[NavinF]

From the LWN article you linked:

>This mechanism works by marshaling parameters to a system call into a single C structure; a pointer to that structure and the size of the structure are passed as the parameters to the system call. That size parameter acts as a sort of version number.

Oh hey, that’s exactly how every WIN32 call works. I see an article from 2003 talking about why Windows is strict about the struct size parameter: https://devblogs.microsoft.com/oldnewthing/20031212-00/?p=41...

> You can't trivially extend structs in a kernel ABI

IMO the article you linked is evidence that this is trivial. Especially for syscalls that will only be called a few times in a process’s lifetime. I dunno why there’s so much bike shedding about this on the mailing list.

Edit: Ahh I didn’t realize you were the Aleksa mentioned in the article. I wish you good luck.

[cyphar]

That Windows article gives a better argument than I ever could as to why putting the size in the argument list is better than in the struct. Some pre-openat2 Linux syscalls are designed in the same way. (Having no forwards nor backwards compatibility but still having struct size versioning really is an interesting design choice...)

But yes, it is relatively trivial -- my point was more that you can't just use a struct in the way the first comment suggested, you need to come up with some scheme (even if it seems trivial in retrospect).

As for the bike-shedding, that's LKML for you (though in fairness it is a bit of a tall order to try to come up with some enforceable API design rules in Linux -- syscalls with half-baked designs being added is less rare than one would hope, so clearly there's not an overarching design principle being applied already, though thankfully it's becoming pretty rare to see a completely borked syscall that clearly has no users being merged).