Hi all I attached an fentry eBPF program to a kernel function, i.e., tcp_transmit_skb(). I want to implement different logic in the bpf program for different calling stack cases, e.g., __tcp_retransmit_skb()->tcp_transmit_skb() and tcp_write_xmit()->tcp_transmit_skb(). I know that I can access stack traces using the bpf_get_stack() helper function. However, in the fentry eBPF program, I don't know the value of the RSP and RBP register, which means I can not locate the return address even if I can get the stack traces. I want to know if there's any way that I can get the return address and thus get the function calling stack in an fentry bpf program. I'd be appreciate if you can help me. Chang Liu Tsinghua University, China
