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

[Z Lim]

Yang, I noticed another thing...

On Fri, Nov 13, 2015 at 10:09 AM, Yang Shi <yang.shi@xxxxxxxxxx> 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.
>
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