[seL4] reading thread registers

Hello, I know there exists a function seL4_TCB_ReadRegisters, which can read the registers of a certain thread, given a/the capability to the thread. Ultimately, I'm interested in reading memory at runtime to determine whether the data I expect is present. So I'm wondering, is there in seL4 an init process, whose registers contain all the working memory of the system? And furthermore, how can I access a capability to a given thread in order to pass it into the ReadRegisters function mentioned above? Cheers, Michael