Re: [PATCH V3 2/2] arm64: bpf: make BPF prologue and epilogue align with ARM64 AAPCS

Yang, I noticed another thing...

On Fri, Nov 13, 2015 at 10:09 AM, Yang Shi yang.shi@linaro.org wrote:

Save and restore FP/LR in BPF prog prologue and epilogue, save SP to FP in prologue in order to get the correct stack backtrace.

However, ARM64 JIT used FP (x29) as eBPF fp register, FP is subjected to change during function call so it may cause the BPF prog stack base address change too.

Use x25 to replace FP as BPF stack base register (fp). Since x25 is callee saved register, so it will keep intact during function call.

Can you please add save/restore for x25 also? :)

It is initialized in BPF prog prologue when BPF prog is started to run everytime. When BPF prog exits, it could be just tossed.