Re: Re: [PATCH] kdb: use correct pointer when 'btc' calls 'btt'

[Daniel Thompson]

On 16/09/2018 20:06, Daniel Thompson wrote:
> On Fri, Sep 14, 2018 at 12:35:44PM +0000, Christophe Leroy wrote:
> > On a powerpc 8xx, 'btc' fails as follows:
> >
> > Entering kdb (current=0x(ptrval), pid 282) due to Keyboard Entry
> > kdb> btc
> > btc: cpu status: Currently on cpu 0
> > Available cpus: 0
> > kdb_getarea: Bad address 0x0
> >
> > when booting the kernel with 'debug_boot_weak_hash', it fails as well
> >
> > Entering kdb (current=0xba99ad80, pid 284) due to Keyboard Entry
> > kdb> btc
> > btc: cpu status: Currently on cpu 0
> > Available cpus: 0
> > kdb_getarea: Bad address 0xba99ad80
> >
> > On other platforms, Oopses have been observed too, see
> > https://github.com/linuxppc/linux/issues/139
> >
> > This is due to btc calling 'btt' with %p pointer as an argument.
> >
> > This patch replaces %p by %px to get the real pointer value as
> > expected by 'btt'
> >
> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> > Cc: <stable@xxxxxxxxxxxxxxx> # 4.15+
>
> Would a Fixes: be better here?
> Fixes: ad67b74d2469d9b82 ("printk: hash addresses printed with %p")

Christophe, When you add the Fixes: could you also add my

Reviewed-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>


Thanks.


> No blame attached to Tobin, but the fixes makes it super clear what
> changed and why this breaks kdb (which was not explicitly called out
> the patch description).
>
>
> Daniel.
>
> > ---
> >   kernel/debug/kdb/kdb_bt.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/debug/kdb/kdb_bt.c b/kernel/debug/kdb/kdb_bt.c
> > index 6ad4a9fcbd6f..7921ae4fca8d 100644
> > --- a/kernel/debug/kdb/kdb_bt.c
> > +++ b/kernel/debug/kdb/kdb_bt.c
> > @@ -179,14 +179,14 @@ kdb_bt(int argc, const char **argv)
> >   				kdb_printf("no process for cpu %ld\n", cpu);
> >   				return 0;
> >   			}
> > -			sprintf(buf, "btt 0x%p\n", KDB_TSK(cpu));
> > +			sprintf(buf, "btt 0x%px\n", KDB_TSK(cpu));
> >   			kdb_parse(buf);
> >   			return 0;
> >   		}
> >   		kdb_printf("btc: cpu status: ");
> >   		kdb_parse("cpu\n");
> >   		for_each_online_cpu(cpu) {
> > -			sprintf(buf, "btt 0x%p\n", KDB_TSK(cpu));
> > +			sprintf(buf, "btt 0x%px\n", KDB_TSK(cpu));
> >   			kdb_parse(buf);
> >   			touch_nmi_watchdog();
> >   		}
> > --
> > 2.13.3