums.arm.com

Dear all,
I am make a simulator for ARM (Cortex-a9). I want to capture process id and multi-thread for applications run on Linux kernel by this simulator, but I don't have good idea to capture it. I thought about CP15.c13 (Context PID register) of ARM but it seems not true for PID from kernel. I also think that Arm hardware will manage PID by stack and capture stack pointer will help to capture PID and multi-thread, but it is very difficult for me to understand about it. Please help me to find a solution to capture them.
Thanks and best regard,

thiet pv over 12 years ago

Note: This was originally posted on 6th September 2011 at http://forums.arm.com

Thanks for your reply,
I learn about contex register of ARM refer http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0344c/Bgbeegaf.html
I think it can help to specify PID of each application. I see that the value of this register is not the same with PID in the linux kernel, but I don't know why?
Do you think that it can help to specify PID?
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thiet pv over 12 years ago

Note: This was originally posted on 6th September 2011 at http://forums.arm.com

Thanks for your answer.
I also think the same you. The value contex id and pid in kernel is different. But I don't understand the mean of that register. Can you say the purpose of contex id register?
I learn and I have idea to specify process and multi-thread for applications by capture stack pointer, because each process will be contained on 8KB stack so if we capture stack pointer for each functions of application we can specify the and multi-thread for an application by hardware.
Do you think? please send me your comments.
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Konrad Anton over 12 years ago

Note: This was originally posted on 6th September 2011 at http://forums.arm.com

You will probably have to interpret the Linux kernel's data structures (task queue etc) in RAM. As Linux is a very portable kernel, I doubt that the ARM port uses ARM specialty registers to store PIDs when most other processor architectures have no such register.
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Peter Harris over 12 years ago

Note: This was originally posted on 6th September 2011 at http://forums.arm.com

This register is only loosely related to PID, and the mapping between PID and the value in this register is not a 1:1 mapping and time variant.

As the previous poster said, PID is a software construct managed by the kernel, and not something which exists in the hardware directly.

Iso
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