linux-kernel - [PATCH] kdb: Fix btc (backtrace on each cpu) crash

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Message-Id: <20181030205334.148162-1-dianders@chromium.org>
Date:   Tue, 30 Oct 2018 13:53:34 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>
Cc:     "Tobin C . Harding" <me@...in.cc>, joe@...ches.com,
        Douglas Anderson <dianders@...omium.org>,
        stable@...r.kernel.org, kgdb-bugreport@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: [PATCH] kdb: Fix btc (backtrace on each cpu) crash

Typing 'btc' on kdb doing all sorts of fail.  Sometimes it would
crash, sometimes display nothing, and sometimes hang.

Bisect tracked this down to the commit ad67b74d2469 ("printk: hash
addresses printed with %p"), suggesting an obvious fix.  The pointer
used internally in kdb shouldn't be hashed, so switch it to %px.

Fixes: ad67b74d2469 ("printk: hash addresses printed with %p")
Cc: stable@...r.kernel.org
Signed-off-by: Douglas Anderson <dianders@...omium.org>
---

 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();
 		}
-- 
2.19.1.568.g152ad8e336-goog