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    SubjectRe: [PATCH] powerpc/ptrace: Add prototype for function pt_regs_check
    On Fri, Feb 15, 2019 at 9:21 AM Christophe Leroy
    <christophe.leroy@c-s.fr> wrote:
    >
    >
    >
    > Le 15/02/2019 à 09:11, Mathieu Malaterre a écrit :
    > > On Sat, Dec 8, 2018 at 4:46 PM Mathieu Malaterre <malat@debian.org> 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 ‘pt_regs_check’ [-Werror=missing-prototypes]
    > >>
    > >> Suggested-by: Christophe Leroy <christophe.leroy@c-s.fr>
    > >> Signed-off-by: Mathieu Malaterre <malat@debian.org>
    > >> ---
    > >> 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 ?
    >

    My bad, I was unaware of GCC behavior for static inline in this case.
    Sorry for the noise.
    Original ugly patch does work though.
    >
    > >
    > >> void __init pt_regs_check(void)
    > >> {
    > >> BUILD_BUG_ON(offsetof(struct pt_regs, gpr) !=
    > >> --
    > >> 2.19.2
    > >>

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