Re: [PATCH bpf-next] riscv, bpf: Fix missing sign-ext for signed 1-byte and 2-byte kfunc args

On 2026/8/14 14:57, [email protected] wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Low] The patch introduces a call to a `sign_extend()` function that is undeclared and undefined, resulting in a compilation failure.
> --
> 
> --- Patch [1]: [PATCH bpf-next] riscv, bpf: Fix missing sign-ext for signed 1-byte and 2-byte kfunc args ---
> commit 47567ad8c96e02d677f1ae5123565efa9cf1b55f
> Author: Pu Lehui <[email protected]>
> 
> riscv, bpf: Fix missing sign-ext for signed 1-byte and 2-byte kfunc args
> 
> This commit updates the RISC-V BPF JIT to sign-extend 1-byte and 2-byte
> kfunc arguments as required by the RV64 ABI. This addresses an issue exposed
> by recent state pruning liveness analysis changes.
> 
>> diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
>> index 10e01ff06312d..0c6de02eb33a8 100644
>> --- a/arch/riscv/net/bpf_jit_comp64.c
>> +++ b/arch/riscv/net/bpf_jit_comp64.c
>> @@ -1784,9 +1784,10 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>>   
>>   			for (idx = 0; idx < fm->nr_args; idx++) {
>>   				u8 reg = bpf_to_rv_reg(BPF_REG_1 + idx, ctx);
>> +				bool sign = fm->arg_flags[idx] & BTF_FMODEL_SIGNED_ARG;
>>   
>> -				if (fm->arg_size[idx] == sizeof(int))
>> -					emit_sextw(reg, reg, ctx);
>> +				if (sign_extend(reg, reg, fm->arg_size[idx], sign, ctx))
>> +					return -EINVAL;
> 
> [Severity: Low]
> Is sign_extend() declared in this context?

No, sign_extend() has been add by commit fd2e08128944a("riscv, bpf: Sign 
extend struct ops return values properly"), and there is no building 
failure.

> 
> It appears this function might be missing from this file or requires an
> unapplied prerequisite patch. Looking through the source, there doesn't
> appear to be a sign_extend() function defined in the RISC-V BPF JIT code
> that matches this 5-argument signature. Will this cause a build failure due
> to an undeclared function?
> 
>>   			}
>>   		}
>>
>