[PATCH bpf-next 0/4] Mixing bpf2bpf and tailcalls for RV64

Björn Töpel bjorn at kernel.org
Tue Sep 26 06:30:14 PDT 2023


Pu Lehui <pulehui at huaweicloud.com> writes:

> In the current RV64 JIT, if we just don't initialize the TCC in subprog,
> the TCC can be propagated from the parent process to the subprocess, but
> the TCC of the parent process cannot be restored when the subprocess
> exits. Since the RV64 TCC is initialized before saving the callee saved
> registers into the stack, we cannot use the callee saved register to
> pass the TCC, otherwise the original value of the callee saved register
> will be destroyed. So we implemented mixing bpf2bpf and tailcalls
> similar to x86_64, i.e. using a non-callee saved register to transfer
> the TCC between functions, and saving that register to the stack to
> protect the TCC value. At the same time, we also consider the scenario
> of mixing trampoline.
>
> In addition, some code cleans are also attached to this patchset.
>
> Tests test_bpf.ko and test_verifier have passed, as well as the relative
> testcases of test_progs*.

Apologies for the review delay. I'm travelling, and will pick it up ASAP
when I'm back.


Björn



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