On Sunday, October 30, 2016 12:45:41 AM CEST Yury Norov wrote:

On Sat, Oct 29, 2016 at 11:02:40PM +0200, Arnd Bergmann wrote:

quoted

On Saturday, October 22, 2016 3:14:04 PM CEST Yury Norov wrote:

quoted

The newer prlimit64 syscall provides all the functionality provided by
the getrlimit and setrlimit syscalls and adds the pid of target process,
so future architectures won't need to include getrlimit and setrlimit.

Therefore drop getrlimit and setrlimit syscalls from the generic syscall
list unless __ARCH_WANT_SET_GET_RLIMIT is defined by the architecture's
unistd.h prior to including asm-generic/unistd.h, and adjust all
architectures using the generic syscall list to define it so that no
in-tree architectures are affected.

The patch looks good, but shouldn't we also hide the actual syscall
implementation if the symbol is not set? It's just dead code otherwise
for new architectures.

I was thinking on it. The patch of James Hogan, b0da6d4415 (asm-generic:
Drop renameat syscall from default list) doesn't do it for renameat(), so
I decided not to do it too. It's not so easy to disable syscalls because arch
may support few ABIs, and some of them may require the syscall. For example,
arm64 supports lp64, aarch32 and ilp32, and first two ABIs need renameat()
and getrlimit/setrlimit.

At now there's no arches that doesn't need renameat() and getrlimit/setrlimit,
and there will be no such arch in nearest future. So there will be no
dead code.

But I agree with you that we need make that implementations 
conditional. If I understand it correctly, we need something like
__ARCH_WANT_SET_GET_RLIMIT in all existing Kconfigs, correct?

I think this patch may be applied as is, and if needed I can send
another patch that disables renameat() and getrlimit/setrlimit soon.

Fair enough. Actually now that I think about it, there are probably
lots of other syscalls that are unused on modern architectures.

It would be good to go through the full list and hide all the ones
that are not referenced, but that is clearly independent of your
patch.

	Arnd