On Tue, Apr 12, 2022 at 04:32:22PM +0800, Chen Zhongjin wrote: > By the way, I was thinking about a corner case, because arm64 CALL > instruction won't push LR onto stack atomically as x86. Before push LR, FP > to save frame there still can be some instructions such as bti, paciasp. If > an irq happens here, the stack frame is not constructed so the FP unwinder > will omit this function and provides a wrong stack trace to livepatch. > > It's just a guess and I have not built the test case. But I think it's a > defect on arm64 that FP unwinder can't work properly on prologue and > epilogue. Do you have any idea about this? x86 has similar issues with frame pointers, if for example preemption or page fault exception occurs in a leaf function, or in a function prologue or epilogue, before or after the frame pointer setup. This issue is solved by the "reliable" unwinder which detects irqs/exceptions on the stack and reports the stack as unreliable. -- Josh
