[RFC] ptrace: add generic SET_SYSCALL request

[Will Deacon]

On Wed, Nov 12, 2014 at 11:06:59AM +0000, AKASHI Takahiro wrote:
> On 11/12/2014 08:00 PM, Will Deacon wrote:
> > On Wed, Nov 12, 2014 at 10:46:01AM +0000, AKASHI Takahiro wrote:
> >> On 11/07/2014 11:04 PM, Oleg Nesterov wrote:
> >>> To me the fact that PTRACE_SET_SYSCALL can be undefined and syscall_set_nr()
> >>> is very much arch-dependant (but most probably trivial) means that this  code
> >>> should live in arch_ptrace().
> >>
> >> Thinking of Oleg's comment above, it doesn't make sense neither to define generic
> >> NT_SYSTEM_CALL (user_regset) in uapi/linux/elf.h and implement it in ptrace_regset()
> >> in kernel/ptrace.c with arch-defined syscall_(g)set_nr().
> >>
> >> Since we should have the same interface on arm and arm64, we'd better implement
> >> ptrace(PTRACE_SET_SYSCALL) locally on arm64 for now (as I originally submitted).
> >
> > I think the regset approach is cleaner. We already do something similar for
> > TLS. That would be implemented under arch/arm64/ with it's own NT type.
> 
> Okey, so arm64 goes its own way :)
> Or do you want to have a similar regset on arm, too?
> (In this case, NT_ARM_SYSTEM_CALL can be shared in uapi/linux/elf.h)

Just do arm64. We already have the dedicated request for arch/arm/.

Will