从信号处理程序获取保存的指令指针地址。

My question is somewhat different from others that have asked about fault addresses. I'm trying to implement a horrible hack to determine, from a signal handler, whether the signal interrupted a syscall or ordinary user code by inspecting the code at the saved instruction pointer and comparing it against the possible syscall entry instructions for the host architecture it's running on. This is part of implementing correct POSIX thread cancellation that does not suffer from the race condition and resource leak described in my old question:My question is somewhat different from others t