From: Douglas Anderson <dianders@chromium.org>
To: Jason Wessel <jason.wessel@windriver.com>,
Daniel Thompson <daniel.thompson@linaro.org>
Cc: kgdb-bugreport@lists.sourceforge.net,
Peter Zijlstra <peterz@infradead.org>,
Douglas Anderson <dianders@chromium.org>,
Christophe Leroy <christophe.leroy@c-s.fr>,
linux-kernel@vger.kernel.org
Subject: [PATCH v3 4/4] kdb: Don't back trace on a cpu that didn't round up
Date: Tue, 6 Nov 2018 17:00:28 -0800 [thread overview]
Message-ID: <20181107010028.184543-5-dianders@chromium.org> (raw)
In-Reply-To: <20181107010028.184543-1-dianders@chromium.org>
If you have a CPU that fails to round up and then run 'btc' you'll end
up crashing in kdb becaue we dereferenced NULL. Let's add a check.
It's wise to also set the task to NULL when leaving the debugger so
that if we fail to round up on a later entry into the debugger we
won't backtrace a stale task.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---
Changes in v3:
- New for v3.
Changes in v2: None
kernel/debug/debug_core.c | 1 +
kernel/debug/kdb/kdb_bt.c | 11 ++++++++++-
2 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 324cba8917f1..08851077c20a 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -587,6 +587,7 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
kgdb_info[cpu].exception_state &=
~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
kgdb_info[cpu].enter_kgdb--;
+ kgdb_info[cpu].task = NULL;
smp_mb__before_atomic();
atomic_dec(&slaves_in_kgdb);
dbg_touch_watchdogs();
diff --git a/kernel/debug/kdb/kdb_bt.c b/kernel/debug/kdb/kdb_bt.c
index 7921ae4fca8d..7e2379aa0a1e 100644
--- a/kernel/debug/kdb/kdb_bt.c
+++ b/kernel/debug/kdb/kdb_bt.c
@@ -186,7 +186,16 @@ kdb_bt(int argc, const char **argv)
kdb_printf("btc: cpu status: ");
kdb_parse("cpu\n");
for_each_online_cpu(cpu) {
- sprintf(buf, "btt 0x%px\n", KDB_TSK(cpu));
+ void *kdb_tsk = KDB_TSK(cpu);
+
+ /* If a CPU failed to round up we could be here */
+ if (!kdb_tsk) {
+ kdb_printf("WARNING: no task for cpu %ld\n",
+ cpu);
+ continue;
+ }
+
+ sprintf(buf, "btt 0x%px\n", kdb_tsk);
kdb_parse(buf);
touch_nmi_watchdog();
}
--
2.19.1.930.g4563a0d9d0-goog
next prev parent reply other threads:[~2018-11-07 1:04 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-07 1:00 [PATCH v3 0/4] kgdb: Fix kgdb_roundup_cpus() Douglas Anderson
2018-11-07 1:00 ` [PATCH v3 1/4] kgdb: Remove irq flags from roundup Douglas Anderson
2018-11-07 1:00 ` [PATCH v3 2/4] kgdb: Fix kgdb_roundup_cpus() for arches who used smp_call_function() Douglas Anderson
2018-11-07 1:00 ` [PATCH v3 3/4] kgdb: Don't round up a CPU that failed rounding up before Douglas Anderson
2018-11-07 11:59 ` Daniel Thompson
2018-11-07 16:44 ` Doug Anderson
2018-11-07 1:00 ` Douglas Anderson [this message]
2018-11-07 12:30 ` [PATCH v3 4/4] kdb: Don't back trace on a cpu that didn't round up Daniel Thompson
2018-11-07 18:44 ` Doug Anderson
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