[PATCH v4 07/16] powerpc: Introduce functions for instruction nullity and equality

[Jordan Niethe]

On Mon, Mar 23, 2020 at 5:46 PM Nicholas Piggin <npiggin at gmail.com> wrote:
>
> Jordan Niethe's on March 20, 2020 3:18 pm:
> > In preparation for an instruction data type that can not be directly
> > used with the '==' operator use functions for checking equality and
> > nullity.
> >
> > Signed-off-by: Jordan Niethe <jniethe5 at gmail.com>
> > ---
> >  arch/powerpc/kernel/optprobes.c      |  2 +-
> >  arch/powerpc/kernel/trace/ftrace.c   | 33 +++++++++++++++-------------
> >  arch/powerpc/lib/code-patching.c     | 16 +++++++-------
> >  arch/powerpc/lib/feature-fixups.c    |  2 +-
> >  arch/powerpc/lib/test_emulate_step.c |  4 ++--
> >  arch/powerpc/xmon/xmon.c             |  4 ++--
> >  6 files changed, 32 insertions(+), 29 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
> > index 1025a7a3b3a8..6027425a85f2 100644
> > --- a/arch/powerpc/kernel/optprobes.c
> > +++ b/arch/powerpc/kernel/optprobes.c
> > @@ -259,7 +259,7 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
> >                               (unsigned long)emulate_step_addr,
> >                               BRANCH_SET_LINK);
> >
> > -     if (!branch_op_callback || !branch_emulate_step)
> > +     if (ppc_inst_null(branch_op_callback) || ppc_inst_null(branch_emulate_step))
>
> Is an instruction null, or zeroes?
ppc_inst_zero() would probably be clearer.
>
> Oh, most of this comes from create_branch and things. Hmm, would rather
> see those functions modified to take a &insn and return an int err.
Good idea.
>
>
> > @@ -437,7 +438,7 @@ int ftrace_make_nop(struct module *mod,
> >        * then we had to use a trampoline to make the call.
> >        * Otherwise just update the call site.
> >        */
> > -     if (test_24bit_addr(ip, addr)) {
> > +     if (!ppc_inst_null(test_24bit_addr(ip, addr))) {
> >               /* within range */
> >               old = ftrace_call_replace(ip, addr, 1);
> >               new = PPC_INST(PPC_INST_NOP);
>
> test_24bit_addr shouldn't be passing a ppc_inst back, but a bool.
True.
>
> Thanks,
> Nick