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@c-s.fr Cc: stable@vger.kernel.org # 4.15+
Would a Fixes: be better here? Fixes: ad67b74d2469d9b82 ("printk: hash addresses printed with %p")
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;
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