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

From: Daniel Thompson
Date: Wed Sep 26 2018 - 07:11:13 EST


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