Switching between stacks is only valid if we are tracing ourselves while on the irq_stack, so it is only valid when in current and non-preemptible context, otherwise is is just zeroed off.
Signed-off-by: Yang Shi <[email protected]> --- arch/arm64/kernel/stacktrace.c | 13 ++++++------- arch/arm64/kernel/traps.c | 11 ++++++++++- 2 files changed, 16 insertions(+), 8 deletions(-) diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 12a18cb..d9751a4 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -44,14 +44,13 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) unsigned long irq_stack_ptr; /* - * Use raw_smp_processor_id() to avoid false-positives from - * CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on sleeping - * task stacks, we can be pre-empted in this case, so - * {raw_,}smp_processor_id() may give us the wrong value. Sleeping - * tasks can't ever be on an interrupt stack, so regardless of cpu, - * the checks will always fail. + * Switching between stacks is valid when tracing current and in + * non-preemptible context. */ - irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id()); + if (tsk == current && !preemptible()) + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); + else + irq_stack_ptr = 0; low = frame->sp; /* irq stacks are not THREAD_SIZE aligned */ diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index cbedd72..7d8db3a 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -146,9 +146,18 @@ static void dump_instr(const char *lvl, struct pt_regs *regs) static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) { struct stackframe frame; - unsigned long irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); + unsigned long irq_stack_ptr; int skip; + /* + * Switching between stacks is valid when tracing current and in + * non-preemptible context. + */ + if (tsk == current && !preemptible()) + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); + else + irq_stack_ptr = 0; + pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); if (!tsk) -- 2.0.2
