Re: [PATCH] powerpc/ptrace: Add prototype for function pt_regs_check

[Christophe Leroy]

Le 15/02/2019 Ã 09:11, Mathieu Malaterre a ÃcritÂ:
> On Sat, Dec 8, 2018 at 4:46 PM Mathieu Malaterre <malat@xxxxxxxxxx> wrote:
> > `pt_regs_check` is a dummy function, its purpose is to break the build
> > if struct pt_regs and struct user_pt_regs don't match.
> >
> > This function has no functionnal purpose, and will get eliminated at
> > link time or after init depending on CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
> >
> > This commit adds a prototype to fix warning at W=1:
> >
> >    arch/powerpc/kernel/ptrace.c:3339:13: error: no previous prototype for âpt_regs_checkâ [-Werror=missing-prototypes]
> >
> > Suggested-by: Christophe Leroy <christophe.leroy@xxxxxx>
> > Signed-off-by: Mathieu Malaterre <malat@xxxxxxxxxx>
> > ---
> >   arch/powerpc/kernel/ptrace.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
> > index a398999d0770..341c0060b4c8 100644
> > --- a/arch/powerpc/kernel/ptrace.c
> > +++ b/arch/powerpc/kernel/ptrace.c
> > @@ -3338,6 +3338,10 @@ void do_syscall_trace_leave(struct pt_regs *regs)
> >          user_enter();
> >   }
> >
> > +void __init pt_regs_check(void);
> > +/* dummy function, its purpose is to break the build if struct pt_regs and
> > + * struct user_pt_regs don't match.
> > + */
>
> Another trick which seems to work with GCC is:
>
> -void __init pt_regs_check(void)
> +static inline void __init pt_regs_check(void)

Does this really work ? Did you test to ensure that the BUILD_BUG_ON 
still detect mismatch between struct pt_regs and struct user_pt_regs ?

Christophe

> >   void __init pt_regs_check(void)
> >   {
> >          BUILD_BUG_ON(offsetof(struct pt_regs, gpr) !=
> > --
> > 2.19.2