Re: [PATCH v5 13/25] m68k: add asm/syscall.h

[Dmitry V. Levin]

Hi Geert,

On Mon, Dec 10, 2018 at 09:45:42AM +0100, Geert Uytterhoeven wrote:
> Hi Dmitry,
> 
> On Mon, Dec 10, 2018 at 5:30 AM Dmitry V. Levin <ldv@xxxxxxxxxxxx> wrote:
> > syscall_get_* functions are required to be implemented on all
> > architectures in order to extend the generic ptrace API with
> > PTRACE_GET_SYSCALL_INFO request.
> >
> > This introduces asm/syscall.h on m68k implementing all 5 syscall_get_*
> > functions as documented in asm-generic/syscall.h: syscall_get_nr,
> > syscall_get_arguments, syscall_get_error, syscall_get_return_value,
> > and syscall_get_arch.
> >
> > Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> > Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
> > Cc: Andy Lutomirski <luto@xxxxxxxxxx>
> > Cc: Elvira Khabirova <lineprinter@xxxxxxxxxxxx>
> > Cc: Eugene Syromyatnikov <esyr@xxxxxxxxxx>
> > Cc: linux-m68k@xxxxxxxxxxxxxxxxxxxx
> > Signed-off-by: Dmitry V. Levin <ldv@xxxxxxxxxxxx>
> > ---
> >
> > Notes:
> >     v5: added syscall_get_nr, syscall_get_arguments, syscall_get_error,
> >         and syscall_get_return_value
> >     v1: added syscall_get_arch
> 
> > --- /dev/null
> > +++ b/arch/m68k/include/asm/syscall.h
> > @@ -0,0 +1,39 @@
> 
> > +static inline void
> > +syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
> > +                     unsigned int i, unsigned int n, unsigned long *args)
> > +{
> > +       BUG_ON(i + n > 6);
> 
> Does this have to crash the kernel?

This is what most of other architectures do, but we could choose
a softer approach, e.g. use WARN_ON_ONCE instead.

> Perhaps you can return an error code instead?

That would be problematic given the signature of this function
and the nature of the potential bug which would most likely be a usage error.


-- 
ldv

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