C中是否有function可以在Linux上获取当前进程的虚拟运行时间？

Question

TL;DR:
What would be the best way to:

1. Get the current process;
2. Access its PCB;
3. Access and return its vruntime value?

I'm trying to implement a new system call (in C) which will return the virtual runtime of the current process.
The virtual runtime is stored in the vruntime field in the process's PCB, but I couldn't find how to access it.

I've been trying to find a way using the process's PID or the process name itself without success. Is there a way to get the process as a struct task_struct variable and access the vruntime field?

Answer 1

There is already one, getrusage(RUSAGE_SELF, &rusage) , implemented in kernel/sys.c:getrusage() .

Answer 2

Your system call will be running in kernel mode in the context of the thread that invoked it, so the following expression will get the current process task_struct:

current_thread_info() -> task

You can then read the vruntime field to a buffer provided by the user, using copy_to_user or similar for safety with respect to untrusted addresses from the caller.