Re: [PATCH v5 bpf-next 2/3] bpf, arm64: Fix tailcall hierarchy

Puranjay Mohan
2024-06-26T12:06:07Z

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Leon Hwang <hffilwlqm@gmail.com> writes:

> This patch fixes a tailcall issue caused by abusing the tailcall in
> bpf2bpf feature on arm64 like the way of "bpf, x64: Fix tailcall
> hierarchy".
>
> On arm64, when a tail call happens, it uses tail_call_cnt_ptr to
> increment tail_call_cnt, too.
>
> At the prologue of main prog, it has to initialize tail_call_cnt and
> prepare tail_call_cnt_ptr.
>
> At the prologue of subprog, it pushes x26 register twice, and does not
> initialize tail_call_cnt.
>
> At the epilogue, it pops x26 twice, no matter whether it is main prog or
> subprog.
>
> Fixes: d4609a5d8c70 ("bpf, arm64: Keep tail call count across bpf2bpf calls")
> Signed-off-by: Leon Hwang <hffilwlqm@gmail.com>

Acked-by: Puranjay Mohan <puranjay@kernel.org>

Thanks,
Puranjay

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