Messages in this thread | | | Subject | Re: [PATCH v3] arm64: fix unwind_frame() for filtered out fn for function graph tracing | From | Jerome Marchand <> | Date | Wed, 17 Jan 2018 16:03:13 +0100 |
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On 16/01/18 18:57, Catalin Marinas wrote: > On Fri, Jan 12, 2018 at 11:48:32AM +0100, Jerome Marchand wrote: >> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c >> index 76809ccd309c..5a528c58ef68 100644 >> --- a/arch/arm64/kernel/stacktrace.c >> +++ b/arch/arm64/kernel/stacktrace.c >> @@ -59,6 +59,10 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) >> #ifdef CONFIG_FUNCTION_GRAPH_TRACER >> if (tsk->ret_stack && >> (frame->pc == (unsigned long)return_to_handler)) { >> + WARN_ON(frame->graph == -1); >> + if (frame->graph < -1) >> + frame->graph += FTRACE_NOTRACE_DEPTH; >> + >> /* >> * This is a case where function graph tracer has >> * modified a return address (LR) in a stack frame > > So do we still allow this to continue if graph == -1? The following line > doesn't seem safe: > > frame->pc = tsk->ret_stack[frame->graph--].ret; >
You're right. We probably should return a error (-EINVAL I guess) if this happens. Note that this shouldn't happen here and if we're confident enough that profile_pc() was the only faulty caller, we could just drop the warning.
Jerome
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