Re: [PATCH v3 1/2] bpf, riscv: add support for timed may_goto

[Feng Jiang]

On 2026/7/16 16:08, Björn Töpel wrote:
> Feng Jiang <jiangfeng@xxxxxxxxxx> writes:
> 
>> Implement arch_bpf_timed_may_goto() for the RV64 JIT. The argument and
>> return value are carried in BPF_REG_AX, and BPF R0-R5 are preserved
>> across the call to the generic bpf_check_timed_may_goto().
>>
>> Enable bpf_jit_supports_timed_may_goto() so the verifier uses the timed
>> expansion path.
> 
> Thanks for working on this!
> 
>> diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
>> index c03c1de16b79..4f88a446278a 100644
>> --- a/arch/riscv/net/bpf_jit_comp64.c
>> +++ b/arch/riscv/net/bpf_jit_comp64.c
>> @@ -1841,7 +1841,13 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>>  		if (ret)
>>  			return ret;
>>  
>> -		if (insn->src_reg != BPF_PSEUDO_CALL)
>> +		/*
>> +		 * arch_bpf_timed_may_goto() is emitted by the verifier and
>> +		 * returns its result in BPF_REG_AX instead of BPF_REG_0, so
>> +		 * skip the normal "move return register into R0".
>> +		 */
>> +		if (insn->src_reg != BPF_PSEUDO_CALL &&
>> +		    addr != (u64)arch_bpf_timed_may_goto)
> 
> Nit: In the future, please use full 100 chars lines, instead of breaking
> the line.
> 
> Would it be possible to add a test for this custom ABI? The fact that it
> was missed in v1 hints that it would be good.
> 
> I asked an LLM to suggest a test [1]. Feel free to be inspired by it.
> ;-)
> 
> 
> Björn
> 
> [1] https://paste.debian.net/hidden/9dd769d6

Thanks Björn! I'll fix the line wrap and add a test for the custom ABI.
Will send a v4 later.

-- 
With Best Regards,
Feng Jiang