Messages in this thread Patch in this message | | | From | Douglas Anderson <> | 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 |
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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
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