linux允许从信号处理程序发出任何系统调用吗?

My understanding is that, in general, the behavior is undefined if you call a non-async signal safe function from a signal handler, but I've heard that linux allows you to call any system call safely. Is this true? Also, the only portable behavior for a SIGSEGV handler is to abort or exit, but I understand linux will actually resume execution if you return, true?My understanding is that, in general, the behav