Re: [RFC PATCH 3/4] riscv: Introduce is_compat_thread() into compat.h

[Andy Chiu]

On Wed, Dec 27, 2023 at 3:25 AM Leonardo Bras Soares Passos
<leobras@xxxxxxxxxx> wrote:
>
> On Sat, Dec 23, 2023 at 1:26 AM Andy Chiu <andy.chiu@xxxxxxxxxx> wrote:
> >
> > On Fri, Dec 22, 2023 at 3:46 PM Leonardo Bras <leobras@xxxxxxxxxx> wrote:
> > >
> > > task_user_regset_view() makes use of a function very similar to
> > > is_compat_task(), but pointing to a any thread.
> > >
> > > In arm64 asm/compat.h there is a function very similar to that:
> > > is_compat_thread(struct thread_info *thread)
> > >
> > > Copy this function to riscv asm/compat.h and make use of it into
> > > task_user_regset_view().
> > >
> > > Also, introduce a compile-time test for CONFIG_COMPAT and simplify the
> > > function code by removing the #ifdef.
> > >
> > > Signed-off-by: Leonardo Bras <leobras@xxxxxxxxxx>
> > > ---
> > >  arch/riscv/include/asm/compat.h | 8 ++++++++
> > >  arch/riscv/kernel/ptrace.c      | 6 +++---
> > >  2 files changed, 11 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/arch/riscv/include/asm/compat.h b/arch/riscv/include/asm/compat.h
> > > index 91517b51b8e27..da4b28cd01a95 100644
> > > --- a/arch/riscv/include/asm/compat.h
> > > +++ b/arch/riscv/include/asm/compat.h
> > > @@ -20,6 +20,14 @@ static inline int is_compat_task(void)
> > >         return test_thread_flag(TIF_32BIT);
> > >  }
> > >
> > > +static inline int is_compat_thread(struct thread_info *thread)
> > > +{
> > > +       if (!IS_ENABLED(CONFIG_COMPAT))
> > > +               return 0;
> > > +
> > > +       return test_ti_thread_flag(thread, TIF_32BIT);
> > > +}
> > > +
> >
> > Does it make sense to use a #ifdef CONFIG_COMPAT clause to group
> > is_compat_thread() and is_compat_flag()? For example,
>
> Hello Andy,
>
> Sure, it does make sense.
>
> But I honestly think that using IS_ENABLED() instead of #ifdef +
> multiple same-named functions works better for code reading, at least
> for small functions such as these.
>
> Does this make sense?
>
> Thanks for reviewing!
> Leo

Hi, yes!

It makes sense to me.

Reviewed-by: Andy Chiu <andy.chiu@xxxxxxxxxx>

Thanks,
Andy

>
>
> >
> > #ifdef CONFIG_COMPAT
> > static inline int is_compat_thread(struct thread_info *thread)
> > {
> >  return test_ti_thread_flag(thread, TIF_32BIT);
> > }
> > static inline int is_compat_task(void)
> > {
> >  return is_compat_thread(current);
> > }
> > #else
> > static inline int is_compat_thread(struct thread_info *thread) { return 0; }
> > static inline int is_compat_task(void) { return 0; }
> > #endif
> >
> > >  struct compat_user_regs_struct {
> > >         compat_ulong_t pc;
> > >         compat_ulong_t ra;
> > > diff --git a/arch/riscv/kernel/ptrace.c b/arch/riscv/kernel/ptrace.c
> > > index 2afe460de16a6..f362832123616 100644
> > > --- a/arch/riscv/kernel/ptrace.c
> > > +++ b/arch/riscv/kernel/ptrace.c
> > > @@ -374,14 +374,14 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
> > >
> > >         return ret;
> > >  }
> > > +#else
> > > +static const struct user_regset_view compat_riscv_user_native_view = {};
> > >  #endif /* CONFIG_COMPAT */
> > >
> > >  const struct user_regset_view *task_user_regset_view(struct task_struct *task)
> > >  {
> > > -#ifdef CONFIG_COMPAT
> > > -       if (test_tsk_thread_flag(task, TIF_32BIT))
> > > +       if (is_compat_thread(&task->thread_info))
> > >                 return &compat_riscv_user_native_view;
> > >         else
> > > -#endif
> > >                 return &riscv_user_native_view;
> > >  }
> > > --
> > > 2.43.0
> > >
> >
>