> Is there a way that these could mediated by a capability without having to incur syscall overhead?
Is that even warranted? What applications can you imagine would make so many clock calls so as to incur noticeable overhead?
Your example of logging costs might work, but I'm very skeptical that user/kernel transition costs for a clock call would drown out the costs of writing the log entry to disk.
But to answer your question directly, the ability to access the clock in a shared memory segment can itself be reified as a handle that's granted to a process. The process would then issue a map operation and provide an address at which to map the clock (or you could just always map it at the same address too if that's preferable for some reason).
Is that even warranted? What applications can you imagine would make so many clock calls so as to incur noticeable overhead?
Your example of logging costs might work, but I'm very skeptical that user/kernel transition costs for a clock call would drown out the costs of writing the log entry to disk.
But to answer your question directly, the ability to access the clock in a shared memory segment can itself be reified as a handle that's granted to a process. The process would then issue a map operation and provide an address at which to map the clock (or you could just always map it at the same address too if that's preferable for some reason).