linux-kernel - Re: Checkpatch bad Warning (Re: [PATCH] powerpc/kgdb: add kgdb_arch_set/remove

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Date:   Thu, 20 Sep 2018 20:36:25 +0000
From:   Paul Burton <paul.burton@...s.com>
To:     Christophe Leroy <christophe.leroy@....fr>
CC:     Michael Ellerman <mpe@...erman.id.au>,
        Joe Perches <joe@...ches.com>,
        Andy Whitcroft <apw@...onical.com>,
        "ralf@...ux-mips.org" <ralf@...ux-mips.org>,
        "jhogan@...nel.org" <jhogan@...nel.org>,
        Paul Mackerras <paulus@...ba.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>
Subject: Re: Checkpatch bad Warning (Re: [PATCH] powerpc/kgdb: add
 kgdb_arch_set/remove_breakpoint())

Hi Christophe,

On Thu, Sep 20, 2018 at 01:23:55AM +0000, Christophe Leroy wrote:
> On 09/20/2018 01:19 PM, Christophe LEROY wrote:
> > Le 20/09/2018 à 15:13, Michael Ellerman a écrit :
> > > Joe Perches <joe@...ches.com> writes:
> > > > On Tue, 2018-09-18 at 09:33 +0000, Christophe Leroy wrote:
> > > > > On the below patch, checkpatch reports
> > > > > 
> > > > > WARNING: struct kgdb_arch should normally be const
> > > > > #127: FILE: arch/powerpc/kernel/kgdb.c:480:
> > > > > +struct kgdb_arch arch_kgdb_ops;
> > > > > 
> > > > > But when I add 'const', I get compilation failure
> > > > 
> > > > So don't add const.
> > > > 
> > > > checkpatch is stupid.  You are not.
> > > > 
> > > > _Always_ take checkpatch bleats with very
> > > > large grains of salt.
> > > > 
> > > > Perhaps send a patch to remove kgbd_arch
> > > > from scripts/const_structs.checkpatch as
> > > > it seems not ever to be const.
> > > 
> > > I think it could/should be const though, it just requires updating all
> > > arches.
> > > 
> > 
> > Yes I was thinking about doing it, but first thing is to change the way
> > MIPS initialises it:
> > 
> > struct kgdb_arch arch_kgdb_ops;
> > 
> > int kgdb_arch_init(void)
> > {
> >      union mips_instruction insn = {
> >          .r_format = {
> >              .opcode = spec_op,
> >              .func    = break_op,
> >          }
> >      };
> >      memcpy(arch_kgdb_ops.gdb_bpt_instr, insn.byte, BREAK_INSTR_SIZE);
> > 
> > 
> > Can this be done staticaly ?

Something like this ought to do the trick:

diff --git a/arch/mips/kernel/kgdb.c b/arch/mips/kernel/kgdb.c
index eb6c0d582626..31eff1bec577 100644
--- a/arch/mips/kernel/kgdb.c
+++ b/arch/mips/kernel/kgdb.c
@@ -394,18 +394,16 @@ int kgdb_arch_handle_exception(int vector, int signo, int err_code,
 	return -1;
 }
 
-struct kgdb_arch arch_kgdb_ops;
+struct kgdb_arch arch_kgdb_ops = {
+#ifdef CONFIG_CPU_BIG_ENDIAN
+	.gdb_bpt_instr = { spec_op << 2, 0x00, 0x00, break_op },
+#else
+	.gdb_bpt_instr = { break_op, 0x00, 0x00, spec_op << 2 },
+#endif
+};
 
 int kgdb_arch_init(void)
 {
-	union mips_instruction insn = {
-		.r_format = {
-			.opcode = spec_op,
-			.func	= break_op,
-		}
-	};
-	memcpy(arch_kgdb_ops.gdb_bpt_instr, insn.byte, BREAK_INSTR_SIZE);
-
 	register_die_notifier(&kgdb_notifier);
 
 	return 0;

Thanks,
    Paul