Re: [RFC][v7][PATCH 8/9]: Define clone2() syscall

Arnd Bergmann
2009-09-30T18:02:14Z

On Wednesday 30 September 2009, Linus Torvalds wrote:
> Umm. I don't think that is possible.
>
> You need architecture-specific code to even get access to all registers to
> copy and get a signal-handler-compatible stack frame. See for example
> arch/alpha/kernel/entry.S with the switch-stack thing etc. I don't think
> there is any way to make that even remotely architecture-neutral.

Right, you still need to save all the registers from the entry code.
I was under the wrong assumption that task_pt_regs(current)
would give the full register set on all architectures.

However, I'd still hope that a new system call can be defined in
a way that you only need to have an assembly wrapper to save
the full pt_regs, but no arch specific code to get the syscall arguments
out of that again. In do_clone(), you need a pointer to pt_regs and
the user stack pointer, but that can be generated from
user_stack_pointer(regs).

Does task_pt_regs(current) give the right pointer on all architectures
or do we also need to pass the regs into the syscall?