Re: [PATCH 00/11] Introduce kernel_clone(), kill _do_fork()

[Christian Brauner]

On Tue, Aug 18, 2020 at 06:44:47PM +0100, Matthew Wilcox wrote:
> On Tue, Aug 18, 2020 at 07:34:00PM +0200, Christian Brauner wrote:
> > The only remaining function callable outside of kernel/fork.c is
> > _do_fork(). It doesn't really follow the naming of kernel-internal
> > syscall helpers as Christoph righly pointed out. Switch all callers and
> > references to kernel_clone() and remove _do_fork() once and for all.
> 
> My only concern is around return type.  long, int, pid_t ... can we
> choose one and stick to it?  pid_t is probably the right return type
> within the kernel, despite the return type of clone3().  It'll save us
> some work if we ever go through the hassle of growing pid_t beyond 31-bit.

It should be safe to switch kernel_clone() to return pid_t. (Afair, the
syscall wrappers all have "long" as return type. (I think Linus provided
some more details on that in another mail. Also see
include/linux/syscalls.h. So the return type for clone3() is really
somewhat a userspace thing, I think.)

I wonder whether I should take the opportunity and switch the advertised
flag arguments for the legacy clone() syscalls and kernel_thread() from
unsigned long to unsigned int so we can get rid of the lower
		.flags		= (lower_32_bits(clone_flags) & ~CSIGNAL),
calls I added to fix sign extension issues glibc ran into...

Christian