Messages in this thread | | | Date | Tue, 21 Feb 2023 09:47:03 +0800 | Subject | Re: [PATCH bpf-next v2] riscv, bpf: Add kfunc support for RV64 | From | Pu Lehui <> |
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On 2023/2/20 22:34, Björn Töpel wrote: > Pu Lehui <pulehui@huaweicloud.com> writes: > >> From: Pu Lehui <pulehui@huawei.com> >> >> As another important missing piece of RV64 JIT, kfunc allow bpf programs >> call kernel functions. For now, RV64 is sufficient to enable it. > > Thanks Lehui! > > Maybe we can reword/massage the commit message a bit? What do you think > about something like: > > "Now that the BPF trampoline is supported by RISC-V, it is possible to > use BPF programs with kfunc calls. >
kfunc and bpf trampoline are functionally independent. kfunc [1], like bpf helper functions, allows bpf programs to call exported kernel functions, while bpf trampoline provides a more efficient way than kprobe to act as a mediator between kernel functions and bpf programs, and between bpf programs.
In fact, it was already supported before the bpf trampoline implementation, I just turned it on. As for RV32 kfunc, it needs to do some registers parsing.
[1] https://lore.kernel.org/bpf/20210325015124.1543397-1-kafai@fb.com/
> Note that the trampoline functionality is only supported by RV64. > > Add bpf_jit_supports_kfunc_call() to the 64-bit JIT." > > > Björn
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