Jonathan Corbet wrote:
Heh, indeed. But we do seem to have a recurring problem of people
wanting to extend sys_foo() beyond the confines of its original API.
I've observed a few ways of doing that:
- create sys_foo2() (or sys_foo64(), or sys_fooat(), or sys_pfoo(),
or...) and add the new stuff there.
The first approach has traditionally been the most popular. If we have
a consensus that this is the way to extend system calls in the future,
it would be nice to set that down somewhere. We could avoid a lot of
API blind alleys that way.
I would argue it is the right approach. It lets the kernel system call
entry dispatch directly to the system call for the "new" case, and to a
compatibility thunk for the "old" case. It has the following desirable
properties:
- No overhead for the "new" case.
- Minimal overhead for the "old" case.
- Easily dealt with by tools like strace that examine system calls.
-hpa
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