Re: [PATCH v7 1/6] arm64: ptrace: add PTRACE_SET_SYSCALL

[AKASHI Takahiro]

Hi Will, Kees

#Sorry for this late ping,

On 10/09/2014 06:23 PM, Will Deacon wrote:
> On Wed, Oct 08, 2014 at 04:30:18PM +0100, Kees Cook wrote:
> > On Wed, Oct 8, 2014 at 9:13 AM, Will Deacon <will.deacon@xxxxxxx> wrote:
> > > On Thu, Oct 02, 2014 at 10:46:11AM +0100, AKASHI Takahiro wrote:
> > > > diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> > > > index fe63ac5..2842f9f 100644
> > > > --- a/arch/arm64/kernel/ptrace.c
> > > > +++ b/arch/arm64/kernel/ptrace.c
> > > > @@ -1082,7 +1082,19 @@ const struct user_regset_view *task_user_regset_view(struct task_struct *task)
> > > >   long arch_ptrace(struct task_struct *child, long request,
> > > >                 unsigned long addr, unsigned long data)
> > > >   {
> > > > -     return ptrace_request(child, request, addr, data);
> > > > +     int ret;
> > > > +
> > > > +     switch (request) {
> > > > +             case PTRACE_SET_SYSCALL:
> > > > +                     task_pt_regs(child)->syscallno = data;
> > > > +                     ret = 0;
> > > > +                     break;
> > > > +             default:
> > > > +                     ret = ptrace_request(child, request, addr, data);
> > > > +                     break;
> > > > +     }
> > > > +
> > > > +     return ret;
> > > >   }
> > >
> > > I still don't understand why this needs to be in arch-specific code. Can't
> > > we implement this in generic code and get architectures to implement
> > > something like syscall_set_nr if they want the generic interface?
> >
> > Personally, I'd rather see this land as-is in the arm64 tree, and then
> > later optimize PTRACE_SET_SYSCALL out of arm/ and arm64/, especially
> > since only these architectures implement this at the moment.
>
> Why? It should be really straightforward to do this in core code from the
> get-go and experience shows that, if we don't do it now, it will never
> happen.

How should I deal with this issue? I would be able to go either way.

Other than that, I will submit v8 patch series with a few very minor updates:
- use compat_uint_t in struct compat_siginfo
- use a new call interface of secure_computing(void)
- modify and clarify comments in syscall_trace_enter()

Thanks,
-Takahiro AKASHI

> > This is my plan for the asm-generic seccomp.h too -- I'd rather avoid
> > touching other architectures in this series, as it's easier to review
> > this way. Then we can optimize the code in a separate series, which
> > will have those changes isolated, etc.
>
> But this doesn't need to touch any other architectures...
>
> Will
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