Messages in this thread Patch in this message | | | From | Douglas Anderson <> | Subject | [PATCH v5 4/4] kdb: Don't back trace on a cpu that didn't round up | Date | Mon, 26 Nov 2018 19:51:33 -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 v5: None Changes in v4: - Also clear out .debuggerinfo. - Also clear out .debuggerinfo and .task for the master. - Remove clearing out in kdb_stub for offline CPUs; it's now redundant.
Changes in v3: - Don't back trace on a cpu that didn't round up new for v3.
Changes in v2: None
kernel/debug/debug_core.c | 4 ++++ kernel/debug/kdb/kdb_bt.c | 11 ++++++++++- kernel/debug/kdb/kdb_debugger.c | 7 ------- 3 files changed, 14 insertions(+), 8 deletions(-)
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c index 1fb8b239e567..5cc608de6883 100644 --- a/kernel/debug/debug_core.c +++ b/kernel/debug/debug_core.c @@ -592,6 +592,8 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, arch_kgdb_ops.correct_hw_break(); if (trace_on) tracing_on(); + kgdb_info[cpu].debuggerinfo = NULL; + kgdb_info[cpu].task = NULL; kgdb_info[cpu].exception_state &= ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); kgdb_info[cpu].enter_kgdb--; @@ -724,6 +726,8 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, if (trace_on) tracing_on(); + kgdb_info[cpu].debuggerinfo = NULL; + kgdb_info[cpu].task = NULL; kgdb_info[cpu].exception_state &= ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); kgdb_info[cpu].enter_kgdb--; 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(); } diff --git a/kernel/debug/kdb/kdb_debugger.c b/kernel/debug/kdb/kdb_debugger.c index 15e1a7af5dd0..53a0df6e4d92 100644 --- a/kernel/debug/kdb/kdb_debugger.c +++ b/kernel/debug/kdb/kdb_debugger.c @@ -118,13 +118,6 @@ int kdb_stub(struct kgdb_state *ks) kdb_bp_remove(); KDB_STATE_CLEAR(DOING_SS); KDB_STATE_SET(PAGER); - /* zero out any offline cpu data */ - for_each_present_cpu(i) { - if (!cpu_online(i)) { - kgdb_info[i].debuggerinfo = NULL; - kgdb_info[i].task = NULL; - } - } if (ks->err_code == DIE_OOPS || reason == KDB_REASON_OOPS) { ks->pass_exception = 1; KDB_FLAG_SET(CATASTROPHIC); -- 2.20.0.rc0.387.gc7a69e6b6c-goog
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